Catalysis for the Valorization of Exhaust Carbon: from CO2 to

Review pubs.acs.org/CR

Catalysis for the Valorization of Exhaust Carbon: from CO2 to Chemicals, Materials, and Fuels. Technological Use of CO2 Michele Aresta,*,† Angela Dibenedetto,†,‡ and Antonella Angelini†,‡ †

CIRCC, Via Celso Ulpiani 27, 70126 Bari, Italy Department of Chemistry, University of Bari, Via Orabona 4, 70125 Bari, Italy

‡

4.1. Enhanced Aquatic Biomass Production 5. Technological Uses of CO2 5.1. Reducing the Impact on Climate Change via Technological Uses of CO2 5.2. Enhanced Oil Recovery, EOR 6. Conclusions: Perspective Use of CO2 Author Information Corresponding Author Notes Biographies References

Z Z AA AB AB AB AB AB AC AC

1. INTRODUCTION

CONTENTS 1. Introduction 1.1. Emission of CO2 1.2. Strategies for Avoiding CO2 1.3. Utilization of CO2 1.4. Used and Avoided CO2 1.5. Separation of CO2 from Flue Gases and Process Streams 2. From CO2 to Chemicals 2.1. Thermal Processes 2.1.1. Urea 2.1.2. Salicylic Acid 2.1.3. Inorganic Carbonates 2.1.4. Inorganic Carbonates as Storage of CO2 2.2. Catalytic Processes 2.2.1. Formic Acid 2.2.2. Other Carboxylates 2.2.3. Organic Carbonates 2.2.4. Carbamates 2.2.5. Acrylates from Ethene and CO2 2.2.6. Reaction of Other Olefins with CO2 2.2.7. Reaction of Dienes with CO2 2.2.8. Reaction of Alkynes with CO2 2.2.9. Relevance of C−H Activation to CO2 Fixation into Chemicals 3. From CO2 to Fuels: The Changing Paradigm in CO2 Utilization 3.1. Reduction to CO 3.2. Reduction to Methanol and Methane (and Cn Species) 3.3. Use of Excess Electric Energy for CO 2 Reduction 3.4. H2 Production for CO2 Reduction 3.5. Use of Perennial Energy for CO2 Reduction 3.6. Photochemical Reduction of CO2 4. Biotechnological Conversion of CO2 © XXXX American Chemical Society

A A A B C

1.1. Emission of CO2

In 2010 the emission of CO2 from anthropic activities amounted at ca. 30 000 Mt, 43% of which was from coal combustion, 36% from oil, and 20% from gas.1 Growth of consumption of the above fuels is quite different, and since 2009 coal is filling much of the world energy demand, due to the large use made in countries like China and India where energy intensive productive activities based on coal are largely expanding thanks to local large reserve of this form of fossil carbon. (Figure 1) Without additional abatement measures, the WEO 2012 projects that emissions from coal will grow to 15 300 MtCO2 in 2035 from 13 100 in 2010: intensified use of coal would substantially increase CO2 emissions.

D E E E F F F G G I I Q R S S S

1.2. Strategies for Avoiding CO2

Several strategies are under assessment for the reduction of fossil-C consumption and CO2 emission. Higher efficiency in electric energy production (it averages today at 100y); the impact of large volumes of CO2 on natural systems; etc. As a matter of fact, CCS has not been accepted by several countries (Germany, Austria, Denmark, and others) and has no future in others. CO2 utilization is today considered with much attention as it would recycle carbon, reducing both the extraction of fossil-C, thus preserving resources, and the emission of CO2. The use of perennial energy sources [sun, wind, geothermal (SWG)] is today in continuous expansion, and especially sun and wind (SW) are considered with much attention for the production of electric energy by using improved technologies: the first photovoltaic (PV) cells built in 1950s in the United States had an efficiency of 4% [solar to electricity (StE)]; today, 20% is a good average efficiency, and in perspective >40% is targeted. PVs are complementing or substituting fossil fuels in several countries and together with wind-derived electric energy represent several percentage points in national energy supply. Renewable energy such as biomass may afford fuels that may substitute fossil fuels in the transport sector in the near future: the 202020 plan (20% of fossil-C substituted with biofuels by 2020) or its 302030 and 502050 extensions are today questioned for their real implementation due to cost, food-

1.3. Utilization of CO2

The utilization of CO2 is today considered with much attention as it could either contribute to cycling carbon, mimicking nature that makes thousands of compounds from atmospheric CO2, or reduce the climate change impact (CCI) by using CO2 instead of chemicals that may have a much more serious impact: see, for example, chlorofluorocarbons (CFCs) that may have a CCI also 10 000 times higher than CO2. The utilization of CO2 can be separated into four categories, namely (i) production of chemicals, (ii) production of fuels, (iii) enhanced biological utilization, and (iv) technological utilization that may not require a CO2 conversion (except the use as agent for the treatment of basic waters that converts CO2 into hydrogen carbonate, HCO3−, or carbonate, CO32‑). The utilization of CO2 has recently acquired a novel perspective justified by the new attitude to exploit the conversion of SWG perennial energy sources into other forms of energy, e.g., electrical or chemical. Such new opportunity offered by the actual and perspective lower cost and longer life of devices opens a new perspective to the conversion of “spent carbon” into “working carbon”.3 Large volumes of CO2 can be converted into fuels making possible a step toward “cycling carbon by mimicking nature”. This would represent an epochal change as it would move the C-economy from a linear- to a cyclic-trend, entering carbon side to side with other goods for which a “recovery and reuse” strategy has already been established long ago (we refer to water, metals, paper, plastics, etc.). However, the utilization of CO2 would allow reduction of its emission into the atmosphere and reduction of the extraction of fossil-C, part of which would be substituted by recycled-C.(Figure 2)

Figure 2. C-cycling: expanding the man-made cycle will reduce the use of natural C-resources. B

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Scheme 1. Used and Avoided CO2 in the Synthesis of Ethene Carbonatea

a

Per each t of EC 0.5 tCO2 are used while either 5.5 or 8.97 t are avoided.

1.4. Used and Avoided CO2

As a matter of fact the natural C-cycle that runs some >750 GtCO2/y is not able to buffer the anthropogenic emissions (30−32 GtCO2/y) despite the latter represent only ca. 4% of the former. This is causing the accumulation of CO2 into the atmosphere with an ever growing reinforcement of the natural greenhouse effect that is possibly causing the increase of the average temperature of our planet. Although there is not clearcut evidence of such a relationship, nevertheless the parallel growing trend of the curves representing the (i) world population, (ii) energy consumption, (iii) CO2 emissions, and (iv) CO2 level into the atmosphere seems to be quite strong evidence of an existing relationship. Therefore, the limitation of the emission of CO2 into the atmosphere is a must if “no-return points” have to be avoided. The utilization of CO2 may become a key technology for our future, supposing that large volumes of CO2 are converted. The actual utilization of CO2 is close to 200 Mt/y that represents a very minor fraction (0.62%) of the emission. To become significant such fraction must be increased at least by 1 order of magnitude or more, rising to at least 10%: this means that 3000 Mt/y of spent-C must be converted into working-C by means of man-made or hybrid synthetic procedures. This big jump needs the development of innovative strategies, as discussed below. The use of fossil-C for converting CO2 into energy rich products (fuels) must be carefully checked in order to avoid that more CO2 is emitted than converted. It is appropriate to spend here some words about the terms “used” and “avoided”, that are not synonyms.

However, the key point is to reduce the emission of anthropogenic CO2 into the atmosphere. As we have already commented above, efficiency strategies in the chemical industry may play a key role in such effort toward the minimization of the emission. A key question is whether or not the implementation of synthetic strategies based on CO 2 guarantees that its emission will be reduced. The answer is that the conversion of CO2 into chemicals and fuels is not per se a guarantee of the reduction of its emission. The real objective must be to “avoid CO2” more than simply to “use CO2”. This means that the new synthetic strategy based on CO2 must emit less CO2 than the ones now on stream, most likely based on fossil-C. There are tools that may be useful for a fast evaluation of a new synthetic option, such as the (i) carbon utilization fraction (CUF), that gives an idea of how much carbon of the reagents remains in the products, and (ii) the carbon footprint (CF), that gives an evaluation of the carbon utilization in a process. Nevertheless only the life cycle assessment (LCA) methodology can quantify the benefits of the CO2-based synthetic methodology in terms of both “avoided CO2“ and reduction of the environmental impact. A simple example that is appropriate for giving the idea of what “used” and “avoided” mean is reported in Scheme 1 that shows that ethene carbonate can be prepared according to several synthetic routes. Routes b and c, in the lower part of the scheme, use phosgene, COCl2, characterized by a high reactivity already at ambient temperature in chlorinated solvents in absence of catalysts. Drawbacks are the toxicity of COCl2 and the production of equimolar C

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that give quite pure CO2. Such practice must be discontinued, and CO2 must be recovered from anthropogenic sources or directly from the atmosphere. It is worth recalling that the lower the concentration of CO2 is in a gas matrix (or higher is the “entropy”), the higher the energetic cost will be of its separation per unit mass or volume. The presence of gaseous pollutants will further increase the energetic and economic cost of separation. Figure 3 shows the various anthropogenic

amounts of carbonate and chlorinated salts and of large volumes of waste chlorinated solvents: As a matter of fact, the use of phosgene is banned in several countries. New syntheses are based on CO2, route a. As shown in the upper part of Scheme 1, the conversion of 1 mol of ethene into ethenecarbonate “uses” 0.5 tCO2 per t of ethene carbonate (EC) produced (on the basis of the stoichiometry of the reaction). The bottom part of Scheme 1 reports the amount of CO2 emitted per tEC produced according to three different synthetic methodologies, amounts calculated by applying the LCA methodology. Route a based on the carboxylation of ethene emits only 0.92 tCO2/tEC, with a quite significant reduction with respect to the routes b and c based on the use of phosgene. Therefore, while the used amount of CO2 is in any case 0.5 t/tcarbonate, the avoided amount can be calculated considering the difference of the emission of CO2 between the old COCl2-based technologies (routes b and c), either 6.62 or 9.89 t/tEC and the innovative one based on CO2, 0.92 t/tEC. Therefore, per each t of carbonate produced 0.5 tCO2 are used while either 5.70 or 8.94 t are avoided. This example is quite illustrative of the two terms “used” and “avoided” and clarifies what must be the real target in research: the minimization of the direct or indirect CO2 emission in new synthetic technologies with respect to those on stream that one wishes to supplant. At this point it can also be emphasized that the utilization of CO2 must reduce the E-factor4 of synthetic processes, i.e., reduce the waste-to-product ratio (Table 1) by implementing more direct syntheses and by using less C- and energy-intensive technologies.

Figure 3. Emission of CO2 by activity sector.1

emission sources: some of them are point and continuous (energy and industrial sectors), and others are discontinuous (heating, transport) and nonpoint. For feeding an industrial application continuous−point sources are necessary: therefore, either power stations or industrial plants have to be targeted. Power stations have a drawback in the diluted stream (in best cases 14% CO2 by volume), and in the presence of SOx and NOy that increases the cost of separation and purification of CO2. The cost of CO2 separation varies in a wide range from 15 to 90 US$/t. A recent assessment5 gives less than 1 ¢/kWh for the recovery from advanced coal plants and less than 1.5 ¢/kWh from gas plants. Apart from the great variability of costs, power stations do not seem the best option for CO2 recovery for utilization. Other production sectors (Table 2) afford more

Table 1. E-Factors of Different Classes of Chemicals industrial application

market (tons year ‑1)

E-factor (twaste/tproduct)

petrochemicals intermediates fine chemicals pharmaceuticals

109 >106 105 104

0.1 0.5−1 5−100 100−250

In summary, reactions converting CO2 must not be “net producers” of CO2 with respect to technologies on stream, considering the entire process, e.g., the separation of CO2, the synthesis of catalysts and their use, the separation of products, and waste and emissions treatment. This is not straightforward to discover for those who do not have familiarity with CF, CFU, LCA. A way to approach “CO2 avoidance” is to develop syntheses that (a) use simple catalytic systems, easily recovered and reused for several cycles; (b) are characterized by high conversion yield of substrates [high turnover number (TON)], high selectivity, and waste (byproducts and solvents) reduction at source; (c) do not use toxic reagents; (d) take place under mild conditions (low temperature and pressure). In a few words, the CO2-based processes must avoid the use of intensive C-, materials-, and energy-conditions. We discuss in this review a number of processes that convert or use CO2: the list may not be exhaustive, but it includes the most important cases that imply the conversion or technological or biological use of at least 1 Mt/y of CO2.

Table 2. Emission of CO2 from Various Industrial Sectors industrial sector

MtCO2/y produced

ethene oxide LNG sweetening ammonia ethene (and other petrochemical processes) fermentation iron and steel oil refineries cement

10−15 25−30 160 155−300 >200 ca. 900 850−900 >1000

suitable CO2 streams for utilization. An interesting option is to recover CO2 directly from the atmosphere that would decouple the use of CO2 from its source. The cost is today quite high being around 80−130 US$/tCO2.6 The energetic cost seems to be affordable: apparently only 3−5% of the fuel produced from the recovered CO2 would be necessary to cover the energy demand for the recovery from the atmosphere.7 As shown in Table 2, ca. 3300−3500 Mt/y of CO2 are emitted from industrial sectors that may represent a convenient

1.5. Separation of CO2 from Flue Gases and Process Streams

A key point is where to get CO2 for an eventual utilization. So far most of the used CO2 has been extracted from natural wells D

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enthalpy change, ΔH°), but due to the entropy effect (gaseous CO2 is one of the reagents) result being endoergonic with a positive standard Gibbs free-energy (ΔG°) and a negative overall thermodynamics of the process characterized by a very low concentration of the products at the equilibrium (also 3400. Other catalysts for CO2 hydrogenation have been described by Laurenczy and co-workers.32 We underline the best performance catalyst (Table 4), RuCl(OAc)(PMe3)4 by Jessop and co-workers,33 with a TOF of 95 000 h−1, improving the discovery of the high activity of RuH2(PMe3)4 in supercritical carbon dioxide by Noyori in 1994.34 Iridium(III) complexes were found to be very active in water, as demonstrated by Himeda in 2007 (who also reviewed the water-soluble catalysts)35 using phenantroline-cyclopentadienyl complexes, and later by Nozaki and co-workers who discovered in 2009 the record active catalyst for CO2 hydrogenation, an Ir(III) hydride with PNP-pincer ligand which was reported to have an extraordinary TON up to 3 500 000.36

Table 4. Recent Improvement of Homogeneous Catalysts for CO2 Hydrogenation catalyst precursor

solvent

additives

RuH2(PPh3)4 RhCl(tppts)3 RuCl(OAc)(PMe3)4 [Cp*Ir(phen)Cl]Cl IrH3(PNP)

benzene H2O scCO2 H2O H2O

NEt3, H2O NHMe2 NEt3/C6F5OH KOH KOH

P(H2,CO2) (atm) 25, 20, 70, 30, 30,

25 20 120 30 30 H

T (K)

t (h)

TON

TOF (h‑1)

ref

RT RT 323 393 393

20 12 0.3 48 48

87 3439 28 500 222 000 3 500 000

4 287 95 000 33 000 150 000

25 31 33 35 36

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Table 5. Homogeneous Catalysts for Formic Acid Decompositiona

a

catalyst

substrate

T (K)

TON

TOF (h‑1)

selectivity

ref

IrH3(PPh3)3 Pt(PiPr3)3 Ru2(μ-CO)(CO)4(μ-dppm)2 [Rh(Cp*)(bpy)(H2O)](SO4) [Ir(Cp*)(bpy)(H2O)](SO4) [Ru(H2O)6](tos)2/TPPTS [RuCl2(benzene)]2/dppe

HCO2H in acetic acid HCO2H in acetone/water HCO2H in acetone HCO2H/HCO2Na in water HCO2H in water HCO2H/HCO2Na in water 5HCO2H/4HexNMe2

391 293 RT 298 363 393 313

>11 000 25 2000 80 40 000 5716

8890 100 ∼500 30 14 000 460 1905

no free CO

48 50 51 52 53 54 55

no no no no no

free free free free free

CO CO CO CO CO

Adapted from ref 49.

thermodynamically advantageous (ΔG° = −33 kJ mol−1). Nevertheless, the decomposition of formic acid is not so simple and easy as it may appear as it can follow two alternative pathways, i.e., the dehydrogenation reaction (eq 12) or the dehydration/decarbonylation reaction (eq 14) which is also moderately exoergonic (ΔG° = −12 kJ mol−1).49d HCO2 H(l) → CO2 (g) + H 2(g)

(13)

HCO2 H(l) → CO(g) + H 2O(l)

(14)

C10H8 + (2‐x)CO2 (1)Na (2)HCl

⎯⎯⎯⎯⎯⎯⎯→ xC10H 7 − CO2 H + (1 − x)C10H6(CO2 H)2 (15b) Al 2Cl 6 /Al

C6H6 + CO2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯→ C6H5CO2 H

Aromatic carboxylic acids can be obtained by several routes. Reacting naphthalene with Na and CO2 followed by treatment with HCl brings products of single and double carboxylation71 (eq 15b). Alkynes have been carboxylated in presence of a base and Cu(I)-complexes. The free acid was released by treatment with HCl.72 The key issue in such a kind of reaction is the C− H activation. More information can be found in section 2.2.9 where such topics are discussed. 2.2.3. Organic Carbonates. 2.2.3.1. Linear Carbonates. Organic linear (or acyclic) carbonates are produced (eq 16) by reacting at room temperature alcohols with COCl2 in the absence of catalysts. Because of the toxicity of COCl2, banned in several countries, substitutes are necessary, indentified in CO2 (eq 17), urea (eq 18), or CO/O2 (eq 19). In this section the use of CO2 and its activated form urea will be discussed.

Clearly, eq 14 is an undesired reaction for the prospective use of CO-free H2 in fuel cells, so that the homogeneous catalysts under development are aimed at selectively promoting the decarboxylation/dehydrogenation pathway. Table 5 presents some of the most active catalysts for HCO2H selective decomposition into CO2 and H2. In the past few years different groups have published new catalytic systems for homogeneous formic acid decomposition. Very recently ionic liquids were employed to dissolve ruthenium catalyst precursors with interesting results, as in the case of RuCl3 dissolved in 1-ethyl-2,3-dimethyl-imidazolium acetate that shows a TOF of 850 h−1 at 390 K and a 100% H2 yield56 or {RuCl2(p-cymene)}2 with a TOF of 600 h−1 at 333 K57 or 1540 h−1 at 353 K with 91% conversion58 in various ionic liquids. In another very recent work,59 [Ru4(CO)12H4] is reported to be the active homogeneous catalyst in DMF for homogeneous formic acid decomposition. RuCl2(DMSO)4 has also been employed with a base for a continuous-flow-reactor for formic acid decomposition.60 Water-soluble catalysts have also been used for hydrogen generation from formic acid. So, half-sandwich rhodium and ruthenium complexes bearing (4,4′dihydroxy-2,2′-bipyridine) or sulphonated phosphine have been shown to be active catalysts.61,62 A mechanistic study of PtH(PP3) [with PP3 = tris[2-(diphenylphosphanyl) ethyl]phosphane] has also been reported at 308 K in CD2Cl2.63 Finally, with a similar approach used for CO2 hydrogenation, an iron-based catalytic system such as [Fe(CO)3(PBn3)2] (Bn = benzyl) + 1 equiv of 2,2′:6′2″-terpyridine (tpy) (TON 247)64 or inexpensive Fe3(CO)12/PPh3/1,10-phenanthroline (TON 126)65 has been used at 333 K under Xe-light irradiation assistance for degradation of triethylamine/formic acid (2:5) mixture. 2.2.2. Other Carboxylates. Acetic acid, CH3CO2H, can in principle be generated by direct carboxylation of methane (eq 15a). Such reaction, enzymatically feasible, has been attempted, but only a very low conversion yield has been achieved.66−70 CH4(g) + CO2 (g) → CH3CO2 H(l)

(15c)

2ROH + COCl 2 + 2base → (RO)2 CO + 2base.HCl (16)

2ROH + CO2 → (RO)2 CO + H 2O

(17)

2ROH + (H 2N)2 CO → (RO)2 CO + 2NH3

(18)

1 O2 → (RO)2 CO + H 2O 2

(19)

2ROH + CO +

Ammonia formed in eq 18 can in principle be recovered and reacted again with CO2 or used for other ammoniation processes. Alternatively, the so-called transesterification reaction could be used that converts a carbonate into another (eq 20). This technology requires that a carbonate is made from CO2 in an easy way: ethene carbonate (Scheme 1) is presently the most suited species made from ethene epoxide (prepared by direct epoxidation of ethene with O2) and CO2. 2ROH + ethene carbonate → (RO)2 CO + HOCH 2CH 2OH

(20)

Of routes 17−19, the direct synthesis 17 is by far the most environmentally friendly process as demonstrated by a LCA study.73 The patent and the scientific literature witness the industrial interest in such processes and the research efforts for identifying the most effective reaction conditions and the most robust and efficient catalyst. A recent review on the synthesis of acyclic carbonates is available in ref 74. Organic carbonates can

(15a) I

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(OCH3)281−84 and n-Bu2Sn[OCH(CH3)2]2.85 The reaction mechanism was proposed considering the isolated compounds supposed as resting species in the catalytic cycle (Scheme 3).

be obtained from inorganic carbonates by reacting group 1 and 2 element carbonates with alkylhalides, RX (X = Cl, Br, I), under phase-transfer conditions (eq 21) to afford symmetrical and unsymmetrical dialkyl carbonates at temperatures below 400 K.75,76 2RX + M 2CO3 → (RO)2 CO + 2MX

Scheme 3. X-ray Structures of Isolated Di-n-butyltin(IV) Compounds

(21)

Satisfactory yields are obtained also by reacting alcohols and organic halides with pressurized CO2 in the presence of strong bases75 in ionic liquids.77 The existing trend to reduce or exclude the use of halogenated organics does not make such routes an effective alternative to phosgene. The catalytic conversion of alcohols and CO2 is by far the most attractive route to organic acyclic carbonates. In principle, the reaction path can be depicted as in eqs 22−25, where A is an acid and B is a base. ROH + B → RO−BH+

(22)

RO− + CO2 → ROC(O)O−

(23)

ROH + A → R+ + AOH−

(24)

RC(O)O− + R+ → ROC(O)OR

(25)

Compounds A and B are obtained from the insertion of CO2 into Sn−OR bonds of the corresponding methoxy precursors. Under CO2, thermal treatment transforms A into B with the concomitant formation of DMC whereas species B gives C and DMC only in the presence of methanol. It is worth noting that C is the species which can be recycled for DMC formation without apparent loss of activity, but it is not the active catalyst. The transformation of A into B and C underlines an increase in nuclearity of the resting species with the formation of Sn−O− Sn linkages, the tin centers being pentacoordinated. It is worth noting that monomeric species are involved in the catalytic cycle, and this makes the kinetics slow, as active catalysts must be formed from inactive oligomers by reaction with methanol. Other soluble alkoxides such as those of titanium(IV)86 and group 5 metals87,88 exhibit activity for DMC formation. In particular, the reaction mechanism with penta-alkoxo species of group 5 elements87−89 has been studied in depth, and the role of the hemicarbonate (Figure 6) which is formed after reaction

Increasing the CO2 pressure may help to shift eq 23 toward the formation of the hemicarbonate, a key reagent for the synthesis of the organic carbonate. Reaction 16 suffers thermodynamic limitations as the ΔG°f is in the range 0 to −4.6 kcal/mol depending on the aliphatic group R; with phenols, the reaction is endoergonic. At the reaction temperature (usually above 400 K) the equilibrium position of eq 17 is shifted to the left, and the equilibrium concentration of the carbonate may be as low as 1−2%, with the thermodynamics adversely affected by the entropic factor due to the use of gaseous CO2. Only under very severe pressure (>300 MPa) is the reaction shifted to the right. Two techniques are usually adopted for running a catalytic process: (i) liquid alcohol pressurized with CO2, or (ii) reaction in a single supercritical phase containing both CO2 and the alcohol. In i, the limiting factor is the solubility of CO2 in the co-reagent alcohol; case ii improves the thermodynamics from the point of view of the availability of CO2 but requires that alcohol and CO2 are in a single phase that, in general, may limit the alcohol concentration (CH3OH affords a single phase above 9 MPa). As a matter of fact, the use of sc-CO2 produces a better conversion of alcohols. So far, great attention has been paid to the synthesis of dimethylcarbonate from methanol and CO2, but recently the synthesis of diethylcarbonate, DEC, is a target due to the fact that DMC and DEC have quite similar properties and DEC can be prepared from bioethanol giving a “bioderived” label to DEC and processes in which it is used. Early reports of catalytic reactions report n-dibutyldialkoxy stannanes, n-Bu2Sn(OR)2 (R = methyl, ethyl, n-butyl), as catalytst.78 At 423 K under 2.8 MPa CO2 pressure DMC was produced using dicyclohexylcarbodiimide (DCC) as chemical scavenger of water: the role of DCC is controversial (see below).79 With Sn-catalysts a 100% selectivity to DMC was claimed. Ethanol was reacted with 1.0 MPa of CO2 in a batch reactor at 443 K for 24 h to yield a 6.6 molar ratio to the Sn catalyst. The alcohol conversion yield was not defined. Later, the structural characterization of tin compounds, in solution and solid-state, allowed definition of the structure of intermediates starting with (CH3)2Sn(OCH3)280 and n-Bu2Sn-

Figure 6. Hemicarbonate as active species of the direct carboxylation of alcohol.

of the monomeric penta-alkoxo species with CO2 has been demonstrated. Dimeric niobium alkoxide complexes first dissociate to give the monomer that reacts with CO2 to afford the niobium hemicarbonate complex that, when heated in presence of alcohol, gives back the starting alkoxide complex producing the dialkylcarbonate as final product. It is noteworthy that if the hemicarbonate is heated in the absence of CO2, it dissociates back to the alkoxo complex. DFT calculations have confirmed that dimethylcarbonate is formed via intermolecular methyl transfer with implication of two molecules of methanol per Nb implying an acid and a base activation of methanol as discussed above (Figure 7). The catalyst is active only until it works in an almost anhydrous medium: this implies that it must be isolated from the reaction liquid medium once the equilibrium is reached and is reused in a new catalytic cycle. The recovery of the catalyst is an expensive operation: this has suggested the use of heterogenized catalysts for an easier recovery. Polystyrenegrafted organotin and Nb-alkoxo species90,91 have been used J

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Figure 7. Comparative analysis of the reaction profile for the formation of DMC from [Nb(OMe)4(OCOOMe)]2 with implication of zero (blue line), one (grey line), or two (red line) methanol molecules in the methylation of the CH3OC(O)O− moiety bonded to Nb.

ypropane, DMP),94 ketals,95 cyanides,96 and butene oxide97−99 have been used leading to an increase in TON. The main issue is that the dehydrated and hydrated forms of the water traps are soluble in the reaction medium, and this makes difficult the postreaction separation process. Physical water trapping is a cleaner alternative that has been demonstrated with molecular sieves 3 or 4 Å:100,101 the drawback is that such traps must be used at low temperature (close to 240 K) in order to prevent carbonate decomposition by acid sites formed on the materials. The temperature switch from >400 K to Mt/y market and are produced via complex or nonselective routes. The presence of an active C−H bond is, thus, a crucial requisite for the direct carboxylation of HCs to occur. As it has been shown above, the activity is linked to the “acidity” of the C−H moiety that can be enhanced either by (i) controlling the substituents in the organic substrate or through (ii) the interaction of the substrate with an ad hoc designed “activating system”, in general, a metal system. The former approach is possible with a limited number of substrates and affords products that may not be of general use; the second approach is much more interesting and can bring a variety of products of industrial use. Such direct functionalization might be very useful with short chain HCs (C1−C4) that do not find a convenient use today. Therefore, the C−H activation plays a key role in the direct carboxylation of organic substrates, a reaction that formally can be represented as a CO2 insertion into a C−H bond.

The potential of such carbene systems has been further investigated, and more recently, the catalytic carboxylation of C−H bonds promoted by gold(I) complexes has been described.288 N-Heterocycles are first activated by the Au(I) complex [(1,3-bis(diisopropyl)-phenylimidazol-2-ylidene)AuOH]] and then react with CO2 in the conditions specified in Scheme 14 to afford, after workup, the carboxylic acid with yield very much depending on the structure of the Nheterocycle and falling in the 1−61% range. Thiazoles show a carboxylation yield up to 61%, while N,O-heterocycles show a conversion up to 3%, N,N- or N,N,N-heterocycles have a best 7% conversion, and condensed N-heterocycles reach a best 8% yield. The interest in such a reaction is that it can be used with several organic substrates. The regioselectivity results are from moderate to high. An interesting aspect is that the gold catalysts can be recovered and recycled and maintain their activity for up to six cycles. The N-heterocycles used in the above work bear quite activated C−H bonds, and the methodology cannot be considered as of general application yet. The mechanism of such carboxylation was explored using stoichiometric reactions and was proposed to step through the formation of a (heterocycle)C−Au bond via water elimination implying the −OH group on Au and the C−H of the heterocycle. This step is followed by the CO2 insertion, followed by reaction with KOH. K+ acts as a shuttle of the carboxylate moiety, and the Au−OH bond is regenerated. The isolated metalla-heterocycle complex and the relevant carboxylate are active in catalysis, and that demonstrates that they are the intermediates in the U

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3. FROM CO2 TO FUELS: THE CHANGING PARADIGM IN CO2 UTILIZATION The conversion of CO2 into fuels requires energy, in the form of heat or electrons, and dihydrogen. Such energy is mainly derived today from fossil-C that cannot be considered as the ideal source of energy for converting back CO2 into energy rich molecules: the amount of produced CO2 would easily be higher than that converted. As a consequence, so far the conversion of large volumes of CO2 into energy products has not been taken into consideration. Quasi-C-free strategies must be implemented for large-scale CO2 reduction: water must indeed be used as source of H2, and perennial primary energy sources must be used to power processes. C-free hydrogen would allow conversion of large volumes of CO2 in a transition-period toward a hypothetical C-free economy. This generation is living a change of paradigm in the utilization of primary perennial energy sources (such as solar, wind, hydro, geothermal energy). It makes sense, thus, to evaluate possibilities of using such C-free-energy available on a large scale for converting CO2 back into energy rich compounds, mimicking nature. Furthermore, the conversion of CO2 may represent a route to the use of H2 for producing fuels that would use the existing network of distribution and the existing car infrastructures. Such H2−CO2 integration may become usable in a short-to-medium-term and may bring the production of fuels (gaseous and liquid) with C-recycling and fossil-C saving for next generations, moving from a linear to a circular C-economy. One could object that if electric energy from sun or wind is available, it could be used directly for substituting fossil-C, without losing efficiency by converting it into chemical energy. The point is that changing the existing infrastructures in the field of personal mobility or road transport or other similar cases is not an easy task. Attempts made to implement largescale use of hydrogen in some of the above applications have met unexpected barriers: as a matter of fact the effort in research in such field is faded. The integration of use of H2 and CO2 would make available conventional fuels produced on a quasi-zero-emission mode in the short-to-medium-term, with C-recycling (that would make more conservative and beneficial the use of fossil-C) and significant reduction of CO2 emission into the atmosphere: this is an opportunity to catch in a transition period. This decade is and will be characterized by an enormous increase of the installed PV technology. PV power installed is growing beyond any expectation as the cost of materials and installations is going down and the payback time is decreasing from the actual 8−11 to foreseen 2 years. This is mainly due to the shift from the actual monocrystalline-Si-technology to thin film technologies. The amount of electric energy produced using thin film technologies for solar light capture and conversion has been estimated by the International Energy Agency, IEA, to cover 20−25% of the electricity market by 2050. Table 7 gives the observed trend of PV power installation worldwide. The expected 9000 TWh of PV and CSP in 2050

clearly shows that PV technologies will soon reach a level of maturity that will enable the exploitation of solar energy for various purposes, among which is electric energy production.291 Figure 1310 shows that PV energy utilization is applicable all over the world: such application seems more limited by political

Figure 13. Worldwide installed PV power (2011).10

decisions than by natural conditions, if it is true that Germany is leading now the exploitation of such technology (Figure 13). Such a new paradigm is essential for the development of new strategies of H2 production from water using PV or for the direct electrochemical conversion of CO2 in water. 3.1. Reduction to CO

The simplest way to convert CO2 into an energetic product is its deoxygenation to afford CO, a reaction that can be carried out either by a thermal or by a radiative route. Such noncatalyzed process is very energy demanding, as shown in eq 47. 1 CO2 → CO + O2 ΔG1000K = 190.5 kJ/mol (47) 2 The produced CO can be burnt with air to give energy and CO2 (Scheme 15). Scheme 15. Energy from Cycling on CO−CO2

The thermal decomposition of CO2 into CO and oxygen (eq 47) can be carried out using concentrators of solar power, CSP.293,296 Temperatures up to 1500 K can be generated in CSP that are suited for CO2 dissociation. The drawback of such technology is its periodicity due to the light−dark daily cycle. Energy accumulators such as molten salts can be used to ensure continuity. It is worth noting that when CO2 is coordinated to a metal system the deoxygenation may occur at room temperature294 or also just above 14 K in a gas matrix295 with oxygen transfer to a substrate. Such a catalyzed deoxygenation process (Scheme 16) would be of interest if a cyclic “reduction of CO2-oxidation of CO” could be implemented on a large scale with production of

Table 7. Rate of Growth of the Power of Installed PV292 year

GW

year

GW

2009 2010 2011

7.2 16.6 40

2020 2030 2040

200 2000 3000 V

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Both reactions are strongly endoergonic and occur at high temperature (>1000 K). This route cannot be taken into consideration for producing H2 for CO2 conversion. A business as usual (BAU) approach is, thus, ruled out. A new approach is needed that does not make use of fossil-C for both producing H2 and driving the conversion reaction, such as the use of water (water-splitting) as source of H2 and the use of perennial energies or “waste” or “excess electric” energy for powering the conversion process. These aspects have been discussed in a dedicated paper.296 The reaction of CO2 with dihydrogen is, thus, a “multipurpose” application that can give positive solutions to two problems: the recycling of carbon and the storage of H2, along with its transportation and use. In fact, coupling CO2 and H2 to produce fuels would allow use of the existing energy storage and transport infrastructures making more attractive and less problematic an eventual large availability of H2 (eventual H2economy). Also, the hydrogenation of CO2 would represent an interesting solution to a old problem: the storage of electric energy, as discussed below.

Scheme 16. Use of CO2 as Oxidant in a Cycle That Produces Energy

useful materials (during the reduction of CO2 to CO) and energy (during the reoxidation of CO to CO2). Obviously, such application is limited by the volume of the species “sub=O” that can be produced and used. Among the Oacceptors, olefins and hydrocarbons can be identified as the most suitable (eq 48) as their “oxidized” forms (epoxides) may

have large, also if not unlimited, application (≫Mt/y) as monomers for polymers. Equation 48 is not a straightforward process and may occur if mediated by metal oxides as catalysts in a two-step process: transfer of O-atom from a metal oxide to the olefin180 and reoxidation of the redudced oxide with CO2. CO produced in eqs 48−49 can be reacted with water vapor in the presence of a suitable WGS catalyst to produce CO2 and dihydrogen (eq 50). While reactions 49−50 have been demonstrated to be possible and could be exploited as the use of CO2 results in a more selective and more controlled process than the dehydrogenation based on the use of only O2, reaction 48 has not yet been demonstrated to be feasible.

3.3. Use of Excess Electric Energy for CO2 Reduction

Nowadays, the electroreduction of CO2 is considered with much attention and particular interest as it can really contribute to cycling large volumes of CO2 and to storing electric energy, an old issue without any real practical and economic solution. It is obvious that it does not make sense to produce electricity by using fossil fuels expressly for such application, but such an option can be used for avoiding the possibility of wasting electric energy produced from fossil carbon. Excess electric energy (e.g., energy produced out of peak hours) could be conveniently converted into chemical energy (fuels) to be used in cars (substituting fuels produced from fossil carbon) or for regenerating electric energy during the peak hours. A similar practice is already implemented in several power stations which pump uphill water during night and use the falling water during the day at peak hours for electricity production: in this way the excess energy produced during a time when less power is demanded by the grid is conveniently stored, and used when the request is higher. Furthermore, the conversion of electric energy into fuels by simultaneous reduction of CO2 also gives an answer to a old issue: the conservation of electric energy. The storage of electricity into batteries is not a practical solution as batteries have a quite low energy density by volume (or even by mass) that ranges from 0.3 to 2.8 GJ/m3, depending on the kind of battery considered (the most efficient are the Li-batteries). Figure 1410,296 gives an idea of how the storage of energy into batteries compares with the storage into chemicals that can be derived from CO2. Chemicals such as methanol or gasoline have an energy density that is from 10 to even 100 times higher than that of batteries.

Cat1

PhCH 2CH3 + CO2 ⎯⎯⎯→ PhHCCH 2 + CO + H 2O (49) cat2

CO + H 2O ⎯⎯⎯→ CO2 + H 2

(50)

3.2. Reduction to Methanol and Methane (and Cn Species)

The CO2-reduction process can be further continued beyond CO, and a number of interesting chemicals can be obtained according to the catalysts and conditions used. (eqs 51−55) CO2 + H 2 → HCOOH

(51)

CO2 + 2H 2 → H 2CO + H 2O

(52)

CO2 + 3H 2 → CH3OH + H 2O

(53)

CO2 + 4H 2 → CH4 + 2H 2O

(54)

(n + 2)CO2 + [3(n + 2) + 1]H 2 → CH3(CH 2)n CH3 + 2(n + 2)H 2O

(55)

3.4. H2 Production for CO2 Reduction

The key issue is the availability of H2. Actually, 90% of dihydrogen is produced from fossil carbon, according to the water gas reaction (eq 56) and wet-reforming of methane (eq 57). C + H 2O(vap) → CO + H 2

Let us consider now the option that is of immediate use: water electrolysis for H2 production using perennial primary energy sources. Table 8 gives the cost of H2 produced using various technologies. According to reaction 58, 1 kg of hydrogen will allow conversion of 7.3 kg of CO2 producing 5.3 kg of methanol.

ΔH °298K = 131 kJ/mol (56)

CH4 + H 2O(vap) → CO + 3H 2 ΔH °298K = 206 kJ/mol

3H 2 + CO2 → CH3OH + H 2O

(57)

6g

W

44 g

32 g

16 g

(58)

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the H2 production cost ranges around 4.5−5 US$/kg, still too high. An abatement of costs is possible using better concentrators, improving the StH conversion efficiency and reducing the overvoltage, doing better than 53 kWh/kg H2 necessary today. If the direct electroreduction of CO2 in water is considered, keeping the photovoltaic conversion efficiency of solar light into electric energy equal to 16−20%,299 and considering a 80% efficiency in the electrolysis and 80% selectivity in a product (Table 9), then one can conclude that it would be possible to Table 9. Comparison of Two Approaches for Solar Energy Storage into Chemicals Obtained from CO2 Reduction: Water Electrolysis to H2 Used for the Synthesis of Methanol, or Direct CO2 Electrolysis in Watera Figure 14. Volume energy density of batteries compared to that of different classes of chemicals.10,296

H2 from H2O electrolysis followed by the catalyzed reaction with CO2 to CH3OH

technology

The production cost of methanol today is 0.08 €/kg. In the best case considering the capex and opex, methanol can be produced from electrolytic hydrogen at a cost of 0.3 €/kg, that is ca. 4 times higher than the current price. What may make positive the balance for industry is the fact that the conversion of CO2 into other products avoids the payment of the C-tax: at the moment such tax (where it exists) varies in a quite ample range: 30−100 €/t, that means 0.03−0.1 €/kg. With this benefit, the cost of production of methanol would be close to 0.16 €/kg or 160 €/t. Combining the use of electrolytic hydrogen with CO2 reduction makes closer the price of production of methanol from excess electric energy-generated hydrogen to the price of production using H2 from gas reforming (assuming that CO2 is available). Excess electric energy produced out of the peak hours could, thus, advantageously be used for water electrolysis and CO2 conversion into methanol, without influencing the electricity availability to day by day users. What will be the real potential of such technology will depend on the up-scale of electrolyzers and the consequent cost of hydrogen.

solar light conversion efficiency electrolysis efficiency PH2/MPa in the electrolyzer PH2/MPa in the chemical conversion T for CO2 conversion products (selectivity) a

direct (photo) electrochemical reduction of CO2 in water

ca. 20%, expected 40%

ca. 20

70−80

60−70

0.1

not applicable

30−50

not applicable

423 K

RT

CH3OH (100)

H2−CO (ca. 20) CH3OH, H2CH2 (ca. 80)

PV is used to power electrolyzers.

convert solar energy into chemical energy (as a single product) with a global efficiency equal to >10%. Such a value is higher than the efficiency of any bioprocess. In fact, plants show an efficiency close to 1.5−2%, and microalgae, the most efficient solar energy utilizers, have an efficiency close to 6−8% in natural environments, reaching 10% in photobioreactors.

3.5. Use of Perennial Energy for CO2 Reduction

H2 could be produced by electrolysis of water using PV. The key parameters to be mastered in water electrolysis are the overvoltage for H2 production and the electrolysis efficiency (ranging from 55% to 80% with a good average at 73%). The existing electrodes allow an average solar-to-hydrogen (StH) conversion efficiency in the range 5−15%, with a best performance of 20% observed when GaInP/GaAs/Ge junction is used, that has a low overpotential. The area necessary for the production of 1 t/d of H2 is in the range 20−40 km2, with a best figure of 10 km2 in the case of the best performing junction given above. The USA-DoE target is to produce H2 at a cost of 2−3 US$/kg (1.5−2.3 €/kg). This requires that the capital costs of installations must be lower than 800 US$/kW at an electricity cost of 0.055 US$/kWh (0.042 €/kWh).298 Today, for a 1 tH2/d production, with a solar input of 6.55 kWh/m2 d, at an StH conversion of 15%, using 1885 reactors each of 18 m2 that require a total area of 33 930 m2 for photons capture (using tracking concentrators) and a capital cost of 3.5 MUS$,

3.6. Photochemical Reduction of CO2

The reduction of CO2 in water can be carried out photochemically, in the presence of suited photocatalysts. The photochemical reduction makes use of semiconductors which are able to absorb light and generate a “hole plus electron” (Figure 15). Electrons reduce CO2, while water is oxidized at the positive hole+. This is a quite appealing solution, but for being of practical application, it requires that (i) sunlight is used, and (ii) O2 (the oxidated form of water) is efficiently produced and separated from the reduction products of CO2. At the moment, the efficiency of water oxidation is still low299−301 and represents a barrier to the exploitation of the system. Moreover, while several semiconductors able to work under UVlight298−301,302a are known, very few are able to work efficiently under solar light irradiation. The goal here is to develop new photocatalysts302b such as mixed oxides that may be able to

Table 8. Cost of Production of Dihydrogen (1 kg) Using Various Technologies296,297 gas reforming

electrolysis with nuclear

electrolysis with electricity from oil powered station

1.10−1.15 €

1.45−1.50 €

3.50−2.20 €

electrolysis with PV electrolysis with wind 2.8−4.0 €

X

3.8−5.20 €

electrolysis with SPC 3.50 €

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thin films the solar conversion efficiency into electric energy may rise from actual 20% to 40%, as reported above. Therefore, PV may support the conversion of large volumes of CO2 in the short-to-medium term. Possibly, photoelectrochemical systems will be operating in the medium term, while photochemical systems will become the winning option in the medium-to-long term (>2030). The specific space requirement per ton of converted CO2, the life of devices, and the investment costs will designate the most effective option. Table 9 compares the state of the art of generation of H2 via electrolysis of water for CO2 chemical reduction to the direct electroreduction of CO2 in water. Data shown in Table 9 demonstrate that there are pros and cons per each technology that have a different maturity. The preliminary production of dihydrogen has weak points such as the need to collect and store it, and the low pressure at which it is generated (ca. 0.1 MPa), compared to the pressure necessary for its use: in the methanol plant 5 MPa are required. However, energy is necessary for storing H2 and pressurizing it to the working pressure in the methanol plant, that will reduce the overall efficiency. Conversely, the high selectivity in methanol is a strong point in favor of this technology. Developing electrolyzers that operate at a pressure higher than 0.1 MPa is a key point. On the other hand, when CO2 is directly reduced in water (by using electrochemical or photoelectrochemical techniques), products of various nature can be obtained, depending on the electrocatalysts or the electrode used. The latter technology is not yet mature, although promising: it may become the winning option in the near future, before the direct photochemical reduction will be mastered to application. As Table 9 shows, often CO is produced in mixture with H2 in the direct reduction of CO2 in water. This is not a negative case: in fact, if the two gases would be produced in a molar ratio H2:CO in the range 1−2, the mixture would find application as syngas for the synthesis of various chemicals (HCs require a higher H2:CO molar ratio than oxygenates). Anyway, in the specific case either component could independently be added to the gas mixture produced by electrolysis of CO2 in water in order to reach the best ratio for its use in the synthesis of gasoline or other compounds. The reduction to methane is considered with much attention for the direct utilization of CH4 in cars and the easier conditions with respect to CH3OH. A critical point with PV is the high environmental impact due to the technologies of production of the used materials. As a matter of fact today the production of H2 via PV has an environmental

Figure 15. Photochemical reduction using solar light and a semiconductor.

drive the target reaction using solar light and working, as much as possible, close to thermodynamic conditions for avoiding overvoltage phenomena and loss of efficiency. Mixed oxides seem to be a quite promising solution as the modification of the electronic properties of the photoactive oxide can be driven by adding a second (or even third) oxide. Several techniques can be used for modifying a semiconductor, as shown in Figure 16, and making it able to use the visible part of the solar spectrum.302b Therefore, the combination of various oxides or the deposition of metals/ligands and photosenitizers on the surface of a given oxide may bring build-up of a material that may use visible light for CO2 reduction in water or waste organics. A multielectron reduction of CO2 is energetically easier than the one-electron reduction.296 Also, a two-electron two-proton transfer is the most likely process to be used, as schematically shown in Figure 16. Considering the fast growth of the knowledge in the area of solar light utilization, it is not incorrect to foresee potential growth of such technology to an exploitation level in the medium term. However, should we use the PV-electrochemical, the photoelectrochemical, or the photochemical approach for the conversion of CO2? Is it better to make use of the photovoltaic energy for producing dihydrogen from water or for a direct reduction of CO2 in water? Is the photochemical reduction a ready technology? It must be pointed out that the use of solar energy is limited by the availability of space for solar light collection. With 6935 MJ/m2 y as average capacity of solar energy collection and 193 kWh/m2 y of produced electricity the PV technology is today the winning option as there are not yet photochemical systems that may directly use solar light at the same level of efficiency. The expectation in this field is that with

Figure 16. Modes of modification of the properties of TiO2 for utilization of the visible part of the solar spectrum:301 (a and b) injection of electrons in the conduction band of TiO2, (c) injection of a hole in the valence band. Y

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our planet. It concurrently converts inorganic carbon-Ci (i.e., CO2 or its hydrated form hydrogen carbonate-HCO3−) into organic compounds and generates dioxygen, necessary for the life of living organisms. Such conversion of Ci into organics can occur either under natural conditions (i.e., up-taking CO2 from the atmosphere where it reaches a concentration equal to 0.038% v/v) or under “enhanced” or “industrial” conditions, that are much different from natural ones. Typical examples of the “enhanced” biological fixation are (i) the cultivation of terrestrial biomass (ornamental plants, some vegetables) in greenhouses under a CO2 concentration in the gas phase of ca. 600 ppm and (ii) the farming of aquatic biomass by dissolving CO2 in water or under a gas phase concentration up to 5−10%, i.e., 130−260 times the natural one. This technology is quite interesting as several algal species can grow in the presence of concentrations of NOx or SOy on the order of 150 ppm: that means that cleaned flue gases from power stations could directly be used for feeding ponds. The CO2 fixation is catalyzed by the enzyme RuBisCO, ribulose-bisphosphate-carboxylase-oxygenase, the most abundant natural enzyme and less selective. In fact, RuBisCO does not follow the usual selectivity of enzymes and at the same time promotes the carboxylation of ribulose (a C-5 sugar) to afford a C-6 sugar (with carbon fixation) and the oxidation of the same C-5 sugar, with a selectivity close to 50%.293 A lot of effort has been put into the genetic manipulation of RuBisCO305 with the intention of increasing the selectivity toward the carboxylation reaction. As a matter of fact, an improvement of the carboxylation by 5−10% would solve all problems relevant to the accumulation of CO2 into the atmosphere as all the anthropogenic CO2 that is causing such accumulation would be fixed into biomass. After more than two decades of trials, it is not quite clear if such biotechnology will have any possibility of implementation on a large scale. However, the fixation under forced conditions remains the most usable “industrial” approach to biological CO2 fixation. On the other hand, an intelligent exploitation of biomass could activate a virtuous cycle that may produce chemicals and/or energy compounds on a close to zero-emission basis, with a positive effect on the reduction of the CO2 emission into the atmosphere. The potential of biomass utilization for the control of the accumulation of CO2 in the atmosphere is under assessment.

impact that is some twice higher than the production using SPC and 5 times higher than the production from wind.303

4. BIOTECHNOLOGICAL CONVERSION OF CO2 The reduction of CO2 in nature occurs in several organisms: animal, vegetal, autotrophic, heterotrophic, anaerobic, or aerobic, following several mechanisms. What happens in leaves (production of polyols) is much more complex and difficult to mimic than what bacteria do (direct reduction of CO2 to other C1 species through multistep two-electron transfers). So, for example, the methanation of organic substrates involves, among others, enzymes that are able to reduce CO2 to CO (carbon monoxide dehydrogenases, CODH) or to formic acid (formate dehydrogenases, FateDH). CO2 can be reduced to the methyl group −CH3 in a tetrahydrofolate (THF) mediated process. CO and −CH3 are coupled to give the acetyl moiety (−COCH3) using a Fe4S4−Ni enzyme and vitamin B12. Formate can be reduced to formaldehyde using the formaldehyde dehydrogenase, FaldDH, enzyme, and formaldehyde can be converted into methanol by the alcoholdehydrogenase, ADH, enzyme. This is an interesting network of reactions that produce energy rich C1-molecules from CO2. Interestingly, the three enzymes (FateDH, FaldDH, and ADH) that convert CO2 into methanol (Scheme 17) are commercial. Scheme 17. CO2 Reduction to Methanol in Water Promoted by FateDH, FaldDH, and ADH

In an attempt to mimic nature, a biotechnological approach to the conversion of CO2 into methanol has been investigated on the basis of the use of the enzymes described above. It has been shown that the trilogy of enzymes FateDH, FaldDH, and ADH are able to reduce CO2 in water at ambient temperature.304 There are 3 mol of NADH consumed per each mol of CH3OH produced (Scheme 17). This approach, also quite appealing, is not economically and energetically viable, unless NAD+ formed upon oxidation of NADH is efficiently recycled, increasing, thus, the ratio CH3OH/NADH to values that can be acceptable for a biotechnological production of methanol. So far, a proof of concept of such application has been reported with a production of 100 mol of CH3OH per mol of NADH used,302 using the photochemical reduction of NAD+ for its recycling. The dream is to be able to mimic the cascade of e−-transfer to CO2 and build a man-made photosynthetic microorganism that may reduce large volumes of CO2 under mild conditions. The use of semiconductors that use visible light for NADH regeneration302b from NAD+ is an interesting step toward the exploitation of an hybrid technology that may produce methanol under enzymatic catalysis from CO2 and water at room temperature, using semiconductors that use visible light for reproducing the active form of the cofactor.

5. TECHNOLOGICAL USES OF CO2 The use of CO2 as a technological fluid includes all those applications in which CO2 is not converted into other chemicals. A list of such uses in given in Table 10209 with the overall market. Table 10. Carbon Dioxide Utilization in Nonchemical Applications technological utilization (ca. 28 Mt/y) additive to beverages water treatment cereal preservation (bactericide) food packaging/conservation extraction (fragrances and caffeine) dry-washing enhanced oil recovery (EOR) use as sc-solvent in chemical processes

4.1. Enhanced Aquatic Biomass Production

Among the industrial uses of CO2, the “enhanced biological fixation”, which corresponds to the production of terrestrial or aquatic biomass under “non-natural photosynthetic conditions”, is increasingly attracting the attention of the scientific and technological world. Photosynthesis is responsible for life on Z

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5.1. Reducing the Impact on Climate Change via Technological Uses of CO2

would generate a lot of waste for their production, or of chemicals that are highly toxic, such as methylbromide, cyanidric acid, methylisocyanide, formaldehyde, sulphonylfluoride, etc.). Usually, the production of chemicals or pharmaceuticals has an associated waste production in the range 5−250 t of waste per ton of product. This waste production is known as the E-factor of a given product (Table 1).4 Therefore, assuming that a compound used as antiparasite or antifungi has an associated organic waste production with an average composition equal to C4, and an E-factor of 70 (we consider a simple molecule), per each ton of marketed product roughly 12.3 kt of CO2 will be emitted. It occurs that the use of CO2 instead of such a chemical (also if CO2 may present a lower specific activity) is a much better solution that substantially reduces the CO2 emission into the atmosphere also if CO2 is vented after use. (iv) When CO2 is used for basic water treatment it usually substitutes sulfuric acid (H2SO4). The emission factors of H2SO4 are on the order of 5 kg SO2 and 0.3 kg SO3 per tH2SO4, while the entire process looks to be exoergonic (−1.1 GJ/t), supposing that (a) all the released energy produced in the hydration of SO3 is recovered in the form of steam, and (b) the use of sulfur obtained from the desulfurization of hydrocarbons is considered not to imply any energy cost.310 As CO2 has the same neutralization power as H2SO4, per each t of CO2 used 2.23 t of H2SO4 will be avoided as well as the relevant environmental impact caused by the sulfate accumulation in water plus the above-mentioned emission of SOx into the atmosphere. In the case heat is not recovered (that may happen), and we consider the energy cost of sulfur production, then the energy consumption must be considered that makes the balance much more in favor of using CO2. (v) Supercritical carbon dioxide (sc-CO2) exists above 304 K and 7.38 MPa. Properties like density and viscosity can be modulated over a quite wide range by changing the two parameters pressure and temperature. The “dense phase fluid” has properties that may vary over a quite large range, from a nonpolar organic solvent, such as pentane or dichloromethane, to more polar solvents. The benefits derived from its use are well-known today,307b so that its utilization is spreading in various industrial sectors, and the replacement of traditional organic solvents with sc-CO2 include the decaffeination of coffee beans; the extraction of fragrances and essences from plants, or proteins or fatty acids and hydrocarbons from algae; the attempted use as solvent for crystallizations; preparation of solid thermal-sensitive pharmaceuticals having controlled size distribution; catalysis (homogeneous and heterogeneous); and the synthesis and modification of polymers including perfluoropolymers, or as mobile phase for supercritical fluid chromatography (SFC), dyeing, dry-cleaning, and nuclear waste treatment. A specific application that might have good potental is the use of l- or sc-CO2 as solvent and reagent, not yet exploited. The most important feature attached to the use of sc-CO 2 is that it can be easily recovered at the end of the process, recompressed, and recycled. It is also worth mentioning that usually most waste organic solvents are burned: the substitution with sc-CO2 when possible would avoid large volumes of emitted CO2. In general, thus, CO2 in its technological applications substitutes species which have a strong impact either on the atmosphere or water or soil: even if at the end of the application CO2 is vented to the atmosphere, the net result is the avoidance of substantial amounts of CO2 equivalents due to

Although the technological use of CO2 does not convert CO2 into storable or disposable materials, and it usually happens that at the end of the application CO2 is vented (it can anyway be recovered and recycled), nevertheless the use of CO2 as technological fluid may contribute to the reduction of the impact on climate change. The benefit comes from the fact that CO2 substitutes other chemicals such as chlorofluorocarbons, CFCs, which have much higher CCI or chemicals that require much energy for their production or, upon use, produce waste with a strong environmental impact. The former case refers, for example, to the use of CO2 as a fluid in air conditioners, the latter to its use as fumigant or for water treatment, among others. Let us consider now some practical applications just to clarify the concepts above: (i) The production and use of CFC causes the emission into the atmosphere of such chemicals. The estimated amount of CCl2F2 (CFC-12, Table 11) released into Table 11. Comparison of the CCI of Some CFCs with That of CO2 (100 y) chemical

CCI

chemical

CCI

carbon dioxide R134a R22

1 1430 1700

CFC-12 CFC-11 HCF-23

8500 4000 14 800

the atmosphere ranged at the end of the 1970s from 420 (estimated by the Chemical Manufacturers Association, CMA) to 500 kt/y evaluated by direct atmosphere monitoring.306 The substitution of equivalent amounts of CO2 to such chemicals produces a great benefit in terms of CCI reduction considering that the CCI of CCl2F2 is 8500 times that of CO2 (Table 11). (ii) Emblematic cases are also the substitution of (a) perchloroethene (C2Cl4, PERC, ca. 3 Mt/y) in dry cleaning or (b) fluorinated cooling gases (e.g., R134) in fixed or mobile air conditioners, ACs. Dense phase CO2 (l- or sc-CO2) has been proposed for several applications,307 such as l-CO2 in drycleaning machines307a as a substitute of PERC. PERC is a highly energy intensive chemical, and its synthesis is highly polluting because of the production of chlorinated waste. If we consider the existing as a stationary state (with the use of PERC as dry-cleaning agent) and take into consideration only the replacement of PERC lost in running the existing equipment, the annual loss of PERC308,309 is equivalent to 2 Mt/y of CO2: this was the minimum estimate for the effect of reduction of CO2 emission in case PERC was substituted with CO2 as cleaning agent. Such expectations were not met on a large scale as novel cleaning agents entered the market. Similarly, the use of sc-CO2 as a fluid in automobile or fixed ACs would allow avoidance of the effect of 3.3 kt/y of lost R-134 (an average of 0.06 kg/y times 55 Mcars circulating), equivalent to 4.7 MtCO2eq. The IPCC estimate for the impact of emissions from buildings conditioning is 0.6 GtCeq or 2.2 GtCO2eq. Therefore, the use of carbon dioxide as fluid in ACs would significantly contribute to reducing the overall CCI, a result that can be assimilated to a reduced CO2 emission into the atmosphere. The figures above are a demonstration of the direct and indirect benefits associated with the technological utilization of carbon dioxide, benefits that are often hidden and difficult to discover. (iii) The use of CO2 as fumigant avoids the use of other chemicals, which would have a complex molecular structure and AA

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may play a key role in the conversion of “exhaust” carbon into “working” carbon by reducing CO2 into energy rich species, either C1 or C2+, that may be used as fuels. Several approaches are possible for the exploitation of such a concept: use of natural photosynthetic microoorganisms for an enhanced CO2 fixation (microalgae or microorganisms grown under nonnatural conditions, i.e., high CO2 concentration), use of hybrid systems that combine enzymes and synthetic systems for an accelerated CO2 fixation, use of synthetic systems that may mimic nature and reduce CO2 in water using photochemical and/or photoelectrochemical systems. The conversion of solar energy into chemical energy for cycling CO2 is quite well-understood today. For industrial exploitation of such a concept, a few key issues have to find a solution, namely, the discovery of efficient systems for solar energy capture, two-photon use for two-electron transfer to CO2 for an easy and fast reduction, efficient charge separation systems (multijunctions that prevent the back flow of electrons and the hole−electron recombination), space separation of oxidation and reduction processes on photocatalysts, preferable production of non-water-soluble organics from CO2 for reducing the processing cost for the recovery of energy rich species, efficient catalysts for water oxidation and selective CO2 reduction, use of cheap and naturally abundant compounds for catalyst making, and use of recyclable materials. The solution of such problems will require time, but all targets may be reached as there is no real (negative thermodynamics, for example) barrier to exploitation. If sufficient resources (human and capital) are located for the solution of such problems, and an active industry−academia participation will be implemented, as has been done for the development of PV-cells, it is foreseeable that in 20−30 years from now the dream “solar-driven conversion of CO2 into chemicals, materials, and fuels” will come through, that will open the door to a “CO2−H2O” economy driven by SWG energy. Figure 17 gives a perspective on the amount of CO2 that can be avoided by using the options described above. It is evident that thermal routes can give a limited contribution to CO2 conversion, while techniques based on the use of solar energy and other perennial energy sources can contribute to largely expand the conversion of “spent” carbon into “working” carbon, avoiding large volumes of CO2.

the elimination of chemicals having a high CCI, and this results in an overall mitigation of the impact on climate change. 5.2. Enhanced Oil Recovery, EOR

The use of CO2 in EOR is a quite old practice in which so far CO2 extracted from natural wells was employed. More likely, CO2 of anthropogenic origin should be used. The use as a fluid for the extraction of oil (instead of high temperature−high pressure vapor water that raises the problems of energy cost and water reuse or discharge) is producing a large economic benefit. Such practice has been estimated to produce an extra income of 400 billion US$/y to U.S. only, in terms of additional extracted oil. Interestingly, in such application a significant part of CO2 (30−50%) remains trapped in rocks so that the oil well behaves as a disposal site.

6. CONCLUSIONS: PERSPECTIVE USE OF CO2 The utilization of CO2 is a strategy that can be efficiently combined with a more intelligent use of fossil-C, guaranteeing the availability of the latter for a longer term and avoiding large volumes of CO2. The BAU model based on the use of fossil-C as source of energy for carrying out thermal reactions can contribute to a limited extent to the conversion of CO2 and recycling of carbon, also in the long term. Such limitation is not due to the lack of technical means, but is often dictated by the energetics of the reactions. In fact, the use of fossil-C derived energy for converting CO2 is not a strategy that will minimize the CO2 emission. Consequently, only processes that require a limited energy input were and will be exploited, targeting a limited market. Chemicals such as carbonates, carbamates, ureas, and carboxylates will be the real target, reaching a volume on the order of >300 Mt/y of used CO2 with a best wish of volume of avoided CO2 lower than 1 Gt/y (Figure 17). The

Figure 17. Perspective contribution of the various technologies to avoiding CO2. Chemicals and materials alone have a limited potential (a few hundred Mt/y), while the manufacture of fuels and enhanced biomasss production may convert large volumes of CO2 avoiding in perspective several Gt/y CO2.10

real potential with chemicals and materials lies in the fact that the direct introduction of the −CO2− moiety into an organic compound will avoid large volumes of CO2 due to the fact that the direct carboxylation, when feasible, will avoid toxic compounds and substitute energy intensive synthetic methodologies, as discussed above. A real jump toward the conversion of large volumes of CO2 with recycling of important amounts of carbon will be possible using biotechnologies and natural or hybrid or “man-made photosynthetic microorganisms”, that

AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Phone: 0039 080 544 2084. Fax: 0039 080 544 3606. Notes

The authors declare no competing financial interest. AB

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Biographies

chapters. She has been an invited speaker at several international conferences.

Michele Aresta, until 2012 Professor of Inorganic Chemistry at the University of Bari, is now Scientific Manager of the National Interuniversity Consortium on Chemical Reactivity and Catalysis and IMM Chair at the NUS, Singapore. He is an expert on carbon dioxide utilization in synthetic chemistry. His scientific interests are in catalysis, biomass conversion, and coordination and metallorganic chemistry. He was founder and Chairman until 2013 of the “International Conference on Carbon Dioxide Utilization, ICCDU” of which he is now Honorary Chair. In 1989 he received the “Renoir Prize” for the diffusion of scientific knowledge, and in 1990 the Award of the Italian Chemical Society for his work on “Carbon Dioxide Activation”. In 2004, he was appointed Honorary Professor at the University of Tianjin, and in 2005−06 he received the Award of the Societé Francaise de Chimie for Inorganic Chemistry. He has also received several certificates of appreciation from the ACS for his organizational activity. He is the author of over 250 papers that appeared in international journals, of over 50 invited papers presented at international conferences, and of several reviews on CO2 utilization. He is the editor of seven books on CO2 utilization.

Antonella Angelini received her master degree in chemistry in 2007 at the University of Bari with a thesis on the synthesis, characterization, and catalytic application of multi-hydrido Rh-complexes. She obtained the Ph.D. in chemical sciences at the same university with a thesis on the development of new homogeneous, heterogeneous, and heterogenized catalysts for the synthesis of dialkyl carbonates from alcohols and CO2. In 2011 she started her postdoctoral activity working within a project financed by TOTAL on innovative methodologies for the synthesis of dialkylcarbonates.

REFERENCES (1) International Energy Agency. CO2 Emission from Fuels CombustionHighlights, 2012 Edition; Imprimerie Centrale: Luxembourg, October 2012; http://www.iea.org/co2highlights/ co2highlights.pdf. (2) International Energy Agency. Energy Technology Perspectives 2012, ETP 2012; OECD/IEA: Paris, 2012. (3) Aresta, M.; Dibenedetto, A.; Angelini, A. Advances in Inorganic Chemistry, CO2 Chemistry; Aresta, M., Dibenedetto, A., Eds.; Elsevier: New York, 2013; Vol. 66, pp 259−288. (4) (a) Aresta, M.; Dibenedetto, A. In Development and Innovation in Carbon Dioxide (CO2) Capture and Storage Technology; Maroto-Valer, M., Ed.; Woodhead Publishing Limited: Cambridge, U.K., 2010; Vol. 2, p 377. (b) Sheldon, R. A. Green Chem. 2007, 9, 1273. (5) Herzog, H. The Economics of CO2 Separation and Capture; University of New MexicoMechanical Engineering: Albuquerque, NM, September 26, 2006; http://www.me.unm.edu/∼mammoli/ ME561_stuff/economics_in_technology.pdf. (6) Holmes, G.; Keith, D. W. Phil. Trans. R. Soc., A 2012, 370 (1974), 4380. (7) Annual Energy Outlook 2005 with Projections to 2025; Energy Information Administration: Washington, DC, February 2005; ftp:// ftp.eia.doe.gov/forecasting/0383(2005).pdf. (8) Aresta, M.; Quaranta, E.; Tommasi, I.; Giannoccaro, P.; Ciccarese, A. Gazz. Chim. Ital. 1995, 125, 509. (9) Aresta, M.; Dibenedetto, A.; Barberio, G. Fuel Process. Technol. 2005, 86 (14−15), 1679. (10) Aresta, M.; Dibenedetto, A.; He, L.-N. Analysis of Demand for Captured CO2 and Products from CO2 Conversion; Report Exclusively for Members of the Carbon Dioxide Capture & Conversion (CO2CC) Program of The Catalyst Group Resources (TCGR); November 2012. (11) Brinckerhoff, P. Accelerating the Uptake of CCS: Industrial Use of Captured Carbon DioxideUrea Synthesis; Global CCS Institute: Docklands Australia, March 1, 2011; www.globalccsinstitute.com. (12) Production of Chemicals; New Zealand Institute of Chemistry: Harewood, New Zealand; http://nzic.org.nz/ChemProcesses/ production. (13) Butterfield, J.; Chater, J. Stainless Steel World, May 2012.

Angela Dibenedetto is Associate Professor at the University of Bari− UNIBA (IT), Department of Chemistry. Her scientific interests are focused on carbon dioxide utilization in synthetic chemistry, catalysis, coordination and organometallic chemistry, green chemistry, marine biomass (algae) production by enhanced carbon dioxide fixation, marine biomass as source of fuels, and chemicals applying the biorefinery concept. Actually she is director of the Interuniversity Consortium on Chemical Reactivity and Catalysis, CIRCC. In 2001 she was the winner of the RUCADI Prize for “Better Carbon ManagementAn Intelligent Chemical Use of CO2” delivered by ACP, Belgium, Carburos Metalicos, Spain, and ENIChem, Italy. She is the author of over 90 scientific papers on carbon dioxide utilization published in international journals since 1995 and several book AC

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(14) (a) Kolbe, H.; Lautemann, E. Annalen 1869, 113, 125. (b) Schmitt, R.; Burkard, E. Ber. Dtsch. Chem. Ges. 1877, 20, 2699. (15) Iijima, T.; Yamaguchi, T. Appl. Catal., A 2008, 345, 12. (16) Solvay, E. U.S. Patent 263981, 1882. (17) Constantz, B. R.; Clodic, L.; Ryan, C.; Fernandez, M.; Farsad, K.; Omelon, S.; Tuet, P.; Monteiro, P.; Brown, G. E.; Geramita, K. (Calera Corporation) U.S. Patent 7749476, 2010. (18) Coustry, F. M.; Hanse, M. EP 1900688 A1, 2006 (19) Formic Acid; BASF The Chemical Company: Ludwigshafen am Rhein, Germany, May 4, 2012; http://www.basf.com/group/ corporate/en/brand/FORMIC_ACID. (20) Farlow, M. W.; Adkins, H. J. Am. Chem. Soc. 1935, 57, 2222. (21) Jessop, P. G.; Ikariya, T.; Noyori, R. Chem. Rev. 1995, 95, 259. (22) Leitner, W. Angew. Chem., Int. Ed. Engl. 1995, 34, 2207. (23) Jessop, P. G.; Joo, F.; Tai, C.-C. Coord. Chem. Rev. 2004, 248, 2425. (24) Federsel, C.; Jackstell, R.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 6254. (25) Inoue, Y.; Izumida, H.; Sasaki, Y.; Hashimoto, H. Chem. Lett. 1976, 863. (26) Leitner, W.; Dinjus, E.; Gassner, F. In Aqueous-Phase Organometallic Catalysis Concepts and Applications; Cornils, B., Herrmann, W. A., Eds.; Wiley-VCH: Weinheim, 1998; p 486. (27) Kovacs, G.; Schubert, G.; Joo, F.; Pápai, I. Catal. Today 2006, 115, 53. (28) Jessop, P. G. In Handbook of Homogeneous Hydrogenation; de Vries, J. G., Elsevier, C. J., Eds.; Wiley-VCH: Weinheim, 2007; p 489. (29) Enthaler, S. ChemSusChem 2008, 1, 801. (30) Wang, W.; Wang, S.; Ma, X.; Gong, J. Chem. Soc. Rev. 2011, 40, 3703. (31) Gassner, F.; Leitner, W. J. Chem. Soc., Chem. Commun. 1993, 1465. (32) Bosquain, S. S.; Dorcier, A.; Dyson, A. P. J.; Erlandsson, M.; Gonsalvi, L.; Laurenczy, G.; Peruzzini, M. Appl. Organomet. Chem. 2007, 21, 947. (33) Munshi, P.; Main, A. D.; Linehan, J.; Tai, C. C; Jessop, P. G. J. Am. Chem. Soc. 2002, 124, 7963. (34) Jessop, P. G.; Ikariya, T.; Noyori, R. Nature 1994, 368, 231. (35) Himeda, Y.; Onozawa-Komatsuzaki, N.; Sugihara, H.; Kasuga, K. Organometallics 2007, 26, 702. (36) Tanaka, R.; Yamashita, M.; Nozaki, K. J. Am. Chem. Soc. 2009, 131, 14168. (37) Tai, C. C.; Chang, T.; Roller, B.; Jessop, P. G. Inorg. Chem. 2003, 42 (23), 7340. (38) Federsel, C.; Boddien, A.; Jackstell, R.; Jennerjahn, R.; Dyson, P. J.; Scopelliti, R.; Laurenczy, G.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 9777. (39) (a) Ziebart, C.; Federsel, C.; Anbarasan, P.; Jackstell, R.; Baumann, W.; Spannenberg, A.; Beller, M. J. Am. Chem. Soc. 2012, 134 (51), 20701. (b) Federsel, C.; Ziebart, C.; Jackstell, R.; Baumann, W.; Beller, M. Chem.Eur. J. 2012, 18 (1), 72. (40) Azua, A.; Sanz, S.; Peris, E. Chem.Eur. J. 2011, 17, 3963. (41) Federsel, C.; Jackstell, R.; Boddien, A.; Laurenczy, G.; Beller, M. ChemSusChem 2010, 3, 1048. (42) (a) Gao, Y.; Kuncheria, J. K.; Jenkins, H. A.; Puddephatt, R. J.; Yap, G. P. A. J. Chem. Soc., Dalton Trans. 2000, 3212. (b) Elek, J.; Nádasdi, L.; Papp, G.; Laurenczy, G.; Joó, F. Appl. Catal., A 2003, 59, 255. (c) Horváth, H.; Laurenczy, G.; Kathó, A. J. Organomet. Chem. 2004, 689, 1036. (43) Ohnishi, Y. Y.; Matsunaga, T.; Nakao, Y.; Sato, H.; Sakaki, S. J. Am. Chem. Soc. 2005, 127, 4021. (44) Tai, C. C.; Pitts, J.; Linehan, J. C.; Main, A. D.; Munshi, P.; Jessop, P. G. Inorg. Chem. 2002, 41, 1606. (45) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165. (46) Himeda, Y. Eur. J. Inorg. Chem. 2007, 2007 (25), 3927. (47) Dibenedetto, A.; Stufano, P.; Nocito, F.; Aresta, M. ChemSusChem 2011, 4 (9), 1311. (48) Coffey, R. S. Chem. Commun. (London) 1967, 923b.

(49) (a) Mellone, I.; Peruzzini, M.; Rosi, L.; Mellmann, D.; Junge, H.; Beller, M.; Gonsalvi, L. Dalton Trans. 2013, 42, 2495. (b) Luo, Q.; Feng, G.; Beller, M.; Jiao, H. J. Phys. Chem. C 2012, 116 (6), 4149. (c) Johnson, T. C.; Morris, D. J.; Wills, M. Chem. Soc. Rev. 2010, 39, 81. (d) Loges, B.; Boddien, A.; Gartner, F.; Junge, H.; Beller, M. Top. Catal. 2010, 53, 902. (e) Bi, Q. Y.; Du, X. L.; Liu, Y. M.; Cao, Y.; He, H. Y.; Fan, K. N. J. Am. Chem. Soc. 2012, 134 (21), 8926. (f) Gan, W.; Snelders, D. J. M.; Dyson, P. J.; Laurenczy, G. ChemCatChem 2013, 5 (5), 1125. (50) Yoshida, T.; Ueda, Y.; Otsuka, S. J. Am. Chem. Soc. 1978, 100, 3941. (51) Gao, Y.; Kuncheria, J. K.; Jenkins, H. A.; Puddephatt, R. J.; Yap, G. P. A. J. Chem. Soc., Dalton Trans. 2000, 3212. (52) Fukuzumi, S.; Kobayashi, T.; Suenobu, T. ChemSusChem 2008, 1, 827. (53) Himeda, Y. Green Chem. 2009, 11, 2018. (54) Fellay, C.; Yan, N.; Dyson, P. J.; Laurenczy, G. Chem.Eur. J. 2009, 15, 3752. (55) Boddien, A.; Loges, B.; Junge, H.; Gartner, F.; Noyes, J. R.; Beller, M. Adv. Synth. Catal. 2009, 351, 2517. (56) Berger, M. E. M.; Assenbaum, D.; Taccardi, N.; Spiecker, E.; Wasserscheid, P. Green Chem. 2011, 13, 1411. (57) Li, X.; Shi, F.; Ma, X.; Lu, L.; Deng, Y. J. Fuel Chem. Technol. 2010, 38, 544. (58) Scholten, J. D.; Prechtl, M. H. G.; Dupont, J. ChemCatChem 2010, 2, 1262. (59) Czaun, M.; Goeppert, A.; May, R.; Haiges, R.; Prakash, G. K. S.; Olah, G. A. ChemSusChem 2011, 4 (9), 1241. (60) Majewski, A.; Morris, D. J.; Kendall, K.; Wills, M. ChemSusChem 2010, 3, 431. (61) Himeda, Y.; Miyazawa, S.; Hirose, T. ChemSusChem 2011, 4, 487. (62) Gan, W.; Fellay, C.; Dyson, P. J.; Laurenczy, G. J. Coord. Chem. 2010, 63, 2685. (63) Rieckborn, P.; Huber, E.; Karakoc, E.; Prosenc, M. H. Eur. J. Inorg. Chem. 2010, 4757. (64) Boddien, A.; Gartner, F.; Jackstell, R.; Junge, H.; Spannenberg, A.; Baumann, W.; Ludwig, R.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 8993. (65) Boddien, A.; Loges, B.; Gartner, F.; Torborg, C.; Fumino, K.; Junge, H.; Ludwig, R.; Beller, M. J. Am. Chem. Soc. 2010, 132, 8924. (66) CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, 2010. (67) Eliasson, B.; Liu, C.-J.; Kogelschatz, U. Ind. Eng. Chem. Res. 2000, 39, 1221. (68) Liu, C. −J.; Xue, B.; Eliasson, B.; He, F.; Li, Y.; Xu, G.-H. Plasma Chem. Plasma Process. 2001, 21, 301. (69) Jiang, T.; Li, Y.; Liu, C.; Xu, G.; Eliasson, B.; Xue, B. Catal. Today 2002, 72, 229. (70) Chantry, P. J. J. Chem. Phys. 1972, 57, 3180. (71) Walker, J. F.; Scott, N. D. J. Am. Chem. Soc. 1938, 60 (4), 951. (72) Yu, D.; Zhang, Y. Proc. Natl. Acad. Sci. U.S.A. 2010, 107 (47), 20184. (73) Aresta, M.; Galatola, M. J. Cleaner Prod. 1999, 7, 181. (74) Ballivet-Tkatchenko, D.; Dibenedetto, A. In CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, 2010; p 169. (75) McGhee, W.; Riley, D. J. Org. Chem. 1995, 60, 6205. (76) Cella, J. A.; Bacon, S. W. J. Org. Chem. 1984, 49 (6), 1122. (77) Jorapur, Y. R.; Chi, D. Y. J. Org. Chem. 2005, 70, 10774. (78) Kizlink, J. Collect. Czech. Chem. Commun. 1993, 58, 1399. (79) Isaacs, N. S.; O’Sullivan, B.; Verhaelen, C. Tetrahedron 1999, 55, 11949. (80) Choi, J.-C.; Sakakura, T.; Sako, T. J. Am. Chem. Soc. 1999, 121, 3793. (81) Ballivet-Tkatchenko, D.; Douteau, O.; Stutzmann, S. Organometallics 2000, 19, 4563. (82) Ballivet-Tkatchenko, D.; Jerphagnon, T.; Ligabue, R.; Plasseraud, L.; Poinsot, D. Appl. Catal., A 2003, 255, 93. AD

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Chemical Reviews

Review

(114) Wang, X. J.; Xiao, M.; Wang, S. J.; Lu, Y. X.; Meng, Y. Z. J. Mol. Catal. A: Chem. 2007, 278, 92. (115) Jung, K. T.; Bell, A. T. J. Catal. 2001, 204, 339. (116) Aresta, M.; Dibenedetto, A.; Pastore, C.; Angelini, A.; Aresta, B.; Papai, I. J. Catal. 2010, 269, 44. (117) Dibenedetto, A.; Aresta, M.; Angelini, A.; Ethiraj, J.; Aresta, B. M. Chem.Eur. J. 2012, 18 (33), 10324. (118) Aresta, M.; Dibenedetto, A.; Bourova, O. A.; Chupakhin, O. N. Stud. Surf. Sci. Catal. 2004, 153, 213. (119) (a) Malone, M. F.; Huss, R. S.; Doherty, M. F. Environ. Sci. Technol. 2003, 37, 5325. (b) Thotla, S.; Mahajani, S. M. Chem. Eng. Res. Des. 2009, 87, 61. (120) (a) Wang, F.; Zhao, N.; Li, J.; Zhao, W.; Xiao, F.; Wei, W.; Sun, Y. Ind. Eng. Chem. Res. 2007, 46, 8972. (b) Zhang, J.; Wang, F.; Wei, W.; Xiao, F.; Sun, Y. Korean J. Chem. Eng. 2010, 27 (6), 1744. (121) Saleh, R.Y.; Michaelson, R.C.; Suciu, E.N.; Kuhlmann, B. U.S. Patent 14540, 1994. (122) Ryu, J. Y. U.S. Patent 140435, 1998. (123) Lin, H.; Yang, B.; Sun, J.; Wang, X.; Wang, D. Chem. Eng. J. 2004, 103, 21. (124) Wang, M.; Zhao, N.; Wei, W.; Sun, Y. Ind. Eng. Chem. Res. 2005, 44, 7596. (125) Wang, M.; Wang, H.; Zhao, N.; Wie, W.; Sun, Y. Catal. Commun. 2006, 7, 6. (126) Guo, L.; Zhao, X.; An, H.; Wang, Y. Chin. J. Catal. 2012, 33 (4), 595. (127) Fan, M.-M.; Wang, H.; Zhang, P.-B.; Ni, B. Q. Chin. J. Inorg. Chem. 2012, 28 (7), 1333. (128) Wang, H.; Lu, B.; Wang, X.; Zhang, J.; Cai, Q.i. Fuel Process. Technol. 2009, 90, 1198. (129) Joe, W.; Lee, H. J.; Hong, U. G.; Ahn, Y. S.; Song, C. J.; Kwon, B. J.; Song, I. K. J. Ind. Eng. Chem. 2012, 18, 1730. (130) Joe, W.; Lee, H. J.; Hong, U. G.; Ahn, Y. S.; Song, C. J.; Kwon, B. J.; Song, I. K. J. Ind. Eng. Chem. 2012, 18, 1018. (131) Wang, D.; Zhang, X.; Gao, Y.; Xiao, F.; Wei, W.; Sun, Y. Catal. Commun. 2010, 11, 430. (132) Wang, D.; Zhang, X.; Zhao, W.; Peng, W.; Zhao, N.; Xiao, F.; Wei, W.; Sun, Y. J. Phys. Chem. Solids 2010, 71, 427. (133) Ryu, J.Y.; Gelbein, A.P. U.S. Patent 866340, 2001. (134) Ball, P.; Fullmann, H.; Heitz, W. Angew. Chem., Int. Ed. Engl. 1980, 19, 718. (135) Heitz, W.; Fuellmann, H.; Ball, P. German Patent 3112794, 1981. (136) Suciu, E. N.; Kuhlmann, B.; Knudsen, G. A.; Michaelson, R. C. J. Organomet. Chem. 1998, 556, 41. (137) Ryu, J.Y.; Gelbein, A.P. U.S. Patent 821225 2004. (138) Wang, D.; Yang, B.; Zhai, X.; Zhou, L. Fuel Process. Technol. 2007, 88, 807. (139) Zhao, W.; Peng, W.; Wang, D.; Zhao, N.; Li, J.; Xiao, F.; Wei, W.; Sun, Y. Catal. Commun. 2009, 10, 655. (140) Wang, H.; Wang, M.; Zhao, W.; Wei, W.; Sun, Y. React. Kinet., Mech. Catal. 2010, 99, 381. (141) Gao, Y.; Zhao, N.; Wei, W.; Sun, Y. Comput. Theor. Chem. 2012, 992, 1. (142) Gao, Y.; Peng, W.; Zhao, N.; Wei, W.; Sun, Y. J. Mol. Catal. A: Chem. 2011, 351, 29. (143) Dubois, J.-L. WO 139080, 2008. (144) Pacheco, M. A.; Marshall, C. L. Energy Fuel 1997, 11, 2. (145) Ainsworth, S. J. Chem. Eng. News 1992, 70, 9. (146) Weissermel, K.; Arpe, H. J. Industrial Organic Chemistry, 3rd ed.; VCH: Weinheim, 1997; p 162. (147) (a) Coates, G. W.; Moore, D. R. Angew. Chem., Int. Ed. 2004, 43, 6618. (b) Darensbourg, D. J. Chem. Rev. 2007, 107, 2388. (c) Darensbourg, D. J.; Mackiewicz, R. M.; Phelps, A. L.; Billodeaux, D. R. Acc. Chem. Res. 2004, 37, 836. (148) Limura, N.; Takagi, M.; Iwane, H.; Ookago, J. Japanese Patent 07,267,944, 1995. (149) Inoe, K.; Oobuko, H. Kokai Tokkyo Koho Japanese Patent 07,206,846, 1995.

(83) Ballivet-Tkatchenko, D.; Chambrey, S.; Keiski, R.; Ligabue, R.; Plasseraud, L.; Richard, P.; Turunen, H. Catal. Today 2006, 115, 80. (84) Kohno, K.; Choi, J.-C.; Ohshima, Y.; Yili, A.; Yasuda, H.; Sakakura, T. J. Organomet. Chem. 2008, 693, 1389. (85) Ballivet-Tkatchenko, D.; Chermette, H.; Plasseraud, L.; Walter, O. Dalton Trans. 2006, 5167. (86) (a) Kizlink, J.; Pastucha, I. Collect. Czech. Chem. Commun. 1995, 60, 687. (b) Kohno, K.; Choi, J.-C.; Ohshima, Y.; Yasuda, H.; Sakakura, T. ChemSusChem 2008, 1, 186. (87) Dibenedetto, A.; Pastore, C.; Aresta, M. Catal. Today 2006, 115, 88. (88) Aresta, M.; Dibenedetto, A.; Pastore, C. Inorg. Chem. 2003, 42 (10), 3256. (89) Aresta, M.; Dibenedetto, A.; Pastore, C.; Pàpai, I.; Schubert, G. Top. Catal. 2006, 40 (1−4), 71. (90) Aresta, M.; Dibenedetto, A.; Nocito, F.; Pastore, C. Inorg. Chim. Acta 2008, 361, 3215. (91) Aresta, M.; Dibenedetto, A.; Nocito, F.; Angelini, A.; Gabriele, B. Appl. Catal., A 2010, 387, 113. (92) Fan, B.; Zhang, J.; Li, R.; Fan, W. Catal. Lett. 2008, 121, 297. (93) Choi, J.-C.; Kohno, K.; Ohshima, Y.; Yasuda, H.; Sakakura, T. Catal. Commun. 2008, 9, 1630. (94) Tomishige, K.; Kunimori, K. Appl. Catal., A 2002, 237, 103. (95) Aresta, M.; Dibenedetto, A.; Dileo, C.; Tommasi, I.; Amodio, E. J. Supercrit. Fluids 2003, 25 (2), 177. (96) (a) Honda, M.; Kuno, S.; Sonehara, S.; Fujimoto, K.; Suzuki, K.; Nakagawa, Y.; Tomishige, K. ChemCatChem 2011, 3 (2), 365. (b) Honda, M.; Kuno, S.; Begum, N.; Fujimoto, K.-I.; Suzuki, K.; Nakagawa, Y.; Tomishige, K. Appl. Catal., A 2010, 384 (1−2), 165. (c) Honda, M.; Suzuki, A.; Noorjahan, B.; Fujimoto, K.-I.; Suzuki, K.; Tomishige, K. Chem. Commun. 2009, 30, 4596. (97) (a) Eta, V.; Arvela, P. M.; Leino, A. R.; Kordás, K.; Salmi, T.; Murzin, D. Y.; Mikkola, J. P. Ind. Eng. Chem. Res. 2010, 49 (20), 9609. (b) Eta, V.; Mäki-Arvela, P.; Wärnå, J.; Salmi, T.; Mikkola, J.-P.; Yu. Murzin, D. Appl. Catal., A 2011, 404, 39. (98) Leino, E.; Mäki-Arvela, P.; Eränen, K.; Tenho, M.; Murzin, D. Yu.; Salmi, T.; Mikkola, J.-P. Chem. Eng. J. 2011, 176−177, 124. (99) Leino, E.; Mäki-Arvela, P.; Eta, V.; Kumar, N.; Demoisson, F.; Samikannu, A.; Leino, A.-R.; Shchukarev, A.; Murzin, D. Yu.; Mikkola, J.-P. Catal. Today 2013, 210, 47. (100) Wagner, A.; Haas, W. Patent WO 022805, 1994. (101) Cheong, M.; Kim, S.-C.; Park, J. B. New J. Chem. 1997, 21, 1143. (102) Aresta, M.; Dibenedetto, A.; Fracchiolla, E.; Giannoccaro, P.; Pastore, C.; Pápai, I.; Schubert, G. J. Org. Chem. 2005, 70, 6177. (103) Aresta, M.; Dibenedetto, A.; Stufano, P.; Aresta, B. M.; Maggi, S.; Papai, I.; Rokob, T. A.; Gabriele, B. Dalton Trans. 2010, 39, 6985. (104) Aresta, M.; Dibenedetto, A.; Stufano, P. Patent IP MI 2009A001221, 2009. (105) (a) Aresta, M.; Dibenedetto, A.; Pastore, C.; Cuocci, C.; Aresta, B.; Cometa, S.; Giglio, E. D. Catal. Today 2008, 137, 125. (b) Tomishige, K.; Yoshida, Y.; Arai, Y.; Kado, S.; Kunimori, K. Catal. Today 2006, 115, 95. (106) Tomishige, K.; Sakaihori, T.; Ikeda, Y.; Fujimoto, K. Catal. Lett. 1999, 58, 225. (107) Tomishige, K.; Ikeda, Y.; Sakaihori, T.; Fujimoto, K. J. Catal. 2000, 192, 355. (108) Zhong, S. H.; Kong, L. L.; Li, H. S.; Xiao, X. F. Ranliao Huaxue Xuebao 2002, 30 (5), 454. (109) Ikeda, Y.; Asadullah, M.; Fujimoto, K.; Tomishige, K. J. Phys. Chem. B 2001, 105, 10653. (110) Tomishige, K. K. Appl. Catal., A 2002, 237, 103. (111) Tomishige, K.; Furusawa, Y.; Ikeda, Y.; Asadullah, M.; Fujimoto, K. Catal. Lett. 2011, 76, 71. (112) Jiang, C.; Guo, Y.; Wang, C.; Hu, C.; Wu, Y.; Wang, E. Appl. Catal., A 2003, 256. (113) Allaoui, L. A.; Acuissi, A. J. Mol. Catal. A: Chem. 2006, 259, 281. AE

dx.doi.org/10.1021/cr4002758 | Chem. Rev. XXXX, XXX, XXX−XXX

Chemical Reviews

Review

(182) Aresta, M.; Quaranta, E.; Tommasi, I. New J. Chem. 1994, 18, 133. (183) Aresta, M.; Dibenedetto, A.; Tommasi, I. Eur. J. Inorg. Chem. 2001, 1801. (184) (a) Aresta, M.; Dibenedetto, A.; Tommasi, I. Appl. Organomet. Chem. 2000, 14, 799. (b) Aresta, M.; Dibenedetto, A.; Tommasi, I. Appl. Organomet. Chem. 2000, 14, 799. (c) Aresta, M.; Tommasi, I.; Dibenedetto, A.; Fouassier, M.; Mascetti, J. Inorg. Chem. 2002, 330 (1), 63. (185) Sun, J. M.; Fujita, S.; Bhanage, B. M.; Arai, M. Catal. Today 2004, 93, 383. (186) (a) Aresta, M.; Dibenedetto, A.; Nocito, F.; Ferragina, C. J. Catal. 2009, 268, 106. (b) Vieville, C.; Yoo, J. W.; Pelet, S.; Mouloungui, Z. Catal. Lett. 1998, 56, 245. (187) Delledonne, D.; Rivetti, F.; Romano, U. Appl. Catal., A 2001, 221, 241. (188) (a) Tomishige, K.; Yasuda, H.; Yoshida, Y.; Nurunnabi, M.; Li, B.; Kunimori, K. Catal. Lett. 2004, 95, 45. (b) Tomishige, K.; Yasuda, H.; Nurunnabi, M.; Li, B.; Kunimori, K. Stud. Surf. Sci. Catal. 2004, 153, 165. (c) Tomishige, K.; Yasuda, H.; Yoshida, Y.; Nurunnabi, M.; Li, B.; Kunimori, K. Green Chem. 2004, 6, 206. (d) Huang, S.; Liu, S.; Li, J.; Zhao, N.; Wei, W.; Sun, Y. Catal. Lett. 2006, 112, 187. (e) Zhao, X.; Sun, N.; Wang, S.; Li, F.; Wang, Y. Ind. Eng. Chem. Res. 2008, 47, 1365. (189) Du, Y.; He, L.-N.; Kong, D.-L. Catal. Commun. 2008, 9, 1754. (190) Huang, S.; Ma, J.; Li, J.; Zhao, N.; Wei, W.; Sun, Y. Catal. Commun. 2008, 9, 276. (191) Sugimoto, H.; Inoue, S. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 5561. (192) Sugimoto, H.; Ohtsuka, H.; Inoue, S. Stud. Surf. Sci. Catal. 2004, 153, 243. (193) Super, M.; Berluche, E.; Costello, C.; Beckman, E. Macromolecules 1997, 30, 368. (194) Inoue, S. In NATO ASI Series, Ser. C, Carbon Dioxide as a Source of Carbon: Chemical and Biochemical Uses; Aresta, M., Forti, G., Eds.; Reidel Publishers, Nato-Asi: Dordrecht, The Netherlands, 1987; p 331. (195) Rokicki, A.; Kuran, W. J. Macromol. Sci., Rev. Macromol. Chem. 1981, 135, C21. (196) (a) Wu, G. P.; Wei, S.-H.; Ren, W. M.; Lu, X.-B.; Xu, T.-Q.; Darensbourg, D. J. J. Am. Chem. Soc. 2011, 133 (38), 15191. (b) Darensbourg, D. J. Chem. Rev. 2007, 107, 2388. (c) Darensbourg, D. J.; Andreatta, J. R.; Moncada, A. I. In CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, Germany, 2010; p 213. (197) Li, H.; Niu, Y. Polym. J. 2011, 43, 121. (198) Gosh, A.; Ramidi, P.; Pulla, S.; Sullivan, S. Z.; Collom, S. L.; Gartia, Y.; Munshi, P.; Biris, A. S.; Noll, B. C.; Berry, B. C. Catal. Lett. 2010, 137, 1. (199) Kim, B. E.; Varghese, J. K.; Han, Y. G.; Lee, B. Y. Bull. Korean Chem. Soc. 2010, 31, 829. (200) Lee, K.; Ha, J. J. Y.; Cao, C.; Park, D. W.; Ha, C.-S.; Kim, I. Catal. Today 2009, 148, 389. (201) After Major Downturn, Global Demand for Polycarbonate Growing Again, Says IHS Chemical Report; IHS Online Pressroom: Englewood, CO, February 13, 2012; http://press.ihs.com/pressrelease/commodities-pricing-cost/after-major-downturn-globaldemand-polycarbonate-growing-agai. (202) Survey of Polycarbonate Market in China; Chemeurope.com, Market Studies: Berlin, 2011; http://www.chemeurope.com/en/ studies/13725/survey-of-polycarbonate-market-in-china.html. (203) Global and China Polycarbonate (PC) And Polyethylene Wax Industry 2013: Market Analysis Research; Press Release Distribution, August 8, 2013; http://www.prlog.org/12189544-global-and-chinapolycarbonate-pc-and-polyethylene-wax-industry-2013-marketanalysis-research.html. (204) High-Tech Plastic Inventor Honored: Makrolon Polycarbonate Inventor Dr. Hermann Schnell Inducted into the Plastics Hall of Fame Bayer Material Science; Bayer Material Science: Leverkusen, Germany, May 14, 2008; http://www.bayermaterialsciencenafta.com/news/

(150) Inoe, K.; Oobkubo, H. Kokai Tokkyo Koho Japanese Patent 07,206,847, 1995. (151) Inoe, K.; Oobkubo, H. Kokai Tokkyo Koho Japanese Patent 07,206,848, 1995. (152) Inaba, M.; Hasegawa, K.; Nagaoka, H. Kokai Tokkyo Koho Japanese Patent 09,067,365, 1997. (153) Ichikawa, S.; Iwane, H. Kokai Tokkyo Koho Japanese Patent 09,235,252, 1997. (154) Tojo, M.; Fukuoka, S. (Asahi Chem. Ind). Japanese Patent 03,120,270, 1991. (155) Bobyleva, L. I.; Kryukov, S. I.; Bobylev, B. N.; Liakumovich, A. G.; Surovstev, A.; Karpov, O.P.; Akhmedyanova, R. A.; Koneva, S. A. (Yaroslavskij Polit. Institut) SU Patent 1,781,218, 1992. (156) Mais, F. J.; Buysch, H. J.; C. Mendoza-Frohn, Klausener, A. (Bayer) EU Patent 543,249, 1993. (157) Kuran, W.; Listos, T. Macromol. Chem. Phys. 1994, 195, 977. (158) Sakai, T.; Kihara, N.; Endo, T. Macromolecules 1995, 28, 4701. (159) Sakai, T.; Tsutsumi, Y.; Ema, T. Green Chem. 2008, 10, 337. (160) Darensbourg, D. J.; Holtcamp, M. W. Coord. Chem. Rev. 1996, 153, 155. (161) Marquis, E. T.; Sanderson, J. R. (Texaco Chemical Co.). U.S. Patent 5,283,365, 1994. (162) Sone, M.; Sako, T.; Kamisawa, C. Kokai Tokkyo Koho Japanese Patent 11,335,372, 1999. (163) Song, J.; Zhang, Z.; Han, B.; Hu, S.; Li, W.; Xie, Y. Green Chem. 2008, 10, 1337. (164) Li, Y.; Zhao, X. Q.; Wang, Y. Appl. Catal., A 2005, 279, 205. (165) Zhang, X.; Wei, W.; Sun, Y. In International Conference on Carbon Dioxide UtilizationICCDU VIII, Oslo, 2005. (166) Yano, T.; Matsui, H.; Koike, T.; Ishiguro, H.; Fujihara, H.; Yoshihara, M.; Maeshima, T. Chem. Commun. 1997, 1129. (167) Yamaguchi, K.; Ebitani, K.; Yoshida, T.; Yoshida, H.; Kaneda, K. J. Am. Chem. Soc. 1999, 121, 4526. (168) Aresta, M.; Dibendetto, A. In 221st ACS National Meeting, San Diego, 2001, Absw 220. (169) Aresta, M.; Dibenedetto, A.; Gianfrate, L.; Pastore, C. J. Mol. Catal. A: Chem. 2003, 245, 204. (170) Aresta, M.; Dibenedetto, A.; Gianfrate, L.; Pastore, C. Appl. Catal., A 2003, 255, 5. (171) North, M.; Pasquale, R.; Young, C. Green Chem. 2010, 12 (9), 1514. (172) Machac, J. R., Jr.; Marquis, E. T.; Woodrum, S. A. U.S. Patent 654,438, 2000. (173) (a) Decortes, A.; Castilla, A. M.; Klei, A. W. Angew. Chem., Int. Ed. 2010, 49, 9822. (b) Riduan, S. N.; Zhang, Y. Dalton Trans. 2010, 39, 3347. (174) (a) Song, J.; Zhang, B.; Jiang, T.; Yang, G.; Han, B. Front. Chem. Eng. Chin. 2011, 6, 21. (b) Ulusoy, M.; Kilic, A.; Durgun, Z.; Tasci, B.; Cetinkaya. J. Organomet. Chem. 2011, 696, 1372. (c) Liang, S.; Liu, H.; Jiang, T.; Song, J.; Yang, G.; Han, B. Chem. Commun. 2011, 47, 2131. (d) Buchard, A.; Kember, M. R.; Sandeman, K. G.; Williams, C. K. Chem. Commun. 2011, 47, 212. (e) Shibata, I.; Mitani, I.; Imakuni, A.; Baba, A. Tetrahedron Lett. 2011, 52, 721. (f) Dengler, J. E.; Lehenmeier, M. W.; Klaus, S.; Anderson, C. E.; Herdtweck, E.; Riege, B. Eur. J. Inorg. Chem. 2011, 336. (g) Kilic, A.; Ulusoy, M.; Durgun, M.; Tasci, Z.; Yilmaz, I.; Cetinkaya, B. Appl. Organomet. Chem. 2010, 24, 446. (h) Ulusoy, M.; Sahin, O.; Kilic, A.; Buyukgungor, O. Catal. Lett. 2011, 141, 717. (175) Kawanami, H.; Ikushima, Y. Chem. Commun. 2000, 2089. (176) Jairton, D.; Roberto, F. D. S.; Paulo, A. Z. S. Chem. Rev. 2002, 102, 3667. (177) Kawanami, H.; Sasaki, A.; Matsui, K.; Ikushima, Y. Chem. Commun. 2003, 896. (178) Jacobson, S. E. EU Patent Appl. 117,147, 1984. (179) Aresta, M.; Quaranta, E.; Ciccarese, A. J. Mol. Catal. 1987, 355, 41. (180) Aresta, M.; Dibenedetto, A. J. Mol. Catal. 2002, 399, 182. (181) Aresta, M.; Ciccarese, A.; Quaranta, E. C1 Mol. Chem. 1985, 1, 267. AF

dx.doi.org/10.1021/cr4002758 | Chem. Rev. XXXX, XXX, XXX−XXX

Chemical Reviews

Review

(232) Shi, M.; Shen, Y. M. Helv. Chim. Acta 2001, 84, 3357. (233) Singh, K. N. Synth. Commun. 2007, 37, 2651. (234) Chaturvedi, D.; Mishra, N.; Mishra, V. Chin. Chem. Lett. 2006, 17, 1309. (235) Chaturvedi, D.; Ray, S. Monatsh. Chem. 2006, 137, 459. (236) Chaturvedi, A.; Kumar, S.; Ray. Synth. Commun. 2002, 32, 2651. (237) Feroci, M.; Casadei, M. A.; Orsini, M.; Palóombi, L.; Inesi, A. J. Org. Chem. 2003, 68, 1548. (238) Feroci, M.; Orsini, M.; Rossi, L.; Sotgiu, G.; Inesi, A. J. Org. Chem. 2007, 72, 200. (239) Ikeda, S.; Takagi, T.; Ito, K. Bull. Chem. Soc. Jpn. 1987, 60, 2517. (240) Srivastava, R.; Srinivas, D.; Ratnasamy, P. Appl. Catal., A 2005, 289, 128. (241) (a) Srivastava, R.; Srinivas, D.; Ratnasamy, P. Tetrahedron Lett. 2006, 47, 4213. (b) Srivastava, R.; Srinivas, D.; Ratnasamy, P. J. Catal. 2005, 233, 1. (242) (a) Castillejos, E.; Jahjah, M.; Favier, I.; Orejón, A.; Pradel, C.; Teuma, E.; Masdeu-Bultó, A. M.; Serp, P.; Gómez, M. ChemCatChem 2012, 4, 1. (b) Tamura, M.; Noro, K.; Honda, M.; Nakagawa, Y.; Tomishige, K. Green Chem. 2013, 15, 1567. (243) Carafa, M.; Quaranta, E. Mini-Rev. Org. Chem. 2009, 6 (3), 168. (244) Honda, M.; Sonehara, S.; Yasuda, H.; Nakagawa, Y.; Tomishige, K. Green Chem. 2011, 13, 3406. (245) Ihata, O.; Kayaki, Y.; Ikariya, T. Macromolecules 2005, 38 (15), 6429. (246) Insulation Material. Energy.gov; May 30, 2012; http://energy. gov/energysaver/articles/insulation-materials. (247) Esposito, F. Composite and Additive Makers Report Mixed 2012 Results. Plastic News; February 28, 2012; http://www. plasticsnews.com/article/20130228/NEWS/130229919/compositeand-additive-makers-report-mixed-2012-results. (248) Methylene Diphenyl Diisocyanate (MDI), Toluene Diisocyanate (TDI) and Polyurethane Market (2011−2016). Markets and Markets, July 2011; http://www.marketsandmarkets.com/MarketReports/mdi-tdi-polyurethane-market-381.html. (249) Chemsystem Report Acrylic Acid, PERP Programme, 08/09, 2010. (250) Pàpai, I.; Schubert, G.; Mayer, I.; Besenyei, G.; Aresta, M. Organometallics 2004, 23, 5252. (251) (a) Alvarez, R.; Carmona, E.; Cole-Hamilton, D. J.; Galindo, A.; Gutierrez- Puebla, E.; Monge, A.; Poveda, M. I.; Ruiz, C. J. Am. Chem. Soc. 1985, 107, 5529. (b) Fischer, R.; Langer, J.; Malassa, A.; Walther, D.; Goerls, H.; Vaugham, G. Chem. Commun. 2006, 2510. (252) (a) Aresta, M.; Pastore, C.; Giannoccaro, P.; Kovàcs, G.; Dibenedetto, A.; Pàp ai, I. Chem.Eur. J. 2007, 13, 9028. (b) Bruckmeier, C.; Lehenmeier, M. W.; Reichardt, R.; Vagin, S.; Rieger, B. Organometallics 2010, 29 (10), 1299. (c) Lejkowski, M. L.; Lindner, R.; Kageyama, T.; Bódizs, G. É.; Plessow, P. N.; Müller, I. B.; Schäfer, A.; Rominger, F.; Hofmann, P.; Futter, C.; Schunk, S. A.; Limbach, M. Chem.Eur. J. 2012, 18 (44), 14017. (253) Del Moral, D.; Osuna, A. M. B.; Cordoba, A.; Moreto, J. M.; Veciana, J.; Ricart, S.; Ventosa, N. Chem. Commun. 2009, 4723. (254) Musco, A.; Perego, C.; Tartari, V. Inorg. Chim. Acta 1978, 28, L147. (255) (a) Doehring, A.; Jolly, P. W. Tetrahedron Lett. 1980, 21, 3021. (b) Albano, P.; Aresta, M. J. Organomet. Chem. 1980, 190, 243. (256) (a) Braunstein, P.; Matt, D.; Nobel, D. J. Am. Chem. Soc. 1988, 110, 3207. (b) Braunstein, P.; Matt, D.; Nobel, D. Chem. Rev. 1988, 88, 747. (c) Musco, A. J. Chem. Soc., Perkin Trans. 1980, 1, 693. (d) Behr, A.; Juszak, K. D. J. Organomet. Chem. 1983, 255, 263. (e) Daniels, J. A. (ICI PLC) EP 0050445, 1982. (257) (a) Behr, A.; Heite, M. Chem. Eng. Technol. 2000, 23, 952. (b) Behr, A.; Heite, M. Chem. Ing. Tech. 2000, 72, 58. (258) Pitter, S.; Dinjus, E. J. Mol. Catal. 1997, 125, 39. (259) Buchmuller, K.; Dahmen, N.; Dinjus, E.; Neumann, D.; Powietzka, B.; Pitter, S.; Schon, J. Green Chem. 2003, 5, 218. (260) Storzer, U.; Walter, O.; Zevaco, T.; Dinjus, E. Organometallics 2005, 24, 514.

index.cfm?mode=detail&id=E89DF360-E1C9-C1A34D5448F476CD06A1. (205) SABIC, Sinopec To Construct 260,000 tonne/year Polycarbonate Plant in China by 2015; Hydrocarbon Processing, May 17, 2011; http://www.hydrocarbonprocessing.com/Article/2829178/SABICSinopec-to-construct-260000-tonneyear-polycarbonate-plant-in-Chinaby-2015.html. (206) Milmo, S. Radical Changes in Production Methods Promise Lower Costs and Emissions, and More Efficient Feedstock Use; ICIS: New York, April 15, 2011; http://www.icis.com/Articles/2011/04/15/9453128/ polycarbonate+may+gain+increased+share+of+engineering+plastics. html. (207) Polyether Polycarbocarbonates Polyols-Polyol Production with Carbon Dioxide. The Urethane Blog; April 20, 2012; http:// urethaneblog.typepad.com/my_weblog/2012/04/polyetherpolycarbonate-polyols.html. (208) Quaranta, E.; Aresta, M. In CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, Germany, 2010; p 121. (209) Carbon Dioxide Recovery and Utilisation; Aresta, M., Ed.; Kluwer Academic Publisher: Dordrecht, The Netherlands, 2003. (210) Vaidya, P. D.; Kenig, E. Y. Chem. Eng. Technol. 2007, 30, 1467. (211) (a) Aresta, M.; Quaranta, E. In Proceedings of International Conference on Carbon Dioxide Utilization, Bari, Italy, 1993, p 63. (b) Belli Dell’Amico, D.; Calderazzo, F.; Labella, F.; Marchetti, F.; Pampaloni, G. Chem. Rev. 2003, 103, 3857. (212) (a) Aresta, M.; Ballivet-Tkatchenko, D.; Belli Dell’Amico, D.; Bonnet, M. C.; Boschi, D.; Calderazzo, F.; Faure, R.; Labella, L.; Marchetti, F. Chem. Commun. 2000, 1099. (b) Jamroz, M. H.; Dobrowolski, J. Cz.; Rode, J. E.; Borowiak, M. J. Mol. Struct. 2002, 618, 101. (213) Dibenedetto, A.; Aresta, M.; Fragale, C.; Narracci, M. Green Chem. 2002, 4, 439. (214) Jamroz, M. H.; Dobrowolski, J. Cz.; Borowiak, M. J. Mol. Struct. 1997, 404, 105. (215) Shim, Y. N.; Lee, J. K.; Im, J. K.; Mukherjee, D. K.; Nguyen, D. Q.; Cheong, M.; Kim, H. S. Phys. Chem. Chem. Phys. 2011, 13, 6197. (216) Kovvali, A. S.; Sirkar, K. K. Ind. Eng. Chem. Res. 2001, 40, 2502. (217) Nagai, D.; Suzuki, A.; Kuribayashi, T. Macromol. Rapid Commun. 2011, 32, 404. (218) (a) Dibenedetto, A.; Pastore, C.; Fragale, C.; Aresta, M. ChemSusChem 2008, 1, 742. (b) Tiritiris, I.; Kantiehner, W. Z. Naturforsch., B: J. Chem. Sci. 2011, 66, 164. (219) Carretti, E.; Dei, L.; Baglioni, P.; Weiss, R. G. J. Am. Chem. Soc. 2003, 125, 5121. (220) Stastny, V.; Anderson, A.; Rudkevivh, D. M. J. Org. Chem. 2006, 71, 8696. (221) Mindrup, E. M.; Schneider, W. F. ChemSusChem 2010, 3, 931. (222) Phan, L.; Andreatta, J. R.; Horvey, L. K.; Edie, C. F.; Luco, A. L.; Mirchandani, A.; Darensbourg, D. J.; Jessop, P. J. J. Org. Chem. 2008, 73, 127. (223) Ray, S.; Pathak, S. R.; Chaturvedi, D. Drugs Future 2005, 30, 161. (224) In Toxicology of Organophosphate and Carbamate Compounds; Gupta, R. C., Ed.; Elsevier: Burlington, MA, 2006. (225) Green, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley and Sons Inc.: New York, 2007. (226) (a) Wu, C.; Cheng, H.; Liu, R.; Wang, Q.; Hao, Y.; Yu, Y.; Zhao, F. Green Chem. 2010, 12, 1811. (b) Li, J.; Guo, X. G.; Wang, L. G.; Ma, Y. X.; Zhang, Q. H.; Shi, F.; Deng, Y. Q. Sci. China: Chem. 2010, 53, 1534. (c) Peterson, S. L.; Stucka, S. M.; Dinsmore, C. J. Org. Lett. 2010, 12, 1340. (227) Tsuda, T.; Washida, H.; Watanabe, K.; Miva, M.; Saegusa, T. J. Chem. Soc., Chem. Commun. 1978, 815. (228) Yoshida, Y.; Ishii, S.; Watanabe, M.; Yamashita, T. Bull. Chem. Soc. Jpn. 1989, 62, 1534. (229) Aresta, M.; Quaranta, E. Italian Patent 1,237,207, 1993. (230) McGhee, W. D.; Riley, D.; Kevin, C.; Pan, Y.; Parnas, B. J. Org. Chem. 1995, 60, 2820. (231) McGhee, W. D.; Talley, J. J. U.S. Patent 5,302,717, 1994. AG

dx.doi.org/10.1021/cr4002758 | Chem. Rev. XXXX, XXX, XXX−XXX

Chemical Reviews

Review

(261) Haack, V.; Dinjus, E.; Pitter, S. Angew. Makromol. Chem. 1998, 257, 19. (262) Behr, A.; Brehme, V. A. J. Mol. Catal. A: Chem. 2002, 187, 69. (263) Behr, A.; Brehme, V. A. Adv. Synth. Catal. 2002, 344, 525. (264) Behr, A.; Henze, G.; Johnen, L.; Reyer, S. J. Mol. Catal. A: Chem. 2008, 287, 95. (265) Behr, A.; Becker, M. Dalton Trans. 2006, 4607. (266) Behr, A.; Bahke, P.; Klinger, B.; Becker, M. J. Mol. Catal. A: Chem. 2007, 267, 149. (267) Holzhey, N.; Pitter, S.; Dinjus, E. (Forschungszentrum Karlsruhe GmbH, Germany) Patent Application WO 9857745, 1998. (268) Zevaco, T.; Dinjus, E. In CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, 2010; p 89. (269) Aresta, M.; Dibenedetto, A.; Pàpai, I.; Schubert, G. Inorg. Chim. Acta 2002, 334, 294. (270) (a) Inoue, Y.; Itoh, Y.; Hashimoto, H. Chem. Lett. 1977, 855. (b) Tsuda, T.; Morikawa, S.; Sumiya, R.; Saegusa, T. J. Org. Chem. 1988, 53, 3140. (271) (a) Hoberg, H. In Carbon Dioxide as a Source of Carbon; Springer: New York, 1987; Vol. 206, pp 275−293 (b) Hoberg, H.; Schaefer, D.; Burkhart, G.; Kruger, C.; Romao, M. J. J. Organomet. Chem. 1984, 266, 203. (c) Burkhart, G.; Hoberg, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 76. (d) Hoberg, H.; Schaefer, D. J. Organomet. Chem. 1982, 238, 383. (e) Albano, P.; Aresta, M. J. Organomet. Chem. 1980, 190, 243. (272) Dingyi, Y.; Yungen, Z. Green Chem. 2011, 13, 1275. (273) (a) Goossen, L. J.; Rodriguez, N.; Mamnjolinho, F.; Lange, P. P. Adv. Synth. Catal. 2010, 352, 2913. (b) Manjolinho, F.; Arndt, M.; Goossen, K.; Goosse, L. J. ChemInform 2012, 43. (274) Huang, K.; Sun, C.-L.; Shi, Z. J. Chem. Soc. Rev. 2011, 40, 2435. (275) Albano, P.; Aresta, M.; Manassero, M. Inorg. Chem. 1980, 19, 1069. (276) Aresta, M.; Tommasi, I.; Dileo, C.; Dibenedetto, A.; Narracci, M.; Ziolkowski, J.; Jezierski, A. Can. J. Chem. 2001, 79, 570. (277) Dyker, G. Handbook of C−H Transformations. Applications in Organic Synthesis; Wiley-VCH: Weinheim, Germany, 2005. (278) Jones, W.; Fehe, F. Acc. Chem. Res. 1989, 22, 91. (279) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507. (280) Godula, K.; Sames, D. Science 2006, 312, 67. (281) Bergman, R. G. Nature 2007, 446, 391. (282) Beccalli, E. M.; Broggini, G.; Martinelli, M.; Sottocornola, S. Chem. Rev. 2007, 107, 5318. (283) (a) Chin, C. S.; Won, G.; Chong, D.; Kim, M.; Lee, H. Acc. Chem. Res. 2002, 35, 218. (b) Conejero, S.; Paneque, M.; Poveda, M. L.; Santos, L. L.; Carmona, E. Acc. Chem. Res. 2010, 43, 572. (284) (a) Fagnou, K.; Lautens, M. Chem. Rev. 2003, 103, 169. (b) Doyle, M. P.; Duffy, R.; Ratnikov, M.; Zhou, L. Chem. Rev. 2010, 110, 704. (285) (a) Chianese, A. R.; Lee, S. J.; Gagne, M. R. Angew. Chem., Int. Ed. 2007, 46, 4042. (b) Furstner, A.; Davies, P. W. Angew. Chem., Int. Ed. 2007, 46, 3410. (c) Albrecht, M.; Van Koten, G. Angew. Chem., Int. Ed. 2001, 40, 3750. (286) (a) Li, Z.; Brouwer, C.; He, C. Chem. Rev. 2008, 108, 3239. (b) Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180. (c) Jiménez-Núnez, E.; Echavarren, A. M. Chem. Rev. 2008, 108, 3326. (287) Aresta, M.; Tkatchenko, I.; Tommasi, I. Ionic Liquids as Green Solvents: Progress and Prospects. In ACS Symposium Series 856; Rogers, R. D., Seddon, K. R., Eds.; American Chemical Society: Washington, DC, 2003; p 93. (288) Boogaerts, I. I. F.; Nolan, S. P. J. Am. Chem. Soc. 2010, 132, 8858. (289) (a) Zhang, L.; Cheng, J.; Ohishi, T.; Hou, Z. Angew. Chem., Int. Ed. 2010, 49, 8670. (b) Boogaerts, I. I. F.; Fortman, G. C.; Furst, M. R. L.; Cazin, C. S. J.; Nolan, S. P. Angew. Chem., Int. Ed. 2010, 49, 8674. (290) Gaillard, S.; Slawin, A. M. Z.; Nolan, S. P. Chem. Commun. 2010, 46, 2742. (291) 6th European Photovoltaic Industry Association-EPIA Market Workshop, Paris, March 2011. (292) Appleyard, D. Renewable Energy Magazine, August 10, 2010.

(293) Carbon Dioxide As a Source of Carbon: Chemical and Biochemical Uses; Aresta, M., Forti, G., Eds.; NATO-ASI; Reidel Publishing: Dordrecht, The Netherlands, 1987, Vol. C 206. (294) Aresta, M.; Nobile, C. F.; Albano, V. G.; Forni, E.; Manassero, M. J. Chem. Soc., Chem. Commun. 1975, 636. (295) Mascetti, J. In CO2 as Chemical Feedstock; Aresta, M., Ed.; Wiley-VCH: Weinheim, Germany, 2010. (296) Aresta, M.; Dibenedetto, A.; Angelini, A. Phil. Trans. R. Soc., A 2013, 371 (1996), 1471. (297) Lipman, T. An Overview of Hydrogen Production and Storage Systems with Renewable Hydrogen Case Studies, A Clean States Alliance Report; May 2011; http://www.cleanenergystates.org/assets/2011Files/Hydrogen-and-Fuel-Cells/CESA-Lipman-H2-prod-storage050311.pdf. (298) Catalysis for Energy: New Challenges for a Sustainable Energetic Development, Santander, Spain, August 18−20, 2010. (299) Hanna, M. C.; Nozik, A. J. J. Appl. Phys. 2006, 100, 074510-8. (300) Khaselev, O.; J. A. Turner, A. Science 1998, 280, 425. (301) GCEP Solar Energy Technology Assessment; Stanford University: Stanford, CA, Summer 2006. (302) (a) Dibenedetto, A.; Stufano, P.; Macyk, W.; Baran, T.; Fragale, C.; Costa, M.; Aresta, M. ChemSusChem 2012, 5, 373. (b) Aresta, M.; Dibenedetto, A.; Baran, T.; Angelini, A.; Macyk, W. Patent application MI2013A001135, 2013. (303) (a) Lemus, G.; Duart, M. Int. J. Hydrogen Energy 2010, 35, 3929. (b) Koroneos, C.; Dompros, A.; Roumbas, G.; Moussiopoulos, N. Int. J. Hydrogen Energy 2004, 29, 1443. (304) Obert, R.; Dave, B. C. J. Am. Chem. Soc. 1999, 121, 12192. (305) (a) Akazawa, T. Carbon Dioxide as a Source of Carbon: Chemical and Biochemical Uses; Aresta, M., Forti, G., Eds.; NATO-ASI; Reidel Publishing: Dordrecht, The Netherlands, 1987; p 83. (b) Parry, M. A. J.; Andralojc, P. J.; Mitchell, R. A. C.; Madgwick, P. J.; Keys, A. J. J. Exp. Bot. 2003, 54 (386), 1321. (c) Andersson, I.; Backlund, A. Plant Physiol. Biochem. 2008, 46 (3), 275. (306) Rowland, F. S.; Tyler, S. C.; Montague, D. C.; Makide, Y. Geophys. Res. Lett. 1982, 9 (4), 481. (307) (a) De Simone, J. Proceedings of ICCDU VI, Breckenridge, CO, 9−14 September, 2001; Vol. 33. (b) Carbon Dioxyde Recovery and Utilization; Aresta, M., Ed.; Kluwer Academic: Dordrecht, The Netherlands, 2003; Section III, p 121. (308) Office of Compliance Sector Notebook Project. Profile of the Dry Cleaning Industry, EPA310-R-95-001; EPA-USA, 1995. (309) Cleaner Technologies Substitutes Assessment for Professional Fabricare Project, 744-B-98-001; EPA-USA, 1998. (310) Mineral Fertilizer Production and the Environment, A Guide to Reducing the Environmental Impact of Fertilizer Production; Technical Report 26, United Nations Environmental Programme Industry and the Environment, UNEP: Geneva, 1996.

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