Catalysts for Steam Reforming of Bio-oil: A Review - Industrial

Subscriber access provided by HACETTEPE UNIVERSITESI KUTUPHANESI

Review

Catalysts for steam reforming of bio-oil: A review Jixiang Chen, Junming Sun, and Yong Wang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b00600 • Publication Date (Web): 03 Apr 2017 Downloaded from http://pubs.acs.org on April 9, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Catalysts for steam reforming of bio-oil: A review Jixiang Chen a,b, Junming Sun a, Yong Wang a,c,* a.

The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States b.

Department of Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China. c.

Pacific Northwest National Laboratory, Richland, WA 99352, United States

*E-mail: [email protected]

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 43

Abstract

Despite of extensive studies on the steam reforming of model compounds (e.g., ethanol), steam reforming of real bio-oil is a more practical means for H2 production. This review summarizes recent advances made in steam reforming of real bio-oil, with an emphasis on catalyst development for the process. Among the catalysts investigated, Ni is shown to be promising given its high activity for C-C and C-H bond cleavage. It also has the added advantage of a low cost of production. Strategies to improve catalyst performance include the mitigation of carbon deposition, inhibition of methanation, as well as promotion of water gas shift reactions. In addition, a discussion on current understanding of the reaction mechanism and catalyst deactivation is included in this review, with the aim to provide insight into the relationship between catalyst structure and performance that will give direction towards the development of high performance bio-oil steam reforming catalysts.


2

Page 3 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction Due to the depletion of fossil fuels and continuous implementation of stricter environmental regulations, the use of sustainable and CO2-neutral biomass as an energy source has attracted increasing attention. Biomass can be readily converted into a liquid product (called bio-oil) via the well-developed and commercially viable process of fast pyrolysis. 1 Bio-oil is a complex mixture of oxygenates emulsified with water, containing more than 200 compounds—such as acids, aldehydes, alcohols, esters, glycols, ethers, ketones, phenolics and their derivatives, carbohydrates, and lignin-derived oligomers—where its composition is dependent on the source of the biomass.2 Past utilization has focused on the production of carbon-containing fuels and chemicals via catalytic upgrading (including hydrodeoxygenation and zeolite cracking)1,3,4 and H2 via steam or aqueous reforming.2,5,6 H2 is not only a clean energy carrier with high energy intensity (127 kJ/g)7 that can be utilized as a high-energy fuel and in fuel cells for generating electricity, but also is an important reactant in hydrogenation and hydroprocessing for chemicals and fuels. Crude bio-oil can be directly reformed to produce H2. However, it contains a lot of nonvolatile materials (around 35-40 wt.%) that include dehydrated sugars and phenolics, that are difficult to reform but readily coked up on the catalyst surface.8 As an alternative, crude bio-oil can be separated into aqueous and hydrophobic fractions through the addition of water. 9,10 The former is easily reformed into H2, and the latter can be used for producing phenolic resins, which are valuable chemicals that can be used as fuel-blending components.5,10 Compared with conventional H2 production by steam reforming of fossil feedstocks, steam reforming of bio-oil is closer to CO2-neutral and therefore a more sustainable process. Steam reforming of model compounds (such as ethanol, acetic acid, acetone, glycerol, and phenolics) in bio-oil has been extensively investigated and summarized in a number of recent


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 43

reviews. 11-18 Given that crude bio-oil and its aqueous fraction are very complex in terms of composition, varying catalytic performance and deactivation behavior from coking has been reported.8,19 Compared with single oxygenated organic model compounds, bio-oil possesses the following features in steam reforming reactions: 20,21 a higher reforming temperature, a more complex reaction network, and higher catalyst deactivation rate. Although steam reforming of some model compounds is well understood, fundamental understanding of steam reforming reactions of bio-oil is still very limited. Currently, related studies mainly include the thermodynamics, kinetics, and catalyst screening as well as the design of reactors and reaction processes which target improving performance of the catalysts in steam reforming of bio-oil. Despite the large number of reviews on the steam reforming of model compounds,11-16 there has been very limited work done summarizing investigations into catalysts for steam reforming of real bio-oil.6 Because of this, a summary on recent advances in steam reforming of real bio-oil (including simulated bio-oils) with an emphasis on catalyst development will now be given. To better understand the structure-performance relationship of the following catalysts, the reaction mechanism and properties of catalyst deactivation are also included in this summary. 2. Steam reforming of bio-oil It is usually accepted that two sequential reactions occur during steam reforming of biomass derived oxygenates (CnHmOk): 22,23 CnHmOk+(n-k)H2O→nCO+(n-k+m/2)H2

(1)

CO+H2O→CO2+H2

(2)

The formation of CO and H2 (Eq.(1)) is then followed by the water gas shift (WGS) reaction (Eq. (2)). The overall reaction is presented as: CnHmOk+(2n-k)H2O→nCO2+(2n-k+m/2)H2

(3)


4

Page 5 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In this particular case, the maximum stoichiometric H2 yield is (2n-k+m/2) mol H2/moloxygenate. In reality, however, the H2 yield is typically lower than the maximum, due to the thermodynamic limitation of the WGS reaction, side reactions such as methanation (Eq.(4) and (5)), and coking. CO +3H2→CH4+H2O

(4)

CO2+4H2→CH4+2H2O

(5)

Additionally, steam reforming of CH4 (Eq. (6)) to produce H2 can take place as well. CH4+H2O=CO+3H2

(6)

In steam reforming reactions, the undesired coking formation is mainly due to the Boudouard reaction (Eq.(7)), decomposition accompanied by dehydrogenation (Eq.(8) and (9)), and the polymerization of oxygenates/hydrocarbons. These undesired reactions are inevitable and detrimental to catalyst stability. Indeed, coke formation has been found to be a main reason for catalyst deactivation as introduced in Section 3 and 4. 2CO=CO2+C

(7)

CnHmOk→CxHyOz+gas(H2, CO2, CO, CH4,CHq)+C

(8)

CHq→coke precursors(olefins+aromatics)→q/2H2+C

(9)

C+H2O=CO+H2

(10)

Thus, it is vital to design a suitable catalyst such that steam reforming, WGS, as well as coke gasification (Eq.(10)) are favorable, while simultaneously inhibiting the methanation and carbon deposition reactions. Based on the bond-cleavage of the oxygenates, C-C, C-H and O-H bond-scissions preferentially produce small fragments and H2, whereas it is beneficial to suppress C-O bond-cleavage as its cleavage will lead to the formation of alkanes (including methane produced from the methanation of CO/CO2). Note that aqueous phase reforming of


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 43

sugar alcohols such as glycerol, in which both dehydrogenation and dehydration (C-O bond cleavage) could be controlled to produce hydrogen and hydrocarbons, has been widely studied and reviewed. 17-18 Details for this particular reaction will not be discussed in this review paper. Based on the catalysts for steam reforming of model compounds, 13,24-28 a wide range catalysts— including both metal and mixed metal oxide catalysts—have been studied in steam reforming of real bio-oil. 3. Supported metal catalyst Supported metal catalysts are widely used for bio-oil steam reforming. The metal components include base metals (Ni, Co and Fe) and noble metals (Pt, Ir, Rh, and Ru). 3.1 Reactivity of different metals Several researches have compared the reactivity of different supported metal catalysts. Xing et.al 29 investigated the performance of MgAl2O4 supported Rh, Pt, Ru, Ir, Ni and Co catalysts (loading from 5 wt%-15 wt%) during the steam reforming of a simulated bio-oil (comprising acids, polyols, cycloalkanes and phenolic compounds) (Figure 1 and Figure 2). At 500 °C, a steam-to-carbon (S/C) ratio of 3.5, and pressure of 1 atm, the carbon conversions on the Rh, Ni and Co catalysts reached 100%, 85% and 75%, respectively, whereas those on the other noble metal catalysts were only about 20% (Figure 1). Interestingly, the Co catalyst presented the highest selectivity to H2, the lowest selectivity to CH4, and the best stability. At a gas hourly space velocity (GHSV) of 15700 h-1, H2 yield reached 94% at a carbon conversion of 100% on the Co catalyst. As shown in Figure 2, at similar initial carbon conversions, the selectivity to CH4 on the Co catalyst was ~1.2%, whereas those on the Rh and Ni catalysts were 7~8%. Catalyst deactivation over time was due to coking. Coke formation rates on the catalyst were found to be, in increasing order, Rh < Co < Ru< Ir < Pt < Ni (Figure 1). The high coke formation rate on Ni


6

Page 7 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


has been widely observed in reforming reactions of both light hydrocarbons and oxygenates, as well as for methanation.8,30,31 The favorable adsorption, solubility, and diffusion of carbon on/in the Ni particles may account for the rapid coke formation reported.30,32,33 To overcome this problem, different strategies have been employed (which are discussed in Section 3.3).

Figure 1 Comparison of catalyst activity and coke formation during the steam reforming of a simulated bio-oil (i.e., a mixture of carboxylic acids, polyols, cycloalkanes and phenolics).29 Reaction conditions: T =500 °C, P=1 atm, GHSV=30,000 h-1; GHSV=3000 h-1 for commercial naptha reforming catalyst RKNR (Haldor Topsoe).


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 43

Figure 2 Comparison of catalysts’ activity and CH4 selectivity versus accumulated molarcarbon fed during steam reforming of a simulated bio-oil (i.e., a mixture of carboxylic acids, polyols, cycloalkanes

and

phenolics)

over

5

wt%

Rh/MgAl2O4,

15

wt%Ni/MgAl2O4,

and

15wt%Co/MgAl2O4.29 GHSV was varied to acheive similar initial conversions: GHSV=90,000 h-1(Rh), GHSV=47,000 h-1(Ni), and GHSV=31,000 h-1(Co). The time-on-stream for Rh, Ni, and Co catalysts were 64, 79, and 123 h, respectively. Domine et al.34 compared the activities of Pt/Ce0.5Zr0.5O2 and Rh/Ce0.5Zr0.5O2 supported on cordierite monoliths for steam reforming of crude bio-oil derived by fast pyrolysis of beech wood residues. At 780 °C and a S/C ratio of 10, the bio-oil was completely converted on both catalysts, while Pt/Ce0.5Zr0.5O2 gave a higher H2 yield (70%, equivalent to ~49 mmol H2/gbio-oil) than Rh/Ce0.5Zr0.5O2 (52%, corresponding to ~36 mmol H2/gbio-oil). The same trend was also observed on the CeZrO2 supported Pt and Rh catalysts in the steam reforming of a crude bio-oil produced by fast pyrolysis of beech wood. 35 This is attributed to the higher WGS reaction activity of Pt than that of Rh.36


8

Page 9 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Recently, a Fe/olivine catalyst has been found to have good performance for the steam reforming of crude bio-oil generated from pyrolysis of coconut shell. 37 At 800 °C, a bio-oil weight hourly space velocity (WHSV) of 0.5 h-1 and the S/C ratio of 2, the carbon conversion and H2 yield reached 97.2% and 79.3%, respectively, which is comparable to commercial Nibased steam reforming catalysts (UC G-90C and ICI 46-1).38 During steam reforming, majority of the phenolics in the bio-oil were converted into hydrogen and C1 products (such as CO, CO2, and CH4). Mixed Fe2+/3+/Fe2+ are suggested to be the active sites for C–C, C–O and C–H breaking, which was only based on the XRD results of the used catalysts where no Fe0 but only FeO and Fe3O4 were detected. Further surface characterization techniques such as XPS could be used to validate whether Fe0 is present or not.

3.2 Influence of support Al2O3 is a commercially viable support, and due to its tunable textural properties and high mechanical strength, it has been widely used as a support for catalysts in the steam reforming of light hydrocarbons and bio-oil (Section 3.3). Additionally, CeO2-ZrO2 mixed oxides, HZSM-5, and carbon nanotubes (CNTs) have been found to be good candidates as supports for the steam reforming of bio-oil. CeO2 and ZrO2, especially the former, are proposed to favor the activation of water and to have high oxygen storage/release capacity.39 CeO2 can also greatly facilitate the WGS reaction. 40-42

Moreover, the incorporation of ZrO2 into CeO2 remarkably increases the oxygen storage

capacity and promotes the mobility of lattice oxygen atoms in the catalyst.42 This unique property of CeO2-ZrO2 mixed oxide is believed to contribute to resistance of carbon deposition and thus cause the observed enhanced steam reforming performance. Indeed, in steam reforming


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 43

of beech wood derived crude bio-oil, the CeZrO2-supported Pt and Rh catalysts (especially CeZrO2-supported Pt) outperforms the Al2O3-supported ones.35 After reaction for 2 h at 860 ± 30 °C and S/C ratio of 10.8, Pt/CeZrO2 gave a H2 yield of ~ 70%, higher than that of the yield on Pt/Al2O3(40%). In the steam reforming of aqueous fraction of bio-oil produced from the pyrolysis of rice hulls, the Ni/CeO2-ZrO2 catalyst (12 wt% Ni, 7.5 wt% Ce) gave a similar initial H2 yield (~58%) to a commercial nickel-based catalyst (Z417) at 600 °C and S/C ratio of 4.9, although it was more stable than the commercial material (Figure 3).43 It is suggested that the hydrocarbon and oxygenated molecules were activated and decomposed on Ni metal sites. At the Ni/support interface, the resulting fragments are then gasified by the lattice oxygen .

Figure 3 Long TOS stability test comparing the steam reforming of aqueous fraction of bio-oil produced from the pyrolysis of rice hulls Ni/CeO2-ZrO2 and Z417 catalysts.43 Ni/CeO2-ZrO2 (12 wt%Ni, 7.5 wt% Ce); S/C=4.9; T=600 °C.


10

Page 11 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


It is generally accepted that the HZSM-5 zeolite is very active for dehydrogenation and C-C cracking. Using 20 wt% Ni/HZSM-5, Qiu et al.44 achieved a H2 yield of ~ 90% with nearly complete conversion of crude bio-oil (CH2.03O0.67·0.89H2O) at 450 ºC and a S/C ratio of 17, which was much higher than that of the Ni/Al2O3 catalyst at ~60% conversion. The H2 yield for the catalyst, however, reached a value of ~ 99.8% at 600 °C. The HZSM-5 supported metal catalyst was also found to be much more active than the Al2O3 supported one for the reforming of liquid hydrocarbons.45 Due to the high surface area, high thermal stability, and high mechanical strength, CNTs have been identified as a promising support material. Using a deposition–precipitation method, Hou et al. 46 synthesized a CNT-supported Ni catalyst (denoted as x %Ni-CNTs, where x% denotes Ni mass content) for the reforming of the volatile organic components generated from the vaporization of a crude bio-oil at temperatures ranging from 60 to 180 ºC (the crude bio-oil was produced from the pyrolysis of sawdust). 15%Ni-CNTs gave a carbon conversion of 94.9% and H2 yield of 92.5% at 550 °C and a S/C ratio of 6.1, which are much higher than those (carbon conversion of ~55% and H2 yield of ~55%) on 15%Ni-Al2O3. The superior performance on NiCNTs is attributed to the formation of small uniform Ni particles on the catalyst. Moreover, the unique graphite structure of CNTs could also promote electron transfer between the support and the metal particles,47,48 resulting in an electronic perturbation on the metallic Ni and subsequently enhanced activity. Apart from the support’s surface chemistry, catalyst shape has also been found to affect the reforming process. The carbonaceous deposit, which is inevitable during steam reforming, may block the catalyst bed in the fixed-bed reactor, while the monolith supported catalysts may alleviate this problem.34


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 43

3.3 Modified Ni/Al2O3 catalyst While noble metals have been reported to show good performance for steam reforming of bio-oil,29,34,35 their high cost may limit wide application. The low-cost of metallic Ni has attracted great attention for steam reforming of bio-oil because it also possesses a high capability for C-C, C-H and O-H bond cleavage.11, 49 Given its commercial application in the steam reforming of hydrocarbons, providing a wealth of experience for catalyst development, Al2O3 supported Ni catalytic system is also expected to be promising in the bio-oil steam reforming reaction. However, the use of Ni/Al2O3 also has two critical drawbacks. First, metallic Ni is very active for undesired methanation and coke formation, and it is less active for the desired WGS reaction. 50 , 51 Second, the surface acidity of Al2O3 promotes unwanted polymerization. To overcome these issues and promote high H2 yield and low carbon deposition, a common strategy adopted is to modify the Ni/Al2O3 catalyst with other metals (e.g. Co and Cu) and metal oxide promoters with redox and basic properties (e.g. La2O3, MgO and CeO2). 3.3.1 Metal promoter Although Co and Cu possess lower activity for C-C bond cleavage than Ni, 52 and low activity for methanation,53,54 they are highly active for the WGS reaction. It is expected that the introduction of Cu or Co into Ni-based catalysts may cause a synergetic effect between them, promoting steam reforming activity. Indeed, Co and Cu have been found to promote the reactivity of Ni catalysts in the steam reforming of small oxygenates (e.g., ethanol, glycerol, and acetic acid) and methane.55-58 This promotion effect was attributed to the formation of bimetallic Ni-Cu (or Co) alloys, where Cu or Co could have either geometrically or electronically modified the Ni particles by forming small ensembles of Ni sites or increasing electron density on Ni via electron transfer from Cu.59-62 In this case, metallic Ni still retains its high activity for C-C bond


12

Page 13 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cleavage, while the methanation and carbon deposition reactions are greatly suppressed and the WGS reaction is promoted. Reducing the ensembles of Ni sites has also been one of strategies to restrain the carbon deposition in the steam reforming of light hydrocarbons.63 The formation of bimetallic alloys also prevents metallic crystallites from sintering,55-57,62,64 which is expected to enhance the catalyst’s stability. In the steam reforming of bio-oil, a positive effect of Co and Cu on the reactivity of Ni/Al2O3 was also reported. Remón et al.

65

investigated the effect of Cu and Co on the

performance of Ni/MgO-Al2O3 prepared by coprecipitation. During steam reforming of the aqueous fraction of the pine sawdust derived (pyrolysis) bio-oil , NiCo/MgO-Al2O3 was found to exhibit the best performance at 650 oC and GHSV of 13,000 h−1, leading to 80% carbon conversion and 0.138 g H2/gorganics within 2 hours. NiCu/MgO-Al2O3 (~63% carbon conversion and 0.093 g H2/gorganics) showed slightly higher performance than Ni/MgO-Al2O3 (~57% carbon conversion and 0.082 g H2/gorganics). Moreover, NiCo/MgO-Al2O3 gave the lowest CH4 yield and was more resistant to coke formation than Ni/MgO-Al2O3. The authors proposed that the smaller Ni crystallites interacting with Co could lead to more oxygen vacancies and labile oxygen species on the support. Consequently, the steam reforming and WGS reaction as well as the gasification of carbon intermediates were promoted. The CeO2-ZrO2 supported Ni-Co bimetallic catalysts were tested in the steam reforming of sawdust derived (pyrolysis) crude bio-oil . 66 While keeping the total metal loading at 12 wt.%, the Ni-Co bimetallic catalysts with various Ni/Co mass ratios were synthesized through the wet impregnation method. At 850 °C and WHSV of 2.62 h–1, the H2 yield increased with the Co content and reached a maximum (72.15%) at a weight ratio of 3/9. The catalyst also showed the lowest coking rate and improved stability when compared to the commercial Ni-based catalyst (MgO ≥ 83 %, Al2O3 ≥ 6%, and Ni ≥ 6%)


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 43

from Qianya Refractory Material Co. Ltd., Wuxi, China (Figure 4). It was found that the increase in Co composition facilitated the WGS reaction, which is consistent with the reported higher activity of Co than that of Ni for WGS reaction.53,67 In steam reforming of the volatiles from the pyrolysis of sawdust at 825 °C and WHSV of 0.71 h−1, Ni-Co/γ-Al2O3 was also found to have higher H2 selectivity (94.83%) than the Ni/γ-Al2O3(85.78%) and Co/γ-Al2O3 (90.07%) catalysts. 68 It is suggested that the synergic effect between Ni and Co plays a key role in the enhanced performance of Ni-Co/γ-Al2O3. In another work, the steam reforming of simulated biooil (a mixture of ethanol, acetone, acetic acid, and phenol with equal masses) was tested on the Al2O3 supported Ce-Ni/Co catalyst,69 which showed a high stability and provided an H2 yield of 83.8% at 700 °C and a S/C ratio of 9.

Figure 4 Stability of the self-prepared catalyst vs. commercial catalysts in the steam reforming of sawdust derived crude bio-oil .66 Reaction conditions: T=850 °C, bio-oil feed rate=12 mL.h-1, WHSV=2.62 h-1.


14

Page 15 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Gong et al. 20 compared a series of Ni based catalysts and found a Ni–Cu–Zn–Al2O3 catalyst to be a promising candidate to efficiently reform bio-oil to H2 and CO2 at low temperature (450~500 °C). In the steam reforming of volatiles (80~180 °C) from the pyrolysis of sawdust, a maximum H2 yield of 87.4% at carbon conversion of 91.8% was obtained on Ni–Cu–Zn–Al2O3 at 500 °C and a S/C ratio of 6.1. A very slow rate of catalyst deactivation was observed during the reaction over a TOS of 10 hours (Figure 5). The authors also found that Ni–Cu–Zn–Al2O3 efficiently dissociated the oxygenated organic compounds at 500 °C, and showed high activity for the WGS and low activity for methanation reactions at 300~600 °C, which could account for the high performance of Ni–Cu–Zn–Al2O3 in the steam reforming reaction.

Figure 5 Stability curves in the steam reforming of volatiles (80~180 °C) produced from the pyrolysis of sawdust over the Ni-Cu-Zn-Al2O3 catalyst.20 (a) Carbon conversion and H2 yield, (b) gas-phase product distribution. Reaction conditions: T=500 °C, S/C=6.9, GHSV=6300 h-1, and P=1.1 atm. In other works, Salehi et al. 70 found that adding 0.5 % Ru to the Ni/Al2O3 catalysts increased the H2 yield in the steam reforming of a commercial crude bio-oil provided by Biomass Technology Group (BTG), in the Netherlands. When the nickel content was 14.1%, the


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 43

maximum H2 yield reached about 85% at 950 °C on the Ru–Ni/Al2O3 catalysts, which was ~14% higher than that on Ni/Al2O3. 3.3.2 Metal oxide promoter Metal oxide promoters are adopted to modify Ni/Al2O3 in order to improve redox properties, passivate acidity, and enhance the ability for adsorbing and activating water on the catalyst. Valle et al.71 have reported the effect of La2O3 on the performance of Ni/α-Al2O3 for the steam reforming of the aqueous fraction of bio-oil generated from flash pyrolysis of sawdust. As shown in Figure 6, the bio-oil was completely converted with the H2 yield reaching up to ~95% on both Ni/α-Al2O3 and Ni/La2O3-αAl2O3 at the beginning of the reaction. However, bio-oil conversion decreased from 100% to 96% and H2 yield gradually dropped from 94% to 65% on Ni/α-Al2O3 within 20 h of TOS operation. In contrast, Ni/La2O3-α Al2O3 showed higher stability with almost constant conversion of around 100% albeit slow decreased H2 yield from 95% to 85%. The catalyst characterizations showed that the presence of La2O3 reduced coke amount and prevented Ni crystallite from sintering. The authors speculate that the favorable effects of La2O3 could be attributed to its water adsorption capacity, basic properties, and the increased surface oxygen population, due to the presence of La3+ and/or the formation of La2O2CO3 carbonate at the surface of the catalyst.


16

Page 17 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6 Evolution of bio-oil conversion with the time-on-stream during the steam reforming of aqueous fraction of sawdust derived bio-oil (a); and H2 yield/selectivity (b) over the Ni/α-Al2O3 and Ni/La2O3-αAl2O3 catalysts.71 Reaction conditions: T=700 °C, GC1HSV=8100 h-1, S/C=12, τ (contact time)=0.45 gcatalyst h (gbio-oil)-1 The effect of CaO and MgO on the performance of Ni/Al2O3 catalysts was investigated by Medrano et al. in steam reforming of the aqueous fraction (consisting of a mixture of acids, alcohols, aldehydes, ketones and sugars) of bio-oil derived from pine wood. 72 The MgO promoted catalyst gave the best performance (carbon conversion of 81.01%, H2 yield of 0.1056g/gorganic) at 650 °C and a S/C ratio of 7.64, followed by the Ni/Al2O3 catalyst (carbon


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 43

conversion of 73.50%, H2 yield of 0.0965 g/gorganic), and then the CaO modified Ni/Al2O3catalyst (carbon conversion of 65.78%, H2 yield of 0.0774 g/gorganic). MgO was proposed to promote the WGS reaction. Similarly, Salehi et al.

70

reported that adding 12 wt.% MgO to 18% Ni/Al2O3

increased the H2 yield from 54% to ~62% in the steam reforming of a commercial crude bio-oil ( Biomass Technology Group ,in the Netherlands). In the steam reforming of crude bio-oil produced from rice husks, 73 Ni/MgO-La2O3-Al2O3 gave a maximum H2 yield of 68.27 % at temperatures of 750–850 °C, S/C ratios of 7–12, and LHSVs of 0.8–1.5 h–1 in a fixed bed reactor. As discussed in section 3.2, CeO2 can facilitate carbon gasification and the WGS reaction due to its redox properties and high oxygen storage capacity.40,41 As a promoter, it also enhances the reactivity of Ni/A12O3 and mitigates the carbon deposition in the steam reforming of crude bio-oil from the pyrolysis of maize stalk.74 As mentioned above, the metal and metal oxide promoters could serve different functions in modifying the metallic Ni sites and supports for the steam reforming. To maximize their promotion effect, the metal and metal oxide promoters have also been simultaneously used to modify Ni/Al2O3 in an attempt to improve the performance of the catalysts. For example, Garcia et al. 77 designed and prepared several multi-component catalysts for the steam reforming of the aqueous fraction of bio-oil from the pyrolysis of poplar wood. It was found that the H2 yield increased in the order of Ni/Al2O3, Ni/MgO-Al2O3, Ni/MgO-La2O3-Al2O3, Ni-Cr/MgO-La2O3Al2O3 and Ni-Co/MgO-La2O3-Al2O3. The presence of MgO, La2O3, Co and Cr resulted in less CO production, and the presence of MgO and La2O3 also restrained the formations of CH4 and benzene, respectively. Xie et al.69 prepared a set of Al2O3-supported Ni-based catalysts such as Ni/Mg, Mg-Ni/Ce, Mg-Ni/Co, Ce-Ni, Ce-Ni/Mg, Ce-Ni/Ce and Ce-Ni/Co, etc.). Among those,


18

Page 19 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the Ce-Ni/Co catalyst was found to be the most active. Steam reforming of simulated bio-oil (mixed acetic acid, ethanol, acetone and phenol with the equal masses) at 700 °C and a S/C ratio of 9 gave an average H2 yield of 83.8% within a TOS period of 8 hours. (Figure 7). Yuan et al.75 designed a multiple component Ni-based catalyst (Ni-Cu-Mg-Ce-Al) for the steam reforming of crude bio-oil derived from the pyrolysis of sawdust. At 500 oC, the carbon conversion and the H2 yield reached about 85.9% and 82.8%, respectively.

Figure 7 Stability test of the Ce-Ni/Co catalyst in the steam reforming of simulated bio-oil (mixed acetic acid, ethanol, acetone and phenol with the equal masses): (a) H2 yields, (b) gasphase product distribution .69 3.4 Other modified catalysts Other than the modified Ni/Al2O3 catalysts, a few other modified metal catalysts were also investigated for steam reforming of bio-oil. MgO modified Ru/Al2O3 was tested for steam reforming of the aqueous fraction of beech wood derived bio-oil (by fast pyrolysis). 76 The aqueous fraction was completely converted on Ru/MgO/Al2O3 pellets at 700 oC, a S/C ratio of 7.2, a GHSV of 5200 h-1 and at a pressure of 1 atm. The selectivity to H2 was close to 100%. The selectivity to CO2 was higher than 90%, and the selectivity to CH4 was very low. Based on the CO-TPR result, the authors suggest that the presence of MgO promoted the spillover of oxygen


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 43

and/or hydroxyl radicals from the support to the metal particles as MgO can enhance the water adsorption on the catalyst.77 Additionally, the Ru/MgO/Al2O3 catalysts with different structural forms (pellet, ceramic foam and ceramic monolith) all showed satisfactory stability (Figure 8).

Figure 8 Durability test on 5% Ru/MgO/Al2O3 pellet catalyst in the steam reforming of the aqueous fraction of bio-oil produced by fast pyrolysis of beech wood (A), ceramic foam (B), ceramic monolith JM(C), and ceramic monolith (D).76 Reaction conditions: T=700 ºC, GHSV=5900 h-1(A), T=800 ºC, GHSV=7200 h-1 (B), T=800 ºC, GHSV=4200 h-1 (C), and T=800 ºC, GHSV=4350 h-1 (D), S/C=7.2, P=1 atm. 3.5 Catalyst synthesis It is well known that catalyst preparation methods and pretreatment conditions usually have an important influence on a catalyst’s structure and performance. However, there are few reports on this relationship in the steam reforming of bio-oil. Remón et al.65 investigated the effect of coprecipitation and impregnation methods on the performance of NiCo/MgO-Al2O3 and


20

Page 21 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


NiCu/MgO-Al2O3 in steam reforming of the aqueous fraction of bio-oil from the pyrolysis of pine sawdust. The coprecipitated NiCo/MgO-Al2O3 and NiCu/MgO-Al2O3 catalysts provided higher carbon conversion, H2 yields, and stability than the impregnated ones did. Valle et al.78 investigated the effect of calcination and reduction temperatures (550~850 °C) on the performance of Ni/La2O3-α-Al2O3 during the steam reforming of the mixture of crude bio-oil and ethanol (20 wt% of ethanol, bio-oil from the pyrolysis of pine sawdust). It was found that the catalyst calcined at 550 °C and reduced at 700 °C gave the highest conversion and H2 yield, and showed the best stability. At 700 °C, GC1HSV(defined in equivalent CH4) of 13,800 h−1, a S/C ratio of 6 and 0.27 gcatalysth(gbio-oil+EtOH)−1, the bio-oil and ethanol were completely converted with a slight decrease in H2 yield from 94% to 87% during a TOS period of 4 hours. The authors suggested that the large Ni0 metal surface area contributed to the high catalyst activity, and the Ni0 particles from reduction of NiAl2O4 spinel were less active than those reduced from Ni oxides because of their larger size. To increase the nickel dispersion, the surfactant cetyl trimethyl ammonium bromide was used to prepare 5%Ni/Ce0.5Zr0.33M0.17O2-δ by coprecipitation79 and its presence caused enhanced catalyst activity, but had a negligible effect on the H2 selectivity. 3.6 Reaction mechanism and catalyst deactivation Insight into the reaction mechanism is important to aid in the design and development of high performance catalysts. However, bio-oil (even its aqueous fraction) contains multiple types of organic compounds, and the reaction networks are complicated during steam reforming. Thus, it is very difficult to investigate the reaction mechanism for steam reforming of bio-oil. Currently, the reaction mechanism for steam reforming of bio-oil is still based on that of a single compound model. A common consensus on the mechanism of steam reforming on the supported


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 43

metal catalysts is that the steam reforming of oxygenates involves two important reactions (also called a bifunctional mechanism).35,76,77,80 It is believed that oxygenates are primarily dissociated on the metal sites to generate adsorbed carbon species while producing H2. Concurrently, water is adsorbed and dissociated on the supports, and the formed –OH groups then migrate onto the metal particles or metal/support interface where they rapidly react with carbon species to produce CO, CO2, and H2. It is also possible that the dissociated water by the support could also negatively affect catalyst performance by over oxidizing the metallic active phase.4,16 It is thus proposed that an appropriate control of the metal/support interface area could favor steam reforming. It is worth noting that some new theories have recently been proposed for the steam reforming mechanism on the Co based catalysts mentioned above.16 Apart from the support, metallic Co nanoparticles (~ 5 nm) have also been found to be active for the dissociation of H2O, which favors the gasification of carbonaceous species during steam reforming reactions. 81 In addition, the nature of supports also plays a pivotal role in controlling the reaction pathways during steam reforming. In the steam reforming of ethanol, for instance, the acidic supports (e.g., Al2O3) facilitate the dehydration of ethanol to ethylene, which is then easily polymerized along with the facilitation of formation of carbonaceous deposits.82 In contrast, the basic supports (e.g., MgO) favored ethanol dehydrogenation to form acetaldehyde.82 Different from acidic and basic supports, reducible supports promoted the formation of acetone.82, 83 The different chemical properties of these intermediates undoubtedly affect the hydrogen yield.25,81 These findings provide further insight into the fundamental understanding of the reaction mechanism of steam reforming.


22

Page 23 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


As mentioned above, even for a single compound model, the steam reforming mechanism is very complicated, and depends on the catalyst properties (such as the nature of metal, the metallic particle size, the oxidation state of the metal and the property of supports/metal oxide promoters) as well as the type of reactants studied. While the insight into the mechanism of single compound can provide valuable information, it is a great challenge to ascertain the steam reforming mechanism of real bio-oil. Although the sintering of the metal crystallites and/or the support is detrimental to steam reforming catalyst stability, carbon deposition plays a major role in catalyst deactivation. Compared with hydrocarbons, oxygenates are more prone to polymerizations (e.g., olefin polymerization and aldol condensation).21 Also, at elevated temperatures, polymerizations become more serious due to the presence of large thermally unstable molecules (e.g., carbohydrates, furans, phenols). 84 Some strategies have been proposed to limit carbon deposition.77,85 One is to mitigate the surface reactions leading to the coke formation. Another one aims at the promotion of water dissociation to facilitate the gasification of coke precursors, and subsequently suppress coke formation. Unfortunately, since water dissociation may also oxidize the metal catalysts, this may lead to a decrease in the number of surface metallic sites, presenting an interesting problem involving the balance of favoring the gasification of surface carbon species and inhibiting the oxidation of the active metal sites.16 Again, the reduction of an ensemble of metal sites is beneficial to suppressing the carbon deposition.85 As indicated in Section 3.3, these strategies can be achieved by modifying metal catalysts with metal and/or metal oxide promoters. 4. Mixed metal oxide catalysts


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 43

Apart from the metal based catalysts, perovskite and 12CaO·7Al2O3(C12A7) compounds have also been found to exhibit good performance as catalysts in the bio-oil steam reforming .86,87 Perovskite is a composite oxide with a formula of ABO3 and redox properties, where the A represents lanthanide metal and B is a transition metal.88 As precursors for Ni, Rh or Co-based catalysts, perovskites have been used for the partial oxidation of CH4 to synthesis gas.89,90 Also, La1−xBaxMnO3, having no metallic components, showed higher performance than the Ni-based catalysts with the ABO3 structure in CH4-CO2 reforming.91 Recently, Chen et al.86 reported the performance of La1-xKxMnO3 perovskite-type catalysts in steam reforming of crude bio-oil obtained from fast pyrolysis of pinewood sawdust. The La0.8K0.2MnO3 catalyst showed the best performance among La1-xKxMnO3 and provided higher carbon conversion and H2 yield than the commercial Ni/ZrO2. The H2 yield reached up to 72.5% under the optimum reaction condition (800 °C, a S/C ratio of 3 and WHSV of 12 h-1). The authors suggested that the nature of bio-oil steam reforming on the La1-xKxMnO3 catalyst should follow a redox mechanism. In La1xKxMnO3

catalysts, the B-site (i.e., Mn) cations possess the capability for the steam reforming.

According to the principle of electron neutrality, the partial replacement of La3+ by K+ led to the change of Mn3+ to Mn4+, where Mn4+ had higher catalytic activity than Mn3+. La1-xKxMnO3 with K solubility closing to the limit (x=0.2) exhibited the best performance. Beyond this limit, the formation of K2Mn4O8 led to a decrease in catalyst activity. The perovskite phase was stable in the reaction atmosphere. However, the La1-xKxMnO3 catalyst still suffered from coke deposition giving rise to its deactivation. C12A7 compound is one of the crystalline phases in the system of CaO and A12O3. Because of reversible absorption of water over a wide temperature range without major structural


24

Page 25 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


changes, C12A7 is considered a zeolite phase. It possesses a cubic structure with the lattice framework [Ca24Al28O64]4+ positively charged. In contrast to conventional zeolites where the cationic species are introduced to compensate for the negative charge caused by the substitution of Si4+ ions by Al3+ions, the anionic species (such OH- and O-) are known to substitute themselves for free oxygen in C12A7 to form derivatives. 92 Wang et al.87 investigated doped [Ca24Al28O64]4+·4O-/M (C12A7-O-/M, M = Mg, K and Ce) catalysts for steam reforming of the volatile fraction of a crude biomass pyrolysis oil. C12A7-O-/18%Mg showed the best performance, which was not a simple add-up of those on MgO and C12A7-O-. At 750 °C, a S/C ratio > 4.0, and a GHSV of 10,000 h-1, the H2 yield reached 80%, and the maximum carbon conversion was 96%. The authors suggested that the O- species may be involved in steam reforming of bio-oil because the OH- intermediates were observed on C12A7-O-/18%Mg after the reaction. It was reported that the O- species were the key active intermediates in low temperature oxidation of hydrocarbons.93 In C12A7-O-/Mg, MgO may enhance the adsorption and dissociation of oxygenate. C12A7-O-/M catalyst deactivation also took place and was mainly attributed to coke formation. As discussed above, perovskite and C12A7 showed good performance for steam reforming of bio-oil due to their redox properties. This implicitly conveys that the metallic component (such as the noble metals Ni and Co) could be unnecessary in steam reforming of bio-oil. However, the synergy between the metallic component and the mixed metal oxides with desired functions (e.g., redox property and basicity) may work better in terms of catalyst efficiency, meaning that further comparison of the two types of catalysts is needed to make more definitive conclusions with regards to synergy and functionality. 5. Summaries and perspectives


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 43

In this review, we summarized recent advances of catalysts for steam bio-oil reforming. While noble metals (such as Pt, Ru and Rh) show high ability for the C-C bond cleavage and low affinity for coke formation, their high cost limits practical utilization. Metallic Ni, the key component of conventional catalysts in steam reforming of fossil feedstocks, is also very active for the C-C and C-H bond cleavage of bio-oil components. From the viewpoint of practical application, the Al2O3 supported Ni catalyst system is very promising. However, although metallic Ni is highly active for methanation, it has a low activity for the WGS reaction, giving rise to lower H2 yields. Moreover, its high affinity to carbon leads to serious carbon deposition that contributes to the catalyst deactivation more than the effects of catalyst sintering does. Moreover, the acidity of Al2O3 favors dehydration and polymerization reactions. To overcome these disadvantages on Ni/Al2O3, the strategies that have been widely adopted include: 1) geometrically and/or electronically modifying metallic Ni with other metals (e.g., Co and Cu with high activity for the WGS and low activity for methanation reactions) not only to alleviate carbon deposition but also to promote the WGS reaction and to suppress methanation; 2) increasing the adsorption and activation of water with metal oxide promoters (e.g., MgO and CeO2) to promote the WGS reaction and alleviate carbon deposition; 3) enhancing the oxygen storage/release capacity with reducible metal oxide promoters (e.g., CeO2 and ZrO2) to accelerate the gasification of carbon deposits; and, 4) neutralizing catalyst surface acidity with basic metal oxides to suppress carbon deposition. Given the complicated component reaction networks during bio-oil steam reforming, a versatile catalyst with multi-functionality is expected to facilitate the conversion of the multiple compounds needed in the steam reforming reaction.


26

Page 27 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fundamental knowledge of bio-oil steam reforming is mainly based on single compound models. In general, a bifunctional mechanism prevails, that is, metal sites are responsible for the activation and transformation of oxygenates, while metal oxide sites serve as locations for the activation of water.35,76,77,80 Recent studies reveal that steam reforming could occur on cobalt nanoparticles supported on an inert support (i.e., C) 16 where nanosized Co particles (i.e., ~ 5 nm) were found to be active for both oxygenate decomposition and water activation.81 In addition, supports also play essential roles in changing the reaction pathways due to their different properties (e.g., acidity/basicity and reducibility).82,83 Furthermore, perovskite and C12A7 mixed oxides, which do not contain the metallic sites while possessing redox function, exhibited high activity in steam reforming of bio-oil.86,87 These observations convey a message that the mechanism of steam reforming is still subject to further in-depth studies in order to ascertain more information about structure-function relationships on the catalysts in question. In situ/operando and time-resolved characterization techniques (such as electron microscopy, FTIR, XAFS and XPS) are expected to be powerful tools in the endeavor to obtain more reliable evidence for the reaction mechanism and the nature of active sites on bio-oil steam reforming catalysts. Catalyst deactivation due to carbon deposition is inevitable in steam reforming of bio-oil. It is very important to alleviate the carbon deposition through the techniques discussed earlier in this report. To this end, further understanding of the carbon deposition mechanism is vital as it is currently not well understood. It is also essential to improve the regeneration ability of potential catalysts since frequent catalyst regeneration may be required due to deactivation over time. The usual regeneration method is to combust carbonaceous deposits using dilute oxygen, during which sintering of nanoparticles on the catalysts could occur. With respect to Ni based catalysts,


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 43

sintering of Ni particles reduces the metal surface area and promotes additional carbon deposition. Highly dispersed and stable Ni catalysts are desirable if they are to be implemented as bio-oil steam reforming catalysts in the future. Apart from improving the performance of the catalysts themselves, integration of catalysis with separation is also a promising route to enhance reaction effectiveness. For instance, coupling steam reforming with CO2 absorption using CaO remarkably increased the H2 yield and H2 content in the gaseous product because the WGS reaction was facilitated more readily. 69,94,95 Additionally, electrochemical catalytic reforming remarkably increased catalyst performance due to the effect of thermal electrons.46,75,96

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interest.

Acknowledgements JC acknowledges the financial support from the China Scholarship Council. JS and YW would like to thank the financial support provided by US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences (DEAC05-RL01830, FWP-47319). We also thank Austin D. Winkelman for proofreading the manuscript.


28

Page 29 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References

1

Liu, C. J.; Wang, H. M.; Karim, A. M.; Sun, J. M.; Wang, Y. Catalytic fast pyrolysis of

lignocellulosic biomass. Chem. Soc. Rev. 2014, 43, 7594–7623. 2

Wang, H. M.; Male, J.; Wang, Y. Recent advances in hydrotreating of pyrolysis bio-oil and its

oxygen-containing model compounds. ACS Catal. 2013, 3, 1047−1070. 3

Hong, Y.; Hensley, A.; McEwen, J. S.; Wang, Y. Perspective on catalytic hydrodeoxygenation

of biomass pyrolysis oils: Essential roles of Fe-based catalysts. Catal. Lett. 2016, 146, 16211633. 4

Sun, J.; Wang, Y. Recent advances in catalytic conversion of ethanol to chemicals. ACS Catal.

2014, 4, 1078. 5

Saidi, M.; Samimi, F.; Karimipourfard, D.; Nimmanwudipong, T.; Gates, B. C.; Rahimpour, M.

R. Upgrading of lignin-derived bio-oils by catalytic hydrodeoxygenation. Energ. Environ. Sci. 2014, 7,103–129. 6

Trane, R.; Dahl, S.; Skjøth-Rasmussen, M. S.; Jensen, A. D. Catalytic steam reforming of bio-

oil. Int. J. Hydrogen Energ. 2012, 37, 6447–6472. 7

Haryanto, A.; Fernando, S.; Murali, N.; Adhikari, S. Current status of hydrogen production

techniques by steam reforming of ethanol: a review. Energy Fuels 2005, 19, 2098–2106. 8

Marquevich, M.; Czernik, S.; Chornet E.; Montané, D. Hydrogen from biomass: steam

reforming of model compounds of fast-pyrolysis oil. EnergyFuel 1999, 13, 1160–1166.


29


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

9

Page 30 of 43

Vispute, T. P; Huber, G. W. Production of hydrogen, alkanes and polyols by aqueous phase

processing of wood-derived pyrolysis oils. Green Chem. 2009, 11, 1433–1445. 10

Czernik, S.; French, R.; Feik, C.; Chornet, E. Hydrogen by catalytic steam reforming of liquid

byproducts from biomass thermoconversion processes. Ind. Eng. Chem. Res. 2002, 41, 4209– 4215. 11

Ni, M.; Leung, D. Y. C.; Leung, M. K. H. A review on reforming bio-ethanol for hydrogen

production. Int. J. Hydrogen Energ. 2007, 32, 3238–3247 12

Haryanto, A.; Fernando, S.; Murali, N.; Adhikari, S. Current status of hydrogen production

techniques by steam reforming of ethanol: a review. EnergyFuels 2005, 19, 2098–2106. 13

Contreras, J. L.; Salmones, J.; Colín-Luna, J. A.; Nuño, L.; Quintana, B.; Córdova, I.; Zeifert,

B.; Tapia, C.; Fuentes, G. A. Catalysts for H2 production using the ethanol steam reforming (a review). Int. J. Hydrogen Energ. 2014, 39,18835–18853. 14

Wei, Z.; Sun, J.; Li, Y.; Datye, A. K.; Wang, Y. Bimetallic catalysts for hydrogen generation.

Chem. Soc. Rev. 2012, 41, 7994-8008. 15

Zhang, H.; Sun, J.; Dagle, V. L.; Halevi, B.; Datye, A. K.; Wang, Y. Influence of ZnO facets

on Pd/ZnO catalysts for methanol steam reforming. ACS Catal. 2014, 4, 2379–2386. 16

Davidson, S. D.; Zhang, H.; Sun, J.; Wang, Y. Supported metal catalysts for alcohol/sugar

alcohol steam reforming. Dalton T. 2014, 43, 11782–11802. 17

Schwengber C. A.; Alves H. J.; Schaffner, R. A.; da Silva, F. A.; Sequinel, R.; Bach, V. R.;

Ferracin, R. J. Overview of glycerol reforming for hydrogen production. Renew. Sust. Energ.


30

Page 31 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Rev. 2016, 58, 259-266. 18

Davda R. R.; Shabaker J. W.; Huber G. W.; Cortright R. D.; Dumesic J. A. A review of

catalytic issues and process conditions for renewable hydrogen and alkanes by aqueous-phase reforming of oxygenated hydrocarbons over supported metal catalysts. Appl. Catal., B 2005, 56, 171–186. 19

Palmeri, N.; Chiodo, V.; Freni, S.; Frusteri, F.; Bart, J. C. J.; Cavallaro, S. Hydrogen from

oxygenated solvents by steam reforming on Ni/Al2O3 catalyst. Int. J. Hydrogen Energ. 2008, 33, 6627−6634. 20

Gong, F.; Ye, T.; Yuan, L.; Kan, T.; Torimoto Y.; Yamamoto, M.; Li, Q. Direct reduction of

iron oxides based on steam reforming of bio-oil: a highly efficient approach for production of DRI from bio-oil and iron ores. Green Chem. 2009, 11, 2001–2012. 21

Kechagiopoulos, P. N.; Voutetakis, S. S.; Lemonidou, A. A.; Vasalos, I. A. Hydrogen

production via steam reforming of the aqueous phase of bio-oil in a fixed bed reactor. Energy Fuels 2006, 20, 2155-2163. 22

Gollakota, A. R. K.; Reddy, M.; Subramanyam, M. D.; Kishore, N. A review on the

upgradation techniques of pyrolysis oil. Renew. Sust. Energ. Rev. 2016, 58, 1543–1568. 23

Montero, Ca.; Oar-Arteta, L.; Remiro, A.; Arandia, A.; Bilbao, J.; Gayubo, A. G.

Thermodynamic comparison between bio-oil and ethanol steam reforming. Int. J. Hydrogen Energ. 2015, 40, 15963-15971. 24

Sohn, H.; Ozkan, U. S. Cobalt-based catalysts for ethanol steam reforming: an overview.

Energy Fuels 2016, 30, 5309–5322.


31


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

25

Page 32 of 43

Sun, J.; Karim, A. M.; Mei, D.; Engelhard, M.; Bao, X.; Wang, Y. New insights into reaction

mechanisms of ethanol steam reforming on Co–ZrO2. Appl. Catal., B 2015, 162, 141–148. 26

Bossola, F.; Evangelisti, C.; Allieta, M.; Psaro, R.; Recchia, S.; Santo, V. D. Well-formed,

size-controlled ruthenium nanoparticles active and stable for acetic acid steam reforming. Appl. Catal., B 2016, 181, 599–611. 27

Braga, A. H.; Sodré, E. R.; Santos, J. B. O.; de Paula Marques, C. M.; Bueno, J. M. C. Steam

reforming of acetone over Ni- and Co-based catalysts: effect of the composition of reactants and catalysts on reaction pathways. Appl. Catal., B 2016, 195, 16–28. 28

Garbarino, G.; Wang, C.; Valsamakis, I.; Chitsazan, S.; Riani, P.; Finocchio, E.; Flytzani-

Stephanopoulos, M.; Busca, G. A study of Ni/Al2O3 and Ni–La/Al2O3 catalysts for the steam reforming of ethanol and phenol. Appl. Catal., B 2015, 174–175: 21–34 29

Xing, R.; Dagle, V. L.; Flake, M.; Kovarik, L.; Albrecht, K. O.; Deshmane, C.; Dagle, R. A.

Steam reforming of fast pyrolysis-derived aqueous phase oxygenates over Co, Ni, and Rh metals supported on MgAl2O4. Catal. Today 2016, 269, 166–174. 30

Bartholomew, C. H. Carbon deposition in steam reforming and methanation. Catal. Rev. Sci.

Eng. 1982, 24, 67-112. 31

Trane-Restrup, R.; Jensen, A. D. Steam reforming of cyclic model compounds of bio-oil over

Ni-based catalysts: Product distribution and carbon formation. Appl. Catal., B 2015, 165,117– 127.


32

Page 33 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


32

Rostmp-Nielsen, J. R.; Trimm, D. L. Mechanisms of carbon formation on nickel-containing

catalyst. J. Catal. 1977, 48, 155-165. 33

Trimm, D. L. The formation and removal of coke from nickel catalyst. Catal. Rev. Sci. Eng.

1977, 16, 155-189. 34

Domine, M. E.; Iojoiu, E. E.; Davidian, T.; Guilhaume, N.; Mirodatos, C. Hydrogen

production from biomass-derived oil over monolithic Pt- and Rh-based catalysts using steam reforming and sequential cracking processes. Catal. Today 2008, 133–135, 565–573. 35

Rioche, C.; Kulkarni, S.; Meunier, F. C.; Breen, J. P.; Burch, R. Steam reforming of model

compounds and fast pyrolysis bio-oil on supported noble metal catalysts. Appl. Catal., B 2005, 61,130–139. 36

Panagiotopoulou, P.; Kondarides, D. I. Effect of the nature of the support on the catalytic

performance of noble metal catalysts for the water–gas shift reaction. Catal. Today 2006,112, 49–52. 37

Quan, C.; Xu, S.; Zhou, C. Steam reforming of bio-oil from coconut shell pyrolysis over

Fe/olivine

catalyst.

Energ.

Convers.

Manage.

2016,

in

press,

DOI:

http://dx.doi.org/10.1016/j.enconman.2016.04.024 38

Marquevich, M.; Czernik, S.; Chornet, E.; Montane, D. Hydrogen from biomass: steam

reforming of model compounds of fast-pyrolysis oil. Energy Fuels 1999, 13, 1160–1166. 39

Takanabe. K.; Aika. K.; Seshan, K.; Lefferts, L. Sustainable hydrogen from bio-oil-Steam

reforming of acetic acid as a model oxygenate. J. Catal. 2004, 227, 101–108.


33


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

40

Page 34 of 43

Pastor-Pérez, L.; Buitrago-Sierra, R.; Sepú lveda-Escribano, A. CeO2-promoted Ni/activated

carbon catalysts for the water gas shift (WGS) reaction. Int. J. Hydrogen Energ. 2014, 39, 17589–17599. 41

Ang, M. L.; Oemar, U.; Kathiraser, Y.; Saw, E. T.; Lew, C. H. K.; Du, Y.; Borgn, A.; Kawi, S.

High-temperature water–gas shift reaction over Ni/xK/CeO2 catalysts: Suppression of methanation via formation of bridging carbonyls. J. Catal. 2015, 329, 130–143. 42

Fornasiero, P.; Dimonte, R.; Rao, G. R.; Kaspar, J.; Meriani, S.; Trovarelli, A.; Graziani, M.

Rh-loaded CeO2-ZrO2 solid-solutions as highly efficient oxygen exchangers: dependence of the reduction behavior and the oxygen storage capacity on the structural-properties. J. Catal. 1995, 151, 168–177 43

Yan, C.; Cheng, F.; Hu, R. Hydrogen production from catalytic steam reforming of bio-oil

aqueous fraction over Ni/CeO2-ZrO2 catalysts. Int. J. Hydrogen Energ. 2010, 35, 11693–11699. 44

Qiu, S.; Gong, L.; Liu, L.; Hong, C.; Yuan, L.; Li, Q. Hydrogen production by low-

temperature steam reforming of bio-oil over Ni/HZSM-5 catalyst. Chin. J. Chem. Phy. 2011, 24, 211–217. 45

Wang, L.; Murata, K.; Inaba, M. Development of novel highly active and sulphur-tolerant

catalysts for steam reforming of liquid hydrocarbons to produce hydrogen. Appl. Catal., A 2004, 257, 43–47.


34

Page 35 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


46

Hou, T.; Yuan, L.; Ye, T.; Gong, L.; Tu, J.; Yamamoto, M.; Torimoto, Y.; Li, Q. Hydrogen

production by low-temperature reforming of organic compounds in bio-oil over a CNTpromoting Ni catalyst. Int. J. Hydrogen Energ. 2009, 34, 9095–9107. 47

Rodriguez, N. M.; Kim, M. S.; Terry, R.; Baker, K. Carbon nanofibers–a unique catalyst

support medium. J. Phys. Chem.1994, 98, 13108–13111. 48

Ouyang, M.; Huang, J. L.; Lieber, C. M. Fundamental electronic properties and applications of

single-walled carbon nanotubes. Accounts chem. Res. 2002, 35, 1018–1025. 49

Leclercq, G.; Leclercq, L.; Bouleau, L. M.; Pietrzyk, S.; Maurel, R. Hydrogenolysis of

saturated hydrocarbons: IV. kinetics of the hydrogenolysis of ethane, propane, butane, and isobutane over nickel. J. Catal. 1984, 88, 8–17. 50

Andersson, M. P.; Abild-Pedersen, F.; Remediakis, I. N.; Bligaard, T.; Jones, G.; Engbæk, J.;

Lytken, O.; Horch, S.; Nielsen, J. H.; Sehested, J.; Rostrup-Nielsen, J. R.; Nørskov, J. K.; Chorkendorff. I. Structure sensitivity of the methanation reaction: H2-induced CO dissociation on nickel surfaces. J. Catal. 2008, 255, 6–19. 51

Ang, M. L.; Oemar, U.; Kathiraser, Y.; Saw, E. T.; Lew, C. H. K.; Du, Y.; Borgna, A.; Kawi,

S. High-temperature water–gas shift reac tion over Ni/xK/CeO2 catalysts: suppression of methanation via formation of bridging carbonyls. J. Catal. 2015, 329, 130–143. 52

Sinfelt, J. H. Specificity in catalytic hydrogenolysis by metals. Adv. Catal. 1973, 23, 91-119.

53

Grenoble, D. C.; Estadt, M. M.; Ollis, D. F. The chemistry and catalysis of the water gas shift

reaction: 1.the kinetics over supported metal catalysts. J. Catal. 1981, 67, 90-102.


35


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 43

54

Mills, G. A.; Steffgen, F. W. Catalytic methanation. Catal. Rev. Sci. Eng. 1974, 8, 59-210.

55

Vizcaíno, A. J.; Carrero, A.; Calles, J. A. Hydrogen production by ethanol steam reforming

over Cu–Ni supported catalysts. Int. J. Hydrogen Energ. 2007, 32, 1450–1461. 56

Chen. L.; Lin, S. D. The ethanol steam reforming over Cu-Ni/SiO2 catalysts: Effect of Cu/Ni

ratio. Appl. Catal., B 2011,106, 639–649. 57

Santo, V. D.; Gallo, A.; Naldoni, A.; Guidotti, M.; Psaro, R. Bimetallic heterogeneous

catalysts for hydrogen production. Catal. Today 2012, 197,190– 205 58

Zhang, F.; Wang, N.; Yang, L.; Li, M.; Huang, L. Ni-Co bimetallic MgO-based catalysts for

hydrogen production via steam reforming of acetic acid from bio-oil. Int. J. Hydrogen Energ. 2014, 39,18688-18694. 59

Huang, T.; Yu, T.; Jhao, S. Weighting variation of water-gas shift in steam reforming of

methane over supported Ni and Ni-Cu catalysts. Ind. Eng. Chem. Res. 2006, 45,150-156. 60

Lin, J.; Biswas, P.; Guliants, V. V.; Misture, S. Hydrogen production by water–gas shift

reaction over bimetallic Cu–Ni catalysts supported on La-doped mesoporous ceria. Appl. Catal, A 2010, 387, 87–94. 61

Gan, L.; Tian, R.; Yang, X.; Lu, H.; Zhao, Y. Catalytic reactivity of CuNi alloys toward H2O

and CO dissociation for an efficient water-gas shift: A DFT study. J. Phys. Chem., C 2012, 116, 745–752.


36

Page 37 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


62

Saw, E. T.; Oemar, U.; Tan, X. R.; Dub, Y.; Borgna, A.; Hidajat, K.; Kawi, S. Bimetallic Ni–

Cu catalyst supported on CeO2 for high-temperature water–gas shift reaction: Methane suppression via enhanced CO adsorption. J. Catal. 2014, 314, 32–46. 63

Trimm, D. L. Catalysts for the control of coking during steam reforming. Catal.Today 1999,

49, 3-10. 64

Wang, Z.; Wang, C.; Chen, S.; Liu. Y. Co–Ni bimetal catalyst supported on perovskite-type

oxide for steam reforming of ethanol to produce hydrogen. Int. J. Hydrogen Energ. 2014, 39, 5644-5652. 65

Remón, J.; Medrano, J. A.; Bimbela, F.; García, L.; Arauzo, J. Ni/Al–Mg–O solids modified

with Co or Cu for the catalytic steam reforming of bio-oil. Appl. Catal., B 2013,132– 133, 433– 444 66

Zhang, Y.; Li, W.; Zhang, S.; Xu, Q.; Yan, Y. Steam reforming of bio-oil for hydrogen

production: effect of Ni-Co bimetallic catalysts. Chem. Eng. Technol. 2012, 35, 302–308. 67

Hu, X.; Lu, G. Investigation of steam reforming of acetic acid to hydrogen over Ni–Co metal

catalyst. J. Mol. Catal., A 2007,261, 43–48. 68

Zhang, Y. H.; Li, W. Z.; Zhang, S. P. Hydrogen production by the catalytic reforming of

volatile from biomass pyrolysis over a bimetallic catalyst. Energ. Source, Part A, 2013, 35, 1975–1982.


37


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

69

Page 38 of 43

Xie, H.; Yu, Q.; Yao, X.; Duan, W.; Zuo, Z.; Qin, Q. Hydrogen production via steam

reforming of bio-oil model compounds over supported nickel catalysts. J. Energ. Chem. 2015, 24, 299–308. 70

Salehi, E.; Azad, F. S.; Harding, T.; Abedi, J. Production of hydrogen by steam reforming of

bio-oil over Ni/Al2O3 catalysts: effect of addition of promoter and preparation procedure. Fuel Process. Technol. 2011,92, 2203–2210. 71

Valle, B.; Remiro, A.; Aguayo, A. T.; Bilbao, J.; Gayubo, A. G. Catalysts of Ni/α-Al2O3 and

Ni/La2O3-αAl2O3 for hydrogen production by steam reforming of bio-oil aqueous fraction with pyrolytic lignin retention. Int. J. Hydrogen Energ. 2013, 38, 1307–1318. 72

Medrano, J. A.; Oliva, M.; Ruiz, J.; García, L.; Arauzo, J. Hydrogen from aqueous fraction of

biomass pyrolysis liquids by catalytic steam reforming in fluidized bed. Energy 2011, 36, 2215– 2224. 73

Lan, P.; Xu, Q.; Zhou, M.; Lan, L.; Zhang, S.; Yan, Y. Catalytic steam reforming of fast

pyrolysis bio-oil in fixed bed and fluidized bed reactors. Chem. Eng. Technol. 2010, 33, 2021– 2028. 74

Fu, P.; Yi, W.; Li, Z.; Bai, X.; Zhang, A.; Li, Y.; Li, Z. Investigation on hydrogen production

by catalytic steam reforming of maize stalk fast pyrolysis bio-oil. Int. J. Hydrogen Energ. 2014, 39, 13962–13971.


38

Page 39 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


75

Yuan, L.; Ding, F.; Yao, J.; Chen, X.; Liu, W.; Wu, J.; Gong, F.; Li, Q. Design of multiple

metal doped Ni based catalyst for hydrogen generation from bio-oil reforming at mildtemperature. Chin. J. Chem. Phys. 2013, 26, 109–120. 76

Basagiannis, A. C.; Verykios, X. E. Steam reforming of the aqueous fraction of bio-oil over

structured Ru/MgO/Al2O3 catalysts. Catal. Today 2007, 127, 256–264. 77

Garcia, L.; French, R.; Czernik, S.; Chornet, E. Catalytic steam reforming of bio-oils for the

production of hydrogen: effects of catalyst composition. Appl. Catal., A 2000, 201, 225–239. 78

Valle, B.; Aramburu, B.; Remiro, A.; Bilbao, J.; Gayubo, A. G. Effect of calcination/reduction

conditions of Ni/La2O3–α-Al2O3 catalyst on its activity and stability for hydrogen production by steam reforming of raw bio-oil/ethanol. Appl. Catal., B 2014,147, 402– 410. 79

Sengupta, P.; Khan, A.; Zahid, M. A.; Ibrahim, H.; Idem, R. Evaluation of the catalytic

activity of various 5Ni/Ce0.5Zr0.33M0.17O2 ‑ δ catalysts for hydrogen production by the steam reforming of a mixture of oxygenated hydrocarbons. Energy Fuels 2012 26, 816−828. 80

Polychronopoulou, K.; Fierro, J. L. G.; Efstathiou, A. M. The phenol steam reforming reaction

over MgO-based supported Rh catalysts. J. Catal. 2004, 228, 417–432. 81

Sun, J.; Mei, D.; Karim, A. M.; Datye, A. K.; Wang, Y. Minimizing the formation of coke and

methane on Co nanoparticles in steam reforming of biomass-derived oxygenates. ChemCatChem 2013, 5, 1299–1303. 82

Llorca, J.; Homs, N.; Sales, J.; de la Piscina, P. R. Efficient production of hydrogen over

supported cobalt catalysts from ethanol steam reforming. J. Catal. 2002, 209, 306–317.


39


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

83

Page 40 of 43

Zhang, B. C.; Tang, X. L.; Li, Y.; Cai, W. J.; Xu, Y. D.; Shen, W. J. Steam reforming of bio-

ethanol for the production of hydrogen over ceria-supported Co, Ir and Ni catalysts. Catal. Commun. 2006, 7, 367–372. 84

Czernik S, Evans R, French R. Hydrogen from biomass-production by steam reforming of

biomass pyrolysis oil. Catal. Today 2007,129, 265–268. 85

Trimm, D. L. Coke formation and minimisation during steam reforming reactions. Catal.

Today 1997, 37, 233–238. 86

Chen, G.; Yao, J.; Liu, J.; Yan, B.; Shan, R. Biomass to hydrogen-rich syngas via catalytic

steam reforming of bio-oil. Renew. Energ. 2016,91, 315–322. 87

Wang, Z.; Pan, Y.; Dong, T.; Zhu, X.; Kan, T.; Yuan, L.; Torimoto, Y.; Sadakata, M.; Li, Q.

Production of hydrogen from catalytic steam reforming of bio-oil using C12A7-O--based catalysts. Appl. Catal., A 2007, 320, 24–34. 88

Mishra, A.; Prasad, R. Preparation and application of perovskite catalysts for diesel soot

emissions control: An overview. Catal. Rev. Sci. Eng. 2014, 56, 57-81. 89

Slagtern, Å.; Olsbye, U. Partial oxidation of methane to synthesis gas using La-M-O catalysts.

Appl. Catal.,A 1994, 110, 99–108. 90

Toniolo, F. S.; Magalhães, R. N. S. H.; Perez, C. A. C.; Schmal, M. Structural investigation of

LaCoO3 and LaCoCuO3 perovskite-type oxides and the effect of Cu on coke deposition in the partial oxidation of methane. Appl. Catal.,B 2012, 117– 118, 156– 166.


40

Page 41 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


91

Bhavani, A. G.; Kim, W. Y.; Lee, J. S. Barium substituted lanthanum manganite perovskite for

CO2 reforming of methane. ACS Catal.2013, 3, 1537−1544. 92

Hayashi, K.; Hirano, M.; Matsuishi, S.; Hosono, H.; Hayashi, K.; Hirano, M.; Matsuishi, S.;

Hosono, H. Microporous crystal 12CaO·7Al2O3 encaging abundant O- radicals. J. Am. Chem. Soc. 2002,124, 738–739. 93

Aika, K.; Lunsford, J. H. Surface reactions of oxygen ions. I. dehydrogenation of alkanes by

oxygen (1-) ions on magnesium oxide. J. Phys. Chem. 1977, 81, 1393–1398. 94

Xie, H.; Yu, Q.; Zuo, Z.; Han, Z.; Yao, X.; Qin, Q. Hydrogen production via sorption-

enhanced catalytic steam reforming of bio-oil. Int. J. Hydrogen Energ. 2016, 41, 2345–2353. 95

Udomchoke, T.; Wongsakulphasatch, S.; Kiatkittipong, W.; Arpornwichanop, A.; Khaodee,

W.; Powell, J.; Gong, J.; Assabumrungrat, S. Performance evaluation of sorption enhanced chemical-looping reforming for hydrogen production from biomass with modification of catalyst and sorbent regeneration. Chem. Eng. J. 2016, 303, 338–347. 96

Ye, T.; Yuan, L.; Chen, Y.; Kan, T.; Tu, J.; Zhu, X.; Torimoto, Y.; Yamamoto, M.; Li Q. High

efficient production of hydrogen from bio-oil using low-temperature electrochemical catalytic reforming approach over NiCuZn–Al2O3 catalyst. Catal. Lett. 2009, 127, 323–333.


41


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 43

Table of Contents (TOC) Graphics


42

Page 43 of 43


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment

43

Catalysts for Steam Reforming of Bio-oil: A Review - Industrial

Recommend Documents