Article pubs.acs.org/EF
Kinetics of Upgrading of Anisole with Hydrogen Catalyzed by Platinum Supported on Alumina Majid Saidi,† Parisa Rostami,† Hamid Reza Rahimpour,† Mohammad Ali Roshanfekr Fallah,† Mohammad Reza Rahimpour,*,†,‡ Bruce C. Gates,‡ and Sona Raeissi† †
Department of Chemical Engineering, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 71345, Iran Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616, United States
‡
S Supporting Information *
ABSTRACT: Kinetics of the reactions of anisole, a model compound representative of lignin-derived bio-oils, with H2, catalyzed by Pt/Al2O3, were investigated with a fixed-bed tubular microflow reactor at 573−673 K, 8−14 bar, and space velocities in the range of 3−240 (g of anisole)/(g of catalyst × h). Selectivity−conversion data were used as a basis to propose an approximate reaction network and estimate parameters in approximate rate equations. The reactions include the following: anisole conversion to phenol by hydrogenolysis, to 2-methylphenol by transalkylation, to 2,4-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,5,6tetramethylphenol by transalkylation and alkylation, to benzene by hydrodeoxygenation (HDO), and to hexamethylbenzene by HDO and alkylation. The primary reactions are satisfactorily represented with the approximation that each is first-order in the organic reactant. The apparent activation energy for the hydrogenolysis reaction that leads to phenol formation is approximately 25.3 kJ/mol, and the alkylation is the reaction class characterized by the highest apparent activation energy.
1. INTRODUCTION Bio-oils formed in pyrolysis processes are oxygen-rich1−3 and undergo a range of reactions during catalytic upgrading that distinguish them from fossil feedstocks.2,4−8 Because of the high polarities and hydrophilic nature of many bio-oil compounds, they are largely immiscible with hydrocarbon-derived fuels and not generally suited toward blending with them.6,9 Furthermore, the acidic character of bio-oil compounds such as carboxylic acids makes them highly corosive, particularly at high temperatures.4 Therefore, there is motivation to convert biooils to form compounds that are compatible with hydrocarbons. Such conversions take place in catalytic hydroprocessing. The main reaction pathways taking place in catalytic bio-oil hydroprocessing include hydrogenation of unsaturated compounds, hydrogenolysis to break C−O bonds, hydrocracking, and hydrodeoxygenation (HDO), accompanied by reactions including dehydration and decarboxylation.10,11 The literature of catalytic HDO12 includes reports of the conversion of whole bio-oil feedstocks,12,13 but it provides little insight into the chemistry of the HDO reactions, although it is evident14 that, because the Caromatic−O bond is stronger than the Cmethyl−O bond, demethylation by the rupture of the Cmethyl−O bond is typically favored kinetically. Investigations of the conversion of anisole (a compound representative of ligninderived bio-oils) with various catalysts have determined the catalyst functions responsible for specific reaction pathways; noble metals (e.g., platinum) catalyze phenol formation,15 and phenol is converted to benzene by breaking of the Caromatic−O bond and then to cyclohexane by hydrogenation of the aromatic ring, which is followed by hydrogenolysis of the Calicylic−O bond.16−18 Acid-catalyzed transalkylation was found to be kinetically significant with acidic catalyst components, such as γ-Al2O3, serving as the support;17 basic supports, such as MgO, are much less active for transalkylation.19 Results of catalytic © XXXX American Chemical Society
hydroprocessing of anisole with monometallic and bimetallic catalysts (e.g., Ni−Cu supported on δ-Al2O3)20 showed that the bimetallic catalyst was more active than just nickel. Nickelphosphide-containing catalysts, especially Ni2P/SiO2, were found to be more active than the conventional petroleum hydroprocessing catalyst NiMo/γ-Al2O3 for anisole conversion,14 and reducible oxide supports, such as TiO2 and CeO2, give high selectivities to aromatic products.6 In an investigation of anisole HDO catalyzed by mesoporous silica (SBA-15 and SBA-16)supported CoMoW, Loricera et al.21 demonstrated the advantages of high support surface areas and opportunities associated with varying the composition of the silica framework. Among the data characterizing HDO of bio-oils and their components, there is a lack of kinetics data. Because of the potential value of such information for preliminary scale-up of HDO processes, we set out to investigate the kinetics of catalytic anisole upgrading in the presence of H2; we report quantitative data characterizing the performance of an alumina-supported platinum catalyst (Pt/Al2O3) over a wide range of conditions.
2. EXPERIMENTAL SECTION 2.1. Reactor System. Catalytic reaction experiments were carried out with a fixed-bed tubular micro-flow reactor, with the catalyst bed mounted on a porous plate in the once-through reactor operated in down-flow mode. The flow system is represented schematically in Figure 1, and details are reported in Table 1. The liquid reactant was introduced into the reactor at room temperature by means of a high-pressure liquid chromatography (HPLC) pump manufactured by Gilson (model 307 HPLC). The liquids were introduced into the system through a low-dead-volume check valve. Received: February 6, 2015 Revised: June 25, 2015
A
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Figure 1. Schematic flow diagram of the fixed-bed tubular microflow reactor. 2.2. Product Analysis. Liquid products were analyzed with a Shimadzu QP 50/50 gas chromatograph−mass spectrometer (GC−MS) equipped with a SGE BPX5 capillary column (0.32 mm × 30 m × 0.25 μm) with helium (50 mL/min) used as the carrier gas. Chromatographic peaks were identified with individual compounds on the basis of mass spectra by matching to a Willy library. The identifications of the most abundant products were verified by comparison to the analyses of authentic standards purchased from Sigma-Aldrich; these standards were benzene, phenol, 2-methylphenol, 2,6-dimethylphenol, 2,4,6trimethylphenol, 2,3,5,6-tetramethylphenol, and hexamethylbenzene. Liquid products were quantified with a Bruker 450 GC equipped with a flame ionization detector. Samples were diluted with acetone to make them single-phase. The GC parameters were as follows: sample volume, 0.5 μL; injector temperature, 573 K; temperature program starting temperature, 323 K; and temperature ramp, 20 K/min, followed by a soak of 35 min. The GC was equipped with an OPTIMA 5 Macherey-Nagel capillary column (30 m × 0.25 mm, with a 0.25 μm film thickness). The detector temperature was set at 548 K, and the gas flow rates were 30 mL/min H2 and 300 mL/min air. The carrier gas flow rate was constant within the column, with a makeup flow to give a combined flow rate of 30 mL/min; the makeup gas was argon. 2.3. Catalyst Loading and Testing. Particles of the Pt/γ-Al2O3 catalyst (1 wt % Pt, Sigma-Aldrich) were placed on the porous plate in the reactor, mixed with about 2 g of inert, non-porous α-Al2O3 particles. The particle size range of the catalyst was less than 100 mesh. The catalyst in a mixture of equimolar N2 + H2 flowing at 20 L/h was heated to the desired reaction temperature and held at this temperature for 20 min prior to the start of liquid reactant flow (99.8% anisole, Merck). Fresh catalyst (0.25−2.00 g) was used for each experiment, and each experiment was typically run for 6 h of continuous operation. The catalytic conversion of anisole was carried out at temperatures in the range of 573−673 K and pressures in the range of 8−20 bar; the liquid anisole flow rates were in the range of 0.03−0.5 mL/min, and the N2 and H2 flow rates were each 20 L/h. The value of the weight hourly space velocity (WHSV) was in the range of 3−240 (g of anisole)/(g of catalyst × h), varied by changing the catalyst mass and liquid flow rates. 2.4. Determination of Mass Balance Closures. Anisole conversions were determined from the flow rate of liquid anisole to the reactor and the flow rates of the liquid condensate and gas product
Table 1. Specifications of Flow Reactor System component of the flow reactor system reactor
carrier gas reactant gas reactant liquid (vaporized in the reactor) catalyst
property/operating conditions 316-L stainless steel; length, 305 mm; inside diameter, 9 mm; outside diameter, 14.5 mm; operating temperature range, 573−673 K; operating pressure range, 8−20 bar N2; flow rate, 20 L/h H2; flow rate, 20 L/h anisole; flow rate range, 0.03−0.50 mL/min Pt/Al2O3; mass, 0.25−2.00 g
N2 was used as the carrier gas, and H2, when present as a reactant, was mixed into the carrier gas stream. Liquid and gas streams were introduced into a hot-box system that included an electric forcedconvection heater that held the components at a temperature of 453 K to avoid possible condensation of reactants or products in the equipment. Anisole and all of the other products are completely vaporized at the reactor conditions (Treactor = 573−673 K, and Thot box = 453 K). The feed vaporizer was present in this heated zone. Preheated liquid was vaporized, and the vapor stream merged with the gas feed stream and flowed to a six-port valve operated by a remote pneumatic control system, so that the feed stream could be directed to either the reactor or a bypass stream. The stream flowing to the reactor passed through 10 μm sintered 316-L stainless-steel filters at both the inlet and outlet of the reactor, thereby protecting the equipment from any catalyst fines that might have formed. At the reactor outlet, after passing through the six-port valve, the product stream flowed out of the hot box to a condenser, which operated at 275−280 K. A type-K thermocouple encased in a 1.5 mm diameter Inconel sheath was inserted axially through the upper end of the reactor and was in direct contact with a thermowell in the catalyst bed; this design allowed for the reading of reaction temperatures with response times of milliseconds. The reactor was housed in an insulated oven, and the entire system was contained within a hot box made of 304 stainless steel and containing an electric convection heater. Liquid product samples were collected periodically downstream of the condenser for analysis. B
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels streams from the condenser. The vapor pressures of anisole and the most abundant products at the outlet temperature of the condenser indicate that they were almost completely condensed.15 The mass flow rate of liquid anisole fed to the reactor in each operating period was measured by the volumetric flow and the density of the anisole (0.995 g/mL). Because the condenser did not drain perfectly, the mass of the condenser and its contents was measured before and after sample collection. The mass of condensed liquid formed in each operating period of 30 min was measured as the sum of the mass of liquid collected from the condenser and that accumulated in the condenser. Because a portion of the products was present in the gas phase, the mass flow rate of the product leaving the condenser in the gas phase was calculated by application of an Antoine vapor pressure correlation along with the measured volumetric flow rate of the gas stream.15 2.5. Data Analysis. Our main goal was to determine kinetics of the reactions of anisole with H2 in the absence of catalyst deactivation and to resolve and quantify the reaction network. Thus, experiments were carried out for short enough times on stream to provide data characterizing the reaction network and kinetics in the presence of fresh catalyst. Anisole conversion (X, calculated as a percentage) and selectivity to the various products i (Si) were calculated from the data as follows: X=
(moles of anisole)in − (moles of anisole)out × 100% (moles of anisole)in
(1)
Si =
molar flow rate of product i molar flow rate of anisole consumed
(2)
Figure 2. Conversion of anisole catalyzed by Pt/Al2O3 in a oncethrough flow reactor at WHSV = 3 (g of anisole)/(g of catalyst × h) as a function of TOS.
Also, conversions of anisole to species i (Xi) were calculated as the number of moles of anisole converted to species i divided by the total moles of anisole fed.
3. RESULTS 3.1. Products of Anisole Conversion in the Presence of H2. The major products of anisole upgrading identified by GC−MS were found to be benzene, phenol, 2-methylphenol, 2,6dimethylphenol, 2,4,6-trimethylphenol, 2,3,5,6-tetramethylphenol, and hexamethylbenzene. The corresponding conversions and selectivities were determined quantitatively. Trace products that were identified only qualitatively were toluene, o-xylene, p-xylene, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,6dimethylanisole, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2,3,4,6-tetramethylphenol, cyclohexane, methylcyclohexanone, and methylcyclohexane. The GC−MS analyses also gave evidence in the products of small amounts of methane, methanol, and water. Also, gas samples were taken online at approximately 30 min intervals to characterize the gas stream during most experiments. It contained mostly N2 (carrier gas), H2 (reactant), and methane, one of the reaction products. 3.2. Mass Balance Closures. The data reported in Table S-1 of the Supporting Information indicate that overall mass balance closures were, with the estimated error of ±5%, equal to 100%. 3.3. Anisole Conversion and Selectivity as a Function of Time on Stream (TOS). The conversion of anisole catalyzed by Pt/Al2O3 as a function of TOS at various temperatures and pressures is represented in Figure 2, and selectivity data are shown in Figure 3. The data demonstrate a slow catalyst deactivation and allow for straightforward extrapolation for determination of the performance of the undeactivated catalyst. The concentrations in the product stream of phenol derivatives remained almost unchanged with increasing TOS, but those of benzene and hexamethylbenzene decreased, indicating that the effect of catalyst deactivation on hydrogenolysis reactions was greater than that on transalkylation reactions. At each of the observed values of TOS, phenol was the most abundant product, and the selectivities for the formation of 2-methylphenol,
Figure 3. Selectivities for the formation of products as a function of TOS in anisole conversion with H2 catalyzed by Pt/Al2O3 at 623 K and 14 bar at WHSV = 3 (g of anisole)/(g of catalyst × h): (a) phenol, 2-methylphenol, and 2,6-dimethylphenol and (b) benzene, 2,4,6trimethylphenol, 2,3,5,6-terramethylphenol, and hexamethylphenol. C
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Figure 4. Selectivity for the formation of the following products in the conversion of anisole catalyzed by Pt/Al2O3 in the presence of H2 at T = 573 K and P = 14 bar. Data for each main product were fitted with a straight line and extrapolated to zero conversion; intercepts of regression lines significantly different from zero selectivity at zero conversion indicate primary products. Primary products in this case are (a) benzene and (b) phenol and 2-methylphenol; the plots with intercepts not significantly different from zero are considered to be evidence of higher-order products, in this case (c) 2,6-dimethylphenol and 2,4,6-trimethylphenol and (d) 2,3,5,6-tetramethylphenol and hexamethylbenzene.
indicate that benzene, phenol, and 2-methylphenol are primary products and that 2,6-dimethylphenol, 2,4,6-trimethylphenol, 2,3,5,6-tetramethylphenol, and hexamethylbenzene are higherorder products. The identifications of the primary and nonprimary products in the conversion of anisole catalyzed by Pt/Al2O3 at 573−673 K and 8−14 bar are consistent with those observed previously.15 3.5. Kinetics of Anisole Conversion to Primary Products. To determine initial rates of the individual reactions giving primary products, the data were plotted as conversion to each primary product as a function of the inverse space velocity. Results obtained at each of the three reaction temperatures are illustrated for phenol formation in Figure 5. These results are typical; the complete set of data for each of the primary products is shown in Figures S-3−S-5 of the Supporting Information. The data in each set fall near a straight line passing through the origin, and the slopes of these lines determine initial reaction rates, which are summarized in Table 2.
2,6-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,5,6tetramethylphenol were all greater than those of benzene and hexamethylbenzene. 3.4. Development of an Approximate Reaction Network. Figure 4 and Figures S-1 and S-2 of the Supporting Information show the selectivity for the formation of the main products in the conversion of anisole catalyzed by Pt/Al2O3 in the presence of H2 at 573−673 K. The data show that the selectivity for the formation of transalkylation products exceeds that for the formation of products of reactions involving breaking of C−O bonds.15,22,23 Extrapolation of the selectivity−conversion data to zero conversion determines which products are primary, those with non-zero intercepts. For extrapolation, the data characterizing each main product were fitted with a straight line. In the data analysis, t and p tests were carried out to investigate the statistical significance of the reported data. Details are given in the Supporting Information. The selectivity−conversion data D
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Table 2. Initial Rates of Formation of the Main Products rate (mol g−1 of catalyst h−1) product phenol 2-methylphenol 2,6-dimethylphenol 2,4,6-trimethylphenol 2,3,5,6-tetramethylphenol hexamethylbenzene
T = 673 K −3
2.29 × 10 3.41 × 10−3 1.92 × 10−3 9.13 × 10−4 6.01 × 10−4 2.75 × 10−4
T = 623 K −3
2.16 × 10 1.38 × 10−3 1.44 × 10−3 4.55 × 10−4 1.14 × 10−4 8.14 × 10−5
T = 573 K 1.35 × 10−3 6.6 × 10−4 5.78 × 10−4 2.25 × 10−4 3.88 × 10−5 2.03 × 10−5
products are presented in Figures S-6−S-8 of the Supporting Information. The plots of conversion to benzene as a function of the inverse space velocity under various conditions indicate that the formation of benzene is not a first-order reaction of anisole to give a primary product. The rate constants for the primary reactions determined from the data shown in the plots are summarized in Table 3. These rate constants were determined from the slopes of the lines representing conversion to each individual primary product as a function of the inverse space velocity (the slopes are the initial reaction rates) and the concentrations of anisole in the reactant vapor (at the temperature of the reaction). A partially quantified reaction network for anisole conversion including these rate constants is shown in Figure 7; the corresponding rate constants are summarized in Table 3. The pseudo-first-order rate constants of the primary reactions are shown in Figure 8. The slopes of these plots determine the activation energies of the primary reactions, as summarized in Table 3. Phenol is the product formed at the highest rate from anisole at each temperature; the rate constant for the formation of 2-methylphenol at 573 K is approximately half of the value of the rate constant for the formation of phenol. The effect of the pressure on the anisole upgrading process is shown in Figures 9 and 10. The data of Figure 9 show that the anisole conversion at 623 K and WHSV = 3 (g of anisole)/(g of catalyst × h) decreased from 50 to 30% as the pressure increased from 8 to 14 bar, but further increases in pressure barely influenced the conversion. The effect of the pressure on selectivity for the formation of various products is shown in Figure 10. Increasing the pressure increases the selectivity for the formation of benzene and phenol, but it decreases the selectivity for the formation of the other products.
4. DISCUSSION The data presented here provide one of the most detailed quantitative characterizations of catalytic hydrodeoxygenation in terms of the reaction network and kinetics. The reaction network represented in Figure 7 is for the most part consistent with the results of numerous researchers.17,21,24−26 The main reaction routes are hydrogenation, hydrogenolysis, hydrodeoxygenation, and transalkylation. Benzene, phenol, hexamethylbenzene, 2-methylphenol, 2,6-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,5,6-tetramethylphenol are identified as the major products, and no methylanisole, cyclohexanol, or cyclohexanone was observed. The data are consistent with the expectation15 that the kinetically most significant reactions proceed by hydrogenolysis of the aromatic carbon−oxygen bond to form phenol as a primary product, followed by phenol conversion to 2methylphenol, 2,6-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,5,6-tetrmethylphenol via transalkylation reactions. On the basis of earlier results,15 we infer that C−H bond breaking (hydrogenolysis or demethylation) takes place on the
Figure 5. Conversion to phenol in the presence of H2 at 14 bar and (a) 573 K, (b) 623 K, and (c) 673 K. The term Xi represents the conversion to phenol.
To determine information about the kinetics of the primary reactions, the conversion data were plotted as (1 − Xi) (where Xi is the conversion of anisole to species (i) on a logarithmic scale versus inverse space velocity. Linear plots indicate pseudo-firstorder reactions to give the individual products, with the slopes of the straight lines determining the pseudo-first-order rate constants. Data obtained at various temperatures are shown for phenol formation in Figure 6. The complete data for each of the E
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Table 3. Pseudo-first-Order Rate Constants and Apparent Activation Energies for Reactions in the Network Representing Anisole Conversion in the Presence of H2 and a Pt/Al2O3 Catalyst reaction
T (K)
ki (L g−1 of catalyst h−1)
573 623 673 573 623 673 573 623 673 573 623 673 573 623 673 573 623 673
12.8 19.2 28.3 6.9 12.8 39.6 5.8 13.7 22.3 2.4 3.5 8.5 0.3 0.9 5.5 0.2 0.5 2.1
product of reaction
1
phenol
2
2-methylphenol
3
2,6-dimethylphenol
4
2,4,6-trimethylphenol
5
2,3,5,6-tetramethylphenol
6
hexamethylbenzene
activation energy, E (kJ/mol) 25.3
55.4
43.4
40.2
93.6
70.1
Figure 7. Approximate reaction network for the conversion of anisole in the presence of H2 catalyzed by Pt/Al2O3 at 573−673 K and 8−14 bar. The rate constants for the primary reactions at each of the three temperatures are summarized in Table 3.
According to this reaction network, most of the products in the conversion of anisole, including 2,6-dimethylphenol, 2,4,6trimethylphenol, and 2,3,5,6-tetramethylphenol, are formed in sequential transalkylation reactions and are not primary products. Although the data are not sufficient to determine kinetics of the formation of the non-primary products with much accuracy (those rate constants lack fundamental meaning), they show that the scission of the Cmethyl−O bond is faster that the scission of the Caromatic−O bond, so that benzene formation via the latter route is dominant. In this pathway, demethylation via scission of the Cmethyl−O bond occurs first, giving phenol as a primary intermediate product, and then phenol is converted to benzene via the direct hydrogenolysis of the Caromatic−O bond. Also, for 2-methylphenol, there are two formation pathways, transalkylation of anisole as a primary product or alkylation of phenol as a secondary product.
Figure 6. Conversion of anisole to phenol in the presence of H2 at each of the three reaction temperatures, where Xi is conversion of anisole to product i on a logarithmic scale.
platinum surface, forming phenol. Another class of bondbreaking reaction involves direct deoxygenation, leading to methanol and benzene. With bifunctional catalysts, such as our Pt/Al2O3, some reactions are catalyzed by the acidic support, specifically, transalkylation. F
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Figure 9. Conversion of anisole in the presence of H2 as a function of the pressure at 623 K and WHSV = 3 (g of anisole)/(g of catalyst × h).
Figure 8. Rate constants for the formation of some primary and some non-primary products in the upgrading process of anisole in the presence of H2 catalyzed by Pt/Al2O3 at 573−673 K and 8−14 bar.
Results that we suggest may be of value for the prediction of conversion of whole bio-oils include the following: The data summarized in Table 3 show that, among the various reactions, transalkylation is characterized by the highest activation energy. If this result is general, selectivities for oxygen removal will be favored by operation at lower temperatures. Furthermore, increasing the pressure improves the selectivity for hydrodeoxygenated products, and both lower temperatures and higher H2 partial pressures are expected to retard catalyst deactivation, resulting from coke formation. Furthermore, if oxygen removal is the principal processing goal, it may be advantageous to replace
Figure 10. Pressure dependence of selectivity for the formation of the main products of the reaction of anisole with H2 at 623 K and WHSV = 3 (g of anisole)/(g of catalyst × h). The anisole conversion at 8, 14, and 20 bar is 48, 30, and 29%, respectively.
acidic supports, such as alumina, with basic supports, such as magnesia, to minimize dealkylation. We suggest that the kinetics parameters reported for the various reactions of anisole reported G
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
(4) Busetto, L.; Fabbri, D.; Mazzoni, R.; Salmi, M.; Torri, C.; Zanotti, V. Fuel 2011, 90, 1197−1207. (5) Bertero, M.; de la Puente, G.; Sedran, U. Fuel 2012, 95, 263−271. (6) Yang, Y.; Ochoa-Hernández, C.; de la Pẽna O’Shea, V. A.; Pizarro, P.; Coronado, J. M.; Serrano, D. P. Appl. Catal., B 2014, 145, 91−100. (7) Biradar, C. H.; Subramanian, K. A.; Dastidar, M. G. Fuel 2014, 119, 81−89. (8) Xiu, Sh.; Shahbazi, A. Renewable Sustainable Energy Rev. 2012, 16, 4406−4414. (9) Majhi, A.; Sharma, Y. K.; Bal, R.; Behera, B.; Kumar. Fuel 2013, 107, 131−137. (10) Gunawan, R.; Li, X.; Lievens, C.; Gholizadeh, M.; Chaiwat, W.; Hu, X.; Mourant, D.; Bromly, J.; Li, Ch.-Z. Fuel 2013, 111, 709−717. (11) Leng, Sh.; Wang, X.; He, X.; Liu, L.; Liu, Y.; Zhong, X.; Zhuang, G.; Wang, J. Catal. Commun. 2013, 41, 34−37. (12) Saidi, M.; Samimi, F.; Karimipourfard, D.; Nimmanwudipong, T.; Gates, B. C.; Rahimpour, M. R. Energy Environ. Sci. 2014, 7, 103−129. (13) Saidi, M.; Rahimpour, M. R.; Raeissi, S. Energy Fuels 2015, 29, 3335−3344. (14) Li, K.; Wang, R.; Chen, J. Energy Fuels 2011, 25, 854−863. (15) Runnebaum, R. C.; Lobo-Lapidus, R. J.; Nimmanwudipong, T.; Block, D. E.; Gates, B. C. Energy Fuels 2011, 25, 4776−4785. (16) Senol, O. I.; Ryymin, E.-M.; Viljava, T.-R.; Krause, A. O. I.; Mol, J. J. Mol. Catal. A: Chem. 2007, 277, 107−112. (17) Zhu, X.; Lobban, L. L.; Mallinson, R. G.; Resasco, D. E. J. Catal. 2011, 281, 21−29. (18) Huuska, M. K. Polyhedron 1986, 5, 233−236. (19) Nimmanwudipong, T.; Aydin, C.; Lu, J.; Runnebaum, R. C.; Brodwater, K. C.; Browning, N. D.; Block, D. E.; Gates, B. C. Catal. Lett. 2012, 142, 1190−1196. (20) Ardiyanti, A. R.; Khromova, S. A.; Venderbosch, R. H.; Yakovlev, V. A.; Heeres, H. J. Appl. Catal., B 2012, 117−118, 105−117. (21) Loricera, C. V.; Pawelec, B.; Infantes-Molina, A.; Alvarez-Galvan, M. C.; Huirache-Acũna, R.; Nava, R.; Fierro, J. L. G. Catal. Today 2011, 172, 103−110. (22) Bhore, N. A.; Klein, M. T.; Bischoff, K. B. Ind. Eng. Chem. Res. 1990, 29, 313−316. (23) Bhore, N. A.; Klein, M. T.; Bischoff, K. B. Chem. Eng. Sci. 1990, 45, 2109−2116. (24) Runnebaum, R. C.; Nimmanwudipong, T.; Block, D. E.; Gates, B. C. Catal. Lett. 2011, 141, 817−820. (25) Gonzalez-Borja, M. A.; Resasco, D. E. Energy Fuels 2011, 25, 4155−4162. (26) Mu, W.; Ben, H.; Ragauskas, A.; Deng, Y. BioEnergy Res. 2013, 6, 1183−1204.
here may be useful for rough estimates of the conversion of whole bio-oil feedstocks, with the rate constants and activation energies of the reactions of the various functional groups (e.g., methoxy groups) represented as the values reported for anisole.
5. CONCLUSION An approximate reaction network for the catalytic conversion of anisole catalyzed by Pt/Al2O3 is reported, including values of rate constants and activation energies for the formation of primary products. Phenol is the principal primary product at 573−673 K and 8−14 bar. Other primary products are formed in transalkylation and hydrogenolysis reactions, with the former catalyzed by the acidic support and the latter catalyzed by platinum. It was observed that, at WHSV = 3 (g of anisole)/(g of catalyst × h), the anisole conversion increased from 12 to 63% as the temperature increased from 573 to 673 K and decreased from 50 to 30% as the pressure increased from 8 to 14 bar at 350 K. We recognize that investigations of the kinetics of reactions of compounds, such as anisole, to provide a quantitative foundation for estimates needed for lignin-derived bio-oils upgrading are still so preliminary that much more information is needed.
■
ASSOCIATED CONTENT
* Supporting Information S
Statistical analysis, overall mass balance closure data (Table S-1), selectivity for the formation of the following products in the conversion of anisole catalyzed by Pt/Al2O3 in the presence of H2 at temperature T = 623 K and pressure P = 14 bar ( Figure S-1), selectivity for the formation of the following products in the conversion of anisole catalyzed by Pt/Al2O3 in the presence of H2 at temperature T = 673 K and pressure P = 14 bar (Figure S-2), plot of conversion to each of the main products as a function of the inverse space velocity at T = 573 K and P = 14 bar (Figure S-3), conversion to each of the main products as a function of the inverse space velocity at T = 623 K and P = 14 bar (Figure S-4), plot of conversion to each of the main products as a function of the inverse space velocity at T = 673 K and P = 14 bar (Figure S-5), conversion of anisole in the presence of H2 at T = 573 K and P = 14 bar to give the main products, where Xi is the conversion of anisole to product i on a logarithmic scale (Figure S-6), conversion of anisole in the presence of H2 at T = 623 K and P = 14 bar to give the main products, where Xi is the conversion of anisole to product i on a logarithmic scale (Figure S-7), and conversion of anisole in the presence of H2 at T = 673 K and P = 14 bar to give the main products, where Xi is the conversion of anisole to product i on a logarithmic scale (Figure S-8) (PDF). The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.5b00297.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
REFERENCES
(1) Saidi, M.; Rostami, P.; Rahimpour, M. R.; Gates, B. C.; Raeissi, S. Energy Fuels 2015, 29, 191−199. (2) Dang, Q.; Luo, Z.; Zhang, J.; Wang, J.; Chen, W.; Yang, Y. Fuel 2013, 103, 683−692. (3) Mohan, D.; Pittman, C. U.; Steele, P. H. Energy Fuels 2006, 20, 848−889. H
DOI: 10.1021/acs.energyfuels.5b00297 Energy Fuels XXXX, XXX, XXX−XXX
