Article pubs.acs.org/EF
Evaluate Impact of Catalyst Type on Oil Yield and Hydrogen Consumption from Mild Hydrotreating Richard J. French,* James Stunkel, Stuart Black, Michele Myers, Matthew M. Yung, and Kristiina Iisa National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States S Supporting Information *
ABSTRACT: Bio-oil derived by fast pyrolysis of biomass represents a potentially attractive source of hydrocarbon transportation fuels. Raw bio-oil, however, is unsuitable for application as a fuel due primarily to high organic oxygen content, which imparts a number of undesirable properties including high acidity and low stability. These problems can be overcome by catalytic hydrodeoxygenation; however, removing oxygen to very low levels by hydrotreating carries a strong economic penalty. Mild hydrotreating (where moderate levels of deoxygenation take place) coupled with coprocessing in a petroleum refinery represents an alternative to deep hydrotreating which may improve the economics of manufacture of hydrocarbon transportation fuels from biomass. This study reports on the effect of catalyst type on the quality of bio-oil produced via mild hydrotreating in a semibatch reactor at three severities. Sulfided Ni−Mo/Al2O3, Pd/C(activated), Pd/char, Pt/char, and Ru/char were compared. Speciation of oxygen functional groups in distillate and bottom products was carried out, and the form of much of the organic oxygen was determined. These results show that a 55% conversion of the carbon in the biomass pyrolysis oil to a low-oxygen (5%), low-acid, volatile, hydrocarbon-miscible liquid product can be achieved. This was, however, possible only with the NiMo−S catalyst. The precious-metal catalysts while producing oil with acceptable carbon conversion, miscibility, and oxygen content did not convert enough acid to produce oil with acid numbers below 15. Water washing was successfully tested for removing residual acids. The various catalysts have different advantages, and using a different catalyst for the two stages of the process may provide the best processfor example ruthenium for minimizing coke during stabilization and nickel or platinum for deoxygenation.
■
volatile, and largely immiscible with hydrocarbons.5−8 Bio-oil can be converted to a gasoline- or diesel-like liquid by catalytic hydroprocessing using catalysts and conditions that are very similar to those used in petroleum hydrodesulfurization, hydrotreating, and hydrocracking processes. Elliott highlighted the history and current status of this technique.7 Fast pyrolysis oils coke severely in a single-stage hydrotreating process,6 and so a two-stage process was developed.9,10 In this improved process, the oil is stabilized at a lower temperature (150−280 °C) before it is fed to a high temperature reactor (350−400 °C) where the majority of the oxygen removal takes place. Standard petroleum-industry hydrotreating catalysts have been used including both sulfided nickel−molybdenum (NiMo−S) and cobalt−molybdenum (CoMo) on γ-alumina support. Hydrotreating followed by hydrocracking can be used to produce finished fuels. A technoeconomic analysis on the production of finished fuels showed the potential for producing the fuels at cost-competitive prices.11 The oil would be hydrotreated in two stages at temperatures of 240−370 °C and 2015−2500 psig pressure to produce hydrotreated oil containing 1.5% oxygen with a yield of 44%. Hydrogen consumption was assumed to be 5 wt % of the feed. This product oil would then be hydrocracked as necessary and separated into gasoline and diesel streams. While these projections are promising, other studies have concluded that
INTRODUCTION Concerns over global climate change and economic and sociopolitical issues associated with energy security and wealth transfer have highlighted the need to develop renewable and sustainable technologies for the manufacture of liquid transportation fuels. The Energy Independence and Security Act of 2007 (EISA) responded to these concerns by establishing goals for renewable fuels production including 36 billion gallons of renewable fuels in 2022 with 21 billion gallons of this amount advanced biofuels. Cellulosic-based transportation fuels must represent at least 16 billion gallons of the advanced biofuels.1,2 It is estimated that the United States alone can sustainably produce a billion tons of biomass per year that could be used for this purpose.3 Biomass-derived fuels can, in principle, be close to “carbon-neutral” where the carbon dioxide released from the process and final products is compensated for by the carbon captured in the next year’s crop. A recent standard (RFS2)4 requires renewable fuels production and use to substantially reduce emissions of greenhouse gases compared to conventional fuels. If biomass is heated rapidly (ΔT/Δt ≈ 1000 K/s) for short residence times (1−2 s) in the absence of oxygen to temperatures in the range of 400−650 °C in a process known as fast pyrolysis, a combustible liquid (bio-oil) retaining ca. 75% of the energy content of the feed material is produced in high yield. Though superficially resembling a heavy fuel oil, this liquid contains about 50% oxygen, 15−30% water, and has many undesirable physical and chemical properties when compared to petroleum liquids. Bio-oil is corrosive, only partly © 2014 American Chemical Society
Received: September 25, 2013 Revised: March 14, 2014 Published: April 1, 2014 3086
dx.doi.org/10.1021/ef4019349 | Energy Fuels 2014, 28, 3086−3095
Energy & Fuels
Article
°C), the Pd had higher activity than Pt but lower acid removal. Pt also gave a lower molar O/C (0.06).21 Precious metals are reported to favor initially hydrogenation of e.g. aromatic rings followed by deoxygenation, whereas traditional sulfides follow a direct deoxygenation route. This may lead to higher hydrogen consumption for precious metal catalysts.16,22 The objective of the current work was to further evaluate the impact of catalyst type - precious metals versus traditional sulfided NiMo catalyst - on mild hydrotreating. Bio-oil was hydrotreated in a semibatch reactor in the presence of precious metal catalysts at varying temperatures and pressures, and the results were compared to those of traditional sulfided NiMo catalysts. The aim was to produce oil suitable as refinery-ready intermediate at a carbon conversion of 55% or above. If we assume 62% carbon yield for pyrolysis12 this translates to overall carbon yield of 34% or above from biomass to hydrotreated oil. The oil quality criteria were good volatility (>90% volatile matter), low oxygen content ( Ru > Pd/C > NiMo−S. Thus, NiMo−S was the most active in reducing acids at low temperatures, which was reflected in the overall lowest acid content for this oil. The major oxygen compounds in the
a
A, B, C, and D denote the oils from the condensers in time order and Res the bottom residue. The miscibility was tested at 10:1 solvent:oil.
(phenols, alcohols, ethers, esters) must be present. A small peak at high pH was sometimes detected in the acid titrations, suggesting phenols, but satisfactory results were not obtained. Acids were not detected in the residue oil samples except with both Pd catalysts at low severity. Carbonyl from the residue samples was not measured because of possible acetone contamination. Carbon NMR and GC/MS were performed on many of the samples to better identify the oxygen species being produced. The 13C NMR results for the original oil and all residue samples are shown in Figure 6. In the original pyrolysis oil slightly over 50% of carbon was in oxygen-free bonds: approximately half of that in aliphatic C−C bonds and a similar fraction in aromatic C−C and C−H bonds. For oxygenated species, CO bonds (acids and carbonyls) were the most prevalent, followed by aliphatic C−O bonds (alcohols, esters, ethers), aromatic C−O bonds, and methoxy bonds. The residues show a significant decrease in oxygenated bonds with the highest fraction (∼10%) 3092
dx.doi.org/10.1021/ef4019349 | Energy Fuels 2014, 28, 3086−3095
Energy & Fuels
Article
refinement of this procedure may well produce an oil with the desired level of acidity. Analysis of Postreaction Catalysts. XRD of fresh and postreaction samples was performed, and the results are shown in Figure 8 with the main crystalline phases labeled. For each
Figure 7. C NMR of condensates for severe conditions compared to residual liquids.
condensates at high severity are phenols, though there are some carbonyls and esters as well. A mix of aromatics, alkanes, and cycloalkanes is also present. Selected samples were analyzed by GC/MS. The GC/MS indicated the presence of high levels of phenolic species at the low severity conditions with nonphenolic aromatics and cyclic alkanes at more severe conditions. The data tables (Supporting Information) show that many of these are double-ring cycloaliphatic compounds and that most of the aromatics have alkyl groups, mostly methyl. The titrations, GC/MS, and NMR are in reasonably good agreement and indicate similar trends. Each method has its strengths and weaknesses. Acids are known to be labile in the GC inlet, and the expected major acidacetic acidis known to elute too close to the solvent peak to be detected under these conditions. The NMR, though quantitative, is only about 80% accurate in assigning the correct functional group.26 Also, the aliphatic side chains appear as alkanes in the NMR but are counted as part of the aromatics in the GC/MS. The GC/MS, though very good for identifying individual compounds, is not quantitative without extensive calibrations, which were not done. Also, when a fit of 70% is indicated, it is likely that an exact match was not obtained but rather it is either a related compound or the GC peak is overlapped with another species. Reduction of Acid Content by Water Washing. The precious metal catalysts all produced oil with acidities that were higher than desired. Therefore, we tested water washing as a means to reduce the oil acidity. The results for condensates B and C for the experiment with the Pd catalyst at 400 °C final temperature are shown in Table 5. These condensates had very high acid numbers. The washing results show that there is a substantial improvement in the acidity with low loss of the organic phase. This is a promising improvement, and
Figure 8. XRD patterns of fresh and postreaction catalysts samples and crystalline phases: (a) fresh NiMo/Al2O3, (b) spent Ni/Mo/ Al2O3, (c) fresh Pd/activated-carbon, (d) spent Pd/activated-carbon, (e) fresh Pd/char, (f) spent Pd/char, (g) fresh Pt/char, (h) spent Pt/ char, (i) fresh Ru/char, (j) spent Ru/char. Abbreviated crystalline phases: Graphite (C), γ-Al2O3 (A).
fresh sample, the corresponding spent sample is shown immediately above it. All of the postreaction catalysts exhibited differences in crystallinity as compared to the fresh materials. The fresh Ni/Mo/Al2O3catalyst displayed only crystalline Al2O3 without any clear presence of metallic or oxide forms of Ni or Mo. The postreaction Ni/Mo/Al2O3 catalyst showed the presence of a mixed oxide phase (NiMO4) as well as Mo2C. The appearance of clear diffraction lines suggests a growth in the crystallite size in addition to any phase changes. The diffraction line near 49° 2θ could not be unambiguously assigned, but it is consistent with Ni3S2. On the Pd/activated-carbon catalyst, the fresh material shows graphitic carbon and the broad peak (20−30° 2θ) associated with carbon supports. On this material, small Pd2O and Pd peaks were observed indicating well-dispersed Pd phases. Following the reaction Pd/activated-carbon exhibited a clear increase in metallic Pd and growth of the particles to a Scherrer-estimated size of 3 nm. The same crystalline phases and sintering behavior was observed on the Pd/char catalyst, with the postreaction Pd/char catalyst having Pd crystallites of 6 nm. Similarly, the Pt/char and Ru/char samples did not show any metallic or oxide Pt or Ru phases on the fresh catalysts, indicating small, well-dispersed phases. On the postreaction samples, metallic Ru crystallites of 7 nm and Pt crystallites of 4
Table 5. Results of Water Washing for the Organic Fractions of Two Condensates from the Pd Run at Severe Conditions condensates
B
C
original CAN water added/organic liq. (g/g) after washing organic phase (% or org. Organic phase (% of organic liq.) CAN in the organic phase acid in organic phase, % of original acid in aqueous phase, % of original
61 1.21
81 1.14
89 33 48% 48%
92 54 61% 50% 3093
dx.doi.org/10.1021/ef4019349 | Energy Fuels 2014, 28, 3086−3095
Energy & Fuels
Article
Coke was measured by difference measurement so the precision is low, but platinum and ruthenium seem to decrease coking with severity while others increase coking with severity. The NiMo−S results suggested a maximum with respect to coke formation at medium severity. The presence of many multiring cycloalkanes in the residue product from the highseverity platinum run (and to a lesser extent the ruthenium) suggests that coking begins with the formation of polynuclear aromatics (PNAs) but then is arrested as the PNAs are hydrogenated to form polycyclic alkanes and probably also hydrocracked to smaller molecules. Hydrocracking of the PNAs and heavy phenolics is consistent with the increase of phenolics in the condensates observed and the presence of phenolics in the condensates even at severe conditions. The presence of cyclic compounds in the condensates and residues is in agreement with other studies reporting hydrogenation, e.g. Elliott who reported guaiacol conversion to cyclohexanols and furfural conversion to cyclopentanone and cyclopentanol.17 These results suggest some strategies for achieving desirable oil properties. The products after the initial stabilization step could be separated into light and heavy fractions and the two fractions hydrotreated separately to reduce hydrogen consumption and potentially improve bio-oil yield. Another strategy would be to hydrogenate with palladium at high severity and, if acid content remains a problem, wash the light fractions to remove the acid. The XRD analysis indicated changes in the catalyst during reaction and underscores the need to develop stable catalyst and supports. The sulfided NiMo catalyst had become oxidized, which is consistent with the impact of steam in the absence of continuous H2S feed.29 While the precious metal catalysts remained nanocrystalline, the analysis suggested all of the highly dispersed metals had undergone crystalline size growth during the course of the catalyst activation and reaction.
nm were observed. These results indicate that while the postreaction catalysts remain nanocrystalline all of the highly dispersed metals undergo crystalline size growth during the course of the catalyst activation and reaction.
■
DISCUSSION In our experiments Pt gave by far the highest carbon yields in gas (up to 22%), followed by Ru, whereas both Pd catalysts gave the lowest gas yields. Wildschut et al.18 also reported highest gas yields for Pt among sulfided NiMo, CoMo, Pt, Pd, and Ru at 350 °C. However, in their experiments Ru gave the lowest gas yields. They also observed high amounts of methane for Pd, whereas we found high methane for Ru and Pt. On the other hand, Elliott and Hart17 reported Ru to give higher CO2 and methane yields than Pd, which is consistent with our results. They did not investigate Pt, which in our experiments gave the highest gas yields. Differences in catalyst formulations and operating conditions may have led to the observed differences for Pd and Ru between the studies. Platinum produced very high yields of carbon dioxide and, at high severity, methane. The acid conversion was relatively high at severe conditions and aqueous carbon low with moderate coke formation and hydrogen consumption. The formation of methane and carbon dioxide as in the high-severity platinum experiment suggests decarboxylation of acetic acid (CH3COOH → CH4 + CO2). Decarboxylation (loss of CO2) is generally regarded as desirable: compared to decarbonylation (loss of CO), more O is removed per mole of carbon lost; compared to dehydration, no hydrogen is consumed or more hydrogen is retained in the oil. However, the observed carbon dioxide is in excess of that formed by decarboxylation of the acid, which would have accounted for about 4.5% of the carbon, and starts at low temperature without methane production. This suggests CO2 is formed over Pt from something more reactive than acetic acid, likely sugars. Methane could also be formed from the demethylation of lignin monomers and other ethers. This seemed to be in particular important for Pt and Ru and also NiMo−S at high severity. Ruthenium on the other hand produced methane throughout the experiment and carbon dioxide only above 340 °C. This indicates that ruthenium is effective at hydrogenation, even at low severity, but less effective at deoxygenation than NiMo−S/ Al2O3 or Pt. This hydrogenation, presumably of alkenes, during the stabilization period is the apparent cause of the low coking observed on the ruthenium catalyst at low severity and renders it a good candidate for catalyst during the stabilization phase. In our experiments sulfided NiMo was the most efficient in reducing acids. Of the precious metals, Pt gave the highest and Pd the lowest acid reduction, in agreement with other studies.22 Acids were mainly present in the condensates from intermediate temperatures indicating that the acids vaporized before they had become deoxygenated. In continuous reactors or batch reactors, the light compounds would be in contact with the catalyst through the final temperatures, and hence the acid deoxygenation would have been higher. Pt also gave lower organic O contents than other precious metal catalysts. Pt gave both the lowest hydrogen consumption and low organic contents, which are consistent with the high CO2 formation. Pd on the other hand had the highest hydrogen consumption despite its poor deoxygenation activity indicating high hydrogenation. It gave the highest oil carbon yields, whereas Ru gave the lowest.
■
CONCLUSIONS Precious metal and traditional sulfided NiMo catalysts were compared for the hydrotreating of pyrolysis oil in a semibatch reactor. In this setup, the palladium catalysts produced good oil yields, but the products were high in acid and low in miscibility. The platinum consumed very little hydrogen but gave somewhat lower yield than the nickel and also gave higher acid content. Ruthenium, while producing oil with low oxygen contents and reasonable acidities, gave the lowest carbon yields. The sulfided NiMo/Al2O3 catalyst could achieve the target of 55% conversion of carbon to organic-phase product with acceptable oil qualities and low hydrogen consumption. The precious metal catalysts, although some gave high yields of carbon in the organic phase, low hydrogen consumption, and/ or good miscibility with hydrocarbons, produced oils with acidity that was higher than the targeted values in these semibatch experiments. Removal of residual acids by water washing or by conducting additional hydrogenation of only the low-boiling products may enable hydrotreating at reduced process severity and thus allow higher oil yields. When selecting the best catalyst, various criteria need to be taken into account. Higher hydrogenation activity would increase the product yield but also hydrogen consumption. Higher decarboxylation activity, on the other hand, would give lower product yields but also lower hydrogen consumption. The ability to remove acid and oxygen are also important factors for consideration. The various catalysts have different advantages, and using a different catalyst for the two 3094
dx.doi.org/10.1021/ef4019349 | Energy Fuels 2014, 28, 3086−3095
Energy & Fuels
Article
(12) Baldauf, W.; Balfanz, U. Upgrading of Fast Pyrolysis Liquids at Veba Oel AG. Biomass Gasif. Pyrolysis 1997, 392−398. (13) Marker, T. L. Opportunities for Biorenewables in Oil Refineries; Final Technical Report 2005; DOE Contract number DE-FG3605GO15085. (14) Fu, X.; Dai, Z.; Tian, S.; Long, J.; Hou, S.; Wang, X. Catalytic Decarboxylation of Petroleum Acids from High Acid Crude Oils over Solid Acid Catalysts. Energy Fuels 2008, 22, 1923−1929. (15) Wang, H.; Male, J.; Wang, Y. Recent Advances in Hydrotreating of Pyrolysis Bio-Oil and Its Oxygen-Containing Model Compounds. ACS Catal. 2013, 3, 1047−1070. (16) Elliott, D. C.; Hart, T. R. Catalytic Hydroprocessing of Chemical Models for Bio-Oil. Energy Fuels 2009, 23, 631−637. (17) Elliott, D. C.; Hart, T. R.; Neuenschwander, G. G.; Rotness, L. J.; Zacher, A. H. Catalytic Hydroprocessing of Biomass Fast Pyrolysis Bio-Oil To Produce Hydrocarbon Products. Environ. Prog. Sustainable Energy 2009, 28, 441−449. (18) Wildschut, J.; Mahfud, F. H.; Venderbosch, R. H.; Heeres, H. J. Hydrotreatment of Fast Pyrolysis Oil Using Heterogeneous NobleMetal Catalysts. Ind. Eng. Chem. Res. 2009, 48, 10324−10334. (19) Wildschut, J.; Iqbal, M.; Mahfud, F. H.; Cabrera, I. M.; Venderbosch, R. H.; Heeres, H. J. Insights in the Hydrotreatment of Fast Pyrolysis Oil Using a Ruthenium on Carbon Catalyst. Energy Environ. Sci. 2010, 3, 962−970. (20) de Miguel Mercader, F. Pyrolysis Oil Upgrading for CoProcessing in Standard Refinery Units, Ph.D. Thesis, University of Twente, 2010. (21) Ardiyanti, A. R.; Gutierrez, A.; Honkela, M. L.; Krause, A. O. I.; Heeres, H. J. Hydrotreatment of Wood-Based Pyrolysis Oil Using Zirconia-Supported Mono- and Bimetallic (Pt, Pd, Rh) Catalysts. Appl. Catal., A 2011, 407, 56−66. (22) Lin, Y.-C.; Li, C.-L.; Wan, H.-P.; Lee, H.-T.; Liu, C.-F. Catalytic Hydrodeoxygenation of Guaiacol on Rh-Based and Sulfided CoMo and NiMo Catalysts. Energy Fuels 2011, 25, 890−896. (23) Nicolaides, G. M. The Chemical Characterization of Pyrolytic Oils; University of Waterloo, Department of Chemical Engineering: Waterloo, Ontario, 1984; pp 17−26, 30−42. (24) French, R. J.; Stunkel, J.; Baldwin, R. M. Mild Hydrotreating of Bio-Oil: Effect of Reaction Severity and Fate of Oxygenated Species. Energy Fuels 2011, 25, 3266−3274. (25) Ben, H.; Ragauskas, A. J. NMR Characterization of Pyrolysis Oils from Kraft Lignin. Energy Fuels 2011, 25, 2322−2332. (26) Wildschut, J.; Arentz, J.; Rasrendra, C. B.; Venderbosch, R. H.; Heeres, H. J. Catalytic Hydrotreatment of Fast Pyrolysis Oil: Model Studies on Reaction Pathways for the Carbohydrate Fraction. Environ. Prog. Sustainable Energy 2009, 28 (3), 450−460. (27) Olcay, H.; Xu, L. J.; Xu, Y.; Huber, G. W. Aqueous-Phase Hydrogenation of Acetic Acid over Transition Metal Catalysts. ChemCatChem 2010, 2 (11), 1420−1424. (28) Chen, L.; Zhu, Y.; Zheng, H.; Zhang, C.; Li, Y. Aqueous-Phase Hydrodeoxygenation of Propanoic Acid over the Ru/ZrO2 and Ru− Mo/ZrO2 Catalysts. Appl. Catal., A 2012, 411, 95−104. (29) Ruddy, D. A.; Schaidle, J. A.; Ferrell, J. R., III; Wang, J.; Moens, L.; Hensley, J. E. Recent Advances in Heterogeneous Catalysts for BioOil Upgrading via “ex Situ Catalytic Pyrolysis”: Catalyst Development through the Study of Model Compounds. Green Chem. 2014, DOI: 10.1039/c3gc41354c.
stages of the process may provide the best processfor example ruthenium for minimizing coke during stabilization and sulfided nickel or platinum for deoxygenation.
■
ASSOCIATED CONTENT
* Supporting Information S
Table 1 and Figure 1. This material is available free of charge via the Internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors gratefully acknowledge the support of the U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with the National Renewable Energy Laboratory and the support of the Department of Energy Office of the Biomass Program under agreement 15590. The authors also gratefully acknowledge Johnson Matthey and Grace Davison for providing the catalysts and Erica Gjersing for the NMR analyses.
■
REFERENCES
(1) U.S. Department of Energy, Biomass Multi-Year Program Plan 2011, Office of the Biomass Program, Energy Efficiency and Renewable Energy. Available at http://www1.eere.energy.gov/ biomass/pdfs/mypp_april_2011.pdf (accessed April 6, 2014). (2) Beaudry-Losique, J. Growing a Robust Biofuels Economy, Venture Capital Forum. August 21−22, 2007. Available at http:// www1.eere.energy.gov/commercialization/pdfs/biomass.pdf (accessed April 6, 2014). (3) U.S. Department of Energy. U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry. Perlack, R. D.; Stokes, B. J. (Leads), ORNL/TM-2011/224; Oak Ridge National Laboratory: Oak Ridge, TN, 2011; 227p. Available at http:// bioenergykdf.net (accessed April 6, 2014). (4) U.S. Environmental Protection Agency, EPA Proposes New Regulations for the National Renewable Fuel Standard Program for 2010 and Beyond 2009. Available at http://www.epa.gov/otaq/ renewablefuels/rfs2_1-5.pdf (accessed April 6, 2014). (5) Czernik, S.; Bridgwater, A. V. Overview of Applications of Biomass Fast Pyrolysis Oil. Energy Fuels 2004, 18, 590−598. (6) Elliott, D. C.; Baker, E. G. Catalytic Hydrotreating of Biomass Liquefaction Products to Produce Hydrocarbon Fuels: Interim Report; Pacific Northwest National Laboratory: Richland, WA, 1986. (7) Elliott, D. C. Historical Developments in Hydroprocessing BioOils. Energy Fuels 2007, 21, 1792−1815. (8) Conti, L.; Scano, G.; Boufala, J.; Mascia, S. Experiments of BioOil Hydrotreating in a Continuous Bench-Scale Plant. Bio-Oil Prod. Util., Proc. EU-Can. Workshop Therm. Biomass Process 1996; pp 198−205. (9) Baker, E. G.; Elliott, D. C. Catalytic Upgrading of Biomass Pyrolysis Oils. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Science Publishers, Ltd.: Barking, England, 1988; pp 883−895. (10) Baker, E. G.; Elliott, D. C. Method of Upgrading Oils Containing Hydroxyaromatic Hydrocarbon Compounds to Highly Aromatic Gasoline. US Patent 5,180,868, 1993. (11) Jones, S.; Valkenburg, C.; Walton, C.; Elliott, D.; Holladay, J.; Stevens, D.; Kinchin, C.; Czernik, S. Production of Gasoline and Diesel from Biomass via Fast Pyrolysis, Hydrotreating and Hydrocracking: A Design Case; Report PNNL-18284 Rev. 1; Pacific Northwest National Lab: Richland, WA, 2009. 3095
dx.doi.org/10.1021/ef4019349 | Energy Fuels 2014, 28, 3086−3095
