Energy Fuels 2010, 24, 2642–2651 Published on Web 03/16/2010
: DOI:10.1021/ef901120h
Fast Pyrolysis of Pine Sawdust in a Fluidized-Bed Reactor William J. DeSisto,*,†,‡ Nathan Hill II,† Sedat H. Beis,† Saikrishna Mukkamala,† Jincy Joseph,§ Cirila Baker,§ Ta-Hsuan Ong,^ Elizabeth A. Stemmler,^ M. Clayton Wheeler,† Brian G. Frederick,‡,§ and Adriaan van Heiningen† †
Department of Chemical and Biological Engineering, and ‡Laboratory for Surface Science and Technology, § Department of Chemistry, University of Maine, Orono, Maine 04469, and ^Department of Chemistry, Bowdoin College, Brunswick, Maine 04011 Received October 2, 2009. Revised Manuscript Received February 1, 2010
Pine (Pinus strobus) sawdust was pyrolyzed in a fluidized-bed reactor between the temperatures of 400 and 600 C. The fixed-bed volume and residence time were optimized to maximize the liquid yield. We report the detailed physical and chemical properties of the bio-oil fraction collected during fast pyrolysis. The liquid yield was maximized at 500 C, whereas increased gas formation occurred at 600 C. 13C NMR of the bio-oil fractions indicated a decrease in the carbohydrate fraction and an increase in the aromatic fraction when pyrolysis temperatures were increased from 500 to 600 C. Over the ranges of our investigation, the effects of the fixed-bed volume and residence time were negligible on the chemical composition of the biooil. Toluene and ethyl acetate bio-oil extracts were analyzed by gas chromatography/mass spectrometry following chemical derivatization. At increased reaction temperatures, the process favored conversion of guaiacols to catechols.
There have been significant efforts examining fast pyrolysis of biomass.6-16 Several processes for achieving fast pyrolysis have been examined and are summarized by Bridgwater,1 including fluidized-bed, rotating-cone, and ablative pyrolysis among others. In addition to the wide variety of processes developed for fast pyrolysis of biomass, the fast-pyrolysis process is influenced by a large number of parameters, including the reaction temperature, residence time of the
1. Introduction The exploration of alternative energy sources, particularly renewable energy sources, is driven, in part, by the negative environmental impact and limited supply of conventional, nonrenewable fossil fuels. Among the choices for renewable energy production, the thermal conversion of biomass is receiving considerable attention.1,2 The thermal conversion of biomass feedstock is initiated by the thermal breakdown of biomass into more fundamental components in the form of char, liquid or bio-oil, and gas. In fast-pyrolysis technology, the yield of bio-oil is optimized through rapid heating and cooling of the biomass in an inert atmosphere. Because biomass is oxygen-rich, the corresponding bio-oil is also oxygenrich and a primary component of the gas fraction is carbon monoxide. These pyrolysis products can then be used as feedstocks to produce a variety of chemicals.3 For example, fuels can be formed through hydrodeoxygenation of the biooil.4 In addition, carbon monoxide can be used in a variety of syntheses such as the Fischer-Tropsch production of alcohols and alkanes.5
(8) Butt, D. Formation of phenols from the low-temperature fast pyrolysis of Radiata pine (Pinus radiata);Part II. Interaction of molecular oxygen and substrate water. J. Anal. Appl. Pyrolysis 2006, 76 (1-2), 48–54. (9) Garcia-Perez, M.; Wang, X. S.; Shen, J.; Rhodes, M. J.; Tian, F. J.; Lee, W. J.; Wu, H. W.; Li, C. Z. Fast pyrolysis of oil mallee woody biomass: Effect of temperature on the yield and quality of pyrolysis products. Ind. Eng. Chem. Res. 2008, 47 (6), 1846–1854. (10) Hoekstra, E.; Hogendoorn, K. J. A.; Wang, X. Q.; Westerhof, R. J. M.; Kersten, S. R. A.; van Swaaij, W. P. M.; Groeneveld, M. J. Fast Pyrolysis of Biomass in a Fluidized Bed Reactor: In Situ Filtering of the Vapors. Ind. Eng. Chem. Res. 2009, 48 (10), 4744–4756. (11) Ingram, L.; Mohan, D.; Bricka, M.; Steele, P.; Strobel, D.; Crocker, D.; Mitchell, B.; Mohammad, J.; Cantrell, K.; Pittman, C. U. Pyrolysis of wood and bark in an auger reactor: Physical properties and chemical analysis of the produced bio-oils. Energy Fuels 2008, 22 (1), 614–625. (12) Kang, B. S.; Lee, K. H.; Park, H. J.; Park, Y. K.; Kim, J. S. Fast pyrolysis of radiata pine in a bench scale plant with a fluidized bed: Influence of a char separation system and reaction conditions on the production of bio-oil. J. Anal. Appl. Pyrolysis 2006, 76 (1-2), 32–37. (13) Kim, S. S.; Agblevor, F. A. Pyrolysis characteristics and kinetics of chicken litter. Waste Manage. 2007, 27 (1), 135–140. (14) Pattiya, A.; Titiloye, J. O.; Bridgwater, A. V. Fast pyrolysis of cassava rhizome in the presence of catalysts. J. Anal. Appl. Pyrolysis 2008, 81 (1), 72–79. (15) Westerhof, R. J. M.; Kuipers, N. J. M.; Kersten, S. R. A.; van Swaaij, W. P. M. Controlling the water content of biomass fast pyrolysis oil. Ind. Eng. Chem. Res. 2007, 46 (26), 9238–9247. (16) Lappas, A. A.; Dimitropoulos, V. S.; Antonakou, E. V.; Voutetakis, S. S.; Vasalos, I. A. Design, construction, and operation of a transported fluid bed process development unit for biomass fast pyrolysis: Effect of pyrolysis temperature. Ind. Eng. Chem. Res. 2008, 47 (3), 742–747.
*To whom correspondence should be addressed. Tel: 207-581-2291. Fax: 207-581-2323. E-mail:
[email protected]. (1) Bridgwater, A. V. Renewable fuels and chemicals by thermal processing of biomass. Chem. Eng. J. 2003, 91, 87–102. (2) Mohan, D.; Pittman, C. U.; Steele, P. H. Pyrolysis of wood/ biomass for bio-oil: A critical review. Energy Fuels 2006, 20 (3), 848–889. (3) Czernik, S.; Bridgwater, A. V. Overview of applications of biomass fast pyrolysis oil. Energy Fuels 2004, 18 (2), 590–598. (4) Elliott, D. C. Historical developments in hydroprocessing bio-oils. Energy Fuels 2007, 21 (3), 1792–1815. (5) Anderson, R. B. The Fischer-Tropsch Synthesis; Academic Press, Inc. (Harcourt Brace Jovanovich): New York, 1984. (6) Bridgwater, A. V.; Meier, D.; Radlein, D. An overview of fast pyrolysis of biomass; Elsevier: New York, 1999; pp 1479-1493. (7) Oasmaa, A.; Kuoppala, E.; Solantausta, Y. Fast pyrolysis of forestry residue. 2. Physicochemical composition of product liquid. Energy Fuels 2003, 17 (2), 433–443. r 2010 American Chemical Society
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Energy Fuels 2010, 24, 2642–2651
: DOI:10.1021/ef901120h
DeSisto et al.
1534-93. The total carbon, hydrogen, nitrogen, oxygen, and sulfur contents were provided by Galbraith Laboratories. Samples were digested by SM method 3030E and analyzed by ICPOES to obtain metal contents. Chemical functional group analysis was determined using NMR, on a Varian Unity Plus 400 NMR. Samples for NMR were prepared in a 1:1 volume ratio with DMSO-d6 and measured in 5-mm tubes and with a broad-band probe equipped for gradient shimming. The 13C NMR spectra were acquired with a 90 pulse angle, full proton decoupling, a 4.5-s pulse delay, and a sweep width of 25 000 Hz. This allowed 7 s for spin-lattice relaxation between pulses, as suggested by Mullen et al.17 The acquisition of 4000 transients resulted in good signal/ noise ratios after approximately 8 h of total measurement time per sample. Spectra were processed using MestreNova to perform baseline corrections and integrate spectra according to the chemical shift regions reported by Ingram et al.11 While relative intensities were reproducible and systematic variations in the functional group compositions with reactor process conditions were observed, the effects of nuclear Overhauser enhancement and the inefficiency of spin-lattice relaxation likely lead to a systematic overestimation of alkyl carbons, relative to other types. 2.4. GC/MS Bio-oil Analysis. Prior to GC/MS analysis, biooil samples were separated into toluene-soluble and ethyl acetatesoluble extracts. Samples were fractionated by first sonicating (Branson 2510, Branson Ultrasonic, Danbury, CT) a mixture of the oil sample (0.5 g) with toluene (5 mL; ACS grade, SigmaAldrich, Milwaukee, WI). The toluene supernatant was decanted, filtered (0.45 μm; Agilent Econofilter, Agilent, Palo Alto, CA), and diluted to 25 mL. Ethyl acetate (5 mL; trace grade, Pharmco, Brookfield, CT) was then added to the remaining oil, sonicated, filtered, and diluted to 25 mL. Aliquots (1 mL; n = 3) of the toluene and ethyl acetate extracts were dried to constant mass at room temperature to determine the mass of bio-oil contained in each extract. The preparation of trimethylsilyl (TMS) derivatives was achieved according to the following procedure. Aliquots of the toluene (1 mL) and ethyl acetate (200 μL) extracts were evaporated under dinitrogen and reacted with 0.5 mL of N-methylN-(trimethylsilyl)trifluoroacetamide (MSTFA; SigmaAldrich) in a sealed container at 80 C for 20 min. All GC/MS analyses were carried out using an Agilent 5973 gas chromatograph/mass spectrometer equipped with a capillary column (ZB-5MS, 30 m, 0.25-mm i.d., 0.25-μm film thickness; Phenomenex, Torrance, CA). The oven temperature was held at 40 C for 4 min, ramped at 5 C/min to 300 C, and held there for 10 min. Injections (1 μL) were carried out in a splitless mode, the injection port temperature was 280 C, and helium was used as the carrier gas. The mass spectrometer was scanned from m/z 14 to 600. Bio-oil extracts were analyzed before and after derivatization. Compounds were identified based upon retention times, comparisons with known standards, and the use of mass spectral libraries. Quantitative determinations were carried out using eicosane as an internal standard.
Table 1. Pine Sawdust Analysis moisture (%) ash (%) C H N O HHV (MJ/kg)
10-13 0.309 0.451 0.068
