Physical and chemical characteristics of aging pyrolysis oils produced from hardwood and softwood feedstocks

Abstract Pyrolysis oils were produced from hardwood or softwood feedstocks in a vacuum batch reactor and trapped at 0 °C. The vacuum process was used to intentionally avoid the presence of entrained char particles. The hardwood feedstock was a pelletized mixture of various Eastern tree species. The softwood samples were de-barked Lodgepole pine (Pinus contorta) and Douglas Fir (Pseudotsuga menziesii) wood cut into the same dimensions as the pellets. The oils’ physical (viscosity) and chemical (speciation) properties were measured as-produced and after aging. The total liquid and char yields ranged from ∼50 to 55% and 25 to 27% respectively. Measured water contents were 30% or more, which are greater typically reported from fast pyrolysis oils produced in fluidized beds. Aging took place in covered glass containers at room temperature over a period of 5 months. Gas chromatography–mass spectrometry (GCMS) was used to characterize the oils’ volatile components. Since bio-oils are mixtures of hundreds of different compounds with wide-ranging molecular weights and polarities, the oils were extracted using benzene followed by methanol. Out of ca. 80 non-polar and 100+ polar compounds GCMS showed a few chemical species present in the freshly produced oils were absent in the aged oils. The oils’ viscosities at shear rates (measured between 1 and 1000 s−1) increased by approximately a factor of 2.5 during aging. To determine if this was due to polymerization reactions during aging or simply water and other volatile material losses, freshly made oils were aged at an accelerated rate by using elevated temperatures (65 °C and 85 °C) in a water-saturated environment between 1 and 7 days. The oils are fairly stable with respect to aging both over long periods of time (months) at room temperature and at elevated temperatures, 65 °C and 85 °C for shorter time periods (days). It is concluded that high water content and char-free characteristics act to slow polymerization reactions.

[1]  A. Bridgwater,et al.  Overview of Applications of Biomass Fast Pyrolysis Oil , 2004 .

[2]  D. Meier,et al.  State of the art of applied fast pyrolysis of lignocellulosic materials - a review , 1999 .

[3]  Ayhan Demirbas,et al.  Political, economic and environmental impacts of biofuels: A review , 2009 .

[4]  Joël Blin,et al.  Biodegradability of biomass pyrolysis oils: Comparison to conventional petroleum fuels and alternatives fuels in current use , 2007 .

[5]  Nicolaus Dahmen,et al.  Cost estimate for biosynfuel production via biosyncrude gasification , 2009 .

[6]  Akwasi A. Boateng,et al.  Bench-Scale Fluidized-Bed Pyrolysis of Switchgrass for Bio-Oil Production† , 2007 .

[7]  D. F. James,et al.  Liquid Fuel Properties of a Hardwood-Derived Bio-oil Fraction , 2008 .

[8]  Stefan Czernik,et al.  Stability of wood fast pyrolysis oil , 1994 .

[9]  Anja Oasmaa,et al.  Fast Pyrolysis Bio-Oils from Wood and Agricultural Residues , 2010 .

[10]  C. Roy,et al.  Step-wise and one-step vacuum pyrolysis of birch-derived biomass to monitor the evolution of phenols , 2001 .

[11]  A. Chaala,et al.  Characterization of bio-oils in chemical families , 2007 .

[12]  Robert J. Evans,et al.  Hydrogen from biomass-production by steam reforming of biomass pyrolysis oil ☆ , 2007 .

[13]  B. McCloskey,et al.  Effect of Metal Doping on the Initial Pyrolysis Chemistry of Cellulose Chars , 2008 .

[14]  M. J. Groeneveld,et al.  Fast Pyrolysis of Biomass in a Fluidized Bed Reactor: In Situ Filtering of the Vapors , 2009 .

[15]  J. Azevedo,et al.  Estimating the higher heating value of biomass fuels from basic analysis data , 2005 .

[16]  A. Corma,et al.  Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. , 2006, Chemical reviews.

[17]  D. Mohan,et al.  Pyrolysis of Wood/Biomass for Bio-oil: A Critical Review , 2006 .

[18]  Manuel Garcia-Perez,et al.  Vacuum pyrolysis of sugarcane bagasse , 2002 .

[19]  S. Czernik,et al.  Study of the Neutralization and Stabilization of a Mixed Hardwood Bio-Oil , 2009 .

[20]  S. Voutetakis,et al.  Hydrogen Production via Steam Reforming of the Aqueous Phase of Bio-Oil in a Fixed Bed Reactor , 2006 .

[21]  W. V. Swaaij,et al.  Catalytic gasification of dry and wet biomass , 2009 .

[22]  M. Fatih Demirbas,et al.  Biorefineries for biofuel upgrading: A critical review , 2009 .

[23]  Anthony V. Bridgwater,et al.  Fast pyrolysis of biomass : a handbook , 1999 .

[24]  Anja Oasmaa,et al.  Fuel oil quality of biomass pyrolysis oils-state of the art for the end users , 1999 .

[25]  Thomas A. Milne,et al.  Molecular characterization of the pyrolysis of biomass , 1987 .

[26]  Calvin Mukarakate,et al.  Current technologies for analysis of biomass thermochemical processing: a review. , 2009, Analytica chimica acta.

[27]  Akwasi A. Boateng,et al.  Distributed processing of biomass to bio‐oil for subsequent production of Fischer‐Tropsch liquids , 2008 .

[28]  H. Vandendool,et al.  A GENERALIZATION OF THE RETENTION INDEX SYSTEM INCLUDING LINEAR TEMPERATURE PROGRAMMED GAS-LIQUID PARTITION CHROMATOGRAPHY. , 1963, Journal of chromatography.

[29]  Manuel Garcia-Perez,et al.  Vacuum pyrolysis of softwood and hardwood biomass: Comparison between product yields and bio-oil properties , 2007 .

[30]  S. Besler,et al.  Inorganic Compounds in Biomass Feedstocks. 1. Effect on the Quality of Fast Pyrolysis Oils , 1996 .

[31]  James P. Diebold,et al.  Additives To Lower and Stabilize the Viscosity of Pyrolysis Oils during Storage , 1997 .

[32]  Young‐Kwon Park,et al.  Influence of reaction conditions and the char separation system on the production of bio-oil from radiata pine sawdust by fast pyrolysis , 2008 .