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in Wiley Online Library (wileyonlinelibrary.com).Understanding of the condensation reactions in bio-oil is the key for efficient conversion into transportation fuel or valueadded chemicals. In this study, the roles of the typical compounds representing the sugars, sugar derivatives, and aromatics found in bio-oil were investigated for their contribution to condensation reactions. Glucose played a key role for the polymer formation due to its decomposition to reactive compounds with multiple hydroxyl groups, carbonyl groups or conjugated bonds. The sugar derivatives, including furfural, hydroxyl aldehyde and hydroxyl acetone, were also found to be reactive toward polymerization. The carboxylic acids were shown to be the catalysts for polymerization and formic acid was much more efficient to catalyze polymerization than acetic acid. The phenolic compounds also promoted the acidcatalyzed reactions. Vanillin contains reactive a carbonyl group, leading to its high tendency toward polymerization. In methanol, various kinds of methanolysis reactions dominated, which significantly suppressed the decomposition of glucose and the polymerization of other compounds. V V C 2012 American Institute of Chemical Engineers AIChE J, 59: 888-900, 2013Experimental conditions: Reactants (Without the acids and the phenolics): levoglucosan, hydroxyl aldehyde, hydroxyl acetone, cyclopentanone, furan, furfural, and water. Others were same to that in Run 1. d Experimental conditions: Reaction medium: methanol; Catalyst: Amberlyst 70 (3 wt %); the reactants were all the compounds listed in Table 1 plus methanol. Other reaction conditions were same as that in Run 1.

The pyrolysis of biomass to produce bio-oil is a very effective way of biomass use. Bio-oil undergoes drastic structural changes as it is upgraded into biofuels or used as a fuel for gasification/combustion. The evolution of aromatic ring systems in bio-oil is a key consideration in bio-oil use. A bio-oil sample produced from the fast pyrolysis of mallee wood at 500°C, its lignin-derived oligomers, and pure cellulose have been pyrolyzed in a novel two-stage fluidized-bed/fixed-bed reactor at temperatures between 350 and 850°C. The product tars were characterized with ultraviolet (UV) fluorescence spectroscopy. Our results indicate that significant portions of aromatic ring systems in the bio-oil could turn/polymerize into solids not soluble in CHCl 3 + CH 3 OH during the pyrolysis at relatively low temperatures, e.g., 350À400°C. This process can be enhanced by the presence of cellulose-/ hemicellulose-derived species in the bio-oil, which are reactive and produce radicals to enhance the polymerization reactions. The pyrolysis of cellulose-derived species in the bio-oil tended to form additional very large aromatic ring systems at temperatures higher than 700°C.

This study investigates fuel and rheological properties of bio-oil/char slurry (i.e., bioslurry) fuels, which were prepared by mixing bio-oil with different concentrations of biochar. The bio-oil and biochar were produced from mallee fast pyrolysis at 500 °C. The excellent grindability of biochar enables desirable particle size reduction of biochar into fine particles, which can be suspended into bio-oil for the preparation of bioslurry fuels. The bioslurry fuels have desired fuel and rheological characteristics, which meet the requirements for combustion and gasification applications. Dependent upon biochar loading, the volumetric energy density of bioslurry is up to 23.2 GJ/m3, achieving a significant energy densification (by a factor >4) in comparison to green wood chips. Bioslurry fuels with high biochar concentrations (11−20 wt %) show non-Newtonian characteristics with pseudo-plastic behavior. The flow behavior index, n, decreases with an increasing biochar concentration. Bioslurry with higher biochar concentrations also demonstrate thixotropic behavior. The bioslurry fuels also have low viscosity (<453 mPa s) and are pumpable at both room and elevated temperatures. The concentrations of Ca, K, N, and S in bioslurry are below the limits of slurry fuel guidelines. Overall, the results in this study suggest that bioslurry fuels achieve substantial volumetric energy densification and are suitable fuels for combustion and gasification applications.