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.

No abstract

Acid-catalyzed conversions of levoglucosan have been investigated in mono-alcohols, poly-alcohols, water, chloroform, toluene, acetone, N,N-dimethyl formamide, dimethyl sulfoxide and some mixed solvents, aiming to mediate conversion of sugars into platform chemicals with solvents. The monoalcohols can stabilize soluble polymers and thus suppress formation of insoluble polymers. Water does not have such an effect, leading to lower yields of levulinic acid. Chloroform cannot effectively dissolve levoglucosan, leading to "dissolving" of levoglucosan in the catalyst and the consequent rapid polymerization. Acetone reacted with sugars, forming substantial amounts of polymer. N,N-Dimethyl formamide poisoned the acid resin catalyst, leading to negligible conversion of levoglucosan. Dimethyl sulfoxide (DMSO) mainly catalyzed the conversion of levoglucosan into 5-(hydroxymethyl)furfural (HMF), 2,5-furandicarboxaldehyde, and the sulfur ether of HMF. DMSO has a low ability to transfer protons, which helps to avoid further contact of HMF with catalytic sites and stabilizes HMF.

No abstract