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.

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The analyses of structure change during pyrolysis of cellulose at different heating rates were investigated to clarify the existent behavior of the cross-linking reaction. For structural analyses of cellulose precursors, FTIR spectra and XRD patterns confirmed that the dehydration reaction to produce water and cross-liked precursor simultaneously occurred with the glycosidic reaction to produce tar during pyrolysis. On the basis of the assumptions that hydroxyl groups in cellulose converted to water, a new parameter index, so-called the degree of dehydration during pyrolysis, X p, including its distribution in char (X c) and tar (X t), was determined. For the cross-linking analyses at low heating rate, cross-linking reaction may occur until approximately 360 °C where X c reached its maximum, while the cross-linked tar seems to be released above 360 °C. For tar analyses, cross-linked dimer can be observed for slow pyrolysis, whereas tar products obtained by flash pyrolysis showed relatively higher yield in cellobiosan with no cross-linked volatiles. Finally, based on previous kinetic models, the modified pathway of cellulose pyrolysis was proposed by considering the proposed parameter related to the dehydration.