Kinetic and mechanistic studies of a biomimetic catalyst for hemicellulosic biomass hydrolysis
Abstract
The use of cellulosic biomass for fuels is limited by unavailability of a cost-effective catalytic platform to convert the feedstock into fermentable sugars. In this study, a biomimetic catalysis concept was proposed. Biomimetic catalysts are a series of dicarboxylic acids with varying chain length that structurally mimicking enzyme active site. Initial screening determined that maleic acid is superior to others with improved sugar yield. When applied to hemicellulosic biomass hydrolysis reaction, optimal condition with maleic acid catalysis resulted in over 90% of xylose yield, compared to only of 70% xylose yield by sulfuric acid catalysis. A kinetic modeling analysis of the reaction suggests that the hydrolysis reaction is higher than 1st-order kinetics, indicating that undissociated form of maleic acid may involve in the catalysis. Low severity reaction conditions are also suggested to be more favorable for hydrolysis versus degradation. However, biphasic hydrolysis pattern becomes apparent at low severity conditions. Xylose degradation pH-rate profile was examined, and transition from acid-controlled to solvent-controlled to base-catalyzed type kinetics were observed in pH 0.5 – 7.0. Under pH 2.2 condition the xylose degradation rate was minimal. Further mechanistic study indicates that an inverse general acid catalysis mechanism is employed by maleic acid for xylose degradation reaction, and this may be associated with the existence of a very-strong short H-bond that is unique to maleic acid.
Degree
Ph.D.
Advisors
Mosier, Purdue University.
Subject Area
Agricultural engineering|Chemical engineering|Energy
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