260591 Production of Biofuels From Simultaneous Conversion of Hemicellulose and Cellulose in Lignocellulosic Biomass

Wednesday, October 31, 2012: 8:30 AM
319 (Convention Center )
James A. Dumesic1, Elif I. Gurbuz1, Stephanie G. Wettstein1 and David Martin Alonso2, (1)Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, (2)University of Wisconsin, Madison, WI

            Replacing petroleum using biomass as source of carbon requires the effective conversion of both the hemicellulose (C5 sugars) and cellulose (C6 sugars) fractions of the lignocellulosic biomass. However, these fractions have different physical and chemical properties making it difficult to employ a unified processing strategy for conversion to fuels and chemicals. Accordingly, typical processing strategies employ a pretreatment step in which the C5 sugars are removed from the C6 sugars, allowing these two classes of sugars to be processed by separate routes. The hemicellulose fraction of biomass is more reactive than the cellulose fraction and thus, using short reaction times and low acid concentrations it is possible to achieve high conversions of C5 sugars to furfural, while preserving the cellulose for other applications. Increasing the reaction time and/or acid concentration leads to the conversion of C6 sugars to levulinic acid, but at the expense of furfural degradation. Herein, a process is presented that achieves the catalytic conversion of both hemicellulose and cellulose to gamma-valerolactone (GVL), using GVL as a solvent.

A key aspect of this processing approach is that presence of GVL minimizes subsequent degradation reactions, which increases the furfural stability and allows for the biomass deconstruction time to be increased. Therefore, the less reactive cellulose fraction of biomass can be converted to levulinic acid, while retaining a high yield of furfural thereby allowing both biomass fractions to be processed in the same reaction step. Furthermore, using a hydrogenation catalyst, furfural can be converted into furfuryl alcohol, which can be converted with high yields over an acid catalyst to produce levulinic acid.

The advantages of this unified processing approach are that (i) the hemicellulose and cellulose are processed together, thereby eliminating the requirement of lignocelluloses fractionation, (ii) both the hemicellulose and the cellulose are converted to the same product, thereby eliminating the need to separate different reaction products, (iii) the solvent used for biomass deconstruction is a product of the process, which eliminates the need of purification steps to remove the solvent (iv) the use of the GVL solvent leads to effective solubilization of biomass, thereby eliminating the formation of solid humin deposits that typically lead to reactor plugging and solids handling problems, and (v) low concentrations of water are used in the process, thereby minimizing deactivation processes typically observed for heterogeneous catalysts under hydrothermal conditions (e.g., structural collapse, leaching).



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