Catalytic Strategies and Catalyst Design for the Conversion of Biomass-Derived Carbohydrates to Chemicals.

摘要

The development of catalytic technologies for efficiently and selectively transforming lignocellulosic precursors to platform molecules, such as 5-hydroxymethylfurfural (HMF) and methyl lactate has been studied. A catalytic process for the production of HMF from glucose is presented by combination of Lewis and Bronsted acid catalyst in a biphasic reaction system. The combination of these catalysts promotes the production of HMF from glucose through a Lewis acid catalyzed isomerization of glucose to fructose followed by a Bronsted acid catalyzed dehydration of fructose to IIMF. Moreover, the production of methyl lactate from hexose and pentoses in the presence of Lewis acidic zeotype catalyst in methanol, Sn-beta zeolite, is described. The production of methyl lactate is found to be independent of the hexose or pentose used since these carbohydrates readily undergo isomerization reactions in the presence of the Snbeta zeolite to their corresponding aldose-ketose-aldose isomers. These isomers are converted to methyl lactate by a series of retro-aldol, dehydration, esterification and isomerization reactions.;Hydrothermally stable niobia catalysts for aqueous phase processing of biomass derived carbohydrates have been synthesized using two different methods. The first method employs atomic layer deposition (ALD) of niobia within the well-defined pores of a mesoporous silica scaffold (SBA-15) to create a mesoporous niobia catalyst. The second synthesis method is based on the addition of small amounts of silica to the niobia framework by a ligand assisted templating approach. The mesoporous niobia obtained through this synthesis approach has been studied as an acid catalyst for the gas-phase dehydration of 2-propanol, and for the dehydration of 2-butanol in both the gas and liquid phases. Furthermore, Pd nanoparticles were dispersed on the niobia-silica materials to create bifunctional catalysts for the transformation of γ-valerolactone (GVL) to pentanoic acid. The addition of silica in the framework helped in improving the hydrothermal stability of the catalysts and also in retaining smaller crystallite sizes for the Pd phase. The synthesis of niobia catalysts by these two methods lead to materials showing superior hydrothermal stability and catalytic activity versus time-on-stream in comparison to commercial niobia catalyst HY-340.