Nonrenewable and environmentally detrimental materials can be replaced in manufacturing applications with affordable, renewable and benign alternatives derived from woody biomass. Platform chemicals are versatile building blocks that can be used in a variety of synthetic pathways to high value products. We have used the Lewis acidity of m-WO₃ in conjunction with HCl as a Brønsted acid in butanol/water solvent systems to convert bio-abundant glucose into the platform chemicals hydroxymethyl furfural (HMF) and racemic lactic acid at temperatures as low as 120° C. Glucose isomerization to fructose was shown to occur over m-WO₃ without dehydrating to form HMF. No fructose conversion was observed over m-WO₃, but dehydration occurred in the presence of a Brønsted acid catalyst. In a typical reaction catalyzed with WO₃ and HCl (0.12 M), performed at 190 ° C for 10 min, we find 78 % glucose conversion and co-production of HMF (45% C-yield), lactic acid (21% C-Yield), and formic acid (8% C-Yield). Ammonia TPD and pyridine DRIFTS experiments were used to quantify and characterize the acid sites on the m-WO₃ surface. Reaction kinetics were analyzed by fitting rate constants for an extended reaction network, which were found to be consistent with kinetic parameters reported by Swift et al. [1]. The rate constant for glucose isomerization indicates high activity of m-WO₃for the MPVO hydride shift reaction, comparable to the best catalysts reported for glucose isomerization to fructose [2]. The MPVO reaction requires Lewis acid sites, which were observed, but also seen were Brønsted acid sites that do not appear to be active for dehydration catalysis. The strength of acid sites present on m-WO₃ was assessed using a microkinetic model of ambient-pressure ammonia TPD, which combines ammonia adsorption microcalorimetry data (reported by Auroux and Gervasini [3]) with DFT calculations performed on tungsten oxide clusters.

James Clark

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