Catalytic conversion of glucose to small polyols over a binary catalyst of vanadium modified beta zeolite and Ru/C

Abstract

Catalytic conversion of glucose, the most abundant carbohydrate, to chemicals of petroleum origin has great desirability in terms of sustainability and industrial implementation. In this work, we attempted to exploit the vanadium-based catalysts with high retro-aldol condensation (RAC) activity for the synthesis of small polyols from glucose. Vanadium species incorporated or anchored beta zeolites were found to work effectively in synergy with 1Ru/AC to produce hydroxyacetone (HA) as the major product (34%) in a semi-continuously stirred tank reactor under 5% glucose concentration. Catalyst characterization by UV-vis and Raman spectral analysis revealed vanadium species mainly stayed in the incorporated form (tetrahedral) at 0.5% of loading and in the supported form (octahedral) at higher loadings up to 8%. Pyridine infrared spectra and temperature programmed desorption of NH3 revealed weak Lewis acid sites in dominance. Vanadium species in the catalysts displayed multiple catalytic roles (isomerization and RAC reaction, and synergism with the hydrogenation catalyst) in the synthesis of HA from glucose. Structure-activity correlation pointed out that the catalytic activity of vanadium species is not dependent on it coordination status, nevertheless, the adjacent vanadium atoms could possibly improve the isomerization rate over the RAC rate in favor of high yield of HA. The catalyst system is recyclable to at least five times without any considerable loss in its activity and structural integrity. The results presented here provide a promising route for the sustainable production of HA and polyols from carbohydrates by using a highly selective vanadium catalyst.