The conversion of renewable biomass feedstocks for sustainable fuels and chemicals production is of great interest to replace those based on fossil fuels with diminishing availability and environment issues. 5-Hydroxymethylfurfural (HMF) is one of the “top 10 value-added chemical from biomass”. As a versatile and important building blocks, HMF is a potential candidate for the production of various chemicals, such as liquid alkanes, biofuels, furan derivatives. Hexose (mainly glucose and fructose) dehydration to produce HMF is a promising routes since it is abundant and easily derived from biomass depolymerization. Compared to fructose, glucose is favoured due to its wide availability and low cost. Various catalysts, including liquid acids, zeolites, heteropolyacid, metal-organic framework, resin and ionic liquid, combined with water-organic biphasic systems are investigated. Mechanism studies indicates the cooperativity of Lewis acid sites (LAS) for glucose isomerization to fructose and Brønsted acid sites (BAS) for fructose dehydration in an aqueous-organic biphasic system is crucial. Low cost zeolites are of great interest since the surface Brønsted and Lewis acidity can be easily tuned by post-treatment, such as dealumination and ion-exchange process. It can result in extra-framework Al species acting as LAS, however, the activity suffers from leaching of EFAl from surface with reaction progress in liquid phase. In this work, amorphous silica-alumina catalysts with various Si/Al ratios have been prepared. All catalysts display similar 27Al NMR spectra as observed for pure alumina. The co-existence of Brønsted and Lewis acids on surface was revealed by 13C MAS NMR spectroscopy using 2-13C-acetone as probe molecules. These catalysts are active in the conversion of glucose into HMF and the catalytic performance improved with suitable BAS/LAS ratio. Since combining the preparation and calcination together at high temperature, these catalysts are quite stable and can be reused for many times without any activity loss.

Surface acidity of atomic dispersed aluminum species in silica for sustainable fuels and chemicals production

256th National Meeting (2018)

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