Conversion of glucose into 5-hydroxymethylfurfural on granular zeolite catalysts

Анотація

Biomass-derived 5-hydroxymethylfurfural (5-HMF) is a potential raw material for the production of a wide range of valuable chemicals and biofuels. Industrial production of 5-HMF from hexoses on solid catalysts is promising nowadays. Acid zeolites have great potential in application as catalysts for the dehydration of sugars. The purpose of this work was to obtain granular zeolite catalysts with optimal acidity and evaluate their effectiveness depending on the nature of the binder used. A zeolite catalyst without binder and samples with 10 wt % of kaolin/alumina were prepared. Their porous characteristics and acidity were studied by means of nitrogen low temperature adsorption/desorption, ammonia thermo-programmed desorption, and pyridine adsorption with IR control. The activity and selectivity of the catalysts for 5-HMF synthesis from glucose in the dimethyl sulfoxide medium at 160 ◦C were studied. The high efficiency of granular samples in glucose transformation into 5-HMF is confirmed. They are not only not inferior to, but even superior to, powdered samples. The component sources of Brønsted and Lewis acidity of the ammonium form of zeolite, which demonstrates acceptable activity (selectivity for 5-HMF is 34 %) despite the small number of Lewis centers, are considered in detail. The highest efficiency is demonstrated by the sample with aluminum oxide, which not only does not significantly deteriorate the microporous characteristics but also improves the mesoporosity of the catalyst. The selectivity towards 5-HMF on it reaches 44%. However, the developed mesoporosity of the sample with aluminum oxide is not critical to its activity. The main influence on the effectiveness of the catalyst in the synthesis of 5-HMF is played by the presence of acid centers of medium strength.