The Isomerization Of Glucose Into Fructose Over Sn-Beta Synthesized Through Isomorphous Substitution

In recent years, the rapid economic development has brought the consumption of fossil resources and serious environmental pollution, the development and utilization of biomass is attracting more and more attention. Glucose is the most abundant simple sugar in nature, which is applied widely. Sn-Beta as a Lewis solid acid catalyst, which can catalyze glucose to fructose efficiently, meanwhile, fructose can easily convert into5-(hydroxymethyl) furfural (HMF) in acid system. However, the Sn-Beta usually requires approximately40days to get a better crystal form by hydrofhermal method, and the addition of the fluorine brought serious environmental pollution. Therefore, we need to find an environment-friendly way to prepare Sn-Beta. From the point of industrialization and environment, Sn-Beta zeolite prepared through post-synthesis can be more potential to isomerize glucose into fructose in aqueous media.Discussing the following aspects in the thesis:(1) Investigating the catalytic activity of several Sn-containing materials in the glucose isomerization reaction. The results showed that Sn-Beta had higher activity than other catalysts in the isomerization reaction. Using Sn-Beta prepared by hydrothermal method as catalyst, the effects of reaction temperature, reaction time, amount of catalyst in the reaction were studied. When40nig Sn-Beta was added into0.4ml of10%glucose solution (mass fraction), glucose conversion and fructose yield were56%and45%respectively for1h reaction time at393K.(2) Using Al-Beta or B-Beta as precursor. Sn-Beta zeolite was successfully prepared by means of the isomorphous replacement method. The method is easy and could not bring environmental pollution. Sn-Beta prepared by the method shows excellent activity in the reaction of glucose isomerization to fructose. The effects of reaction temperature, reaction time, amount of catalyst, solvent and sodium halide additives in the reaction were studied. The results showed that under the optimized preparation and reaction conditions, isomorphous replacement2h at773K and30mg Sn-Beta was added to0.4ml of10%glucose solution, the maximum yield to fructose reached43%at about66%glucose conversion for2h reaction time at120℃(3) Investigating the reusability of the catalyst for the glucose isomerization reaction. The catalyst could be regenerated by calcination and the catalytic activity was relatively stable for four times in the glucose isomerization reaction, which indicating that Sn-Beta has a preferable reusability.