Abstract:With an aluminum-free beta molecular sieve as the silicon source and tin (IV) chloride pentahydrate as the tin source, a microporous and mesoporous hierarchical Sn-Beta zeolite catalyst was prepared by two-step hydrothermal recrystallization under the action of a mesoporous template agent, cetyltrimethylammonium bromide (CTAB). The hierarchical Sn-Beta molecular sieve was then used in the isomerization of glucose to fructose. The properties of the sieve were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and nitrogen adsorption-desorption isotherm. The effects of reaction temperature, reaction time, amount of catalyst, and molar ratio of silicon/tin on glucose conversion and fructose yield were investigated, and the reusability and regeneration of the novel catalyst were also studied. The results showed that the hierarchical Sn-Beta molecular sieve had not only the typical framework structure of BEA-type micropore molecular sieves, but also the mesopore structure. In the catalytic isomerization of glucose, the yield of fructose could reach 47.20% when the reaction temperature was 120 ℃, the reaction time was two hours, the molar ratio of silicon oxide/tin oxide was 100, and 4 g of catalyst and 40 mL glucose (10 wt%) were used. Additionally, the catalyst exhibited a good regenerative property and reusability.
