Immobilization of 12-Tungstophosphoric acid in alumina-grafted mesoporous LaSBA-15 and its catalytic activity for alkylation of o-xylene with styrene

摘要

This paper dealed with the immobilization of 12-Tungstophosphoric acid (HPW) in alumina-grafted mesoporous LaSBA-15 and its catalytic activity for alkylation of o-xylene with styrene were also studied. All the samples were characterized by elemental analysis, nitrogen adsorption, FT-IR spectra, diffuse reflectance UV-vis spectra, XPS, ~(27)Al MAS NMR and NH3-TPD. Results showed that the mesopore structure of LaSBA-15 was maintained well even after the surface modification and the subsequent immobilization step of HPW. It was demonstrated that grafting of silica with small alumina clusters at partial to full surface coverage could produce isolated basic sites to anchor the molecular HPW. Among the catalysts investigated, when the content of alumina was suitable (20 wt.%), it exhibited the best catalytic performances in terms of yield and stability. This behavior may be owing to high dispersion of the HPW species on the surface modified LaSBA-15 and the strong interaction between the HPW and the support in the presence of alumina, thus prevent HPW leaching from the support.