Oxidation activity of Ti-beta synthesized by a dry-gel conversion method

摘要

Ti-beta zeolite was synthesized in the presence of sodium cations by a dry-gel conversion method using tetraethylammonium hydroxide as a structure-directing agent. As evidenced by diffuse reflectance UV spectroscopy, incorporated titianium species were tetrahedrally coordinated in the zeolites and neither anatase-like phase nor hexacoordinated titianium species belonging to an amorphous titanosilicate phase was detected at the sodium content of lower than 1.0 mol%. It was found that the Ti-beta catalysts gave very high H2O2 conversion and selectivity in the oxidation of cyclohexene in methanol used as solvent. The C-6-C-8 cyclic alkenes and alkanes reacted faster than corresponding linear alkenes and alkanes, showing the lack of steric impediments in the pores of Ti-beta. Dimethylcyclohexanes were more reactive when tertiary H atoms predominantly occupy the equatorial position than when they occupy the axial position. Ti-beta samples exhibited high activity also for the oxidation of C-6-C-8 cyclic alcohols. (C) 1998 Academic Press. [References: 25]