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

Ti-beta zeolite was synthesized in the presence of sodium cations by a dry- gel conversion method using tetraethylammonium hydroxide as a structure-dir ecting agent. As evidenced by diffuse reflectance UV spectroscopy, incorpor ated titianium species were tetrahedrally coordinated in the zeolites and n either anatase-like phase nor hexacoordinated titianium species belonging t o an amorphous titanosilicate phase was detected at the sodium content of l ower 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 tha n corresponding linear alkenes and alkanes, showing the lack of steric impe diments in the pores of Ti-beta. Dimethylcyclohexanes were more reactive wh en tertiary H atoms predominantly occupy the equatorial position than when they occupy the axial position. Ti-beta samples exhibited high activity als o for the oxidation of C-6-C-8 cyclic alcohols. (C) 1998 Academic Press.