SYNTHESIS, CHARACTERIZATION, AND CATALYTIC PROPERTIES OF TITANIUM SILICOALUMINOPHOSPHATE TAPSO-5

Titanium-containing silicoaluminophosphates with the AFI structure type (TAPSO-5) have been synthesized hydrothermally. Titanum could be incorporated into the SAPO-5 structure without formation of TiO2 up to Ti/Si = 0.05 in the precursor gel. Under the synthesis conditions, Ti4+ ions were most likely isolated and tetrahedrally coordinated in the siliceous domains of the crystals, as evidenced by u.v.-vis and i.r. spectroscopies. The materials were found to be active as catalysts in epoxidation reactions at low temperatures. In contrast to pure aluminophosphate molecular sieves, the presence of large amounts of SiO2 in TAPSO-5 increased the hydrophobic character of the material, and both H2O2 and tert-butyl hydroperoxide could be used as oxidants. The activity of the catalyst in the epoxidation of cyclohexane as well as the nature of the products obtained strongly depended on the peroxide used.