ACTIVITY OF TI-BETA CATALYST FOR THE SELECTIVE OXIDATION OF ALKENES AND ALKANES

Ti-Beta zeolites with different titanium and aluminum contents have been prepared by changing the concentration of Ti and Al in the synthesis gel and the crystallization time. The gels were prepared from Aerosil as silica source. Ti-Beta samples were characterized by XRD, I.R., SEM, and diffuse reflectance (DR) spectroscopy in the UV-visible region. According to the characterization data, in the calcined dehydrated samples, titanium is incorporated into the framework of the zeolite Beta in a tetracoordinated state. No anatase phase was observed in the DR spectra. The catalytic activity for the selective oxidation by H2O2 of alkanes and alkenes with different molecular sizes was measured and compared with that of TS-1 under the same experimental conditions. For molecules whose diffusion is not restricted in either MFI or BEA structures, the intrinsic activity of the Ti centers is lower in Ti-Beta than in TS-1. However, the large-pore Ti-Beta catalyst shows superior activity compared to the medium-pore TS-1 for the oxidation of bulkier molecules. © 1994 Academic Press, Inc.