Epoxidation of propylene using supported titanium silicalite catalysts

The propylene epoxidation using supported titanium silicalite TS-1 catalyst was systematically investigated in a fixed bed reactor. Different supports such as SiO2 and Al2O3 were used and two molding methods were adopted to prepare the catalyst. Strip TS-1 catalyst of 1 min x 2 mm dimensions is obtained by the extruding method. Use Of SiO2 as the support rather than Al2O3 is better because the latter has strong acidity that promotes the side reaction of propylene oxide (PO) with the solvent. With the decrease of the amount of TS-1 in TS-1/SiO2, the PO selectivity increases. The lamina TS-1 catalyst, the core of which is an inert ball used as the support and the shell of which is a TS-1 lamina of 0.1-0.2 min, exhibits better performance than the strip TS-I catalyst owing to its shorter diffusion path for reaction heat, raw material and product. The lamina TS-1 catalyst was used in the fixed bed reactor for about 200 h. The results indicate that it is a promising catalyst in propylene epoxidation. The effect of aluminum impurity was also investigated. It has been shown acid sites originating from framework aluminum can catalyze the side reaction and a small amount of base can inhibit it. In conclusion, diffusion and the concentration of acid sites are the two main factors influencing the performance of titanium silicalite catalyst in propylene epoxidation. (C) 2002 Elsevier Science B.V. All rights reserved.