Propylene epoxidation with hydrogen peroxide over palladium containing titanium silicalite

The epoxidation of propylene to propylene oxide with H2O2 was studied over palladium impregnated and reduced titanium silicalite (TS-1), over merely impregnated titanium tilicalite and over untreated titanium silicalite. The use of such catalytic systems in the epoxidation of proplyene with a H-2-O-2 mixture motivated us to assess the influence of operating conditions and the effect of the Pd loading on the epoxidation capability of the titanium silicalite catalyst. Concerning the operating conditions TS-I was found to be very active even at temperatures as low as 10 degrees C. Lowering the H2O2 concentrations to only 2 wt.% of H2O2 caused the PO yield to increase slightly over TS-I and 1% Pd/TS-1. TS-I catalysts that were merely impregnated with [Pd(NH3)(4)]Cl-2 were less active than the catalysts that were reduced after impregnation, though the latter is more active in the decomposition of H2O2. The deactivation of TS-1 after impregnation with [Pd(NH3)(4)]Cl-2 was probably caused by the blocking of the Ti sites by ammonia, since the impregnation with PdCl2 did not cause any decrease in activity. Reducing the catalyst removes the ammonia and improves the catalytic performance of the Pd loaded catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.