Continuous epoxidation of propylene with oxygen and hydrogen on a Pd-Pt/TS-1 catalyst

Propylene epoxidation over a Pd-Pt/TS-1 catalyst with in situ formed hydrog en peroxide was carried out in a fixed bed reactor under high pressure cond itions. The continuous operation allowed the study of catalyst deactivation and changes in product distribution with time-on-stream. The initial propy lene oxide selectivity was very high. 99% at 3.5% conversion, but the catal yst deactivated rapidly with time-on-stream and successively the formation of methyl formate became the prevalent reaction. Using carbon dioxide, inst ead of nitrogen, had a beneficial effect on the formation of propylene oxid e, and even higher yields were obtained when increasing the pressure from 5 0 to 120 bar (supercritical fluid phase). Thermal analysis (TA-MS and TA-FT IR) indicated that catalyst regeneration requires oxidation at elevated tem perature; washing with an organic solvent is less efficient. The serious ca talyst deactivation and the striking shift in the selectivity pattern of th e catalyst is traced to competing alcohol oxidation on platinum metal. (C) 2001 Elsevier Science B.V. All rights reserved.