Selective Oxidation of Propene with Air to Propylene Oxide, a Case Study of Autoxidation Versus Catalyitc Oxidation with AMM-Catalysts

摘要

The formation of propylene oxide from propene by birect oxidation with air has been studied with a series of new microporous amorphous catalysts containing isolated active sites. Although the materials showed good activities as heterogeneous oxidation catalysts, the formation of acroleine dominated in the gas phase. Oxidation selectivities of the various catalysts are reported Significant PO-formation was only observed under reaction conditions in volving pressures larger 5 bar. Promoting effects of solvents or additives lide acetaldehyde could be excluded. Best results were observed in continuous gas phase flow experiments. All catalysts studied proved detrimental to the PO-yield and control experiments pointed to catalyst free autoxidation conditions. A factorial design followed by an optimization of the reaction conditions provided PO-selectivities of 60% at propene conversion of 11.4% (T = 290 deg C; pressure = 25 bar; propene content = 75%; total feed = 39.5 ml/min) at continuous reaction conditions. By passivation the inner reactor surfaces with gold, a PO-selectivity of 62.8% at a propene conversion of 15.1% could be obtained, indicating, that autoxidation of propene may become a serious contender in the search for improved production processes. This work is a case study of attempted catalyzed selective oxidation with air illustrationg potential pitfalls and misleading interpretations.