LAUSR

Propylene production through propane dehydrogenation (PDH) is endothermic, and high temperatures required to achieve acceptable propane conversions lead to low selectivity and severe carbon-induced deactivation of conventional catalysts. We developed a catalyst-membrane system that removes the hydrogen by-product and can thus achieve propane conversions that exceed equilibrium limits. In this codesigned system, a silica/alumina (SiO2/Al2O3) hollow-fiber hydrogen membrane was packed with a selective platinum-tin (Pt1Sn1/SiO2) PDH catalyst on the tube side with hydrogen diffusing from the tube to the shell side. We demonstrate that the catalyst-membrane system can achieve propane conversions >140% of the nominal equilibrium conversion with a propylene selectivity >98% without deactivation of the system components. We also show that by introducing oxygen on the shell side of the catalyst-membrane system, we can couple the endothermic PDH reaction on the tube side with exothermic hydrogen oxidation on the shell side. This coupling results in higher rates of hydrogen transport, leading to further enhancements in the propane conversion as well as desired thermoneutral system operation. Editor’s summary Propylene is an important feedstock in polymer synthesis, and there is a need for alternative sources to meet demand. Almallahi et al. designed a reactor for propylene synthesis from propane in which a selective platinum-tin catalyst supported in silica is packed in the inside wall of a hollow-tube silica-alumina hydrogen membrane. Thermodynamic limits for propane dehydrogenation were exceeded by up to 40% with high selectivity by using membranes to remove the hydrogen by-product. Reaction of the hydrogen with oxygen in the sweeping gas to form water generated heat to help drive the endothermic dehydrogenation reaction. —Phil Szuromi Oxidation of membrane-extracted hydrogen could help deliver heat to the endothermic propane dehydrogenation reaction.