On the applicability of PdAg membranes in propane dehydrogenation processes

Abstract

The applicability of PdAg membranes in the propane dehydrogenation process has been evaluated in this work. The integration of membranes into the propane dehydrogenation process has the potential of making a significant step forward in energy and resource efficiency of the selective production of propylene. To assess the compatibility of the PdAg membrane with the process conditions of propane dehydrogenation, two double-skin PdAg membranes were exposed to the emulated process conditions of two cases: 1. A fully integrated membrane-reactor system (higher temperature) and 2. A cascade of catalyst and membrane separator units (lower temperature). The results of this study showed that at high temperature (475–500 °C) strong reduction of the hydrogen flux is observed during exposure to reactant and product containing mixtures. The reason for this is the deposition of carbonaceous species on the active sites of the membrane. Additionally, also the lifetime of the membrane (in terms of selectivity) was significantly lower due to the regeneration performed at high temperature in diluted air. The lower temperature experiments (300–350 °C) showed a much lower degree of deactivation and at the same time the membrane could be regenerated in air repeatedly without visible reduction of its selectivity. These findings show that the DS-PdAg membrane can be repeatedly exposed to reaction-regeneration cycles at acceptable activity and without significant loss of selectivity when operated in a cascade configuration at a temperature at or below 350 °C.