Design and optimization of a catalytic membrane reactor for the direct synthesis of propylene oxide

Using numerical simulations, a new membrane reactor is proposed for the direct synthesis of propylene oxide (PO) in liquid phase. The reactor is a combination of two consecutive catalytic reactor units, one for the hydrogen peroxide (H₂O₂) synthesis on a Pd/SiO₂ catalytic membrane layer, and the second for the conversion of hydrogen peroxide with propylene (C₃H₆) to PO on a titanium silicalite-1 (TS-1) catalytic layer. The membrane reactor is described numerically by a set of kinetic-diffusion mass balance equations. The optimization of the reactor design is achieved by determining membrane pore size, thickness and gas pressures which provide conversion and selectivity performance comparable to the industrial requirements. An optimal pore size of 0.2-0.4μm was found for the Pd/SiO₂ membrane layer. The results show that a Pd/SiO₂ membrane thickness of 250μm and a TS-1 layer of 100μm are necessary to ensure conversion and selectivity performance of the catalytic membrane reactor comparable to the industrial ones. Calculated these optimized dimensions of the membrane reactor, a total membrane area of 84,000m² is required for the production of 300kton/year of propylene oxide.