Nanoporous Zeolite-A Sheltered Pd-Hollow Fiber Catalytic Membrane Reactor for Propane Dehydrogenation

Pd-based membranes are used for separation of H2 from different feed stocks; however, their application is limited in the presence of hydrocarbons due to coke deposition on the membrane surface under operation conditions. Herein, we have developed a triple-layered membrane with a nanoporous Linde type A zeolite on the outer side and an ultrathin (1 μm) Pd membrane on the inner side of the Al2O3 hollow fiber substrate. The membrane was successfully synthesized and tested for hydrogen separation in the presence of lighter hydrocarbons. The presence of uniform nanosize pores in the zeolite layer acts as a barrier for the hydrocarbons to come in contact with the Pd membrane and selectively allows H2 to permeate through the membrane. The membrane showed enhanced performance in the presence of lighter hydrocarbons (C3H8 and C3H6) compared to the only internal coated Pd membrane. The membrane showed excellent stability in the presence of propane and propene at 600 °C for 72 h of operation. The triple-layered membrane was used for propane dehydrogenation reaction using 7.5 wt % Cr/Al2O3 catalyst at 600 °C, and the catalytic activity and stability of the catalytic membrane reactor were evaluated. The results revealed a propane conversion in the membrane reactor ∼15% higher than that in the conventional fixed bed catalytic reactor, which is attributed to the continuous removal of hydrogen from the product mixture during the course of the reaction.