Cobalt-promoted Zn encapsulation within Silicalite-1 for oxidative propane dehydrogenation with CO2 by microwave catalysis at low temperature

Abstract

The oxidative dehydrogenation of propane by CO2 (CO2-ODHP) is an attractive and sustainable process that can simultaneously produce propylene and reduce CO2, but C3H8 and CO2 are relatively inert at low temperatures. Herein, we developed novel approach for oxidative dehydrogenation of propane with CO2 by microwave catalysisat low temperature. A novel microwave catalyst, cobalt-promoted Zn encapsulation within Silicalite-1 (Zn8Co1@S-1+SiC), has been synthesized by confining Zn and Co species within Silicalite-1 zeolite via the hydrothermal method. This microwave catalyst achieved C3H8 conversion of 68%, CO2 conversion of 16%, and C3H6 selectivity of 88% under microwave irradiation at a low temperature of 500°C. In comparison, under the conventional reaction mode of the identical conditions, shows only C3H8 conversion of 14% and CO2 conversion of 5%. Characterizations showed that encapsulating Zn and Co species within Silicalite-1 zeolite inhibits metal loss and generates more Lewis acid sites, thereby enhancing dehydrogenation activity. The combination of zinc and cobalt demonstrated a synergistic effect. The carbon deposition on the Zn8Co1@S-1 catalyst was reduced from 5.75% to 4.62% by introducing CO2 into the propane dehydrogenation to propylene. In addition, the activation energy of oxidative propane dehydrogenation with CO2 under microwave irradiation was reduced (85.05 kJ/mol→ 46.54 kJ/mol). The superior catalytic performance under microwave irradiation at low temperatures can provide guidelines for propane dehydrogenation with microwave catalyst design and process enhancement.