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 a novel approach for oxidative dehydrogenation of propane with CO₂ by microwave catalysis at low temperature. A novel microwave catalyst, cobalt-promoted Zn encapsulated within silicalite-1 (Zn₈Co₁@S-1 + SiC), has been synthesized by confining Zn and Co species within a silicalite-1 zeolite via a 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, in the conventional reaction mode of the identical conditions, it shows only C₃H₈ conversion of 14% and CO₂ conversion of 5%. Characterization studies showed that encapsulating Zn and Co species within the silicalite-1 zeolite inhibits metal loss and generates more Lewis acid sites, thereby enhancing the 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⁻¹ → 46.54 kJ mol⁻¹). The superior catalytic performance under microwave irradiation at low temperatures can provide guidelines for propane dehydrogenation with microwave catalyst design and process enhancement.