Design of a CrZrOx–Cu2MnOx@Na2WO4 catalyst–oxygen carrier system for efficient chemical looping oxidative dehydrogenation of propane†

Abstract

In the utilisation of most oxide-based propane dehydrogenation (PDH) catalysts, each reaction–regeneration cycle necessitates both coke combustion and hydrogen reduction to achieve complete regeneration of the catalyst. However, the need for hydrogen reduction makes it difficult to use such catalysts in chemical looping oxidative dehydrogenation (CL-ODH) processes. This study prepared a series of CrZrO_x catalysts with Cr/Zr atomic ratios ranging from 0.02 to 1 using a co-precipitation method. Electron paramagnetic resonance (EPR) analysis revealed that the catalyst surface in its oxidised state is rich in oxygen vacancies. These vacancies created numerous coordinated unsaturated Zr (Zr_cus)-based active sites directly linked to the catalyst's unique catalytic activity. This catalyst was paired with a Cu₂MnO_x@Na₂WO₄ oxygen carrier to perform the CL-ODH of propane. The results demonstrated that the catalyst–oxygen carrier coupling system significantly enhanced single-pass propane conversion in the PDH process, increasing the initial propane conversion from 27.2% to 35.9%. The enhanced conversion, along with the observed hydrogen consumption over time, confirmed that the PDH process was coupled with hydrogen oxidation via the lattice oxygen of the oxygen carrier. This coupling broke through the thermodynamic equilibrium, thereby significantly improving the single-pass propane conversion. These findings provide valuable insights for designing novel catalyst systems tailored for the CL-ODH of propane.