Role of Active Site and CO2-Interacting Surface Species in Dry Reforming of Methane over Strontium Promoted Ni Catalyst Supported by Lanthanum-Zirconia.

Abstract

In the context of global warming, the dry reforming of methane (DRM) has gained significant attention due to its ability to simultaneously deplete two greenhouse gases, i. e. CH₄ and CO₂, and generate syngas. Herein, strontium-promoted Lanthanum-zirconia supported Ni catalysts are investigated for DRM and characterized by X-ray diffraction, surface area and porosity, FTIR-RAMAN spectroscopy, and temperature-programmed experiments. The Ni/LaZr catalyst contains formate and oxycarbonate-like CO₂-interacting species, while strontium-promoted catalysts have additional ionic CO₃ ^2- species. The current catalyst system of 2 % strontium-promoted Ni/LaZr has active sites derived from three types of NiO: easily reducible, moderately interacted, and strongly interacted. During the DRM reaction over the current system, CO₂ is a better oxidant than O₂ for removing carbon deposits. Additionally, the catalysts attain higher reducibility under oxidizing gas (CO₂) and reducing gas (H₂) during the DRM reaction. For optimal hydrogen yield of approximately 60 % within 420 minutes of operation over Ni2Sr/LaZr catalyst, a balance between the population of active site Ni and CO₂-interacting surface species is necessary.