Regeneration of Ni-Zr Methane Dry Reforming Catalysts in CO2: Reduction of Coking and Ni Redispersion

Abstract

Bimetallic Ni-Zr layers on top of a Zr metal substrate are oxidatively transformed into an active Ni metal-ZrO2 interfacial state under methane dry reforming (DRM) conditions, which exhibits progressive coking with increasing DRM cycle number and time. Complementing established anticoking catalyst- and process-design strategies, the efficiency, as well as the structural and surface-chemical consequences of the intermediate regeneration of the active state using pure CO2, were studied. By combining repeated catalytic DRM testing, X-ray photoelectron spectroscopy, and chemically resolved scanning electron microscopy, we show that catalyst regeneration using the inverse Boudouard reaction not only depletes the main part of the deposited coke efficiently but also leads to an improved and particularly active catalyst state exhibiting redispersion of Ni toward small particles and optimized Ni/ZrO2 interfacial dimensions.