Interstitial carbon in an active RuO2 catalyst and its stabilization under low temperature CO2 methanation reaction conditions

Abstract

Lowering the reaction temperature in CO2 methanation promotes methane generation due to thermodynamic constraints and increases economic viability. Carbon-doped RuO2 catalyst with the stabilization of the ruthenium oxy-carbonate phase can be very active for low temperature CO2 methanation. However, a critical aspect is the generally low stability of interstitial carbon ad-atoms, where their removal during reaction can result in catalyst deactivation. In this work, the stabilization mechanism of the ruthenium oxy-carbonate active phase under reaction conditions is studied and achieved by combining advanced operando spectroscopic tools with catalytic studies. Three sequential processes (carbon diffusion, metal oxide reduction, and decomposition of the oxy-carbonate phase) are discussed, being influenced by the reaction conditions. We demostrate how to control the reaction variables and catalyst composition to promote carbon diffusion, stabilising the oxy-carbonate catalytically active phase under steady state conditions, and maintain catalyst activity and stability over long operation times.