Strategies for improving sulfur resistance of lean methane oxidation catalysts: Progresses and future perspectives

Abstract

Thanks to the high abundance and high calorific value, methane is increasingly used to replace petroleum and coal, but the trace amount of unburned methane has a significant greenhouse effect. Catalytic lean methane oxidation (LMO) is a feasible way to consume unburned methane, but its catalysts can be easily deactivated by sulfur-containing feedstocks. This review aims at summarizing the mechanisms of sulfur-induced deactivation and reviewing strategies for improving sulfur resistance of LMO catalysts. Firstly, mechanisms of catalyst deactivation caused by sulfur-containing feedstocks are discussed. It can be summarized as that the sulfur-induced sulfates and sulfites obstruct accessibility of CH4 to active sites and lead to catalyst deactivation. Then, current strategies for improving sulfur resistance in terms of catalyst design and reaction condition optimization are reviewed. As for catalyst design, obstruction of SO2 adsorption via active phase modification and construction of core–shell structure are stressed, and introduction of sacrificial component to delay SO2-induced deactivation are discussed in detail. High temperature and anti-sulfur impacts of H2O and NOx are also summarized for reaction condition optimization. In addition, mechanisms and factors of catalyst regeneration are briefly elucidated. At last, future perspectives are provided for designing catalysts with high sulfur resistance in LMO reactions.