Recent progress on catalysts for low-concentration coal mine gas oxidation
During the coal extraction process,the emission of low-concentration coal mine gas signifi-cantly contributes to greenhouse gas emissions.Catalytic oxidation is an effective strategy for converting the coal mine gas to carbon dioxide,thereby alleviating the greenhouse effect.However,the activity and stability of most reported catalysts remain inadequate for widespread application.The reaction mechanisms of coal mine gas oxidation are summarized,and the recent progress and future perspectives for catalyst design are presented.C—H activation is the rate-determining step in coal mine gas oxida-tion reactions.Noble-metal catalysts with high activity for C—H activation and metal oxide catalysts with high thermal stability are widely used for coal mine gas oxidation.Regarding the noble-metal cata-lysts,the type of active metals significantly influences C—H activation.Modification of the supports and the addition of additives can adjust the distribution of active metals.For metal oxide catalysts,modification of catalyst structure and composition can regulate the surface areas,oxygen vacancy con-centrations,and chemical bonds,thereby improving catalytic activity.In addition,the water resistance and sulfur resistance of catalysts are vital for the stable oxidation of coal mine gas.The construction of an encapsulated structure and a specific active metal structure are conducive to water desorption.Fur-thermore,the addition of dopants can adjust electronic structure of active metals,thus enhancing the water resistance of catalysts.With regard to sulfur resistance,the construction of an encapsulated struc-ture to weaken sulfur adsorption and the addition of a sacrificial component to delay sulfur deactivation are two commonly-used strategies.
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