A review on dry reforming of methane over perovskite derived catalysts

Dry reforming of methane (DRM) is widely studied as one of the potential routes for syngas production from two greenhouse gases (CH4 & CO2) and can reduce the net emission of these gases if the energy used for it is derived from non-hydrocarbon source. Many conventional metal/support catalyst systems, though are highly active, deactivate within few hours due to surface coke deposition or sintering of the active metal clusters. In order to overcome these challenges and withstand the extreme operating temperatures of DRM, active metals can be incorporated into crystalline oxides like perovskites, pyrochlores, hydrotalcites and hexaaluminates. These metal-containing oxides, once the active metal is reduced, produce a highly dispersed active catalyst. This review emphasizes the application of perovskite-derived catalysts in dry reforming of methane. Perovskites are crystalline oxides with general formula of ABO3, where A is generally a rare earth, alkaline earth or alkali metal cation while B is a transition metal cation. The exsolution process involved in the reduction of perovskite catalysts produces smaller size metal particles which in turn dictate the superior catalytic performance of these materials. Preparation methods, ?A? and/or ?B? site partial substitutions and additional use of high surface area supports (like mesoporous silicates and basic oxides) for dispersing perovskite catalysts, greatly influence the physicochemical and catalytic behavior of these perovskite derived catalysts. ?A? site substitutions generally enhance the oxygen mobility in the perovskite structure by generating oxygen vacancies which suppress the carbon deposition, while bimetallic synergistic effects are produced by addition of a second metal at the ?B? site which tend to increase the activity and stability of these catalysts. This review also includes a detailed discussion on the mechanism of DRM in perovskite derived catalysts.