Research advance in methanation catalysts for synthetic natural gas and their catalytic mechanisms

The technology of synthetic nature gas( SNG) is an effective way for the conversion of highcarbon energy to rich-hydrogen and low-carbon energy.It is an important way of clean utilization of coal that natural gas is prepared from synthesis gas via methanation reaction by using coal as the raw material in future.In this paper,the research status of SNG at home and abroad and the application of methanation reaction in SNG were introduced.The preparation methods and the chemical structural characteristics of the common carriers for supported oxides Ni-based catalyst,such as Al2O3,ZrO2,SiO2and TiO2,and the catalyst additives in methanation catalysts for CO and CO2were expounded.The research status of the novel catalyst carriers( MWCNT,SiC and LaFeO3),noble metal catalysts,amorphous alloy catalysts andperovskite catalysts,and the effects of their preparation methods on the catalyst performance were discussed.The reasons of catalyst deactivation due to high-temperature sintering,catalyst poisoning and coke deposit were analyzed and the improvement methods of the commercial catalysts for methanation were put forward.The mechanisms of the methylene,the surface carbon and the shift-methanation for CO methanation were described,respectively.There existed various differences among the reaction mechanisms for CO2methanation in recent years,but the theory that carbon containing intermediate species were generated in the catalytic process was recognized.The research directions for methanation catalysts in future,including the development of new methanation catalysts( low temperature catalyst,catalyst doping and modification),new composite carriers,anti-sulfur catalysts( molybdenum,and tungsten based catalysts),development of the new methanation process and the further research on methanation mechanism,were out lined.