Effect Of Zirconia Morphology On Sulfur-Resistant Methanation Performance Of MoO₃/ZrO₂ Catalyst

Synthetic natural gas?SNG?production from coal is one of the ways of clean utilization of coal.It is good for the environment,the upgrading coal industry and the national security.The key technology of coal to SNG is the development of high efficient sulfur resistant methanation catalyst.Two kinds of ZrO₂ support with different morphologies were prepared by facile solvothermal method in different solvents.Their supported Mo-based catalysts were prepared by impregnation method and the effect of zirconia morphology on the performance of sulfur-resistant methanation was examined.The MoO₃/m-ZrO₂catalyst has weaker interaction between support and active Mo speices than the MoO₃/t-ZrO₂ catalyst,which facilitates to forming active species of nanocrystalline MoS₂ layers for sulfur-resistant methanation.The weaker interaction of molybdenum species with m-ZrO₂ is related with the more covalent character of the Zr-O bond and more oxygen defective structure of m-ZrO₂.A larger number of Lewis acid centers appear on the surface of m-ZrO₂,which verified the substantial vacancies on m-ZrO₂exposing coordinately unsaturated Zr³⁺and Zr⁴⁺cations.The effects of Mo loading and sulfuration technique on sulfur-resistant methanation over MoO₃/ZrO₂ catalyst were investigated.The results showed that m-ZrO₂ is superior to t-ZrO₂ in dispersion of molybdenum oxide species due to more active Mo species.The optimum sulfuration temperature of MoO₃/m-ZrO₂ is 300°C.Higher sulfidation temperature than 300°C is not benifical for the sulfidation and transformation of molybdenum oxide.The catalyst sulfided ant 300°C with temperature rise at 1?/min has higher selectivity and activity than those sulfided at constant temperature and stepwise sulfidation.Based on the above findings,the effect of additive on the performance of catalyst prepared by co-precipitation method and solvothermal method were discussed.It was found that appropriate additive are beneficial to stabilize the potential energy of Zr ions and make the catalyst stable thermodynamically by preventing phase change of the crystals.The addition of oxalic acid is favorable for the loading of Mo species in the process of impregnation.This is beneficial to the generation of active components,and is conducive to improve the performance of sulfur-resistant methanation.