Effect Of ZrO₂ Particle Size On The Catalytic Performance Of Mo-based Catalyst Towards Sulfur-resistant Methanation

Coal to natural gas could utilize the abundant coal resource in our country to clean fuel,which could relieve the pressure of natural gas and optimize the energy structure.Methanation reaction is the core technology of SNG production from coal,and the technology of sulfur-resistant methanation will make the process simplified and economical.Mo catalysts with ZrO₂ as the support showed high sulfur-resistant methanation performance at low temperature.Therefore,the paper focus on the ZrO₂support,by adding Al₂O₃ and size control synthesis of ZrO₂ nanocrystal obtain the structure information and catalytic performance of Mo/ZrO₂ catalyst.The effect of ZrO₂ on the structure and activity of Mo/ZrO₂ was summarized at last.The effect of Al₂O₃ on the catalytic activity and stability of Mo/ZrO₂-Al₂O₃catalyst was investigated by introducing Al₂O₃ into Mo/ZrO₂ catalyst.It was found the surface area and the stability of catalysts increased while the catalytic activity decreased.Two methods were used to prepare Mo/ZrO₂-Al₂O₃ catalyst.It was found the catalytic activity of catalyst prepared by co-precipitation was lower than the catalyst by deposition-precipitation method.But the high-temperature stability of catalyst prepared by co-precipitation was higher,which caused by the formation of ZrO₂-Al₂O₃ solid solution and the increase of surface area.In this work,the effect of ZrO₂ particle size on the surficial and structural properties and catalytic performance of Mo-based catalysts towards sulfur-resistant methanation was investigated.The results showed that the catalytic activity correlated closely with the particle size of ZrO₂.The supports and catalysts were characterized by N₂-adsorption,XRD,Raman,H₂-TPR and TEM to obtain the information about their morphology and structure in order to understand the structure-activity relationship.The results evidence that smaller ZrO₂ particle not only had higher surface area which was beneficial for the dispersion of surface Mo species,but also weaken the interaction between MoO₃ and support.Since them,ZrO₂ support with small particle size favors the formation of monolayer MoS₂ with short length.Catalytic activity evaluation determined that MoS₂/ZrO₂ catalyst with smaller ZrO₂particle size exhibited higher catalytic activity of sulfur-resistant CO methanation due to more edge sites on MoS₂.Impregnation of zirconium hydroxide method was used to prepare Mo/ZrO₂catalysts in sulfur-resistant methanation.The results showed that catalyst prepared by impregnation of zirconium hydroxide achieved the highest CO methanation activity compared with catalysts prepared by impregnation of zirconia and co-precipitation.Characterization results illustrated catalyst prepared by impregnation of zirconium hydroxide had larger surface area and higher concentration of surficial Mo species.Then the preparation conditions were optimized including zirconia precursors,alcohol washing and drying and calcining in N₂ atmosphere.