Ni Catalyst From Supported Perovskite For CO Methanation

In the recent years,Conversion of coal to synthetic natural gas?SNG?via methanation reaction is attracting great attention in China,which not only provides a solution for full utilization of the coal resource,but also eases the supply and demand contradictions of natural gas.Ni-based catalysts are frequently employed in industry and academic research due to their low price and relatively high activity for CO methantion.However,Ni catalysts often suffer from sintering as well as coke formation during the methanation process,resulting in catalysts deactivation.Therefore,developing an anti-sintering and/or anti-carbon deposition catalyst for the CO methanation reaction would be of great importance.In this paper,precursor LaNiO₃/ZrO₂ were fabricated to prepare Nano nickel catalysts for CO methantion based on the role of Ni,ZrO₂ and La₂O₃ in CO methanation.In addition,the effect of LaNiO₃ loading,preparation method,space velocity and doping Co in B site were studied for CO methanation.A series of catalyst precursor xLaNiO₃/ZrO₂?x=15%,20%,25%?were prepared by citrate complexing method,and the catalysts were characterized by BET,XRD,H2-TPR.After reduction the xLaNiO₃/Zr O₂ catalysts precursor preferred to form Ni nanoparticles highly dispersed on ZrO₂ and modified with La₂O₃?Ni-La₂O₃/Zr O₂?,and the catalysts had high catalytic activity for CO methanation.With the increase of LaNiO₃,the methanation catalytic activity was first increased and then decreased.20%LaNiO₃/ZrO₂ catalyst showed the highest CO conversion and CH4 selectivity.Besides,the effect of space velocity between 7500 and 30000 ml g-1 h-1 was studied,with the increased of space velocity,the catalytic activity was first increased and then decreased.The catalyst 20%LaNiO₃/Zr O₂ obtained the maximum catalytic activity at15000 ml g-1 h-1.For comparison,NiO-La₂O₃/ZrO₂ was prepared by traditional impregnation method,which also produces Ni-La₂O₃/Zr O₂ catalyst after reduction.The results suggest that Ni/La₂O₃-ZrO₂ derived from LaNiO₃/ZrO₂ showed a higher dispersion of Ni on ZrO₂ and exhibited higher CO conversion and CH4 selectivity.Meanwhile,the LaNiO₃/ZrO₂ catalyst showed excellent stability owing to the significant improvement in both anti-carbon deposition and anti-sintering.The catalyst prepared according to this scheme intensified the interaction between Ni and La₂O₃,thus favoring thesynergistic effect of La₂O₃ and Ni,which led to the high dispersion of Ni nanoparticles as well as the very good anti-sintering and anti-carbon deposition ability.The effect of doping Co in B site of LaNiO₃ for CO methanation was studied.A series of catalysts precursor 20%LaNi_1-xCo_xO₃/ZrO₂?x=0.1,0.2,0.3?by citrate complexing method,and after reduction the catalysts precursor favored to form Ni-Co-La₂O₃/Zr O₂.The characterization of XRD,TPR and TEM suggested that the Ni-Co alloy was formed after reduction.Ni3+ and Co3+ are evenly distributed at atomic level in the precursor of LaNi1-x CoxO₃,so during the reduction,Ni and Co can reduce from LaNi1-x Cox O₃ together and prefer to form Ni-Co alloy.With the increase of Co doping,the methanation catalytic activity declined gradually.Besides,the stability of catalyst decreased after doping.The results of H2-chemisorption suggested that the doping of Co in B site was not favor the dispersion of the metal.