Preparation Of Low-containing Ni-based Catalyst Supported On Rutile For Methanation

Fuel cells convert chemical energy directly into electrochemical energy with high efficiency and low emission of pollutants.The polymer-electrolytemembrane fuel cell utilizes hydrogen as a fuel.However,the platinum anode is poisoned in the presence of small amounts of CO in the hydrogen stream and thus the acceptable CO concentration must be below 10 ppm.A trace-level of CO concentration in hydrogen can also make noble catalysts poisoning in hydrogenation processes of synthesis ammonia and petrochemical industry.Most of the hydrogen is made from coal in our country,and about 0.2-2 vol.%of carbon monoxide is usually contained in the hydrogen stream from the water-gas shift reactor.Furtunely,the methanation of carbon monoxide is usually employed to purify the hydrogen product.Since the carbon monoxide methanation is strongly exothermic,low temperature benefits the equilibrium conversion of CO.Meanwhile,the methanation of CO in raw hydrogen is more energy saving when operated at relatively low temperature.Focusing on Ni-based catalysts for this reaction,the study dealt mainly with two aspects:The effect of crystal phase of TiO₂ on the catalytical performance and selection of sutiable metallic promoter?M?in order to optimize the preparation method for Ni-M/TiO₂ catalyst.The mechanical mixtures of commercial Anatase and Rutile were used as the support for Ni-based catalysts after impregnation.The catalyst supported on Rutile exhibited the highest methanation activity.The catalystst supported on Rutile also showed the outstanding activity,when the TiO₂ was prepared by precipitation of TiOSO4 and then calcinatined at different temperature.The Ni-Ti interaction is in favour of the dispersion of Ni particle when the commercial Rutile is used as support and the catalysts with Anatase support exihibit poor capacity in the uptaken of H2 and CO caused by stronger Ni-Ti interaction,which leads to lower acitivity in CO methanation.Accordingly,the commercial Rutile was used as the sutiable support for Ni-based catalysts prepared by co-impregnation with La2O3 or CeO₂ as the promoters.Based on evaluation results,the Ni-M/TiO₂ catalyst containing 2 wt.%La2O3 showed the highest methanation activity,because La2O3 improves the dispersion of Ni and increases the amount of surface active sites.Therefore,the La2O3?2 wt.%?-modified Ni?10 wt.%?catalyst exhibited higher reaction activity and stability after 500?calcination and 450? reduction.