Study Of Stability On Nickel-based Catalysts And Thermodynamics For Syngas To Methane

As one of the most essential steps in the production of synthetic natural gas?SNG?,great efforts have been made to develop CO methanation process by researchers.A catalyst with high activity and stability for CO methanation particularly important for coal to syngas.However,under the process condition of CO methanation?H₂/CO?3,300⁶00?,1³MPa?,carbon deposition,nickel particle sintering and support hydrolysis probably happen and lead to deactiviation of catalyst Ni/Al₂O₃.In this paper,a Ni/MgO-Al₂O₃ catalyst with high activity and stability was obtained by investigating effects of MgO-Al₂O₃ composite support preparation conditions and MgO content on catalyst stability.Besides,the effects of reaction conditions and composite of feed gas on product distribution and carbon deposition for CO methanation were investigated by thermodynamic calculation.Meanwhile,the effects of reaction conditions and composite of feed gas on performance of catalyst was investigated.?1?MgO-Al₂O₃ composite supports with different calcination temperature,precipitation agent and MgO content were prepared by co-precipitation,and stability of Ni/MgO-Al₂O₃ catalysts were investigated for CO methanation.The result shows that Ni/MgO-Al₂O₃catalyst is most stable when calcination temperature is 800?,NH₄OH as precipitation agent and the mass ratio of MgO/Al₂O₃ is 0.05.In addition,the catalysts were characterized by means of X-ray diffraction?XRD?,temperature programmed reduction?TPR?,BET and temperature programmed surface reaction?TPSR?and so on to research deactivation of catalyst.?2?A thermodynamic analysis was made on the effects of temperature,pressure,and the composite of feed gas on CO methanation.The results indicated that lower temperature,higher pressure,and a larger H₂/CO ratio are favorable for the increase of CO conversion and CH₄ selectivity.It was found that the behavior of carbon deposition can be alleviated by improving pressure,H₂/CO ratio and adding steam into feed gas.In addition,the impact of reaction conditions and he composite of feed gas on performance of Ni-base catalyst was investigated on the basis of thermodynamics analysis.Experimental results show that catalytic performance and the behavior of carbon deposition were distinctly by above-mentioned parameters,which is substantially consistent with thermodynamics calculation result.