Surface Structure Modulation Of Ni-Based Catalyst And Study On Sulfur-Resistant Performance

Since the 13th Five-Year Plan period,the natural gas demand in China has continued to rise,the supply gap has continued to increase,and coke oven gas synthetic natural gas has developed rapidly and become an important supplement to unconventional natural gas in China.However,coke oven gas contains various forms of sulfide such as H₂S.In the process of synthesizing natural gas,sulfur and nickel will form stable nickel sulfide to cause catalyst poisoning and deactivation.The adsorption poisoning of sulfur is irreversible within the operating temperature range of the catalyst adsorption,and its destruction exceeds the carbon deposition and sintering of catalyst.In this paper,in view of the problem of sulfur poisoning on deactivation of nickel-based methanation catalysts,the activity and sulfur resistance of catalysts prepared by different methods are evaluated at first.Secondly,the activity and sulfur resistance of catalysts prepared with different nickel contents are evaluated to optimize the nickel loading.Finally,different additives and their loads are optimized,and the sulfur resistance performances of four forms sulfur are evaluated over the optimized catalyst.The main research contents and results are as follows:(1)Nickel-based catalyst with Ni O content of 20wt.%are prepared by impregnation method and precipitation method.The results show that the low-temperature activity and sulfur resistance of the Ni-Al₂O₃ catalyst prepared by the precipitation method are better than the Ni/Al₂O₃ catalyst prepared by the impregnation method.(2)x Ni-Al₂O₃ catalysts with different Ni content(x=20,30,40,50wt.%)are prepared by precipitation method.The results show that as the Ni content increases,the low-temperature performance and sulfur resistance of the catalyst gradually improve.Among them,the low-temperature performance and sulfur resistance of the 40Ni-Al₂O₃ and 50Ni-Al₂O₃ catalysts are the best.Combined with economic considerations,the 40Ni-Al₂O₃ catalyst is preferred for subsequent research;with the increase of Ni content,the high-temperature stability and resistance to carbon deposition of the catalyst gradually improve,and the 50Ni-Al₂O₃ catalyst has the best high-temperature stability and resistance to carbon deposition.(3)X/Ni-Al₂O₃ catalysts are obtained by adding Mo,Mn,Fe and Zn as additives on the 40Ni/Al₂O₃ catalyst.The study shows that the addition of additives leads to the decrease of the low-temperature activity of the catalyst and has a certain impact on the sulfur resistance of Mo/Ni-Al₂O₃ catalyst,among which the sulfur resistance of Mo/Ni-Al₂O₃ catalyst is the best.(4)x Mo/Ni-Al₂O₃ catalysts(x=5,7.5,10,12.5,15,20wt.%)are prepared by maceration method.It is found that with the increase of Mo O₃ loading,the low-temperature activity of the catalyst gradually decreases,and the sulfur resistance first increases and then decreases.Among them,the sulfur resistance of 12.5Mo/Ni-Al₂O₃ catalyst is the best.the surface of the nickel-based catalyst,the toxicity of the morphological sulfur is C₄H₄S>CS₂>COS>H₂S,and the addition of Mo makes the catalyst more resistant to H₂S and CS₂,but less resistant to COS and C₄H₄S.