Experimental Research On Svngas Methanation Over Ni-based Catalvsts

With the rapid development of economy,the demand for natural gas of China is increasing year by year.Meanwhile,China's energy characteristic is "rich in coal,lean in oil,less in gas".China is short of natural gas and needs to import a lot from overseas.But China is rich in coal energy and renewable resources-biomass.Therefore,using coal or biomass resources to generate natural gas is an effective way to relieve the shortage of natural gas in China.Syngas methanation is a key technology in natural gas synthesis and was systematically studied in this paper.Catalyst Ni/TiO₂ was prepared by deposition precipitation and co-precipitation,respectively.The effect of preparation method on catalytic performances was studied.It was found that catalyst Ni/TiO₂ prepared by co-precipitation method had better catalytic performances because of higher dispersion of active component on support,larger specific surface area and more active site amounts.Co-precipitation method was selected for the preparation of Ni/Al₂O₃,Ni/ZrO₂ and Ni/CeO₂ catalysts,and their performances in methanation were investigated in this study.The results showed that the catalytic activity at low temperature followed the order:Ni/Al₂O₃>Ni/ZrO₂>Ni/CeO₂.Under the conditions of P=1MPa,GHSV=20000ml/g.h,H₂/CO=3,T= 380?,catalyst Ni/Al₂0₃ presented the best catalytic performance with the highest CH4 selectivity of 94.5%and the CO conversion of 100%.The characterization results indicated that the dispersion of the active component Ni was the main factor affecting the catalytic activity and the one with higher dispersion gave better performance.The study in the influence of H₂S on CO methanation was researched on catalyst Ni/Al₂O₃,having the best catalytic performance.The stability of the catalyst was studied on the conditions of P=1MPa,GHSV=20000ml/g.h5 H₂/CO=3,T= 440? and with H₂S content of 0,100ppm and 200ppm.It was found that the existence of H₂S reduced the stability of the catalyst and higher H₂S content gave worse catalytic stability.When H₂S content reached 200ppm,catalyst Ni/Al₂O₃ deactivated quickly after reaction of only 5 hours.Catalyst Ni/MCM-41 prepared by deposition precipitation was studied in CO₂ methanation.Results showed that catalyst Ni/MCM-41 had better catalytic activity in CO₂ methanation.The CO₂ conversion and CH4 selectivity increased when the temperature from 260 to 460?,but decreased as the airspeed increased.Pressure had a positive influence on catalytic performance.When the pressure increased from 0.1 MPa to 1.5 MPa,the maximum value of CO conversion and CH4 selectivity increased from 73.3%,98.5%to 91.2%,99.6%,respectively.The addition of CeO₂ improved catalytic performance of Ni/MCM-41 and catalyst Ni/20%CeO₂-MCM-41 exhibited the best catalytic activity at atmospheric pressure of 85.6%and 99.8%for CO₂ conversion and CH4 selectivity,respectively.