| In recent years,the demand for natural gas has been increased year by year,in 2018,is already the world's first natural gas importer in our country,and our country as an agricultural country abundant biomass resources,biomass syngas methanation technology can make the biomass utilization,therefore straw methanation technology can become an effective way to make up for a lack of gas supply.In this paper,Ni/Al2O3 monolithic catalyst was prepared from biomass gasification simulation syngas H2:CO=3:1?ratio of material content?,Ni as the active component,Al2O3as the carrier and cordierite as the substrate.The influence of different factors on the structure and performance of catalyst was studied respectively.Then the catalyst under the best preparation condition was modified by 10%Na OH to improve the methanation performance and methane selectivity of the catalyst.First of all,this study of respectively with different catalyst preparation methods?impregnation method and sol-gel method?,temperature?250-550°C?and airspeed?6000-14000 m L/?g·h??under the condition of the influence of catalyst structure performance,the results found that the impregnation of Ni/Al2O3 monolithic methanation catalyst of sol-gel method is obviously better than the performance of Ni/Al2O3 monolithic catalysts.When the reaction condition is H2:CO=3:1 and the airspeed is 10,000 m L/?g·h?,the methanation performance of Ni/Al2O3 monolithic catalyst prepared by impregnation method reaches the best at the temperature of 400°C,and the CO conversion rate is 96.8%and the CH4selectivity is 96.0%.When reaction conditions for H2:CO=3:1,the temperature of 400°C,in the pitot experiments,impregnation of Ni/Al2O3 monolithic catalyst affected by space velocity is small,the CO conversion and CH4 selectivity are stable at about 90%,show the performance of methanation,and with the increase of reaction airspeed,the CO conversion and CH4 selectivity of Ni/Al2O3 monolithic catalyst prepared by sol-gel method showed a decreasing trend.Secondly,the best catalyst preparation method--impregnation method was used to prepare Ni/Al2O3 monolithic catalysts with different Ni contents?the amount of material?,with Ni contents of 10%,15%and 20%respectively.The results showed that the CO conversion and CH4 selectivity of the three catalysts had the same trend,and all showed a"volcanic"trend.When H2:CO=3:1 and air velocity 10,000 m L/?g·h?,the Ni/Al2O3 monolithic catalyst with 15%Ni content showed the best methanation performance at 400°C,under which the CO conversion rate and CH4 selectivity were 96.8%and 96.0%,respectively.The methanation performance of the Ni/Al2O3 integral catalyst with 20%Ni was followed by that of the Ni/Al2O3 integral catalyst with 10%Ni was the worst.Finally,the Ni/Al2O3 monolithic catalyst with Ni content of 15%prepared by impregnation method was modified by alkali,and the modification time was 1 h and 2 h respectively.Compared and analyzed the methanation structure performance of the catalyst before and after modification,the results showed that the Ni/Al2O3 monolithic catalyst modified for 2 h reached the best methanation performance at 400°C under the conditions of H2:CO=3:1 and the space velocity of 10000m L/?g·h?,at which time the CO conversion rate was 97%and the CH4 selectivity was100%.For CO conversion,the trend of CO conversion of the unmodified Ni/Al2O3 integral catalyst is basically the same as that of the modified Ni/Al2O3 integral catalyst for 2 h,while the overall trend of CO conversion of the Ni/Al2O3 integral catalyst for 1 h of modification is lower than that of the unmodified Ni/Al2O3 integral catalyst..For CH4 selectivity,the modified Ni/Al2O3 monolithic catalyst is obviously better than the unmodified Ni/Al2O3 monolithic catalyst,indicating that the Ni/Al2O3 monolithic catalyst modified by 10%Na OH for 2 h can improve the methane selectivity of the catalyst. |
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