Application Of Ni-based Alloy Core-shell Catalyst In CH₄-CO₂ Reforming

The CH₄-CO₂ reforming reaction can make rational use of CH₄ and CO₂,which is of great significance for reducing greenhouse gas emissions and mitigating energy crisis.Ni-based catalysts have the advantages of low cost and good reactivity,and are widely used in the research of CH₄-CO₂ reforming reaction.However,the Ni-based catalyst tends to generate carbon deposits in the reaction,which causes a decrease in catalyst activity and leads to deactivation.Therefore,how to improve the carbon deposition resistance of the Ni-based catalyst is currently urgent problems.In this paper,a series of Ni-based catalysts were prepared.The activity and carbon deposition resistance of the catalyst in the CH₄-CO₂reforming reaction were investigated by changing the type,content,reaction conditions and calcination mode of the active center of the catalyst.The experiment yields the following results and conclusions:?1?The effect of Ni content on the performance of Ni/MOR supported catalyst was investigated.It was found that with the increase of Ni content,the total carbon conversion showing first increased and then decreased.The 10Ni/MOR catalyst had the highest conversion of44.33%,but a large amount of carbon was produced in the reaction,resulting in a decrease in activity.The carbon content increased showing a trend of increasing first and then decreasing,and the carbon content of15Ni/MOR catalyst was the smallest.and the activity tends to be stable in the reaction.?2?Core-shell catalyst with Ni/ZSM-5 as core and amorphous SiO₂as shell was prepared by sol-gel method.The Ni metal particles suppress the aggregation of the Ni particles due to the spatial effect,and the carbon deposition resistance ability are improved.The Core-shell catalyst separates the carbon deposits and the nickel active sites,thereby improving the activity of the catalyst.The activity of 10Ni/ZSM-5@SiO₂is superior to that of other catalysts,and the conversion rate reaches 88%.?3?Ni-Sn alloy catalysts were prepared by equal volume impregnation-hydrogen reduction method.It was found that when the reduction temperature was 500°C,the alloy structure was formed well,and the activity of the catalyst decreased with the increase of Sn,from the original 93.29%to 7.51%.which indicated that the addition of Sn would inhibit.The activity of Ni decreases with the decrease of Ni-Sn ratio.When Ni/Sn?1,the carbon deposition amount is almost 0 g/g_catat h,because the addition of a large amount of Sn occupies the formation of carbon on the Ni surface.The nuclear position,which increases the carbon deposition resistance of the catalyst.?4?Ni-Co alloy catalyst was prepared by the equal volume impregnation-hydrogen reduction method.It was found that the alloy was formed well at a reduction temperature of 900°C and a Ni/Co molar ratio of 1/1 to 1/1.5,and the total carbon conversion rate reaches 71.33%.The formation of the Ni-Co alloy helps to increase the activity and stability of the catalyst in the CH₄-CO₂ reforming reaction.When the Ni/Co molar ratio is 1/1.5,The conversion rates of CH₄,CO₂ and total carbon reached59.67%,82.52%,71.33%,and the carbon deposition on the catalyst was smallest.After 50h,the conversion rate decreased from 66.02%to65.06%,and it was hardly deactivated.?5?Ni-Co alloy core-shell catalysts with Ni-Co/?-Al₂O₃ as core and amorphous SiO₂ as shell were prepared by sol-gel method.The effects of different SiO₂ films on the reactivity were investigated.The study found that the coating of a layer of SiO₂ on the Ni-Co alloy catalyst can resist carbon deposition,When the amount of TEOS is increased from 0 g to 4.8 g,and the carbon deposition resistance is strong.However,the conversion rate has dropped from 71.33%to 12.94%.Although the SiO₂ film can effectively separate the carbon deposit,it is not conducive to the contact between the catalyst and the raw material gas,and affects the mass transfer.