Preparation Of Ni-TUD-1 Catalyst And Its Catalytic Performance For CO₂ Low-temperature Methanation

With the current development of society,CO2 emissions are increasing,and its excessive emission brings a series of environmental pollution problems,CO2 methanation reaction is one of the effective ways of CO2 resource utilization.Ni-based catalysts have become widely used in CO2 methanation reactions because of their excellent catalytic performance,abundant resources and low price.As CO2 methanation is a strong exothermic reaction,high temperature is not conducive to a positive reaction,and the Ni active components are prone to agglomeration,sintering and deactivation during the reaction process,which greatly reduce the reaction performance;Low temperature thermodynamics is favorable,but limited by kinetics,CO2 activation ability is low.Therefore,improving the reactivity of catalysts at low temperature is the key to improving the performance of CO2 methanation reaction.Studies on Ni-based catalysts have shown that the dispersion of Ni active components on the support affects the CO2 conversion and reaction stability,and the metal-support interaction affects the formation rate and selectivity of reaction products.Choosing the ideal support is critical for Ni-based catalysts to catalyze CO2 low-temperature methanation.In this paper,we aim to develop Ni-based catalysts with high activity and stability at low temperature,and choose the mesoporous silica material TUD-1 as the catalyst support,which has a simple preparation method,high surface area(up to 1000 m2g-1)and high stability.By changing the Ni contents and the preparation method of the catalyst,a series of Ni-based catalysts supported by TUD-1 were synthesized.The effects of the dispersion degree,particle size and support of Ni active components in the catalyst on the CO2 low-temperature methanation performance were studied.The main research content and results are as follows:1.A series of Ni-TUD-1 catalysts with different Ni content(20%,30%,40%,50%,60%)were prepared by a gel-assisted one-pot synthesis method to study their CO2 low-temperature methanation performance.When the Ni content increased from 20%to 40%,the CO2 conversion of the catalyst increased significantly.The Ni content is 40%,the catalyst has the best catalytic performance.The CO2 conversion of 40%Ni-TUD-1 reached 65.42%at 225℃.Continuing to increase the Ni content to 50%and 60%,the corresponding CO2 conversion did not change significantly,about 65%.40%Ni-TUD-1 compared to 40%Ni/TUD-1 and 40%Ni/SiO2 prepared by the equal volume impregnation method,the CO2 conversion increased by 46.7%and 61.46%,respectively.In situ XRD indicated that the reaction activity centre of 40%Ni-TUD-1 is Ni,and in situ DRIFTS showed that the reaction was involved in CO2 hydrogenation to CH4 through the formate intermediate pathway.2.The effect of technological conditions(reaction temperature,reaction pressure and space velocity)on the CO2 methanation reaction of 40%Ni-TUD-1,40%Ni/TUD-1 and 40%Ni/SiO2 catalysts were investigated.The CO2 conversion of all catalysts increased with the increase of temperature and pressure,and decreased with the increase of space velocity.The CH4 selectivity of 40%Ni/SiO2 increased first and then decreased with the increase of temperature,increased with the increase of pressure,and decreased with the increase of space velocity.However,the CH4 selectivity of 40%Ni-TUD-1 and 40%Ni/TUD-1 remained essentially unchanged.The results show that the reaction conditions were 225 ℃,2 MPa and 3600 h-1,the CO2 conversion of the 40%Ni-TUD-1 catalyst was 65.42%,while 40%Ni/TUD-1 and 40%Ni/SiO2 were 18.72%and 3.96%,respectively.