Study On Carbon Oxides Methanation Performance Of Ni-based Catalyst

In 21 century,the two of the biggest challenges are environmentally sustainable development and sustainable use of natural resources.COx methanation through catalytic hydrogenation reactions is an effective way to solve CO₂-related environmental problems and to make better use of carbon resources.As other catalytic conversion processes,the catalyst plays the most important role in COx methanation reactions.Among the studied catalysts,Ni-based catalyst has excellent performance for COx methanation reaction.More over,Ni-based catalyst is considered as one of the most promising catalysts due to the wide resources and low price of Ni.In this paper,a series of Mn-promoted 15 wt% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method.The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO₂ methanation was investigated.Mn improved CO₂ methanation activity of 15 wt% Ni/Al2O3 catalysts especially at low temperatures.The reason was that the presence of Mn increased the number of CO₂ adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support.The best CO₂ conversion was achieved with the Mn content was 1.71 %.Based on this,the effect of preperation methods on Mn-Ni/Al2O3 catalyst was investigated.The result showed that the incipient wetness impregnation method was better than the deposition precipitation method because it weakened the interaction between the nickel and support and increased the reducibility of NiO.The Ni/ZrO₂ catalysts were synthesized using the combustion methods and the effect of combustion mediums including ethanol,n-propanol,urea,glycol,glycerol was studied.The results illustrated that the combustion mediums significantly affected the catalytic pore structure,interaction between the active metal and support,Ni dispersion,Ni particle size,the crystal structure of ZrO₂ and CO₂ adsorption capacity.The Ni/ZrO₂ catalyst synthesized using urea as the combustion medium had the best catalytic activity.The effect of preparative variables of the urea combustion method on Ni/ZrO₂ catalyst for CO₂ methanation was also investigated.Based on our previous study,we investigated the catalytic activity of the Mn-Ni /Al2O3 and Ni/ZrO₂-U-0.4 catalysts for co-methanation of CO and CO₂ due to their excellent CO₂ methanation activity.The two catalysts gave the different results.The 1.71Mn-Ni/Al2O3 catalyst had good performance of co-methanation.However,the Ni/ZrO₂-U-0.4 catalyst in co-methanation reactions neither had good CO methanation activity nor good CO₂ methanation activity.The co-methanation tests on the 1.71Mn-Ni/Al2O3 and Ni/ZrO₂-U-0.4 catalysts all indicated that: in the co-methanation process,the CO methanation was more competitive than CO₂ methanation and CO₂ methanation was more sensitive to the reaction temperature and the space velocity than CO methanation.