Study On CH₄-CO₂ Reforming Performance Of Supported Ni-modified Molybdenum Carbide Catalyst

Carbon dioxide reforming of methane reaction(DRM)has good commercial value,which can realize the reaction conversion between difficult to activation of methane and carbon dioxide,to form the synthetic gas-hydrogen and carbon monoxide that widely used in the field of industry.This reaction utilizes two greenhouse gases,CH4 and CO2,to reduce greenhouse gas emissions,and is one of the best technical routes for greenhouse gas utilization and emission reduction.At the same time the syngas produced has a lower H2/CO ratio,and the mixture can serve as the feedstock for a variety of downstream processes,such as Fischer-Tropsch synthesis and oxo-synthesis.So carbon dioxide reforming of methane has multiple values in terms of the science,economy and environmental protection.The transition metal molybdenum carbide has a noble metal-like property,whereas at normal pressure,the ?-Mo2C catalyst is rapidly deactivated in DRM due to bulk phase oxidation.It is known that transition metal carbides show chemical properties similar to those of noble metals.Herein,On the one hand,the activation of methane can be promoted due to the presence of nickel.On the other hand,carbon dioxide is activated by the transition metal carbides.By adjusting the molar ratio of nickel to carbide,a catalytic oxidation-carbonation cycle could be established over Ni modified carbide catalyst.In this paper,we prepare the different impregnation sequences catalysts.The DRM properties of the catalyst samples prepared by different impregnation sequences were investigated.Compare with the catalytic performances of catalysts achieved by three different immersion methods in DRM reaction,to obtain optimal preparation methods,namely,impregnation metal Mo and Ni step by step.A series of Ni/Mo2C-CNTs catalysts were successfully prepared from the precursors with the Mo content ranging from 9.6 to 30 wt%and their catalytic activities for dry reforming of methane(DRM)were evaluated.CH4-TPSR and CO2-TPO over the fresh samples proved that the Mo content was 17.6 wt%(Ni/Mo=1)catalytic has the best catalytic stability for DRM,attributed to its high activity for CH4 dissociation and high resistance to oxidation.Moreover,the influence of temperature on catalytic efficiency of catalyst(Ni/Mo2C-CNTs(17.6)),was investigated at 800?,850? and 900?.The result shows that when the reaction temperature is 850?,the catalyst has the highest reaction catalytic efficiency and the strongest activity.The R1/R2 ratio is the highest,which promotes the oxidation-carbonization cycle of the catalyst.The Ni/Mo2C/?-Al2O3 catalyst was prepared by commercial carrier ?-Al2O3 and its activity was investigated.We found that its activity is much lower than that of the CNTs-supported Ni/M02C catalyst,and it is not suitable as a carrier for the Ni/M02C catalyst.According to previous studies,there are three ways to convert transition metal molybdenum carbide.CH4-CO2 reforming reaction:redox type,noble metal type mechanism and Mo2C??-M0O2?Mo?Mo2C type.For the reaction mechanism of Ni-modified molybdenum carbide catalyst in DRM,this paper first proposes a new cycle mode:Ni/Mo2C(?)Ni/MoO2(?)Ni/Mo(?)MoNi4(?)Ni/Mo2C Based on the use of reforming reaction product H2,in order to further extract CO from hydrogen-rich gas,we also conducted a preliminary study on CO selective oxidation(PROX)of Co4N/Pt/?-Al2O3 and Co2P/?-Al2O3 catalysts under hydrogen-rich conditions.