Structural Design And Catalytic Performance Of Co-based Catalysts For CO₂ Reforming Of Methane

Carbon dioxide reforming of methane（CH₄-CO₂）technology has great significance because it can effectively convert two greenhouse gases（CO₂ and CH₄）into syngas for methanol synthesis and the production of other chemicals.At present,because of the constraints of development of catalysts,the process has not yet achieved large-scale industrial applications.This paper first prepared Co-based catalysts with different supports and systematically studied the support effect on catalytic performance in CH₄-CO₂ reforming.It is found that Co/Al₂O₃ and Co/MgO catalysts possess best catalytic performance.On the basis of the above results,we prepared the Co-MgAl catalyst with LDHs structure and the Co-Al₂O₃ with ordered mesoporous structure.Then we explored the structure-activity relationship of Co-based catalysts for CH₄-CO₂ reforming.To this goal,we analyzed the phase composition,physicochemical properties,morphology and carbon deposition by means of characterization techniques such as XRD,TG-DSC,H2-TPR.The main conclusions are obtained as followings:1.For the Co-based catalysts prepared by impregnation with the metal loading of 15 wt%and the calcination temperature of 500 ℃,the order of catalytic activity for CH₄-CO₂ reforming follows:CO/Al₂O₃>Co/CeO₂ ≈Co/MgO>Co/ZrO₂.Besides,the CO/Al₂O₃ had better stability.The results of N2 adsorption,TEM and H2-TPR showed that the Co/Al₂O₃ possessed high specific surface area and strong metal-support interaction,which can improve the dispersion of Co particles.In addition,the results of TG-DSC show that there was a little carbon deposition in Co/Al₂O₃,while Co/MgO was almost free of carbon deposition.2.Co-MgO-P,CO-Al₂O₃-P and Co-MgAl catalyst with LDHs structure were prepared by the constant PH precipitation method with Co load of 10 wt%and 600 ℃ calcination temperature.And the catalytic performance of catalysts for CH₄-CO₂ reforming was investigated.The results showed that the Co-MgAl catalyst had excellent catalytic activity and stabilit.N2 adsorption and TEM showed that owing to the high specific surface area and the strong interaction between Co and MgAl,the Co-MgAl catalyst possessed higher dispersion of metal Co and better carbon deposition resistance.At the same time,CO₂-TPD showed that the alkaline strength of Co-MgAl was higher than Co-MgO-P,which was also an important reason for the good performance of carbon deposition resistance.3.In the conditions of 10 wt%Co loading,600 ℃ calcination temperature,the ordered mesoporous CO-Al₂O₃ catalyst（Co-Al-E）and conventional Co-Al₂O₃ catalyst（Co-Al-C）was prepared by EISA one pot and conventional impregnation method respectively.Subsequently we compared the two catalysts’ catalytic performance of CH₄-CO₂ reforming and found that the CH₄ conversion of Co-Al-E catalyst was about 20%higher than that of Co-Al-C.The results of small angle XRD,TEM and N2 adsorption showed that Co-Al-E catalyst have the highly dispersed Co particles,which benefited from the regular pore structure and the strong metal-support interaction.