Preparation Of Transition Metal Phosphide Catalysts For CO₂ Reforming Of CH₄

Energy shortage and environmental issues are two major crises.CO₂reforming of methane has both industrial and environmental significance,which can effectively alleviate these two problems.Ni-based catalysts have been widely applied to CO₂reforming of methane because of their low price and high activity,but the carbon deposition is still inevitable and stability is poor.Therefore,it is significant to search for efficient and stable catalyst system.In recent years,transition metal phosphides have gained extensive interest in the field of catalysis,especially in hydrogenation reactions,where they have achieved excellent activity.Among them,MoP has excellent anti-carbon deposition performance,so it is important to study its activity in CO₂reforming of methane.In this thesis,MoP-SG catalyst with high reforming activity was prepared by sol-gel method.Noble metal Ru and transition metal Zr were introduced to further improve its catalytic activity.The physicochemical properties of the catalyst were studied by characterizations.The results are as follows:1.The effect of preparation method on catalytic performance of MoP catalyst was investigated.MoP-SG catalyst with citric acid/MoP=1（molar ratio）exhibited the highest activity among the catalysts synthesized by sol-gel method and citric acid can effectively reduce the catalyst particle size.Then,the MoP-SG catalyst was compared with MoP-NM catalyst synthesized by normal method.The results showed that the MoP-SG catalyst had higher reforming activity due to smaller particle size,larger specific surface area and more active sites.No carbon deposition was observed,which proves good stability of the catalyst.2.The effect of Ru content on catalytic performance of MoP catalyst was studied.The catalytic activity increased first and then decreased after introducing Ru,and the Ru_0.005MoP catalyst exhibited the highest activity.The results show that the Ru was successfully doped into MoP,and Ru_0.005MoP catalyst has smaller particle size and larger specific surface area,which are important parameters for its high activity.At the same time,excellent carbon resistance leads to good stability.3.The effect of different introduction methods of Zr on reforming performance of MoP catalyst was studied.The reforming performance followed the sequence of Zr_0.01MoP-IM>Zr_0.01MoP-DP>Zr_0.01MoP-PIM.The characterization results show that Zr_0.01MoP-IM catalysts have the smallest particle size,the strongest interactions with Zr and MoP,and good reducibility,while Zr mainly interacts with surface oxidation species in Zr_0.01MoP-DP and Zr_0.01MoP-PIM catalysts,which is an important reason for the differences in the activity of the three catalysts.