Catalytic Performance Of Transition Metal Phosphide For Dry Reforming Of Methane

Methane and carbon dioxide are not only two main greenhouse gases,but also two important carbon sources.Therefore,it has become a research hotspot for the reasonable exploitation and utilization of greenhouse gases.CH4-CO2 catalytic reforming procerss exhibits extremely high environmental benefits and industrial values in the conversion and utilization of greenhouse gases and the production of clean energy.In order to obtain satisfactory catalytic performance,dry reforming of methane should proceed at a relatively high temperature.Ni catalysts are most extensively investigated reforming catalysts due to plentiful reserve and modest price.It is worth noting that both activity and stability of the current Ni catalysts are still unsatisfactory for industrial applications.Molybdenum phosphide(MoP)has metal properties,good thermal stability,chemical stability and excellent oxidation resistance.As a new catalytic material,MoP has shown excellent catalytic performance in CH4-CO2 reforming reaction.Therefore,this thesis focus on designing and preparing an unique and efficient reforming catalyst,which is obtained by adding different types of metal promoters in to MoP.In this thesis,MoP catalyst was synthesized by temperature programmedreduction(TPR),And then metal(Zr),rare earth metals(Ce,La)and alkaline earth metal promoters(Ca,Mg)were introduced by impregnation method.Effect of different promoters in MoP catalyst and loading content of promoters for CH4-CO2 reforming reaction was investigated.The stability of MoP catalyst with Zr,Ce and La promoters was tested,and the catalysts were systematically studied by various characterization methods.The main conclusions are as follows:1.Adding proper amount of Zr promoter can effectively improve the catalytic performance of MoP catalyst.When the content of introduced Zr is X=0.01(mole fraction of Zr/MoP),the CH4 conversion of Zr0.01MoP catalyst has increased by 20%,which can reach 75.2%.The results of N2 adsorption characterization show that the introduction of Zr promoter can block the pore channels of MoP catalyst,resulting in the decrease of specific surface area.XRD and TEM characterization show that introduced Zr promoter exists in the form of ZrO2,which can reduce the particle size of MoP catalyst.The results of H2-TPR and XPS characterization show that there was a strong interaction between Zr and MoP.In addition,the addition of Zr to MoP can suppress the enrichment of P on the surface.This leads to more molybdenum sites being exposed on the surface of the samples,which may affect the reforming activity.2.Different kinds of promoters have different effects on the catalytic performance of MoP catalyst.Rare earth metal promoters(Ce,La)can effectively improve the activity and stability of MoP catalyst compared with alkaline earth metal promoters(Ca,Mg),but the improvement effect is not as good as that of Zr.The characterization results show that the introduction of Ce and La promoters can also reduce the particle size and specific surface area.There is some interaction between Ce,La and MoP in Ce0.01MoP and La0.01MoP catalysts.It can be seen that various promoters have different effect on the on the structure parameters of MoP catalyst,such as particle size and interaction,which may be account for affecting the MoP catalytic performance.