Compared with the unmodified Mn-Na2WO4/SiO2 catalyst,X-Mn-Na2WO4/SiO2 catalysts modified with Sr,Y,and Nd elements,respectively increase methane conversion rate at 800℃ by 7.02%,35.26% and 28.43%,and enhances the C2 yield by 4.52%,13.26% and 11.87%,respectively.It is indicated by O2-TPD and CO2-TPD analysis that the content of lattice oxygen and the strength of the surface alkaline sites of the catalysts can effectively be enhanced through doping with Sr,Y,or Nd elements,which hence promotes methane to activate.Among these modified catalysts,Y-Mn-Na2WO4/SiO2 catalyst,as its is served to catalyze the oxidative coupling of methane (OCM),delivers a methane conversion rate of 66.22% and a C2 yield of 36.46% at 800℃.It is verified by XPS analysis that the electron density of Na is increased by the addition of Y,which makes it easier for W and Mn to migrate to the surface,providing the lattice oxygen required for activating methane,thus improving the catalyst’s performance in catalyzing OCM.
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