Effect of yttrium and praseodymium on properties of Ce 0.75Zr 0.25O 2 solid solution for CH 4–CO 2 reforming

Abstract

Ce 0.75Zr 0.25O 2 solid solutions doped with Y 3+ or Pr 4+/Pr 3+ were prepared by the co-precipitation method, and their physicochemical properties were characterized by means of N 2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, FT-Raman, and H 2 temperature-programmed reduction and thermogravimetric analysis. Their performance in CH 4–CO 2 reforming was also tested in an atmospheric fixed-bed reactor. Ce 0.75Zr 0.25O 2 and Y 3+ or Pr 4+/Pr 3+ doped Ce 0.75Zr 0.25O 2 solid solutions are of CaF 2 structure, and the thermal stability of Ce 0.75Zr 0.25O 2 is enhanced by doping Y 3+ or Pr 4+/Pr 3+. Comparing with Ce 0.75Zr 0.25O 2, the migration of bulk lattice oxygen species become easier and the content of surface oxygen species is higher in the doped Ce 0.75Zr 0.25O 2, which is due to either oxygen vacancies or/and structural distortion resulted from the doping. The activity of the solid solutions in CH 4–CO 2 reforming is closely related to the surface oxygen species. Y 3+ or Pr 4+/Pr 3+ doped Ce 0.75Zr 0.25O 2, especially the former, show higher activity than Ce 0.75Zr 0.25O 2, and Y 3+ doped Ce 0.75Zr 0.25O 2 possesses better stability. All of the catalysts have good coke resistance. The catalyst deactivation is mainly due to the catalyst sintering.