Comparative study on cubic and tetragonal Ce x Zr 1-x O 2 supported MoO 3 -catalysts for sulfur-resistant methanation

Abstract

Abstract In this paper, two kinds of Ce x Zr 1-x O 2 solid solution carriers with different Ce/Zr ratio were prepared by one-step co-precipitation method: the cubic Ce 0.8 Zr 0.2 O 2 and the tetragonal Ce 0.2 Zr 0.8 O 2 support. The MoO 3 /Ce 0.8 Z r0.2 O 2 and MoO 3 /Ce 0.2 Zr 0.8 O 2 catalysts were prepared by incipient wetness impregnation method for comparative study on sulfur-resistant methanation reaction. The N 2 adsorption/desorption, X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron (XPS), transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen (H 2 -TPR) were undertaken to characterize the physico-chemical properties of the samples. The results indicated that the prepared MoO 3 /Ce x Zr 1-x O 2 catalysts have a mesoporous structure with high surface area and uniform pore size distribution, achieving good MoO 3 dispersion on Ce x Z r1-x O 2 supports. As for the catalytic performance of sulfur-resistant methanation, the cubic MoO 3 /Ce 0.8 Zr 0.2 O 2 exhibited better than the tetragonal MoO 3 /Ce 0.2 Zr 0.8 O 2 catalyst at reaction temperature 400 °C and 450 °C. CO conversion on the cubic MoO 3 /Ce 0.8 Zr 0.2 O 2 catalyst was 50.1% at 400 °C and 75.5% at 450 °C, which is respectively 7% and 20% higher than that on the tetragonal MoO 3 /Ce 0.2 Zr 0.8 O 2 catalyst. These were mainly attributed to higher content of active MoS 2 on the surface of catalyst, the enhanced oxygen mobility, increased Mo-species dispersion as well as the excellent reducibility resulted from the increased amount of the reducible Ce 3+ on the cubic MoO 3 /Ce 0.8 Zr 0.2 O 2 catalyst.