Effect of Calcination Temperature and Pretreatment with Reaction Gas on Properties of Co/gamma-Al2O3 Catalysts for Partial Oxidation of Methane

摘要

The effects of calcination temperature and feedstock pretreatment on the catalytic performance of Co/?-Al2O3 catalysts were studied for partial oxidation of methane (POM) to synthesis gas, with emphasis on the role of feedstock pretreatment. The physicochemical properties of the catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and Raman spectroscopy. The results showed that the pretreatment of the catalyst by reaction gas significantly improved the catalytic activity and stability for the POM reaction. On the other hand, the effect of calcination temperature was less significant. Although the initial activity was increased by an increased calcination temperature, the catalyst without the feedstock pretreatment suffered a rapid deactivation. The reaction-atmosphere pretreatment was revealed as a process that mainly modified the surface structure of the catalyst. In that process, the formation of a CoAl2O4-like compound led to high Co metal dispersion after reduction, and the transformation of the carrier into a-Al2O3 occurred over the catalyst surface. Both the high dispersion of cobalt and the presence of a-Al2O3 surface phase were assumed as the important factors resulting in an excellent catalytic performance in terms of high activity and high stability.