Deactivation studies over NiO/γ-Al2O3 catalysts for partial oxidation of methane to syngas

Two types of NiO/gamma -Al2O3 catalysts prepared by the impregnation and the sol-gel method were used for the partial oxidation of methane to syngas at 850 degreesC (GHSV similar to 1.8 x 10(5) l kg(-1) h(-1)). The effects of the carbon deposition, the loss and sintering of nickel and the phase transformation of gamma -Al2O3 support on the catalytic performance during 80 h POM reaction were investigated with a series of characterization such as XRD, BET, AAS, TG, and XPS. The results indicated that the carbon deposition and the loss and sintering of nickel could not cause the serious decrease of catalytic performance over NiO/gamma -Al2O3 catalyst during the short-time reaction. However, the slow process of the support gamma -Al2O3 phase transforming into alpha -Al2O3 could slowly decrease the performance of NiO/gamma -Al2O3 catalysts. Aimed at the reasons of the deactivation, an improved catalyst was obtained by the complexing agent assisted sol-gel method. (C) 2000 Elsevier Science B.V. All rights reserved.