Effects of preparation methods of ZrO2 support on catalytic performances of Ni/ZrO2 catalysts in methane partial oxidation to syngas

ZrO2 was prepared by hydrothermal method (denoted as HT method), the method of drying and calcinating of alcogel in N-2 (denoted as AN method) and conventional precipitation method (denoted as CP method). And 14% Ni/ZrO2 catalysts were prepared by impregnation method. The physico-chemical properties of supports and catalysts were characterized by XRD, TEM, N-2-adsorptioin. The effects of preparation methods of ZrO2 support on the catalytic performances of 14%Ni/ZrO2 in methane partial oxidation (POM) at 700 degrees C, 1.0 x 105 ml/(g(cat) h) and ambient pressure were investigated. The experimental results showed that ZrO2 particles prepared by HT method were uniform and spindle-like with the size of 100 nm x 400 nrn, while ZrO2 particles prepared by AN method were spheric and small with the size of 20-40 nm. As for ZrO2 prepared by CP method, its particles were un-uniform and the size distribution of its particles was wide from 20 to 100 nun. The reaction results of POM illustrated that the 14%Ni/ZrO2 catalysts in which ZrO2 was prepared by HT and AN methods, had small Ni particles and showed high ability of resistance to carbon deposit and high stability of time on-stream (TOS). The 14%Ni/ZrO2-CP catalyst had large Ni particles and showed an serious deactivation within 50 h of TOS due to the formation of large amount of carbon deposit on the surface of catalyst. The results from TEM and TPO showed that encapsulated carbon deposit was formed on small Ni particles and was active for oxidation, while carbon nano-tube was mainly formed on large Ni particles and was inert for oxidation. (c) 2007 Elsevier B.V. All rights reserved.