α-Alumina-Supported Nickel Catalysts Prepared from Nickel Acetylacetonate: A TPR Study

Abstract

Supported Ni catalysts with low metal loadings prepared by impregnation of α-alumina with nickel acetylacetonate (Ni(acac)2) have been studied by temperature-programmed reduction (TPR). The effect of the metal loading (between 0.4 and 1.7 wt%), washing and drying, and calcination temperature on the reduction profile, temperature of maximum reduction (TM), and H2/Ni ratio has been investigated. Metal–support interactions already exist at the impregnation step. The decomposition–reduction products of the organic moiety perturbing the TPR profiles and H2consumptions were suppressed when drying was done at 250°C. Two distinct metal species could be distinguished according to the calcination temperature. The one withTMvalues ≤615°C occurred at calcination temperatures ≤400°C, whereas at 600°C and above, a second species was characterized byTMvalues of 900°C and higher. The two species existed in different proportions in the solids calcined above 400°C and below 600°C. Some indication supported the formation of a nickel aluminate spinel-type phase when the solid was calcined at 600°C and above accounting for the high temperatures needed to reduce nickel oxide.