Nickel on TiO 2-modified Al 2O 3 sol–gel oxides : Effect of synthesis parameters on the supported phase properties

Abstract

Nickel catalysts supported on Al 2O 3-TiO 2 sol–gel mixed oxides were prepared by equilibrium wet impregnation (EWI) and the resulting oxidic precursors were characterized by AAS, N 2 physisorption, XRD and UV-Vis DRS. By varying the support composition different nickel speciation on the calcined precursors was evidenced. The main role of TiO 2 appeared to be two-fold: (a) inhibition of the formation of hardly reducible spinel-like species and (b) increased dispersion of the metallic phase (as determined by H 2 chemisorption). For equimolar Al 2O 3-TiO 2 supports a H 2 chemisorption suppresion effect in the case of ∼10 wt.% Ni catalyst suggested an strong metal support interaction state (SMSI). By increasing the metal loading (∼20 wt.%) this phenomenon was no longer observed and a beneficial influence of the support composition on the properties of the metallic phase was registered.