A study of Ni/Al2O3 and Ni–La/Al2O3 catalysts for the steam reforming of ethanol and phenol

摘要

La2O3/gamma-Al2O3, NiO/gamma-Al2O3 and NiO/La2O3/gamma-Al2O3 samples have been prepared by conventional impregnation, using silica-free gamma-Al2O3 support. The materials have been characterized, as such or after reaction, with XRD, skeletal IR, UV-vis-NIR, XPS and FESEM techniques. The catalytic activity has been evaluated in ethanol decomposition through temperature programmed surface reaction (TPSR); and in ethanol steam reforming (ESR); and in mixed ethanol and phenol steam reforming (EPSR as a model reaction for biomass tar steam reforming) in a continuous flow reactor. Ni on alumina exists as a surface NixAl2O3+x spinel, evident by XRD, skeletal IR and vis spectroscopy measurements. La disperses on alumina in a disordered state. In the ternary system, XPS reveals significant Ni-La interactions. The addition of some lanthanum further increases the activity of Ni/Al2O3 for ESR and EPSR. Fresh unreduced catalysts are conditioned in the feed at temperatures above 973 K. Conditioned catalysts give rise to full conversion of reactants in ESR and EPSR at 873 K and higher temperatures, but are severely deactivated by sulfur. The sudden start of the steam reforming activity at 873 K likely corresponds to the temperature onset for the activation of water by metallic nickel.