Steam reforming of ethanol–phenol mixture on Ni/Al2O3: Effect of magnesium and boron on catalytic activity in the presence and absence of sulphur

Abstract

The steam reforming of ethanol/phenol mixture (168gTOT/Nm3, ethanol: phenol 2:1mol), assumed as a model for tar mixtures, has been studied over Ni/Al2O3, Ni-Mg/Al2O3 and Ni-B/Al2O3 catalysts. The effects of reaction temperature and of the presence of sulphur have been investigated. Catalysts have been characterized by XRD, IR of adsorbed CO, TPR, UV–vis spectroscopies. IR studies of adsorbed water and phenol have also been performed.The addition of Magnesium shows an activating effect on Ni/Al2O3 but also increases sensitivity to sulphur poisoning. This has been associated to the formation of large Ni metal particles over the MgxAl2O3+x support surface formed by the penetration of Mg ions in the subsurface of alumina, and to the low activity of the surface of such a modified support in the conversion of the organic reactants. A possible role of Mg in a different, possibly more efficient, activation of water is envisaged. The addition of boron in small amounts reduces activity, mainly if boron is added to the support before impregnation of Ni. A slight positive effect in reducing the deactivation due to sulphur is observed when boron is added after nickel.