Ce-promoted Ni/SBA-15 catalysts for anisole hydrotreating under mild conditions

Abstract

Ce-containing SBA-15 materials with Ce/Si molar ratio ranging from 0 to 0.08 were prepared by mixing an acidic suspension of colloidal CeO2 particles along with the surfactant during the synthesis of mesostructured silica. The obtained solids were characterized by powder X-ray diffraction (XRD), N2 sorption isotherms, TEM, UV–vis, and Raman spectroscopy. Structural analyses confirmed that all the samples present a well-ordered hexagonal mesoporous structure, with larger pore diameter and volume than unmodified SBA-15 due to the incorporation of the lanthanide promoter. According to the characterization results different cerium species, namely dispersed Ce species and CeO2 crystallites, are formed depending on the Ce/Si ratio of the Ce-SBA-15 materials. On the other hand, Ni/Ce-SBA-15 catalysts were prepared by wet impregnation of the mesoporous supports and the comparison of the different samples showed that the incorporation of Ce progressively enhances Ni dispersion. These catalysts were assayed for hydrotreating of anisole at temperatures in the 270–290°C range and moderate hydrogen pressure (7bar). Such process is relevant for the upgrading of bio-oils derived from the pyrolysis of lignocellulosic biomass. Catalytic activity tests reveal that conversion of anisole progressively improves with increasing Ce/Si ratio and exceeds 30% at 290°C for the catalyst with Ce/Si=0.08. In these conditions the main product is methoxycyclohexane in all cases. However, almost a two-fold increment of benzene yields can be obtained with Ce-promoted catalysts when compared to Ni/SBA-15. This enhancement of the selectivity towards aromatic is very promising for the development of a green route for the production of those chemicals.