Hydrodeoxygenation of anisole as bio-oil model compound over supported Ni and Co catalysts: Effect of metal and support properties

Abstract

Hydrodeoxygenation (HDO) is considered one of the most promising routes to convert the pyrolysis bio-oils produced from lignocellulose into biofuels very similar to those derived from petroleum. This work reports results obtained in the catalytic HDO of anisole over non-conventional hydrotreating catalysts based on metallic Ni and Co supported on micro-mesoporous carriers of different acidity. Anisole has been chosen as representative of those compounds, containing a methoxy-phenyl group, which are abundant in lignocellulose pyrolysis bio-oils. The effect of both metal phase and support properties on their performance as HDO catalysts has been studied. With this aim, three supports with different textural and acidic properties have been employed: hierarchical ZSM-5, mesostructured pure silica SBA-15 and mesostructured Al-SBA-15. The reactions have been carried out in a stainless steel high pressure batch reactor at 220°C and with 50bar of pure hydrogen.The interaction of the metallic species (Ni or Co) with the porous supports, as well as their dispersion, is strongly affected by the support nature and the presence of Al. Thus, it has been found a synergetic effect between the acid sites of the supports and the metallic active phases, which favors and enhances the HDO of anisole. In the case of the acidic supports, Ni-based catalysts (Ni/Al-SBA-15 and Ni/h-ZSM-5) show larger anisole conversions compared to Co-based materials. The strong interaction with the acidic supports of the latter hinders the total Co reduction prior to the reaction, being probably the major reason of their lower activity. Hydrodeoxygenation, hydrodearomatization and isomerization reactions take place extensively over Ni/h-ZSM-5, revealing it is a promising catalyst for bio-oil processing in order to attain high quality fuel production.