Hydrodeoxygenation of lignin-derived platform chemicals on transition metal catalysts

Bio-oil obtained from the pyrolysis of waste biomass is a potential alternative to fossil fuels. However, the presence of high oxygen content makes it unsuitable for direct use as a fuel, and therefore, upgradation of bio-oil is required. The catalytic hydrodeoxygenation (HDO) has been widely used for the upgradation of bio-oil to transportation fuels and value-added chemicals. However, since bio-oil is a complex mixture of different compounds, the exact mechanism for the bio-oil HDO is unknown. Phenolics, such as m-cresol, guaiacol, phenol, anisole, etc., derived from lignin pyrolysis, have been widely studied as model compounds to understand the HDO pathway of bio-oil. The activity and selectivity of these reactions are governed by different catalytic parameters, such as type of metal and support, nature of active sites, size of the catalyst, etc. The effect of these parameters on the selective production of aromatics and cyclic hydrocarbons through HDO of phenolics is briefly discussed in this chapter. In order to develop an efficient catalyst for the HDO reactions metal functionality, the optimum ratio of acid sites and acidity of the support should be taken into consideration.