Hydroprocessing challenges in biofuels production

Biofuels production from biomass of lignocellulosic, vegetable oils and algae origins as well as from municipal solid waste via hydroprocessing (HPR) is in various stages of development. The conversion of biomass from these sources to biofeeds and chemical composition of the latter are presented. Differences between the mechanism and kinetics of HPR reactions occurring during the HPR of biofeeds and petroleum feeds are evaluated. Fundamental aspects of conventional and non-conventional HPR catalysts, with emphasis on their applications in biofuels production are discussed. Catalysts exhibiting high activity and stability under conditions encountered during the HPR of biofeeds are identified. They include catalysts consisting of conventional metals (Mo/W and Co/Ni) supported on various supports as well as novel catalytic phases containing noble metals as well as phosphides, carbides, nitrides and borides of transition metals in combination with supports varying widely in surface acidity. The studies on coprocessing biofeeds with the feeds of petroleum origin as well as those on blending biofuels with petroleum fuels were reviewed. Improvement in properties of petroleum diesel, particularly in terms of diesel number, can be achieved by blending with biodiesel from vegetable oil sources.Developments in upgrading biofeeds in aqueous environment (subcritical water, supercritical water and supercritical alcohols) in the presence of various catalysts and hydrogen, are addressed.

Carboxylic acids and esters in biofeeds can be converted to hydrocarbons under hydroprocessing conditions via tentative mechanism shown here. Glycerides and fatty acids in biofeeds of vegetable oil origin are source of a high cetane number (>80) liquids. In terms of catalyst selection and hydrogen consumption, the production of biofuels from biofeeds of lignocellulosic origin and particularly from algae biomass is more challenging.Figure optionsDownload high-quality image (122 K)Download as PowerPoint slide