Upgrading of bio-oil from biomass pyrolysis: Current status and future development

Abstract

For the sustainable production of fuel, biomass pyrolysis processes have appeared as a promising alternative for the efficient utilization of biomass. The liquid product obtained from biomass pyrolysis, i.e., bio-oil has a very complex composition including large proportion of organic oxygenated hydrocarbon compounds and appreciable amount of water. The high oxygen content of the bio-oil creates many major drawbacks that hinder its vast application. The quality of bio-oil is not applicable for direct transportation purposes, and its upgrading is mandatory before it can be used practically in power engines. The abovementioned drawbacks can be overcome by the catalytic hydrodeoxygenation of bio-oil, in which the functional groups containing oxygen are removed and replaced by hydrogen atoms. For this purpose of selectively activating and breaking the C-O bonds while trying to maintain the C-C bonds intact, processing knowledge base of petroleum industry may not be utilized for hydrodeoxygenation of bio-oil. Therefore, novel catalysts, solvents, and processes need to be developed. This chapter reviews the state-of-the-art results obtained from the research and development of these technologies. The pros and cons, potential of future applications, challenges related to these technologies, and opportunities to maximize economic and environmental benefits while minimizing pollution are highlighted. Besides, the application of molecular modeling in the integration with experiment is highlighted in this chapter as a new paradigm for mechanistic studies, which could open new avenues to design and develop catalysts for a plethora of bio-oil upgrading processes that require high activity and selectivity. Finally, the breakthrough applications of novel sonochemical technique in biomass treatment and conversion are introduced in this chapter.