Economical utilization of renewable energy sources is one of the viable solutions to reducing our dependency on fossil-based energy. Biomass is the only renewable energy source that can provide liquid fuels. In general, liquid fuels are obtained from biomass using either thermochemical or biochemical conversion method. Fast pyrolysis, a thermochemical process, is getting a lot of attention because all the three products (char, bio-oil and gas) have high potential as biomass energy feedstocks. Fast pyrolysis is a high temperature process in which biomass is thermally cracked into smaller compounds in an inert atmosphere at high heating rate. The vapor from this process is quickly condensed to liquid, which is called pyrolysis oil or bio-oil. The favorable conditions for maximum yield of oil are in the range of 400-600 oC and residence time of a few seconds and particle size less than 2 mm. Bio-oil is a chemically complex mixture of more than 300 compounds. Heating value of bio-oil is comparable with the heating value of other conventional liquid fuels – evidence that it can be used as a transportation fuel. The possible utilization of bio-oil are however limited because of some negative attributes such as low pH, low heating value, high oxygen content, and high viscosity.
Gravity can be used to separate bio-oil into two phases - top aqueous phase and lower viscous tar phase. The aqueous phase contains mainly water and carbohydrates and the tar phase contains primarily lignin derived compounds. An aqueous phase reforming (APR) is a process in which hydrogen is produced from carbohydrate solutions. The uniqueness of the APR is that the reforming occurs at liquid state without volatilizing water. Hence, the energy requirement for the APR is lesser than the conventional steam reforming. In addition, the APR occurs at a low temperature and high pressure (200-300 oC and 10-90 bar) which favors water-gas shift reaction. There are a number of physical and chemical techniques to upgrade tar portion of bio-oil to a high quality fuel such as emulsification, solvent addition, hydro treatment and catalytic cracking. Hydrodeoxygenation (HDO) is one of the promising techniques for bio-oil to improve its heating content. The HDO is a process in which high pressure hydrogen is added into bio-oil in the presence of catalyst. Hydrogen reacts with oxygenated components to produce hydrocarbons and water. The operating conditions of HDO are around 250-450 oC and 150 bar. This study will explore the possibility of simultaneous reforming and hydrodeoxygenation of bio-oil.
Since the composition of bio-oil will be different for different feedstocks, four types of feedstocks have been selected for bio-oil production. The study of simultaneous APR and HDO of bio-oil will be carried out at different temperature, pressure and different types of catalyst. The challenging part for this study is the selection of the best catalyst which favors both the reactions with high conversion and stability. Effect of pressure, temperature and residence time on the quality of bio-oil over different catalysts will be reported. The best catalyst will be selected and the operating parameters will be optimized. This study will be carried out in a high pressure batch reactor. The chemical and physical analysis of bio-oil will be quantified before and after the reaction. Product gas analysis also will be carried out using GC coupled with thermal conductivity detector.