Hydrodeoxygenation Process for Converting Glycerol into Bio-crude

Bio-energy is a clean (containing negligible sulfur and being near-carbon neutral), renewable and abundant source of energy. Bio-energy can be a potential alternative to fossil fuels for the production of energy and chemicals. Due to the world's increasing energy demands, declining petroleum reserves and growing concerns over the detrimental environmental effects of fossil fuels, there is an increased interest in the production of bio-fuels (bio-ethanol, bio-diesel and bio-oils) from biomass feedstocks. The increased production of bio-diesel by trans-esterification of vegetable oils has resulted in a glut of glycerol as a by-product. Economically beneficial utilization of the glycerol would greatly enhance bio-diesel plant production economics.;The support materials: MgO, AC (activated carbon), gamma-Al2O 3 and X-type zeolite were found to have a negligible catalytic effect by themselves, with a maximum bio-oil yield of 3.7 wt.% for the zeolite when tested without catalyst metals. Subsequent experiments with catalyst metals revealed a positive correlation between support acidity and bio-oil yield. This effect was confirmed by upgrading glycerol in the presence of acidified zeolite which produced a remarkably higher yield of bio-oil (∼34 wt.%) even without metal catalyst loading. Co, Ru and Mo were found to be the almost equally effective metal catalysts, increasing bio-oil yield to ∼13 wt.% when loaded on to Al2O3. Ru was found to greatly increase glycerol gasification. The most effective combination of metals and support for the hydrodeoxygenation (HDO) of glycerol was determined to be MoCoP/zeolite achieving a maximum bio-oil yield of ∼40 wt.%. The role of phosphorus as a catalyst promoter was discussed. Sulfidation and reduction of the MoCoP/zeolite catalyst resulted in drastic reductions in bio-oil yield contrary to results reported in published literature. The bio-oil products were found to consist mostly of substituted phenols, ketones, and to a lesser extent alcohols, ethers and cycloalkanes. The bio-oil had a higher carbon contents and much lower oxygen contents than the glycerol feedstock. The bio-oils reached a maximum HHV of 33 MJ/kg.;In Part II of this research, the HDO of glycerol into bio-crude was investigated in order to determine the optimum conditions required to produce high quality (low oxygen) bio-oil. These experiments were conducted using the best catalyst out of those tested in Part I (MoCoP/Zeolite) and investigated the effects of residence time, reaction temperature, hydrogen pressure, and solvent on bio-oil yield. The reaction products of these experiments were characterized in a similar manner to Part I. The fresh catalysts were characterized by ICP-AES, N2 isothermal adsorption, XRD and spent catalysts were characterized by XRD and TGA. The optimum conditions for the hydrodeoxygenation of glycerol into bio-crude in the presence of MoCoP/zeolite catalyst were found to be: 300°C reaction temperature, 5 MPa initial hydrogen pressure, 60 min reaction time and 100% glycerol feed. While dilution of the glycerol feedstock with water had a negative effect on bio-oil yield, HDO of pure glycerol produced the highest bio-oil yield (40 wt.% at 300°C, 1 hand 5 MPa H2). The amount of char deposited on the spent catalyst decreased with extended reaction time, increased reaction temperature, and elevated initial hydrogen pressure.;Keywords: Glycerol; Bio-crude; Hydrodeoxygenation; Hydro-treating, Catalysts;Part I of this research investigated the effectiveness of various catalysts in the conversion of glycerol into bio-crude at elevated temperature and pressure. The reactions were carried out in an autoclave micro-reactor at a temperature of 300°C and an initial pressure of hydrogen of 5 MPa. Gaseous products were collected and analyzed by Micro-GC. The solid products were removed by filtration while the liquid products were separated into water soluble products (unreacted glycerol, acids, alcohols) and water insoluble products (bio-oil/bio-crude) by extraction with water and ethyl acetate. The bio-crude obtained was comprehensively characterized to determine its physical/chemical properties.