No abstract

Bio-oil, a promising renewable fuel candidate obtained from the hydrothermal liquefaction/pyrolysis of agricultural waste, contains significant amount of oxygen in the form of oxygenated compounds such as aldehydes, ketones, aliphatic/aromatic acids, alcohols, and ethers. This prevents it from being used directly as a fuel. Technologies that can lower the oxygen content of bio-oil are desired. The present work was driven towards the deoxygenation of bio-oil. To understand the mechanism of deoxygenation, guaiacol was selected as a model compound. The deoxygenating ability of acid site (support) and hydrogenation ability of metal were leveraged in this work. Highly acidic mixed oxide support such as ZrO 2 -Al 2 O 3 was used to synthesize a bimetal catalyst Ni-Mo/ZrO 2 -Al 2 O 3 , and the said catalyst was used for deoxygenation of bio-oil/model compound in tetralin as hydrogen donor solvent. The effects of reaction time, temperature, and hydrogen pressure on the conversion were examined. Results showed that 100% guaiacol conversion was obtained with 45.3% phenol and 11.1% cyclohexane yield at 330°C and 30-bar H 2 pressure and reaction time of 10 hr.Poly(ethylene oxide)-block-poly(propylene oxide)-block-(polyethylene oxide) (P123), zirconium propoxide (23−28% free alcohol), aluminum isopropoxide, diglycol, guaiacol, phenol, naphthalene, tetralin, cyclohexane, o-cresol, and p-cresol were all obtained from Sigma-Aldrich, Edmonton, Canada. Anhydrous ethanol, 70% nitric acid, and 30% aqueous ammonia were obtained from Fischer Scientific, Saskatoon, Canada.

Traditional pretreatment methods have several disadvantages, including lower efficiency in terms of cellulose purity, high cost and incomplete separation of biomass components. Considering this, we compared different pretreatment processes and studied their effect on separation of biomass components. Effective delignification was achieved by alkali pretreatment with sodium hydroxide and ammonia. Among alkalis, sodium hydroxide treatment requires less severe process condition like lower concentration, temperature and pressure compared to ammonia pretreatment and produces enzyme amenable substrate, which made sodium hydroxide ideal for biomass pretreatment. Efforts were mounted to optimize sodium hydroxide pretreatment on wheat straw in terms of reaction temperature, reaction time and reagent concentration to produce enzymatically amenable substrate. The best experimental results were obtained when biomass was treated with 2% sodium hydroxide at 130°C for 30 minutes, which was found to extract lignin and significant amount of hemicellulose from biomass.