Study On The Preparation Of Catalysts For Conversion Of Water-Soluble Bio-Oil To Oxygen-Containing Fuel

With the growing severity of energy crisis, biomass, which is considered as important source of future energy and fine chemicals, has attracted wide attention as a kind of clean and renewable energy. Catalytic conversion is an effective biomass converting technology. The liquid fast pyrolysis product is known as raw bio-oil, which could convert to hig-quality liquid fuel after catalytic upgrading process.Raw bio-oil always consists of a variery of aldehydes, carboxylic acids, ketones and phenols, which lead to high oxygen content, high acidity, low hydrogen to carbon effective ratio (H/Ceff) and instability of bio-oil. The upgrading process aims to improve the property of raw bio-oil. In this work, representative chemicals were selelected as model compounds of those aldehydes, carboxylic acids, ketones and phenols with low H/Ceff, which would undergo hydrogenation reacrion to get compounds with high H/Cefr, such as alcohols.Furfural was chosen as model compound of aldehydes. Cu-Mg-Al-hydrotalcite based catalysts and CNT-supported Ni-based catalysts were prepared and introduced to the hydrogenation of furfural in aqueous. The results showed that when the reaction was conducted at 140℃ for 10h with an initial hydrogen pressure of 4MPa catalyzed over Cu-Mg-Al-hydrotalcite based catalysts(Cu/Mg/Al=2.5:12.5:5, catalyst amount of 1.5wt.%), the conversion of furfural was up to 98%. Cyclopentanol with high H/Ceff was the main product with a yield of 93%. When the reaction was carried out over Ni/CNT at 140℃ for 10h with an initial hydrogen pressure of 5MPa, the furfural conversion and cyclopentanol selectivity were 96% and 88%, respectively.Acetic acid was chosen as model compound of carboxylic acids. The hydrogenation reaction of acetic acid was carried out over Cu-Mg-Al-hydrotalcite based catalysts, Ni/CNT, Cu/CNT and NiMo/CNT catalysts. NiMo/CNT catalysts exhibited better catalytic activity with better acetic acid conversion rate and lower esterification ability, in comparison with other catalysts. Then one-step hydrogenation esterification(OHE) was carried out between acetic acid and acetaldehyde as acetic acid was one of the most difficult to be hydrogenated in bio-oil. Experimental results indicated that acetaldehyde conversion was up to 66% with an ethyl acetate selectivity of 21.8%, when the OHE reaction was carried out at 150℃ for 8h with an initial hydrogen pressure of 5MPa over NiMo/CNT catalysts. In addition, when adding H2 for twice during the OHE reaction, the acetaldehyde conversion and ethyl acetate selectivity could improve to 81.4% and 36.8%, respectively.Acetol was chosen as model compound of ketones. The hydrogenation reaction of acetol was carried out over Ni/CNT, NiMo/CNT and NiCu/CNT catalysts. Experimental results showed that NiMo/CNT and NiCu/CNT exhibited better catalytic ability. The addition of metal Mo and Cu would inhibit the growth of Ni particle, and the mean particle size decreased, which would improve the catalytic ability. The surface acidity improved in NiCu/CNT catalysts with the presence of subtle medium strong acid sites, and weak acid sites gradually move to higher temperature. When the reaction was carried out at 150℃ for 8h with an initial hydrogen pressure of 5MPa over NiCu/CNT catalysts, acetol could convert to 1,2-propanediol with high H/Ceff, the acetol conversion and 1,2-propanediol selectivity were 95% and 94%, respectively.Guaiacol was chosen as model compound of phenols. The hydrogenation reaction of guaiacol was carried out over Co/CNT, Ni/CNT, NiCo/CNT and NiCo/ZSM-5 catalysts. Experimental results showed that NiCo/CNT showed decreased mean particle size, better dispersibility and exhibited better catalytic ability for the conversion of guaiacol to compounds with high H/Ceff. In addition, catalysts with suitable weak acid sites would help to convert guaiacol to compounds with high H/Ceff. When the reaction was carried out at 200 ℃ for 10h with an initial hydrogen pressure of 5MPa over NiCo/CNT catalysts, the guaiacol conversion and cyclohexanol selectivity were 93% and 80.3%, respectively.Furfural, acetic acid, acetol, and guaiacol were chosen to prepare synthetic bio-oil. The hydrogenation of synthetic bio-oil were carried out over Ni/CNT, NiMo/CNT, NiCu/CNT, NiCo/CNT catalysts. Research results indicated that all kinds of catalysts exhibited different catalytic ability for the upgrading of synthetic bio-oil, while taking catalyst types, reaction temperature, initial hydrogen pressure into consideration. Furthermore, the product distributions changed with the catalyst used, and the alcohol content in upgraded synthetic bio-oil improved with the decrease of the amount of other aldehydes, carboxylic acids, ketones and phenols with low H/Ceff, which confirmed that all the catalysts exhibited good catalytic activity for the upgrading of synthetic or raw bio-oil.