Study On The Conversion Of Model Compounds Of Aldehyde, Acid And Phenol For Bio-oil Upgrading

Biomass, as a clean renewable resource, is considered to be an important source of future energy and chemical products. Compared to any other renewable energy, it has a more favorable development, popularization and application prospects. In many ways in the biomass conversion process, the production of liquid fuels is regarded as the most effective one. For example, biomass is fast pyrolyzed at elevated temperature and the resulting gas is rapidly cooled to get crude bio-oil, and then, after catalytic upgrading to get high-quality liquid fuels.Crude bio-oil contains a variety of aldehydes, phenols, and carboxylic acids, which cause the bio-oil instability and affect the combustion performance of bio-oil. Therefore, these harmful ingredients are hoped to preferentially get rid of in the process of bio-oil upgrading. This paper focuses on the treatment of aldehydes, acids and phenols in bio-oil. To begin with, the paper proves the feasibility of one-step hydrogenation-esterification (OHE) of aldehydes and acid to get stable combustible ester as a catalytic method for bio-oil upgrading. And then, it focuses on the hydrodeoxygenation (HDO) reaction of phenol, a representative of phenolic compounds. Metal-acid bifunctional catalysts can be used for both the OHE of aldehyde and acid (the metal sites catalyzes hydrogenation of aldehydes to generate alcohols, acid sites then catalyzes acids and generated alcohols to form esters), and the HDO of phenol.Firstly, the study takes butyraldehyde and acetic acid as model compounds and proves that OHE of butyraldehyde and acetic acid can be achieved on the catalysts5%Pt/Al2(Si03)3or5%Pt/HZSM-5. The reaction conditions were optimized, and moderate conditions (150℃for reaction temperature,15atm for hydrogen pressure and0.2g for catalyst amount) are deemed suitable for high yields of esters. Subsequently, the OHE situation of Furfural (FAL) and Acetic acid (HAc) were investigated. It is feasible both on mixed bifunctional catalyst and on composite bifunctional catalyst. Compared to the physical mixture of5%Pd/C+Al2(SiO3)3, there is a better synergistic effect between metal sites and acid sites over5%Pd/Al2(SiO3)3for the OHE of Furfural and HAc. A moderate reaction condition would be required to obtain high yields of alcohol and ester along with lower byproduct yields. Other components, typically present in bio-oils, have little effects on the OHE of FALand HAc. On these basis, the carrier of the bifunctional catalyst has been improved, the Al-SBA-15mesoporous material was used as the carrier of catalyst for OHE of Furfural and HAc. It is proved that Al-SBA-15is much better than Al2(SiO3)3in terms of yield to desired products; and that Al-SBA-15only with medium acidity favors the ester ific at ion of Furfurl alcohol and HAc, thus benefits the OHE of FAL and HAc. In view of the greater accessibility of large molecules to acid sites in Al-SBA-15relative to Al2(SiO3)3or HZSM-5, this OHE method using mesoporous materials supported metal as catalysts is a more promising route for catalytic upgrading of real bio-oil.After effectively dealing with aldehydes and acids, the work turns to the treatment of phenols. Pt (or Pd) was loaded on the organic sulfonic acid functionalized SBA-15to form the organic-inorganic hybrid catalyst, and then it was used for the first time to catalyze the HDO of phenol. Reaction conditions were optimized. Under optimal conditions, the conversion of phenol is94.1%, and the selectivity to target product cyclohexane is98.6%, which are comparable with the best results reported in the literature. A preliminary analysis of the reaction mechanism shows that the HDO of phenol takes place on the hydrogenation-hydrogenolysis path over monofunctional catalyst which possesses only metal sites. However, over bifunctional catalyst which possesses both acid sites and metal sites, the HDO of phenol takes place mainly on the hydrogenation-dehydration-hydrogenation way.The organic-inorganic hybrid catalyst preparation method is simplified and improved by in-situ synthesis method. Phenol conversion of99.5%and cyclohexane selectivity of99.0%are obtained. This is currently the best results. There are good prospects for application.