Researches On The Bio-oil Catalytic Reforming For Hydrogen Production And Dimethyl Oxalate Hydrogenation For Ethylene Glycol Synthesis

Biomass energy is a green, clean and renewable energy. With the global depletion of fossil resources and deterioration of environment, efficient utilization of biomass energy has become increasingly important. Biomass fast pyrolysis can convert solid biomass of low energy density to liquid bio-oil of relatively high energy density and transport convenience. The bio-oil yield can be up to70%. However, bio-oil has several disadvantages associated with high water content, high oxygen content, low pH value and high viscosity. Thus it cannot be directly used as power fuel oil and must be upgraded. Catalytic reforming technology can efficiently convert bio-oil of rich water into widely-used hydrogen. The produced hydrogen can be used not only in the field of internal combustion engines and fuel cells but also as hydrogen resource for bio-oil upgrading process. Therefore, this thesis focuses on the bio-oil catalytic reforming for hydrogen production and the synthesis of ethylene glycoly via dimethyl oxalate hydrogenation.Firstly, ethanol was selected as a bio-oil model compound to carry out studies of the influence of different catalyst preparation methods on the performance of Ni/Al2O3catalyst. It was found that the catalyst prepared by coprecipitation method had high activity. For ethanol reforming reaction, hydrogen yield was maximized to88%and ethanol conversion reached99%. The opimized decomposition route of ethanol on the Ni(111) surface was identified via density functional theory (DFT) calculation:CH3CH2OHâ†'CH3CH2O*â†'CH3CH2*â†'CH3C*-â†'CH3*+C*.Secondly, acetic acid, hydroxylacetone and phenol were selected to study the catalytic reforming for hydrogen production over Ni/nano-Al2O3catalyst. The Ni/nano-Al2O3catalyst exhibited high activity for all the three above organics. At the temperature of700℃. acetic acid conversion reached98.2%with hydrogen yield of87%and hydroxylacetone conversion reached98.7%with hydrogen yield of97.2%. Phenol had a slightly lower conversion of84.2%and the hydrogen yield was69%. Meanwhile, for these three organics, the stability of catalyst was more than10h. Subsequently, preliminary analysis of energy consumption of catalytic reforming was carried out.Series of Co-Fe catalysts without support were prepared and used for catalytic reforming of acetic acid for hydrogen production. The results indicated that pure cobalt catalyst had highest activity. Acetic acid can be converted completely, and the hydrogen yield can reach highly to96%at the low reaction temperature of400℃. The stability of catalyst was more than65h. Furthermore, the optimized decomposition route of acetic acid on the Co(111) surface was identified by DFT calculation:CH3COOHâ†'CH3COO*â†'CH3CO*â†'CH3*+CO*.Molecular distillation technology was adopted to separate the rice husk bio-oil into two different fractions:water-rich distillation fraction and water-less residual fraction. Results of catalytic reforming of the water-rich distillation fraction on Ni/Al2O3catalyst revealed that the carbon conversion of95%and hydrogen mass yield of135(mg g-1organics) were obtained under the optimum reaction conditions. The catalyst stability reached11hours. Besides, an interesting found was that all the water invovled in the reforming reaction came from the crude bio-oil without any extra supply, which contributed to significant reduction in water consumption of the catalytic reforming for hydrogen production. Furthermore, the most likely decomposition pathway of acetic acid, hydroxyacetone, furfural and phenol on the Ni(111) surface were identified via DFT calculations.Finally, ethylene glycol synthesis from dimethyl oxalate hydrogenation over Cu/SiO2catalysts was studied. The Cu/SiO2catalysts were prepared by urea hydrolysis method. The100%conversion of dimethyl oxalate and98%selectivity of ethylene glycol were obtained over the catalyst with Cu loading content of15.6%.