Catalytic Conversion Of Cellulose Into Ethylene Glycol By Coupling Of Hydrolysis Hydrogenation

Ethylene glycol is an important organic chemical raw material, and used widely in food, paint, pharmaceutical, textile and dyeing industries. Cellulose composed of glucose units by β-1,4-glycosidic is a natural polysaccharide polymer, and it can be converted to ethylene glycol by the catalyzed hydrolysis-hydrogenation. There are some conventional catalysts H2SO4 and Pt/C which are utilized in the reaction, but they have some shortcomings, such as low selectivity, environmental pollution, and corrosion of equipment. Therefore, to seek a novel catalyst with the good catalytic performance for the hydrolysis-hydrogenation becomes imperative.The hydrolysis-hydrogenation was investigated over the catalytic system of Raney Ni and proton acid. It was found that the synergistic effect of Raney Ni and phosphotungstic acid (TPA) enhanced the catalytic performance of the composite catalytic system, and the unique properties of TPA such as "pseudoliquid phase" behavior and its Kiggen structure improved the catalytic performance. The optimum reaction conditions were obtained as follows:Cellulose 0.5 g, Raney Ni 0.10 g, TPA 0.02 g, water 25.0 mL, hydrogen pressure 5.0 MPa, reaction time 4 h, reaction temperature 245℃. Under the above reaction conditions, the conversion of cellulose and the selectivity of ethylene glycol were 100% and 56.2% respectively. Furthermore, the recovery Raney Ni had a good reusability in the reaction.M/SBA-15 (Ru, Ni, Pd, Rh, Pt, Au) mesoporous molecular sieve catalysts were prepared and characterized by a series of analytical tools, such as XRD, SEM, TEM, H2-TPR, BET, etc. The results showed that the synthesized samples are expected M/SBA-15 catalysts. The synthesized mesoporous molecular sieves were used to catalyze the hydrolysis-hydrogenation. The results showed that the composite catalytic system composed with Ru/SBA-15 and TPA was an efficient catalyst for the reaction.The optimum reaction conditions were obtained as follows:Cellulose 0.5 g, Ru/SBA-15 0.10 g, TPA 0.02 g, water 25.0 mL, hydrogen pressure 5.0 MPa, reaction time 4 h, reaction temperature 245℃, which gave 100% conversion of cellulose and 55.5% selectivity of ethylene glycol. However, the reusability of Ru/SBA-15 catalyst was poor because of the pore structure damage.Based on the impregnation method, TPA was loaded to Ru/SBA-15, and then novel composite mesoporous molecular sieve catalyst TPA+Ru/SBA-15 was produced and characterized. It was found that TPA+Ru/SBA-15 have both catalytic centers of acidic hydrolysis and hydrogenation, and both were loaded on SBA-15. The factors that influence the hydrolysis hydrogenation of cellulose reaction were examined, and the optimum reaction conditions were obtained as follows:Cellulose 0.5 g, TPA+Ru/SBA-15 0.10 g, water 25.0 mL, hydrogen pressure 5.0 MPa, reaction time 4 h, reaction temperature 245℃. Under the above reaction conditions, the 100% conversion of cellulose and 47.7% selectivity of ethylene glycol were obtained. It was also found that the reusability of TPA+Ru/SBA-15 was bad which was due to the pore structure damage.In conclusion, this study synthesized and characterized some mesoporous molecular sieve catalyst, and used them to catalyze the hydrolysis hydrogenation of cellulose reaction. The results showed that the catalytic systems had the good catalytic performance, but their reusability was not good due to the pore structure damage, so more work needs to be done. Otherwise, the obtained results may be provided some guidance for the hydrolysis hydrogenation of cellulose over molecular sieve catalyst.