Kinetics And Controllable Preparation Of Cu/SiO₂ Catalyst For Hydrogenation Of Dimethyl Oxalate

Ethylene glycol?EG? is an important chemical, which is widely used in polyester manufacturing, antifreeze additives and so on. With the rapid development of Chinese economy, the demand of EG is also increasing. The main industrial approach to produce EG is hydration of ethylene oxidation. However, it is affected by crude oil resource shrinks and oil crisis, and combining with the energy structure in China, the EG producing route via syngas attracts more and more interest. The hydrogenation of dimethyl oxalate?DMO? to EG is a green and efficient method because of mild reaction condition, high atom economy and low pollution. In this dissertation, the kinetics of DMO hydrogenation, controllable preparation of silica-supported copper catalysts and its catalytic performance for hydrogenation of DMO to EG was studied in detail.The kinetics experiments were carried out in a fixed-bed reactor to investigate the catalytic reaction kinetics of DMO hydrogenation over Cu/SiO₂ catalyst. The optimal kinetics model was selected and the corresponding kinetics parameters were gotten. The model could predict the kinetics behavior for DMO hydrogenation well. It suggested that the ester and hydrogen molecule were adsorbed on two different active sites with dissociative states for DMO hydrogenation system, and the rate-control step is the dissociative adsorption of ester. Thermodynamic and statistical analysis showed that the model was suitable. A ?synergy mechanism? with two different active sites?Cu0-Cu+? was deduced based on this kinetics model and copper species characterization.The Cu/SiO₂ catalysts prepared by hydrolysis precipitation and ammonia evaporation method for DMO hydrogenation to EG were investigated. The 30Cu-TEOS exhibit better catalytic performance because of larger surface area of catalyst and Cu0, higher Cu dispersion and ratio of Cu+/?Cu0+Cu+?. The hydrolysis precipitation method was a better preparation method for Cu/SiO₂ catalysts to obtain suitable catalyst structure and ratio of copper species with different valence.The Cu-TEOS catalysts with different copper loading were prepared by hydrolysis precipitation method and their catalytic performance was investigated. Large surface area and small copper particle were obtained on the catalyst prepared by this method. The characterization showed that the amount of copper phyllosilicate varied with different copper loading. 30Cu-TEOS had optimal catalytic performance because of the largest Cu0 and Cu+ surface area. It was also found that the Cu+ surface area determined by XPS and N2 O titration exhibited positive correlation with the space time of yield of EG, which proved that Cu+ is the key for catalytic activity of DMO hydrogenation.