Synthesis Of Dimethyl Oxalate By The Carbon Monoxide Coupling Reaction In Gas-phase

The process of producing ethylene glycol (EG) by using syngas is important to the development of chemical industry for our country. As the key step of the process of producing EG by using syngas, synthesis of dimethyl oxalate (DMO) by the carbon monoxide coupling reaction in gas-phase was attracted growing attention. Furthermore, DMO is also a vital chemical product and raw material. Thus, it is significant to study the CO coupling reaction to form dimethyl oxalate in gas-phase. The main works in this dissertation included support effects, reaction condition, and the method of catalyst preparation. The characterization methods such as XRD, XPS and BET were used to investigate the change of catalyst in the process of preparation and reaction.In the study of catalyst Pd/α-A_l2O₃, the results indicated that theα-A_l2O₃ support affected greatly reactivity of catalyst. Two supports which were chose from different manufactures showed best catalytic activity for Pd/α-A_l2O₃. When the reaction condition were optimized as following: Pd loading 1%(weight percentage), temperature 145℃-155℃, catalyst volume 4mL, the flow rates of methyl nitrite(MN) 15mL/min, CO 30mL/min, N₂ 25mL/min, the conversion of MN was 84.2%, and the selectivity of DMO was 96.3%. The catalytic activity of Pd/α-A_l2O₃ had kept unchanged after 160h lifetime test.In further study of catalyst, Zn was added to Pd/α-A_l2O₃ as a promoter. First, we found that the process of impregnation method could obviously affect the catalytic activity of Pd-Zn/α-A_l2O₃. Pd-Zn/α-A_l2O₃-Ⅱin which Pd was loaded onα-A_l2O₃ before Zn performed better catalytic activity than Pd-Zn/α-A_l2O₃-Ⅰin which Zn was loaded onα-A_l2O₃ before Pd. The loading content of Zn had great influence in the activity of Pd-Zn/α-A_l2O₃-Ⅰ, while it had little effect on that of Pd-Zn/α-A_l2O₃-Ⅱ. Through XRD, XPS, BET characterizations, it was observed that the active component of Pd-Zn/α-A_l2O₃-Ⅱis Pd0, and the catalyst did not change after the reaction. The effect of space velocity of reactions on the activity of Pd-Zn/α-A_l2O₃-Ⅱwas also investigated. When temperature 145℃-155℃, the flow rates of MN, CO, N₂, were 15 mL/min, 30 mL/min, 25 mL/min, respectively, space velocity was 4200h-1, the conversion of MN was 81.2%, the space-time yield(STY) of DMO was 1744.4 g/L·h.