Study On Copper Silicate Catalyst For Catalytic Hydrogenation Of Dimethyl Oxalate

Ethylene glycol is an important chemical material widely used in the production of polyester, antifreeze, adhesive and so on. Traditional way of production by oil as the raw material to produce, with the growing scarcity of oil resources, The "Coal-to-EG" technology attracts more and more attention of the researchers. The route involves the gasification of coal to syngas, followed by the coupling CO with nitrite esters to oxalates and then the hydrogenation of oxalates to EG, among which the hydrogenation of oxalates to EG is crucial in the industrialization of Coal-to-EG route. Cu-based catalysts, inherent disadvantages of poor stability and short lifetime limited their application. More efforts, such as improving the preparation methods, modifying the supporters or adding the promoters, have been paid to make up their defects. Exploring the narure of catalytic sites is of great fundamental importance. Although the points of view for understanding catalytic essence of hydrogenation of oxalates to EG are still controversial, seeking ways to regulate surface composition, morphology, electronic state of catalyst is believed to be the key for developing Cu based catalysts with high performance for oxalate hydrogenation. This paper adopts coprecipitation preparation of copper silicate catalyst, precipitation was studied in the process of interaction between active component and carrier, and investigates the corresponding variable parameters effect the performance of the catalyst, preparation technology was optimized. In addition, to solve the problem of catalyst under the condition of high temperature sintering deactivation easily, the catalysts were modified by Zn to improve the thermal stability. The following results were obtained.(1) In the precipitation process of preparation of catalyst, the way of precipitation has great influence of particle size and the copper species dispersion on the carrier. Copper nitrate drip into the silicate according to the precipitation of the catalyst performance is superior to sodium silicate drip into the copper nitrate precipitation catalyst system, namely the precipitation method was suitable for good dispersion of catalyst active species, active center. In the process of precipitation, precipitation rate slightly influence on the reaction conversion and little influence on the objective product selectivity. With the increase of the settling time is slow sedimentation rate, that is, a slight increase conversion rate of dimethyl oxalate. Copper silicon than had a greater influence on the catalytic performance of catalysts, copper silicon ratio is too low, the catalyst activity less, catalytic activity is weak; Copper high silica than the active species gather each other easily, particles grew up, uneven distribution and catalyst activity and reduces. Experiments show that the optimal Cu:Si ratio was 0.85:1.(2) In the process of modified zinc to the copper silicate catalyst study, the introduction of zinc have different effects on catalyst. Experiments show that copper and zinc components with sodium silicate precipitation at the same time, the effect on each other and dispersed zinc in copper species. Zinc and affected by the performance of the introduction of the amount of catalyst, amount of zinc into youth cannot have obvious effect, and the introduction of active center will package quantity too much. So suitable catalyst composition for Cuo.8 Zno.2/SiO2, the selective catalyst conversion are better as a result, the stability test also showed that is relatively stable.