Preparation Of The Cu/SiO₂ Catalysts By Sol-Gel Method And Its Performances In Hydrogenation Of Dimethyl Oxalate

Ethylene glycol(EG) is one of the important chemical materials. The synthesis route of oxalates via catalytic coupling reaction of CO and then catalytic hydrogenation of oxalate to EG is suitable for Chinese resources structure of much more coal than petroleum, and has advantages in mild reaction condition and high selectivity of EG. So it has very good development prospect. But the Cu/SiO2 catalyst of EG from hydrogenation of oxalate has poor stability, which becomes a technology difficulty and a bottleneck of the synthesis route from synthesis gas.Sol-Gel method has some advantages for stabilizing of active sites in supported copper catalyst, so a series of Cu/SiO2 catalysts for hydrogenation of dimethyl oxalate(DMO) to EG were prepared by the sol-gel method in this paper, and the effects of the preparation conditions of Sol-Gel method on the properties and catalytic performance was studied. And the influence of reduction activation on the properties of Cu/SiO2 catalysts was studied too. Cu particles aggregation for different reduction temperature was researched, and the optimal reduction temperature was obtained.The results show that Sol-Gel method used to prepare Cu/SiO2 catalysts for hydrogenation of DMO, can keep copper species dispersing uniformly on the SiO2 support, and the copper species could be reduced easily. By means of TEOS hydrolyzing and combining with copper species to the skeleton of catalyst, controlling reasonable aging time, the cover of silica on the catalytically active sites is suppressed, which leads to higher catalytic activity. The best conditions for preparing Cu/SiO2 catalysts by Sol-Gel method are pH 6-8, age temperature 40℃, age time 1.5h.The average size of Cu particles increases gradually with the reduction temperature of Cu/SiO2 catalysts increasing. But the biggest average size of Cu particles is only 6.3nm, this indicate that Cu/SiO2 catalysts prepared by the sol-gel method have good thermol stability. The variation of reduction temperature may change the ratio of Cu0 and Cu+ or copper crystal defect, the DMO conversion and the EG selectivity is not changed greatly. The catalyst activity is highest when reduction temperature is 350℃. Under the operation conditions of reaction temperature 200℃, reaction pressure 2.0MPa, the mole ratio of H2 and DMO 60, and liquid hourly space velocity(LHSV) of DMO 1.0g·h-1·(g-cat)-1, the DMO conversion and the EG selectivity achieved 100% and 95%, respectively.