TiO_2/SiO_2催化碳酸二甲酯与乙酸苯酯酯交换合成碳酸二苯酯

Transesterification of Dimethyl Carbonate and Phenyl Acetate to Diphenyl Carbonate over TiO_2/SiO_2 Catalysts

采用等体积浸渍法制备了TiO2/SiO2催化剂,并将其用于催化碳酸二甲酯(DMC)与乙酸苯酯(PA)酯交换合成碳酸二苯酯(DPC),考察了催化剂制备条件和反应条件对酯交换反应的影响。实验结果表明,以550℃下焙烧制得的负载量为4%(w)的TiO2/SiO2为催化剂,在反应温度170℃、反应时间7 h、PA用量39.00 g、n(DMC)∶n(PA)=1∶2、催化剂用量1.6 g的优化条件下,DMC转化率为79.21%,碳酸甲苯酯和DPC的总选择性为93.66%。TiO2/SiO2催化剂的活性随使用次数的增加而下降;FTIR和XRD的表征结果显示,催化剂失活的主要原因是活性组分TiO2的流失;反应体系中极少量的水对酯交换反应的影响很大。

TiO2/SiO2 catalysts are prepared by an isochoric impregnation method and their activities in the transesterification of dimethyl carbonate（DMC） and phenyl acetate（PA） are examined. The effect of catalyst dosage, TiO2 content in TiO2/SiO2, calcination temperature, reaction temperature, reaction time and mole ratio of DMC to PA on the transesterification and catalyst stability is investigated. Under the optimized conditions： reaction temperature 170 ℃, reaction time 7 h, PA dosage 39.00 g, n（DMC） ： n（PA） 1 ： 2, TiO2 loading 4%（w）, catalyst calcination temperature 550 ℃ and catalyst dosage 1.6 g, the conversion of DMC and the total selectivity to both methyl phenyl carbonate and diphenyl carbonate reach 79.21% and 93.66%, respectively. The catalyst activity quickly falls with the increase of the reused times. The results of FTIR and XRD show that the loss of TiO2 in the catalyst is serious which inactivates the catalyst in the transesterification. A little of water in the reaction system is very disadvantageous to the transesterification.