Study On The Disproportionation Of Products Of The Transesterification Of Dimethyl Oxalate With Phenol

Much attention has been paid to the synthesis and applications of Diphenyl carbonate (DPC) because it can be used as an environmentally benign chemical intermediate. The transesterification of dimethyl oxalate (DMO) with phenol to diphenyl oxalate (DPO) followed by decarbonylation of DPO to DPC is a promising non-phosgene route. In the former work, more attention has been paid on the transesterification of DMO with phenol to produce the intermediate, methyl phenyl oxalate (MPO). In this thesis, the disproportionation of MPO over TiO2/SiO₂ catalyst on particle support under vacuum was studied and reactive distillation of the course was discussed.First of all, internal standard method with HP-5 capillary column and SP-3420 chromatograph was established. Ethyl benzoate was selected as the internal standard material. The internal standard equation of DPO was y=1.6366x+0.0319, R2=0.99852. It was proved that the method had good accuracy, recovery and precision.TiO2/SiO₂ catalyst based on particle SiO₂ support showed better reactivity and selectivity on the transeserification of DMO with phenol and the disproportionation of MPO to DPO. A mass of DMO in the transesterification course inhibited the disproportionation which has a small equilibrium constant. As a result, selectivity and yield of DPO were low. The removing of DMO and phenol under vacuum broke the equilibrium of reaction so that the disproportionation of MPO was improved. Accordingly, yield of DPO was increased from 17.7% to 37.2%.In the study of disproportionation of MPO, it was found that optimal operating pressure, catalyst concentration and catalyst loading amount were 37.3kPa, 1.4 wt.% and 2wt.% respectively. In the reactive distillation, it was found that optimal operating pressure and relux ratio were 37.3kPa and 2:1 respectively.By means of XRD, FT-IR analysis of adsorbed pyridine, NH3-TPD and SEM, it can be concluded that the dispersion of TiO₂ on the support had an importand impact on conversion of the disproportionation of MPO. High dispersion of TiO₂ improved the disproportionation, and the production of crystal TiO₂ inhibited the reaction. The other conclusion was the type and amount of acid on the catalyst surface had an important impact on selectivity of the disproportionation of MPO. Large amount of Lewis acid sites of weak and moderate strength was exactly the reason that TiO2/SiO₂ catalyst had a high selectivity of the disproportionation of MPO.After the product of the disproportionation under vacuum was treated through washing and vacuum filtering, DPO with content over 98% could be obtained.