The Study Of Heterogeneous Catalyst On The Synthesis Of Diphenyl Carbonate By Transesterification

The catalyst for synthesis of diphenyl carbonate(DPC) by transesterification of dimethyl carbonate(DMC) with phenol were studied and heterogeneous catalysts PbO/TiO2 and PbTiO3 were prepared for this reaction in this paper. TG, XRD, NH3-TPD, SEM were employed for catalyst characterization. The relation of the catalytic structure and activity was also investigated.1) A series of catalysts were prepared for synthesis of diphenyl carbonate (DPC). PbO was proved to be an efficient catalyst for transesterification. Different supported catalysts were prepared as Pb(NO3)2 for precursor. PbO/TiO2 showed excellent catalytic activity in this reaction. under suitable contidion: at reaction temperature 180℃, n(phenol): n(DMC)=3: 1, with PbO loading of 30 %(mass fraction), reaction time 12 h, the yield of MPC and DPC could reach 16.6 % and 13.5 % respectively.2) In the experiment, The catalyst PbO/TiO2 which had no acidity had higher catalytic activity than PbO/Hβwhich had acid center on the synthesis of DPC.3) A new phase PbTiO3 was generated in the process of preparing catalyst PbO/TiO2. It was showed the loss of the active component PbO was serious during the reaction. The yield of MPC and DPC was declined to 9.3 % and 5.1 % respectively after the catalyst reused one time.4) Pyrochlore-type Pb2Ti2O6 was obtained by hydrothermal methods. It was founded the catalyst obtained by precursor Pb(CH3COO)2 and Ti(OBu)4 at the molar ratio 1.2: 1 had the highest activity.5) The impact of calcination temperature on this reaction was investgated. The catalytic activity increased when the calcination temperature rised and declined after the calcinations temperature exceeded 500℃. At 200℃, Pb2Ti2O6 exist acid centers, but the acidity disappeared when the calcination temperature exceeds 300℃. Meanwhile, Pb2Ti2O6 began to recrystallinze at 300℃and fully transformed into perovskite PbTiO3 at 500℃.6) Under optimal reaction condition: at reaction temperature 180℃for 11 h, DMC: PhOH =1: 4, w(perovskite PbTiO3 )=3.0 g, the yield of MPC and DPC could reach 16.9 % and 9.7 % respectively. After reused four times, the catalyst remain the PbTiO3 phase and The yield of MPC and DPC was declined to 10.1 % and 5.3 % .