The Study Of The Preparation Of Diphenyl Carbonate In Membrane Reactor

Polycarbonates（PCs） are an important engineering thermoplastic with good mechanical and insulating properties. The most practical process for the production of PCs is the reaction of the melt polymerization of bisphenol-A with diphenyl carbonate（DPC）, so DPC is an essential feedstock for the green production of PCs. The most practical method for the manufacturing of DPC is the transesterification of phenol and dimethyl carbonate（DMC）. But the reaction suffers from low yield and selectivity even at elevated temperature due to a critical thermodynamic limitation. In this study, coupling of reaction and separation in membrane reactor using Ti-HMS-1 as catalyst and NaY or Silicate-1 membrane as separative unit were put forward to solve this problem. The Ti-HMS-1 and molecular sieve membrane were characterized by XRD, TEM, FT-IR, UV-Vis diffuse reflectance. The main results are as follows:（1） Pure mesoporous molecular sieve（Ti-HMS-1） with microporous zeolite structure unit can be assembled from titanosilicate-1 precursors with didecylamine（DDA） as structure directors. For the first time, Ti-HMS-1 was used to catalyze the transesterification of dimethyl carbonate with phenol, the total selectivity for MPC and DPC was up to 98.8% with a phenol conversion of 6.4% in the reaction;（2） The continuous NaY membrane with thickness of 8μm was synthesized by secondary growth using EMT zeolite as seed on α-Al₂O₃ support. When it was used to separate the mixture of MeOH/DMC（50wt%DMC） at 50℃, the flux and separation factor was about 0.139kg/（m²·h） and 13.4 respectively. The continuous Silicate-1 membrane with thickness of 5μm was also prepared on α-Al₂O₃ support in situ synthesis method. When it was used to separate the mixture of MeOH/DMC（50wt%DMC） at 50℃, the flux and separation factor was about 0.127kg/（m²·h） and 2.7 respectively;（3） Using Ti-HMS-1 as catalyst and NaY molecular membrane as separative unit in membrane reactor, the conversion of phenol increased from 6.4% to 7.0% and the selectivity for MPC and DPC decreased a little from 98.8% to 96.7%. Using Ti-HMS-1 as catalyst and Silicate-1 membrane as separative unit in membrane reactor, the conversion of phenol was increased from 6.4% to 6.6% and the selectivity for MPC and DPC was almost the same.