绿色生产碳酸二苯酯的催化膜及膜反应过程研究

In the green production of diphenyl carbonate by transesterification of dimethyl carbonate with phenol exist some problems such as the low equilibrium conversion resulted from the thermodynamic limit, the cumbersome technology process and the higher energy consumption and higher equipment costs. In order to solve these problems, we propose to apply the catalytic membrane reactor to the reaction. The processes of reaction and separation are carried out in the same reactor. Through the separation founction of the catalytic membrane,the products continuously removed from the reaction system, thus the thermodynamic equilibrium is broke, and both the conversion rate of dimethyl carbonate and the yield of the diphenyl carbonate are enhanced. The Y-type zeolite membranes that play a role of separation are grown on α-Al2O3 substrates by the secondary growth method. After that, Ti-HMS-1 zeolite membranes that play a role of catalyst are prepared by dip coating method on the Y-type zeolite membranes, then the Ti-HMS-1/Y zeolite membranes, which possess both the catalytic and separation functions, are obtained. The Ti-HMS-1 zeolite membranes possessing higher (hydrothermal) thermal stability and catalytic properties are synthesized by introducing TS-1 microporous zeolite primary building units into the walls of mesoporous molecular sieves HMS, which method is also favor to the catalytic performance improvement of Ti-HMS-1 membranes; Reveal the formation and catalytic mechanism of the zeolite membranes to guide the optimal design of membrane formation and the catalytic reaction. To carry out this project is not only meaningful to the new process of the reaction producing diphenyl carbonate by transesterification of dimethyl carbonate with phenol, but also instructive to the integration of other macromolecules catalysis and separation process.

针对碳酸二甲酯与苯酚酯交换制备碳酸二苯酯的绿色合成反应受热力学限制，平衡转化率低，现有工艺过程繁琐、能耗和设备费用较高等问题，提出将催化膜反应器应用于该过程，使反应与分离在同一反应器内进行，通过催化膜的分离作用，使产物不断移出反应体系，打破热力学平衡，提高碳酸二甲酯的转化率及碳酸二苯酯的产率。采用二次生长法在α-Al2O3载体上生长起分离作用的Y型分子筛膜，再采用浸涂法，在Y膜上生长具有催化作用的Ti-HMS-1分子筛膜，进而得到兼具催化和分离功能的Ti-HMS-1/Y分子筛膜；将TS-1微孔分子筛结构单元引入HMS介孔孔壁，制得具有更高（水）热稳定性的Ti-HMS-1膜，该法亦有助于调节膜的催化性能；通过揭示分子筛膜的形成机制和催化机理，指导膜材料及本催化反应的优化设计。本项目的开展不仅对碳酸二甲酯与苯酚反应制备碳酸二苯酯的新工艺有重要意义，对其他大分子的催化和分离一体化亦有指导意义。

本项目针对碳酸二甲酯与苯酚酯交换制备碳酸二苯酯的绿色合成反应受热力学限制，平衡转化率低，现有工艺过程繁琐、能耗和设备费用较高等问题，提出将催化膜反应器应用于该过程，使反应与分离在同一反应器内进行，通过催化膜的分离作用，使产物不断移出反应体系，打破热力学平衡，提高碳酸二甲酯的转化率及碳酸二苯酯的产率。.本项目的研究内容及研究结果包括如下几个方面：.1、采用二次生长法在α-Al2O3载体上生长起分离作用的Y型分子筛膜，并详细考察了该膜对碳酸二甲酯和甲醇混合体系的分离性能。.以实验室合成的EMT型沸石为晶种，在组成为（物质的量）n SiO2: n Al2O3: n Na2O: n H2O=10: 1: 14: 840的二次生长液中，室温下搅拌陈化24 h，于100℃下晶化6 h制备得到NaY沸石膜，膜层连续致密，没有杂晶。该膜用于分离MeOH/DMC体系，随着原料液中甲醇浓度(20-80 wt%)的增大，总渗透通量(0.115-0.137 Kg/(m2•h))增加，分离因子(34.2-5)降低；随着原料液温度(30-80℃)的升高，总渗透通量(0.09-0.179 Kg/(m2•h))增大，分离因子降低(20.9-3)。.2、采用原位水热法，通过调控合成液的陈化时间及温度，晶化时间及温度，合成液的组成等合成参数，在Y膜上生长出连续的具有催化作用的Ti-HMS-1膜。 .以在120℃晶化3 h的TS-1前驱体为硅源和钛源，十二烷基胺（DDA）为模板剂，在100℃晶化48 h得到质量最优的膜层Ti-HMS-1/Y微孔-介孔膜，厚度约为3 μm。在沸水中煮10h，仍然保持介孔结构。.3、将制备出的材料用于碳酸二甲酯与苯酚酯交换制备碳酸二苯酯的绿色合成反应，考察了催化分离一体化膜反应器对该反应的影响。.在175℃下连续进行抽真空操作反应9 h，PhOH的转化率为0.69％，DPC选择性为2.97％，MPC选择性为86.50％。转化速率可达5.43×10-2 mol/g•h，此值远远高于粉体催化剂的5.58×10-6mol/g•h。.4、揭示出膜材料的形成机制。有两种可能的成膜方式：.一：当合成液搅拌时间较长时在体相已经形成了六方排列的介孔结构，此时载体表面吸附的是介孔分子筛；.二：当搅拌时间较短，此时在体相内未形成六方排列的介孔结构，载体表面吸附的是棒状胶束，胶束在载体表面组装形