【作者】 王靖岱；

【导师】 阳永荣； 陈纪忠；

【作者基本信息】 浙江大学 ， 化学工程， 2002， 博士

【摘要】 负载化是催化剂工程设计中常用的手段。以无机物为载体的茂金属催化剂已得到了广泛的研究和应用，但随之带来催化剂活性降低、聚合物灰份较多、薄膜中鱼眼的产生和聚合物性能的降低等问题。近年来，出现了以聚合物为载体的负载型茂金属催化剂，由于其成本低、易制备、能保持高活性、分子量分布较窄、产品中灰份含量低、颗粒形态良好、无粘釜现象以及适用于气相和淤浆聚合等优点日益受到关注。但通常的化学法制备手段由于颗粒形态可控性差、制备繁琐、成本昂贵，限制了其应用前景。因此，既能避免冗长、昂贵的常规负载步骤，又能得到颗粒形态良好的高活性载体型茂金属催化剂成为研究者孜孜追求的目标。 超临界溶液快速膨胀技术（rapid expansion of the supercritical solution，RESS）由于在喷射过程中，极大的流速和极快的膨胀速度产生强烈的机械扰动和巨大的过饱和率，前者产生一致的成核条件，并因此形成很窄的颗粒粒径分布，后者导致产生微小颗粒，从而获得粒径均匀的超细粒子。因此超临界溶液快速膨胀技术成为制备负载型茂金属催化剂极具潜力的方法之一。同时，超临界溶液快速膨胀技术与许多实际应用密切相关，如双峰聚合物的制备、新型高分子合金、高分子对药物释放的控制等，也与许多交叉学科如：高分子化学、催化科学、热力学和药学等相关。因此，将超临界溶液快速膨胀技术应用于茂金属领域的研究有着重要的理论意义和显著的应用背景。 本论文工作以丙烷为超临界溶剂，首次利用超临界溶液快速膨胀技术（RESS），成功制备了以聚苯乙烯为载体的二氯二茂钛茂金属催化剂颗粒，并通过乙烯淤浆聚合考察了催化剂的聚合特性。论文围绕着这一中心任务，进行了以下四个方面的研究工作：（1）固体溶质二氯二茂钛和聚苯乙烯在超临界丙烷中的热力学相行为；（2）固体溶质二氯二茂钛和聚苯乙烯在超临界溶液快速膨胀过程中的结晶行为；（3）双RESS法制备以聚苯乙烯为载体的茂金属催化剂；（4）催化剂聚合特性的考察。具体的工作如下： 1．二氯二茂钛在超临界丙烷中的溶解度测定和缔合模型的建立。建立了固体溶质在超临界条件下的溶解度测定装置，静态法测定了在较宽的实验条件范围内（温度：383.15～408.15K，压力：10～35Mpa）二氯二茂钛在超临界丙烷中的溶解度，发现溶解度随温度、压力的增大而增大，表明Cp2TiCl₂／SCF-C₃H₈体系不存在反向区。在分析超临界集聚现象的基础上，结合缔合理论和气固吸附理论，得到了固体溶质在超临界流体中的溶解机理，提出了二氯二茂钛在超临界丙烷中溶解度的缔合模型。并通过实验数据的优化模拟，得到了模型参数。数据分析表明，缔合模型能够模拟预测一定操作范围内（T_r=1～1.2，P_r=2.3～4.3）二氯二茂钛 中文摘要 在超临界丙烷中的溶解度，平均相对误差仅为1．81％。尤为重要的是，缔合模型 的六个参数都包含了一定的物理意义，脱离了通常由于模型参数的经验性带来的 计算盲目性，有助于提高计算固体溶质在超临界流体中溶解度的正确性。 2．聚苯乙烯在超临界丙烷中的溶解度测定和溶液模型的建立。静态法测定了温度为383．15－408．15 K、压力为 10－35 MPa范围内聚苯乙烯在超临界丙烷中的溶解度。实验数据表明，聚苯乙烯的溶解度很小，数量级处于 10＊10”＼摩尔分率) 之间。且溶解度随温度、压力的增大而增大，可见PS用CF( 体系不存在反向 区。与此同时，本文将无热溶液的FloryHuggins理论应用到超临界流体，建立 了聚合物在超临界溶剂中的溶解度的溶液模型，并通过实验数据的优化模拟，得 到了模型参数。数据分析表明，溶液模型能够较好地反映聚合物溶液的特征，且 能较为精确地模拟预测聚苯乙烯在超临界丙烷中的溶解度，平均相对误差仅为 4．ZI％。3．二氯二茂钛和聚苯乙烯微细颗粒的制备和粒子竞争生长机理的提出。设计并建立了一套超临界快速膨胀过程的实验装置，以丙烷为超临界溶剂，分别进行了RESS法制备二氯二茂钛和聚苯乙烯超细粒子的系统研究，发现增加溶液浓度。提高预膨胀压力、增大喷嘴直径、减小喷嘴长度、增加流体速率、降低样品收集距离，都能有效地降低颗粒粒径。而预膨胀温度对不同溶质表现为不同的效果，CP。TICI。颗粒粒径随预膨胀温度的升高而增大，而PS颗粒则随预膨胀温度的升高而降低，说明CP。TICI。晶核的生长主要在膨胀室内完成的，而PS晶核的生长则主要是在喷嘴内完成的。从流体动力学和成核理论出发，建立了超临界溶液快速膨胀的流动模型和晶体成核生长模型，并提出了超临界溶液快速膨胀技术微细粒子生长的竟争机理，即过程工艺参数对于沉析颗粒粒径的影响取决于成核过程和晶体生长过程的共同作用，而不仅仅为一个方面作用的结果。同时发现，成核主要发生在超音速自由膨胀段。而晶体生长的主要机理是碰撞聚并生长，并且在马赫盘处，由于存在较高晶粒浓度的环境气氛，颗粒将继续聚并生长。 利用聚合物粒子能够复制催化剂颗粒形态的“复制”原理进行MSS研究，通过催化剂和聚合物的亚更多还原

【Abstract】 Metallocene catalysts have a great deal of advantages, such as high activity, narrow molecular weight distribution, and the outstanding catalytic capacity of copolymerization. Except these advantages, there are still several problems, such as the difficulty in controlling polymer morphology with soluble homogeneous catalysts, the inability to be used in continuous slurry and fluidized-bed gas-phase processes, significant reactor fouling, and the very large amount of MAO needed to achieve higher metallocene catalytic activity, are needed to be solved if metallocene catalysts would be used widely in industry. Although immobilizing metallocene complexes on an inorganic support can solve these problems to a certain extent, the surface properties of supports strongly influence the behavior of its supporting catalysts, and immobilization often depresses catalyst activities at some extent. Moreover, the supports influence the processing properties of polymer for their containment in polymer as additional ash. Recently, metallocenes with organic or polymer materials as the supports, although rarely reported, are of great interests in industry and academic research, because polymer-supported metallocenes can offer the following advantages: easy preparation and low cost; preserving fairly high activity and the features such as single-site, narrow comonomer and molecular-weight distribution, and high ability to incorporate comonomers with unsupported metallocenes; lower inorganic residues in polymer products in comparison with inorganic supports such as Si02, A^Os, MgCb; capacity of controlling the morphology of the polymer to reduce the possibility of reactor fouling, and the adaptation to slurry and gas phase polymerization process.The solubility of solids in supercritical solutions is a very sensitive function of temperature and pressure. Because supercritical fluids are highly compressible, small changes in pressure can result in large changes in density and the solve power; the rapid expansion of supercritical solution thus gives rise to very large supersaturation ratios. The speed at which pressure perturbations propagate within the fluid allows precipitation from an essentially uniform medium and clearly distinguishes this process from conventional crystallization, where temperature gradients give rise to a wide distribution of nucleation rates within the solvent. The uniform conditions within the nucleating environments should result in the production of particles that are more even in morphology and narrower in size distribution than those produced by conventional crystallization technique. So the RESS technique is recommended to prepare the polymer-support metallocenes particles with good morphology and narrow size distribution. At the same time, detail knowledge of rapid expansion of the supercritical solution is of interest to chemistry as well as to thermodynamics, pharmaceutics and so on. And this technique associates with a wide range of applications such as bimodal resin, polymer alloy and biocompatibility of artificial organs in medicine. Therefore, the study of the RESS is of important theoretical meaning and has an evident application background.The thesis investigated systematically the preparation of polystyrene-supportedmetallocenes catalyst [Cp2TiCl2] particles by RESS. And the metallocenes microparticles by RESS were characterized through ethylene slurry polymerization. It could be divided into four main sections: (1) the thermodynamic behavior of binary system Cp2TiCl2/SCF-C3H8 and PS/SCF-C3H8, (2) nucleation behavior of solute in supercritical solution, (3) preparation of polymer-supported Cp2TiCl2 through coprecipitation, (4) polymerization characteristic of metallocenes microparticles prepared by RESS. In the first section, the author mainly discussed the binary phase behavior and the dissolution of solid solute in supercritical solution. In the second section, a systematic investigation of effects of process conditions on the characteristics of solid products was performed and discu更多还原