【作者】 张斌；

【导师】 吴鹏； 杨为民；

【作者基本信息】 华东师范大学 ， 物理化学， 2014， 博士

【摘要】 乙苯是重要的石油化工大宗有机化学品,其下游产品如工程塑料、合成树脂、合成橡胶等是建筑、汽车、电子及日用品等行业的重要原材料,用途非常广泛。目前,乙苯的生产主要是苯和乙烯在分子筛催化剂下通过烷基化反应进行,主要包括气相烷基化法和液相烷基化法。其中,液相烷基化法具有工艺流程简单、操作简便、产品质量优、能耗物耗低等优点,已逐步替代气相烷基化法而成为乙苯生产的主流工艺。本文以苯和乙烯液相烷基化为目标反应,围绕分子筛催化材料的研究,开展了层状MWW分子筛的合成、分子筛晶体结构的后处理修饰、物化表征及催化性能等方面的工作,具体分为以下几个部分：第一部分、MCM-22分子筛的合成、表征及催化性能的研究。通过对MCM-22分子筛合成条件的详细考察,包括硅铝比、碱度、模板剂用量和种类、晶化助剂、晶化温度及晶化时间等多种因素,成功制备了一系列不同硅铝比的MCM-22分子筛,扩展MCM-22合成范围的限制,并进行了100mL反应釜合成的重复性研究和2L反应釜的放大合成。通常,MCM-22合成过程要使用剧毒的六亚甲基亚胺(HMI)作为模板剂,而且其生产和使用均受到严格控制,我们采用低毒、易得的哌啶(PI)为替代模板剂合成的MCM-22分子筛,具有相当的结晶度、硅铝比和孔容,而且其晶粒尺寸更小、比表面积更大。在苯和乙烯液相烷基化制乙苯的反应中,其催化性能和以HMI为模板剂合成的MCM-22分子筛相当,具有潜在的工业应用价值。第二部分、MCM-56分子筛的后处理合成、表征及催化性能的研究。从上述不同硅铝比的MCM-22前驱体出发,采用温和的酸性溶液进行预处理,使MCM-22前驱体的层间模板剂局部脱除,再经过滤、洗涤、烘干及焙烧等步骤后获得MCM-56分子筛。这种后处理合成MCM-56的优点在于通过酸处理可局部脱除MCM-22层间的有机模板剂,扰乱MCM-22分子筛转变为3D的MCM-22分子筛,可极大拓展常规水热无法合成出的MCM-56分子筛的硅铝比范围。与常规MCM-22分子筛相比,后处理MCM-56分子筛的外表面积有明显的提高,在苯和乙烯液相烷基化制乙苯反应中,具有更高的反应活性、乙基苯收率及更优的反应稳定性。第三部分、介孔MCM-22分子筛的合成、表征及催化性能的研究。采用硬模板法将炭黑引入到合成母液中,通过合成配比的优化,成功制得了一系列不同硅铝比的MCM-22分子筛,该分子筛以微孔为主、含有4-10nm的介孔孔道,而且所得分子筛具有更大的外表面积,有利于反应物与催化活性中心的接触以及反应产物的快速扩散。在苯和乙烯液相烷基化制乙苯反应中,介孔MCM-22分子筛的乙烯转化率明显提高、乙基苯的选择性和稳定性也有不同程度的提高,显示出微孔-介孔MCM-22分子筛的优越催化性能。第四部分、扩孔型MCM-22分子筛的合成、表征及催化性能的研究。以二甲基二乙氧基硅烷(DEDMS)为硅烷化试剂,对MCM-22前驱体进行晶体结构的修饰。为了避免硅烷化过程中脱铝现象的发生,在处理体系中加入醇类试剂,不仅可合成出不同硅铝比的层间12元环的扩孔型IEZ-MCM-22分子筛,而且可有效降低分子筛的脱铝,尽可能地保留分子筛的酸性,在裂解反应中表现为更高的1,3,5-三异丙苯的转化率。更多还原

【Abstract】 Ethylbenzene is an important petrochemical organic chemicals, and its down-stream products such as engineering plastics, synthetic resin, synthetic rubber are important raw materials which have close relationship with construction industry, auto industry, electron industry and daily necessities. At present, the manufacture of ethylbenzene mainly includes the gas-phase process and liquid-phase process via benzene alkylation with ethylene. The liquid-phase process will gradually replace the gas-phase process in virtue of its advantages, such as simple process, superior product quality, low energy consumption and material consumption.The benzene alkylation with ethylene under liquid-phase was chosen as the objective reaction in this dissertation. The synthesis of postsynthetic modification of crystal structure, physical and chemical characterization and catalytic performance were carried out. The work on the investigation for catalytic materials was divided into the following four parts.The first part includes synthesis, characterization and catalytic properties of MCM-22zeolite. A detailed investigation on synthesis conditions, such as silica to alumina molar ratio, alkali concentration, template amount and type, crystallization-supporting agent, crystallization temperature and time was carried out. A series of MCM-22zeolite with different silica to alumina molar ratio were synthesized which could expand the range of alumina content in bulk. In addition, repetitiveness in100mL stainless autoclaves and amplification experiments in2L hydrothermal synthesis reactor were carried out. What is more important, the highly toxic hexamethyleneimine whose production and usage are strictly controlled was successfully replaced by piperidine serving as a templating agent in the synthesis of MCM-22. The MCM-22zeolite synthesized using piperdine with low toxicity owns same crystallinity, smaller particle size and larger specific surface area in comparision with that synthesized using hexamethyleneimine, which exhibited good catalytic performance in benzene alkylation with ethylene and showed a potential industrial application. The second part includes synthesis, characterization, and catalytic properties of MCM-56zeolite. The MCM-22precursors with different silica to alumina molar ratio were post-treated under mild acid to partially remove template between the MWW layers, then the MCM-56were obtained by further filtration, washing and drying steps. Compared with3D MCM-22zeolite under directly calcined MCM-22precursors, the MCM-56had a larger external surface and a wide range of silica to alumina molar ratio. The MCM-56with higher conversion, selectivity and stability was then superior to3D MCM-22in the liquid-phase benzene alkylation with ethylene.The third part includes synthesis, characterization, and catalytic properties of mesoporous MCM-22zeolite. Mesoporous MCM-22zeolite with Si/Al ratios of15-45have been hydrothermally synthesized with the presence of carbon black particles as hard template. In comparison to conventional MCM-22, the mesoporous MCM-22zeolite possesses intercrystal mesopores that are beneficial to increase the accessibility of catalytic sites to bulky molecules by decreasing mass transfer limitations. The mesoporous MCM-22exhibited higher ethylene conversion, higher selectivity to ethylated benzenes and better stability than conventional MCM-22, potentially showing an excellent catalytic performance and serving as a promising solid-acid catalyst in petrochemical industry.The fourth part includes synthesis, characterization, and catalytic properties of interlayer expanded MCM-22zeolite (IEZ-MCM-22). The MCM-22precursors were alkoxysilylated with diethoxydimethylsilane under controlled conditions to modify the interlayer structure of MCM-22. The addition of ethanol in the treatment could avoid the dealumination of MCM-22precursors, then the12member ring IEZ-MCM-22was obtained with the retain of alumination as much as possible. The obtained IEZ-MCM-22showed high activity in the cracking of1,35-triisopropylbenene.更多还原