Synthesis, Characterizations And Catalytic Performance Of Zeolite Materials For Liquid-Phase Benzene Alkylation With Ethylene

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.