| Catalyst materials of ZSM-5 zeolites possess high molar ratio of silica to alumina and uniform three-dimensional pore size that are responsible for great potential applications in the petrochemical and fine-chemical catalysis. However, the sole presence of micropores will limit the diffusion of organic macromolecules in it. Hierarchical ZSM-5 zeolites have micropores and mesopores, and the zeolite crystals of them have been scaled down from the micrometer to the nanometer scale, which leads to the presence of high surface area and well-defined pore structure. These features result in better adsorption and catalytic properties. Therefore the development in this field is of great interest in recent years. In view of this, hierarchical ZSM-5 zeolites prepared by using the second template as additives are chosen for this thesis, and the performances of the catalysts have been investigated in the alkylation of benzene and ethylene. The results are summarized as follows.Firstly, ZSM-5 zeolites were synthesized by using organic template via hydrothermal crystallization. Factors affecting the synthesis of ZSM-5 zeolites were studied, including crystallization time and temperature, aging time and temperature as well as the types of organic templates. And the average diameter of ZSM-5 zeolite microspheres was about 1-5μm. So the better crystallization condition was: age at 60?C for 3h, and then crystallize at 175?C for 24h, while the as-prepared sample had higher crystallinity up to 95.1% and uniform particle size.In Chapter 3, hierarchical ZSM-5 zeolites were prepared by using polyaniline (PANI) as additive on the basis of the conventional synthesis methods, and the effects of different crystallization times were investigated. The samples crystallized for 3h showed supermicropores with the pore size of 1.8nm and mesopores with the pore size of 2.6nm, and presented rectangle shape with nanocrystals of 10-20nm. With the increase of crystallization time, the process of dissolution-recrystallization occurred on the surface of zeolite nanoparticles, and the bigger ones grew up gradually and the smaller ones dissolved, which led to the presence of the supermicropores (1.8nm) and mesopores (2.6nm and 4.0nm).In Chapter 4, hierarchical nanocrystalline ZSM-5 zeolites were fabricated via pre-crystallization method different from the conventional hydrothermal method, using organosilanes as additives. The results showed that, the as-prepared samples exhibited dispersed ellipsoidal shape with the size of 400-800nm, which included lots of nanocrystals with the size of 10-20nm. Moreover, these samples had hierarchical porous structures, the supermicropores (1.7nm) and mesopores (2.1nm and 3.5nm). However, the ZSM-5 zeolites prepared without using organosilanes as additives presented irregular shape with a broad particle size distribution from 30nm to 600nm. The samples synthesized without pre-crystallization also had similar morphology and crystallinity.In Chapter 5, the performances of all the as-synthesized samples had been investigated in the alkylation of benzene and ethylene. The ZSM-5 zeolite obtained under the favorable crystallization conditions had showed better catalytic activity: the single pass conversion of ethylene (X%) and the selectivity of ethylbenzene (SEB%) were 58.53% and 82.51%, respectively. The samples modified by PANI or organosilanes led to the increase of X% and the slightly decrease of SEB%. For example, ZSM-5A prepared by using 3-aminopropyltrimethoxysilane (APTMS) as organic additive, because of its hierarchical structures, exhibited better catalytic activity: X% and SEB% were 69.57% and 80.96%, respectively.
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