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Mesoporous materials mesoscopic structure and morphology control

Author: HuJunZuo
Tutor: TangYi
School: Fudan University
Course: Physical and chemical
Keywords: Mesoporous materials HMS Morphology Control Layered structure Worm-like holes Two-hole structure Distribution of mesoscopic structures Particle size distribution Nanozeolites Multi-level channel Polymer -induced colloid aggregation method Zeolite microspheres Zeolite hollow spheres Alkylation Reaction
CLC: TB383.4
Type: Master's thesis
Year: 2009
Downloads: 157
Quote: 0
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Abstract


Although mesoporous materials research history of only ten years, its unique structure and properties has attracted scientists from many fields. Since mesoporous materials have good hydrothermal stability, high surface area, high porosity, pore size is relatively large and adjustable in a certain range, making it in catalytic macromolecules, biological processes, selective adsorption, functional materials, etc. many have broad application prospects. Studies have shown that in addition to pore morphology and size, the macro-structure of mesoporous materials also have an important impact on its application. Mesoporous materials with different morphologies have different surface area, pore length are not the same, and thus its mass transfer resistance are very different; same time, the size and morphology of the material also determines its ease of operation and the separation into degrees . Therefore, the morphology control of mesoporous materials mesoporous materials has long been a hot area of ??research. This paper will present the two preparation methods of mesoporous materials, respectively mesoporous material morphology and pore control. For classic in surfactant micelles as template mesoporous materials prepared by sol-gel method, we select a relatively few studies of the HMS (hexagonal mesoporous silica) for the study. HMS while its three-dimensional pore Unicom straight channel relative to other mesoporous material is more conducive to pore diffusion of guest molecules to the adsorption and catalysis have broad application. However, the same disorder because of this worm-like pore space, making the HMS material taken isotropic growth, and thus its morphology becomes difficult to control. In the second chapter, we found a way to control both the morphology and mesoscopic structures HMS easy way: through modulation system alcohol-water ratio and surfactant and co-solvent type, you can get lotus-shaped, staggered flakes, potato-like vesicles, hollow vesicle, rip the ball and a series showing change in morphology of the law HMS material. Through its in-depth characterization of the above we find that contain lamellar morphology and worm-like mesoporous two different, and different macroscopic morphologies of mesoporous spatial distribution is not the same. In-depth study on the system we propose a mechanism to explain this peculiar morphology variation and two-hole structure. The start of the reaction layer / vesicular micelles determines the macroscopic morphology of the final product. Holes must be formed during the reaction and the layered structure to a worm-like structure of the conversion result, the underlying reason is due to lower concentration of surfactant, concentration of alcohol rise and increase the degree of polymerization of silicate caused. Lamellar phase in the horizontal direction in the evolution of mesoscopic structures on the basis of the initial skeleton affect the macroscopic morphology. In addition, we also used the particle nucleation and growth rate differences reveal different alcohol concentrations silica microspheres / change the size distribution of nanoparticles. Another method of manufacturing the novel mesoporous molecular sieve is based microporous Microporous - multi-pore mesoporous zeolite material. Such materials may be contained in the mesoporous easier access to the guest molecules inside the material for adsorption and catalysis, while its cell wall composition of the crystalline zeolite containing a large number of pores and is rich in acidic sites. Such that it has a more excellent catalytic performance. In many Microporous - mesoporous pore zeolite material multistage approach, the polymer-induced colloid aggregation method (polymerization-induced colloid aggregation, PICA) as easy to control, synthetic effect been more and more attention. Chapter III by using nano-zeolite unwashed raw materials were prepared using PICA microporous - multi-level pore mesoporous zeolite microspheres, which greatly simplified the process and to be used in low PICA France nanodrugs aluminosilicate zeolite assembly . We also examined the different urea-formaldehyde polymerization reaction sites difference in speed of the product morphology, and through the control system acidity and urea formaldehyde content was successfully prepared microporous - multi-level pore zeolite mesoporous hollow spheres. Finally, we have to butene alkylation reaction as a probe reaction, compared to the multi-level ball ordered pore zeolite β and general differences in the catalytic activity of β zeolite verified microporous - multistage ordered mesoporous structure advantage.

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