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Efficient, low cost and large scale hydrothermal synthesis of mesoporous silica material stability improvements

Author: SongMingJuan
Tutor: ZhaoDongYuan；NiuGuoXing
School: Fudan University
Course: Chemical Engineering
Keywords: mesoporous materials Large-scale Synthesis Hydrothermal Stability Oil FCC Hydrogenation
CLC: O643.36
Type: Master's thesis
Year: 2011
Downloads: 219
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Abstract


In 1992, Mobile Company successful synthesized ordered mesoporous silica (alumino) molecular sieves M41S series using cationic surfactant as a template and inorganic silicon source under alkaline conditions. For their large surface area, highly order structure, adjustable pore size and variable composition, they extended zeolite from microporous to mesoporous field and attracted the close attention and great interest of many scientists. For the past few years, many new concepts were continually introduced and the innovation structure and composition frequently appeared in the mesoporous materials field. Meanwhile, the application fields had been explored and widened. Due to the enthusiasm of scientists put into this area, mesoporous materials have become one of international hot spots among material, chemical, polymer, biology, pharmaceutical and many other subjects.This thesis includes two parts:the first part is high efficiency and low cost and large-scale synthesize SBA-15 mesoporous materials. The second part is study on the hydrothermal stability of mesostructured silica SBA-15 materials.The second chapter introduced the efficient, low-cost large-scale synthesis of SBA-15 mesoporous molecular sieve through one new technology. Traditional routes have many disadvantages, just like long production cycle, low single reactor production capacity, and requires a lot of expensive surfactant P123 as template. What’s more, during the synthesize process, the emission of waste acid water and surfactant will cause a great impact on the environment and other issues. In this chapter, the first time put forward two low-cost and efficient synthesis new processes of SBA-15 mesoporous materials. The author employed a new route in order to improve the production efficiency. Simply speaking, it’s hydrolysis several times and crystallization one time, which significantly shortened the production cycle. Besides, using the industrial grade silicon source instead of reagent grade silicon source as raw materials can greatly reduce the synthesis costs. Mesoporous materials, obtained by the new process, maintained high surface area, large pore volume, high degree of ordering, uniform and adjustable pore size as synthesized by traditional routes.The third chapter is a further improvement based on chapterⅡ. In this part we used a mother-solution recycled method to large-scale synthesized SBA-15 mesoporous materials which can make the produce costs obviously reduced. Just like chapterⅡ, production same maintain the unique properties as that synthesized by tradition route. Systematic study on how to improve the hydrothermal stability of SBA-15 mesostructures materials were introduced in chapterⅣ. On one hand, owing to the hydrolysis of silanol on the pore wall, the thickness of the wall and the surface hydrophobicity caused the hydrothermal stability of SBA-15 can’t meet the need of industrial production. On the other hand, size effect and species interactions caused by the introductions of other species likewise reduced the stability. In this chapter, the author firstly used (NH4)SiF6 solution treated SBA-15 powder that can greatly improve their hydrothermal stability. Through these post-processing techniques, SBA-15 mesoporous molecular sieve can keep the mesostructure more than 14 days in pure water at 100℃. Dramatically, the structure of the SBA-15 materials maintained more than 12 hours in pure steam at 800℃which is similar to industrial condition. All of the results showed us that the hydrothermal stability of the treated productions can meet the requirements of the oil FCC hydrogenation process.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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