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Industrial synthesis of MCM-41 mesoporous molecular sieves

Author: WeiDongWei
Tutor: GuoYiQun
School: Zhengzhou University
Course: Industrial Catalysis
Keywords: mesoporous molecular sieve characterization synthesis Al W electrolyte
CLC: O643.3
Type: Master's thesis
Year: 2004
Downloads: 157
Quote: 0
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Special attention Have been given to the mesoporous silicate molecular" sieves because of their potential for use in areas of catalysis, immobilizationof ative enzyme,prepration of functional materials,soption and separations of bulky molecules.The most commonly studied mesoporous phase is MCM-41,which contains hexaonally ordered mesopores with diameter form 1.5 to over 10nm.The mesoporous molecular sieve has been synthesized under the mild conditions,in which crystallizing temprature is 100C for l~5d and the mol-ratio of the slurry mixture is SiO2:Na2O:CTAB:H2SO4:H2O=7:2.08:(0.7~3.5):(l~1.36): (350~546),using industrial water glass and C16H33(CH3)3NBr(CTAB) as original materials, H2SO4 as an adjustable agent of pH value of the slurry. The characterization of its pore structure is carried out by XRD and pore distributing measurment.The possibility to introduce Al element into the mesoporous silicate molecular sieves enables the application of this materials in acid-catalyzed reaction,by increasing the acidity of them ,such as esterification of of bulky molecular, alkylation of aromatic hydrocarbon..Therefore,the synthesis of mesoporous molecular sieve Al-MCM-41 using industrial material has an important theoretical and practical significance.The synthesis of mesoporous molecular sieves Al-MCM-41 had been accomplished successfully in a hydrothermal system, under the alkaline condition .The technique of X-Ray Diffraction was used to identify the effects of the systhesis condition ( crystralizing temperature, crystralizing time ,Si/Al) on the crystral structure of MCM-41;IR, Pyridine-TPD&the chemical analytical method of Al content were used to characterize its pore stucture and properties. The results showed that the more suitable crystrallization of mesoporous molecular sievesMCM-41 can be obtained at the condition of crystralizing temperature 120C and crystralizing time 24 hours . Al element has incorporated into the framework of mesoporous molecular sieve MCM-41.It is reported that mesoporous molecular sieve MCM-41 containing heteroatoms in its skeleton such as Al, V, Fe,Zr,Cu,Ti,Cr,Mn,Si,B,Sn has been synthesed,but mesoporous molecular sieve W-MCM-41 has not been synthesed in a hydrothermal system by far. A serial of differentwolframium content mesoporous molecular sieves W-MCM-41 have been synthesed using industrial materials,in a hydrothermal system .The characterization of its structure is earried out by XRD,IR. The content of wolramium is determined by UV Spectrophotometry.The thermal and hydrothermal stabilities of common MCM-41 molecular sieve is a more critical factor in determining its potential applications.This is because that water is the most widly used medium for chemical modifies and modification conditions ,catalysis reactions, soption and separations.Thus,the synthesis of mesoporous materials with high thermal and hydrothermal stability is a topic of great interet. One method of increasing its high thermal and hydrothermal stability is increase the pore wall thickness of MCM-41.A serial of mesoporous molecular sieves MCM-41 was synthesed with the addition of salts such as NH4Cl,NaCl, NaNO3,Na2SO4 and were characterized using XRD and pore distributing measurment techniques.The influnce of kinds of concentration of salts on pore wall thickness and structure was examined. It was found that the addition of salts increased the pore wall thickness of MCM-41 at some extent,the influnce on pore diameter was small.

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