Open System Step Synthesis Of Mesoporous Molecular Sieve

Special attention have been given to the mesoporous silicate molecular sieves because of their potential use in areas of catalysis, adsorption and separation and preparation of functional materials. Compared with the microporous molecular sieves, the mesoporous molecular sieves have the infungible function in areas of adsorption and separation of bulky molecules, immobility of active enzyme,loading high efficient catalyst and catalysis oxidation and hydrogenation of bulky molecules because its aperture is more than 2nm,and can be adjusted in the rangeof 2nm to 10nm according to purpose.In many mesoporous molecular sieves, hexagonally symmetrical MCM-41 is one of the materials studied most commonly for its most applications.At present, the means to synthesize mesoporous molecular sieves is mostly hydrothermal deposited crystallization which must use pressure vessel in industrialized application. Reports have been not seen that mesoporous molecular sieves are synthesized straightly in open-vessel.A convenient and economic method for direct preparition of MCM-41 was studied in an open vessel by using waterglass as the silicon source,(CH₃)₃C₁₆H₃₃NBr(CTMAB) as template,H₂SO₄ as the adjustable agent of pH value of slurry .XRD and nitrogen adsorption show that the product has a highly ordered stucture and the hexagonal arrangements of uniformly size pores distribution. An influence of n(Si)/n(CTMAB),pH value of slurry, crystallizing temprature and time was discussed. According to the experiment results ,the optimized conditions for synthesis of mesoporous molecular sieves in an open system are : n(Si)/n(CTMAB)=5⁷, pH=10.5¹0.7, T=373K, t=12²4h.Because the catalysis of the mesoporous silicate molecular sieve MCM-41 isweak for its weak acidity , the possibility to introduce the active substance Al element into the mesoporous molecular sieve MCM-41 enables the application of this material in acid-catalyzed reaction by increasing their acidity, such as esterification of bulky molecular and alkylation of aromatic hydrocarbon. Therefore, the synthesis of the mesoporous molecular sieve Al-MCM-41 by using industrial materials has an important theoretical and practical significance.The mesoporous molecular sieve was synthesized by using silica from water glass of industry, aluminum from Al2(SO4)3 , H2SO4 for adjusting the pH of the slurry and CTMAB as template in an Open-vessel. The mole ratio of the slurry mixture was: n(SiO2) : n(Na2O) I n(CTMAB) I /i(A12(SO4)3) : n(H2O)=7 : 2.08 : 1.4 I (0.0875⁰.7) : 530. The product was producted by making the mixed slurry crystallize for 24h at the temperature of 373K. The characterization of its crystal order and framework aluminum was carried out by means of XRD, IR and chemistry analysis. The effect of /i(Si)//i(Al) and pH of the slurry on the crystal parameter of the mesoporous molecular sieve was discussed.A new catalyst can be synthesized which has particular catalysis function by introducing idiocratic metal atom into the framework of mesoporous molecular sieve MCM-41. Adulterated titanium ion has the function of oxidation and deoxidation catalysis for its alterable bond. So mesoporous materials containing Ti are very good liquid-phase selective catalyst.Ti-MCM-41 which aperture is bigger than TS-1 can catalyze the oxidation reaction of many bulky molecule organic matter. The samples Ti-MCM-41 of different Ti content have been synthesized in an open vessel by changing the pH of slurry ,and characterized by XRD,FT-IR,UV-Vis and UV-Raman.