Synthesis,Characterization And Catalytic Activit Of Substituted Mesoporous Molecular Sieves

Using V-MCM-4 1 as an example, this thesis emphasized on the preparation of substituted mesoporous molecular sieve and, by the techniques of X-Ray diffraction(XRD), IR spectra and thermogravimetric(TGA), the effects of incorporation on the structure and configuration. Besides these, we also use the oxidation of styrene to investigate the relativity between its preparation and catalytic activities. Through the routine of sol-gel, the vanadium-substituted mesoporous molecular sieve, V-MCM-4 1, which has high degree of crystallization, has been prepared at the room-temperature. Respectively, the surfactant, the source of silicate, and the source of vanadium is cetyltrimethylammonium bromide(CTMA), tetraethyl orthosilicate(TEOS), and vanadyl sulfate. The composition of the gel is Si:SurfV:H20=1:O.2:x:100, x=25--200. The pH of the gel, the crystallizing-temperature, and the crystallizing-time have certain effects on the structure of mesoporous molecular sieve. It has shown that the incorporation of vanadium can significantly increase the value of ao and the degree of crystallization of V-MCM-4 1 decresed with the increasing of V content in the wall. In this study, we still obtained the good-crystallized mesoporous molecular sieve when the Si/V has achieved 25. As a type of catalyst, V-MCM-4 1 can show high catalytic activities in the oxidation of styrene. Using H202 as oxidant and acetonitrile as solvent, the conversion of styrene can be as high as 79% at certain conditions. The main product of this reaction is benzaldehyde, which has selectivity of 77%. The results of this study indicated that the factors of preparation, such as the pH of gel, the source of alkali, the crystallizing-time, the crystallizing-temperature, the calcining temperature, and the sequence of addition of ingredients have some effects on the activities of V-MCM-4 1. The others substituted MCM-41 also have some high catalytic activities in this reaction. The sequence of the activities is Cr- MCM-4 I >Ti-MCM-4 1 >Mo- MCM-4 1 >Mn- MCM-4 1.