Pavlenko A. Synthesis and modification of mesoporous silicas by supramolecular self-assembly in organomineral systems

The dissertation is devoted to elaboration of methods of template synthesis of highly ordered MCM-41 type materials and mesoporous titanium-containing silicas Ti-MCM-41 by incorporation titanium into silica framework by isomorphous substitution of silicon atoms. The effect of precursor and surfactant nature on the geometrical characteristics of mesoporous materials has been investigated. The optimum synthesis conditions of highly ordered MCM-41 type silicas and bimodal mesoporous matrices have been determined. It was developed the reproducible technique for synthesis in mild conditions of products exhibiting of typical highly ordered MCM-41 materials structure with exclusively narrow pore size distribution and high specific surface area. In acid conditions the mesoporous titanium-containing silicas with TiO2 contents from 1 up to 70 mol. % were synthesized. By the developed technique at the use cationic surfactants with different chain lengths Ti-substituted MCM-41 materials with TiO2 contents from 1 up to 15 mol % were obtained. It was detected that Ti-MCM-41 silicate with regular nanostructure and 15 mol % TiO2 contents reveals the bimodal pore distribution involved mesopores having highly ordered hexagonal MCM-41 structure as well as secondary macropores forming textural porosity. It was shown that at equal titanium contents (1 mol. %) a maximum catalytic activity in the reaction of benzene hydroxylation displays the Ti-MCM-41 material obtained with C16H33(CH3)3NBr used as a template. Pyrolytic carbon deposition at thermal decomposition of methylene chloride vapor was studied on surface of MCM-41 silica. Formation of nanotubes, nanofibres and amorphous carbon particles was detected depending on pyrolysis conditions.