The Synthesis And Application Of Mesoporous Silica Meterial By Anionic Amino Acid Surfactant

The synthesis and application of spherical particles has been of particular importance since Stober et al. first obtained monodispersed silica spheres in strong base utilizing TEOS (TEOS) in 1968. The investigations of hollow materials have been provided fundamental conditions owing to the hollow sphere materials and reliable synthesis methods. In the field of preparing hollow spheres, it is necessary to control the size and morphology and simplify the method, which plays important role in applying these materials to practice.Mesoporous silica nanotubes are feasible in the areas of microstudy, nanodevices, Drug loading,gas storage and catalysis for several reasons. On one hand, as mesoporous materials, they possess large specific surface areas and pore volumes, adjustable pore structures, tunable pore sizes, modifiable surface properties and controllable morphology. On the other hand, mesoporous silica nanotubes have three unique surfaces:external surfaces, inside diameter, and mesoporous structure of pipe wall.Morphology controllable mesoporous silica nanotubes was synthesized and the tuning of the morphology and structures was thoroughly investigated employing anionic surfactants as the templates in this paper. First, mesoporous hollow spheres and mesoporous silica nanotubes were synthesized utilizing Chiral anionic surfactant N-myristoyl-L-alanine (C14-L-Ala) as the structure-directing agent,N-trimethoxysilylpropyl-N,N,N-trimethylamonium(TMAPS) as co-structure-directing agent, tetraethoxylsilane (TEOS)as the Inorganic precursors. The formation mechanism of mesoporous silica hollow spheres was clarified by examining the influence of different reaction conditions on the morphology and structures, and the hollow spheres were thereby applied to the hydrodesulfurization of gasoline.Second, it has been found that the kinetic controlling step influences the morphology and structures of mesoporous hollow spheres significantly. Besides, the ionization degree of the solution is essential in the formation of mesoporous hollow spheres. And the ionization degree (molar ratio of charges and surfactants) of the surfactants are easily affected in the presence of acids. Therefore, pH of the solution is the key point in the formation of mesoporous hollow spheres. As CSDA, TMAPS provides positive charges for anionic surfactants, and the accumulating of CSDA also determines the final mesoporous structures. Moreover, evaluating the performance of gasoline hydrodesulfurization by mesoporous hollow spheres, the catalyst is able to desulfurate the gasoline and exhibits satisfactory selectivity. In other words, olefin is not saturated when the sulfides of the full range FCC gasoline are removed utilizing the catalyst. And the desulfurization rate of the catalyst is 40%.Furthermore, organic nano-templates were formed by the self-assembly of the partial neutralized surfactants. After adding structure directing agents and silica sources, reassembly occurred and mesoporous silica nanotubes were obtained. Amorphous silicon dioxides on the outer surface were removed by hydrothermal treatment, and the passable rate of the mesoporous tubes was increased as a result.