Synthesis of Large Pore Disordered MSU-Type Mesoporous Silicas through the Assembly of C₁₆(EO)₁₀ Surfactant and TMOS Silica Source: Effect of the Hydrothermal Treatment and Thermal Stability of Materials

Abstract

Decaoxyethylene cetyl ether [C 16 (EO) 10 ] has been employed as templating agent for large pore disordered MSU-type mesoporous silicas synthesis. The effect of the hydrothermal treatment (heating time and temperature) on the textural properties, in particular, pore diameter of materials has been investigated. The obtained materials have been characterized by different techniques such as X-ray diffraction, scanning and transmission electron microscopy and nitrogen adsorption-desorption analysis. The thermal stability of the compounds is also evaluated. Our results show that the pore diameter depends strongly on the heating time and temperature. This is the result of a competition between the stretching of the surfactant chains, which can lead to the breakdown of the walls separating adjacent pores, and the reorganization of micelles with heating time and temperature. At higher temperature or for longer durations, a more extended surfactant molecular conformation can be obtained, which leads to materials with larger pore sizes. A reorganization of the micellar solution during the hydrothermal treatment in autoclave can also simultaneously occur to give materials with smaller pore diameter. It is found that compounds prepared with the nonionic surfactant exhibit an enhanced thermal stability compared to those synthesized with cetyltrimethylammonium bromide (CTMABr) as templating agent. This higher stability is related to the synthesis pathway and the structure of materials.

Gold nanoparticles supported on ceria-modified mesoporous titania as highly active catalysts for low-temperature water-gas shift reaction

“…The gold loading and particle size are given in Table 1. The TEM micrographs of the mesoporous titania support and the corresponding gold catalysts [6] have a disordered structure with a large number of wormhole-like channels lacking a long range packing order as previously reported [18][19][20]. Ceria-modified mesoporous titania support has a disordered structure with an aggregation of the nanoparticles.…”

Preparation of mesoporous titania solid superacid and its catalytic property

“…Fig. 1(a), a single narrow diffraction peak can be observed in the 2θ range from 3 • to 5 • , it is well known that diffraction peak at low angle XRD pattern characterizes a mesostructured material [21,22], showing that TiO 2 with mesoporous structure was successfully synthesized. On the other hand, from Fig.…”

Cloud point curve of nonionic surfactant related to the structures of mesoporous materials

“…In the same year, Attard et al [9] with octaethylene glycol monododecyl ether (C 12 EO 8 ) and octaethylene glycol monohexadecyl ether (C 16 EO 8 ) as template also obtained mesoporous silica. Then using these kinds of surfactants a series of compounds have been prepared by different groups [10][11][12][13][14][15][16][17]. However, the major drawback of pure silica mesoporous materials is their low stability [18].…”