Treballs Finals de Grau d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Curs: 2014-2015, Tutora: Esther Santamaría Hernández
In fields such as medicine, diagnostic applications... or operations such as catalysis, chromatographs, the adsorption of gases and liquids... materials with large values of specific surfaces are required because surface phenomena are involved in operations. Recently, mesoporous materials have been studied with the aim of having the highest possible surface area.
Mesporous materials have pore diameter between 20 and 50 Å, with high values of specific surfaces. The order of the pores in space influences the value of the specific surface obtained. When porous are ordered in the space the surface area is greater than when the porous are disordered. In order to maximize the value of the specific surface, it is desirable to obtain ordered mesoporous materials.
It is possible to obtain different properties of silica materials with small variations in the processes of its synthesis in these materials. This is why the synthesis of mesoporous materials is studied with the aim of have them ordered such as getting (or not) mesoporous materials.
Nowadays, the TEOS or TMOS silica sources are used in obtaining mesostructured silicas. These sources of silica are intended to be replaced by substitutes and the use of sodium silicate as an alternative source of silica may have greater advantages on an industrial scale because, among other reasons, it is cheaper than TEOS or TMOS.
It also aims to obtain an alternative process of silica synthesis mesoporous materials because nowadays acid catalysts are used as a proton source involving a washing process which can be avoided by using ion exchange resins as proton source.
Therefore, the use of sodium silicate as well as the use of ion exchange resins in columns provides greater benefits from the industrial punt of view.
This is why this project is based chiefly on the synthesis of mesoporous material using a column with ion exchange resin. The variables studied are the relations of surfactant: water and the ratio of sodium silicate: water. They are chosen from previous studies in the synthesis of mesoporous materials. The variable to maximize is the surface area of the materials obtained.
Ion exchange column should be studied because working ranges must be known in order to obtain desired mesoporous materials. The first step is to obtained ion exchange resin column rupture curves.
Microscopy techniques such as TEM and SEM and other techniques as BET and SAXS are used in order to characterize the synthesized mesoporous silica materials from the ion exchange column.
The results obtained are subjected to statistical analysis using the "Statgraphics Plus 4.1" program having Pareto charts and estimated response surfaces.
The last step is to study the influence of the ratio of surfactant:water and sodium silicate:water in the studied range. It has been found that the ratio of sodium silicate:water a maximum value of the obtained specific surface is obtained corresponding with the maximum management of these materials. In the range studied, the ratio of surfactant:water has not been a significant variable in the value of specific surface area of the materials obtained.