Unified Formation Mechanism of Disordered Mesoporous Silica, Structured by Means of Nontemplating Organic Additives
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- 作者：Jia Wang ; Johan C. Groen ; Marc-Olivier Coppens
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：December 11, 2008
- 年：2008
- 卷：112
- 期：49
- 页码：19336-19345
- 全文大小：479K
- 年卷期：v.112,no.49(December 11, 2008)
- ISSN：1932-7455
文摘
TUD-C and TUD-M are two novel mesoporous zeolite composites. Tetrapropyl ammonium hydroxide (TPAOH) plays the well-known templating role in the formation of the zeolite micropores. The role of TPAOH in the formation of the disordered mesopores of a controlled size can be described as “nontemplating structure-directing”. For the first time, this type of structure-directing is systematically investigated and compared with templating. Supra-molecular templates are not involved. The nontemplating structure-directing mechanism in the TEOS-TPAOH-H2O system consists of three steps: (1) formation of silica nanoparticles in the presence of TPAOH during homogenization of the solution; (2) development of a gel with extended silica framework during the mild evaporation of ethanol and water; and (3) drying of the gel. TPAOH plays an important role in each of these steps. The key parameters for a successful synthesis are pH, solution composition, and temperature. It is shown that this type of structure-directing is a rather general phenomenon, since many organic molecules can play a role similar to TPAOH. However, the required synthesis conditions vary between different molecules. The mechanism is investigated by means of ATR-IR, TEM, N2 sorption, and NMR experiments.