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Abstract:
Using the newly developed tubular reactor concept that allows the analysis of fast reactions, such as the formation of a solid from solution, with slow analytical techniques, one could demonstrate that MCM-41 type materials can form very rapidly under certain conditions. Siliceous MCM-41 prepared from TEOS starts to develop in less than a minute; the structure formation is complete after about 3 min. From then on only condensation processes in the silica framework occur. The rate limiting step in this reaction might in fact not be the assembly but rather the hydrolysis of the alkoxide. For the mesostructured titania material synthesized with titanium oxo sulfate as the precursor, the formation of the mesostructure is even more rapid and faster than the shortest time detectable with the present instrumentation. A diffraction peak at 2˚C (2 theta) is clearly discernible even after less than a second. Also in this case, though, further condensation takes place in the inorganic framework subsequently.
