Reproducible synthesis of high quality MCM-48 by extraction and recuperation of the gemini surfactant

High quality MCM-48 can be repeatedly and reproducibly prepared, as a novel method for the extraction, recuperation and re-use of the gemini surfactan t has been optimized. Gemini surfactants have the general formula [CnH2n+1N +(CH3)(2)(CH2)(s)N+(CH3)(2)CmH2m+1] . 2Br, and have been shown to produce M CM-48 in a very convenient way. In each cycle, more than 95 wt% of the surf actant is extracted under mild conditions. The extracted surfactant does no t degenerate during this treatment and can be re-used many times. The MCM-4 8 produced by this soft extraction, has a narrower mesoporous pore size dis tribution and a larger pore radius than materials prepared by normal temper ature-programmed calcination. The surface of the extracted MCM-48 still con tains sufficient silanol groups, although some silanol groups have been rep laced by methoxy groups. The number of silanols on the surface of the MCM-4 8 has been titrated by surface reaction with hexamethyldisilazane, followed by quantification of the liberated NH3.