Characterization of MCM-48 Silicas with Tailored Pore Sizes Synthesized via a Highly Efficient Procedure

Abstract

MCM-48 silicas have been prepared via a high-yield synthesis procedure using mixtures of cationic alkyltrimethylammonium surfactants (alkyl chain length from 12 to 20 carbon atoms) and neutral cosurfactants. This is the first reported successful synthesis of MCM-48 using eicosyltrimethylammonium surfactant. The samples, especially those synthesized using cationic surfactants with cetyl, octyl, and eicosyl chains, were found to exhibit a high degree of structural ordering, which manifested itself in very well-resolved X-ray diffraction (XRD) patterns, and remarkably narrow capillary condensation steps after the template removal. The latter could be achieved not only via calcination, but also via ethanol/HCl washing. The unit-cell size and pore size of MCM-48 were found to be determined by the alkyl chain length of the cationic surfactant used. The calcined MCM-48 samples had BET specific surface areas of about 1100 m2 g-1, large primary mesopore volumes (up to 1.15 cm3 g-1), XRD d211 interplanar spacings f...