Efficient synthesis of high-quality MCM-48 silicas through mixed surfactants and pH adjustment route

Abstract

Abstract Using the mixture of cetyltrimethylammonium bromide (CTAB) and p-Octyl polyethylene glycol phenyl ether (OP-10) as the template, MCM-48 silicas were facilely synthesized with low molar ratio of CTAB to silica (0.139:1) and low concentration of mixed surfactants (ca.5%) and within a wide range of OP-10/CTAB ratio (0.08∼0.25). For direct comparison, MCM-48 silica was also prepared with only CTAB as the structure director. These materials were thoroughly characterized by XRD, N 2 sorption analysis, HRTEM, TG-DSC and 29 Si MAS NMR. Characterization results obtained by these techniques indicated that the mixed cationic-nonionic surfactants' route allowed better framework condensation compared to the only CTAB templating method. It was also found that a gel, which had been crystallized for a certain time, after being subjected to pH adjustment gave an efficient synthesis with a high yield amounting to about 95% on the silica recovery.