Synthesis of mesoporous MCM-48 using fumed silica and mixed surfactants

Abstract

With mixed surfactants of cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) as template agents and fumed silica as a silica source, mesoporous molecular sieves MCM-48 were hydrothermally synthesized under various conditions. Results indicate that high-quality MCM-48 was successfully prepared by substituting fumed silica for the traditional silica source of tetraethylorthosilicate. The effects of synthesis parameters such as quantity and composition of template agent(s), crystallization temperature, crystallization time, and the solution temperature to which fumed silica being added on the structure, morphology, relative degree of crystallization, and thermal stability of the resultant material were quantitatively investigated based on the analyses of XRD, N 2 sorption/desorption, and SEM. The optimized conditions for a high-quality MCM-48 were crystallization time of 60–84 h, crystallization temperature of 100 °C, and n(TX-100)/ n(CTAB) of 0.2. Moreover, it was found, for the first time, that the solution temperature to which fumed silica being added plays an important role for the synthesis of MCM-48, and n(TX-100)/ n(CTAB) ratio is crucial for the formation of pure MCM-48 structure.