Synthesis of microporous molecular sieves by surfactant decomposition

Microporous molecular sieves can be synthesized under the high temperatures of 165-180 degreesC and high pH of 10-12.5, using surfactant cetyltrimethylammonium bromide (CTAB) as a template. It was found that various factors, such as temperature, alkalinity, Si:Al ratio and the presence of a small amount of organic alkylammonium species (TMA(+), TPA(+)) can affect the nature of the microporous materials obtained. In the wide range of Si:Al ratios, we can obtain such zeolites as sodalite, analcime, omega, ZSM-35, mordenite, ZSM-5 and silicalite. The experimental results suggest that the decomposition products of CTAB act as templates instead of surfactant CTAB itself. The synthesis condition of high pH (> 10) and high temperatures (greater than or equal to 165 degreesC) can ensure the decomposition of CTAB, which is quite essential for the formation of microporous molecular sieves.