Microwave-assisted single-surfactant templating synthesis of mesoporous zeolites

摘要

A single-surfactant templating method was explored for the synthesis of mesoporous zeolites under microwave irradiation, which allowed programming of temperature and time over a wide range of conditions and resulted in a significant reduction of the synthesis time. Most importantly, this approach eliminated the use of an organic molecular template for creating microporous zeolitic structure. Two preparation methods were examined: one-pot and two-step synthesis routes. The synthesized materials were shown to be micro-mesoporous structures consisting of zeolitic crystallites (ZSM-5/Mordenitetype) embedded into amorphous domains of hexagonally ordered mesoporous silica, MCM-41, with properties comparable with those reported for the samples obtained by dual templating and autoclave heating. Mesopores were created by soft-templating, whereas the crystalline microporous framework was formed in the absence of organic molecular template under microwave irradiation. One of the samples was tested as a catalyst in the cracking of vacuum gas oil, which resulted in obtaining hydrocarbons in the range of liquefied petroleum gas, gasoline and diesel, indicating that the mesoporous zeolitic materials prepared via single-surfactant templating under microwave irradiation are effective catalysts for the pyrolysis of vacuum gas oil. Both the synthesis procedure and the presented application of mesoporous zeolites address a few aspects of green chemistry and sustainability.