Template removal by ion-exchange extraction from siliceous MCM-41 synthesized by microwave-assisted hydrothermal method

Abstract

Cetyltrimethylammonium (CTA+) bromide is a template in the synthesis of MCM-41 which is normally removed by calcination. This work focuses on removal of CTA+ by ion-exchange extraction from a siliceous MCM-41 synthesized by microwave-assisted hydrothermal method. The extraction was first conducted with aqueous and methanolic solution of NH4Cl under sonication. Methanol was a better solvent and further used with salts of various cation and anion. The extraction in the presence of ammonium salts was better than sodium and potassium salts due to the less change of the MCM-41 structure. In contrast, the type of anion in the ammonium salts had no effect on the removal efficiency. The methanolic solution containing NH4Cl was further studied from 15 min to 120 min and from 30 °C to 60 °C. The longer time and higher temperature improved the template removal but the extraction for 15 min at 60 °C was sufficient in terms of energy consumption.