Synthesis of 2-cyanoethyl-modified MCM-48 stable to surfactant removal by solvent extraction: Influence of organic modifier, base and surfactant

A 2-cyanoethyl grafted MCM-48 mesoporous silicate, which was stable to surfactant removal by solvent extraction, was synthesised by co-condensation of 2-cyanoethyltriethoxysilane and tetraethyl orthosilicate in basic conditions using cetyltrimethylammonium bromide as surfactant. The presence of the organic group was verified by infrared analysis. Additional studies confirmed that the concentration of sodium hydroxide used for this synthesis influenced the mesopore properties. MCM-41 and MCM-48 were formed using a narrow range of base concentrations while preparations outside this range gave disordered materials with reduced porosity. Materials synthesised using various quantities of cetyltrimethylammonium bromide showed that MCM-48 was formed over a range of surfactant concentrations although the order varied considerably. The mesopore phase was further adjusted by altering the concentration of 2-cyanoethyltriethoxysilane modifier. Preparations using 0-10 and 20 mol% organic modifier (of total silica) produced MCM-48 and MCM-41, respectively, while greater modifier concentrations gave disordered materials with significantly diminished porosity characteristics.