Several Factors Affectingthe Novel Synthesis of Mesoporous Aluminosilicate MCM-41 through Non-hydrothermal Conditions

摘要

In order to elucidate the effect of synthesis conditions of Al-MCM-41 on the characteristics of the resultant samples, Al-MCM-41 samples were synthesized through non-hydrothermal reactions under diverse conditions. The following conditions were found to be favorable to prepare Al-MCM-41 with well ordered 2D-hexagonal structure from the reaction mixtures of lower Si/Al ratios: simultaneous addition of Si and Al sources into the solution containing both template of surfactant and anti-foaming agent, in neutral to acidic media (pH 3-7), at temperatures above Krafft point of the surfactant, and under vigorous stirring. These conditions may be associated with assembly of aluminosilicate sources with uniform composition (i.e., constant Si/Al ratio) around the template micelles, promoting hydrolysis and/or condensation of aluminosilicate and forming Al-MCM-41 with highly-ordered structures. Relatively weak acid sites are mainly consisted of Al-MCM-41 and similar distributions of acid strength are observed for the samples with different Si/Al species. Dealkylation reactions of 1,3,5-triisopropylbenzene, which are well known to proceed on Bronsted acid sites are catalyzed more effectively on Al-MCM-41 samples than on HY-zeolites. This means that at least, a part of Al was incorporated into the silica framework of MCM-41 structure as tetrahedrally coordinated species in Al-MCM-41 samples prepared in the present study.