AlCl3-Grafted Si–MCM-41: Influence of Thermal Treatment Conditions on Surface Properties and Incorporation of Al in the Structure of MCM-41

Grafting of AlCl3 onto Si–MCM-41 using the reaction of anhydrous AlCl3 from its CCl4 solution with terminal Si–OH groups of Si–MCM-41 under reflux at two different concentrations of AlCl3 relative to Si–MCM-41 has been studied. The influence of thermal-treatment conditions (viz., temperature and gas atmosphere, such as vacuum, static or flowing air, and flowing N2) on bulk and surface properties of the AlCl3-grafted Si–MCM-41 has also been investigated. The AlCl3-grafted Si–MCM-41 samples before and after thermal treatment were characterized by Fourier transform infrared, 27Al magic-angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, and energy disperse X-ray analysis (EDAX) analysis and also for their surface area and concentration of strong acid sites (measured in terms of the pyridine chemisorbed at 400°C). The incorporation of tetrahedral Al in the MCM-41 structure with the creation of strong acid sites could be accomplished by thermally treating the AlCl3-grafted Si–MCM-41, particularly in a flow of N2 at 400°C.