Controlled Synthesis of Mesoporous Silicas MCM-48 and MCM-41 by Using Mixed Templates

Mesoporous silica MCM-48 and MCM-41 were hydrothermally synthesized in alkaline medium by using mixed cationic-nonionic triblock copolymer surfactant (P123, 2-methyloxirane; oxirane; CAS No. 9003-11-6)as template. By altering the ratio of CTAB (cetyltriethylammonium bromide) to TEOS (tetraethoxysilane , tetraethyl silicate), the mesoporous molecular sieves were obtained with different structures. The amount of CTAB can be largely decreased by adding P123 into the synthesis system. It is found that the molar ratios of CTAB/TEOS between 0.12 and 0.13 are favorable for the formation of highly ordered MCM-48 mesostructure and that of CTAB/TEOS between 0.04 and 0.08 are favorable for the formation of highly ordered MCM-41 mesostructure. XRD, TEM and N2 sorption measurements show that the products have highly ordered mesostructure with high surface area, large pore volume and narrow pore size distribution.