Hydrothermal synthesis of MCM-41 using different ratios of colloidal and soluble silica

The influence of different ratios of colloidal (Cab-O-Sil, HiSil-915 and sodium silicate) and soluble (tetramethylammonium silicate) silica on the physicochemical properties (surface area, porosity, degree of structural order, thermal stability, density of free silanol group) of MCM-41 has been investigated. MCM-41 materials synthesized hydrothermally have been characterized by XRD, N2 physisorption, and IR spectroscopy. The results show that colloidal silica (HiSil-915 or Cab-O-Sil) to soluble silica ratio corresponding to 80:20 favors the formation of MCM-41 material with higher degree of structural order and uniformity of mesopores than those synthesized from the conventional ratios (∼70:30). Also, a new approach for tailoring the pore diameter within a modest range (∼20-30 Å) and controlling the other properties (surface area, porosity, and pore wall thickness) of MCM-41 has been demonstrated in this study. MCM-41 materials synthesized from Cab-O-Sil have thicker pore walls (15-20 Å) and show better thermal stability than when HiSil-915 is used.