The Synthesis And The Modification Of Silica-based Mesoporous Materials M41S

Silica-based mesoporous material M41S possesses a series of excellent qualities such as regular arrangement of channels, narrow pore size distribution and tailorable pore size, high specific surface area, huge adsorptive volume and so on. These make the materials have wide application prospect in many fields. M41S have been synthesized in the hydrothermal treatment and the influence factors of on the synthesis of M41S have been discussed in the paper. Meanwhile, we also explore the change of structure and quality resulted from the incorporation of ions such as Ti4+,B3+, Al3+ and so on.We studied systematically the effect of the ratios of agents (CTAB/TEOS, NaOH/TEOS,H2O), hydrotherm parameters (temperature and time) and so on in the preparation of M41S, and concluded: the ratios of CTAB/TEOS and NaOH/TEOS are the two key factors in determining the sort of M41S. The system with a low ratio of NaOH/TEOS(≤0.3) is only fit for the synthesis of MCM-41, but not for MCM-48, no matter what the ratio of CTAB/TEOS is. MCM-48 can be synthesized on condition that the ratio of CTAB/TEOS reaches to a certain value(≥0.2) in the system with a high ratio of NaOH/TEOS(≥0.48). The conditions favorable to the synthesis of MCM-41 are the ratio of CTAB/TEOS 0.1, NaOH/TEOS 0.24-0.36, hydrothermal temperature from 90oC-120oC, hydrothermal time 48h. However, the ratio of CTAB/TEOS 0.2-0.4, NaOH/TEOS at 0.48, H2O/TEOS 64.6-101.9 and hydrothermal temperature at 110oC are advantageous to the synthesis of MCM-48.We discuss the influence of basic media (NH3.H2O, EDA, NaOH/TEOS) on the synthesis of MCM-41. As-synthesied samples obtained in weak basic media (NH3.H2O, EDA) possess more thermal stability than in the strong one(NaOH) at room temperature. And hydrothermal treatment can improve the order and density of the framework of samples synthesized in weak basic media. at room temperature. The smaller the ratio of NH3/TEOS is more helpful for the synthesis of samples. The contraction from calcination of samples obtained in EDA medium is proporational to the ratio of EDA/TEOS at room temperature. The samples obtained in mixed basic media (NaOH/TEA ) have thicker wall and more thermal stability than in NaOH medium, but pore size is smaller correspondingly.The incorporation of B3+ can improve the order of the framework of MCM-41, but B3+ in SiO2 matrix is unstable and easy to be hydrolyzed, which eventually results in the collapse of framework. The incorporation of Ti4+ can damage the order of the framework of M41S. It results in changes of the intensity of adsorptive peaks at about 1220cm-1, 960cm-1, 777cm-1 in the spectra of FT-IR. Especially, intensity change of peak at about 777cm-1 has been considered as the indication of Ti4+ incorporated into the matrix of M41S. Incorporation of Al3+ can damage the order of the framework of MCM-48 obviously, which is indicated by change of the intensity at about 1220cm-1, 960cm-1,730cm-1 in the spectra of FT-IR.