Abstract: Siliceous MCM-41 samples with two different pore size and metal substituted MCM-41 samples with different metals have been synthesized at different pH of the mixture, and characterized by X-ray powder diffraction and nitrogen adsorption analysis. The results show that all the samples exhibit a typical XRD diffraction of MCM-41 and an adsorption isotherm of type Ⅳ, but there exists a considerable amount of amorphous siliCA In the samples. The sample prepared at pH=11(MCM-3) shows the best in quality among the others, and has less content of amorphous silica phase. When the MCM-3 is regarded as a standard, the sample prepared without pH adjustment contains only 36% of pure MCM-41 crystallites, while the sample prepared at pH=10.5 has 84% of pure MCM-41 phase. It has also been observed that the quality of the resulted samples is decreased when a shorter chain surfactant is used. When the metal substituted M-MCM-41 (M=Al, Mn, Fe, V) is prepared at pH=11, their quality can be improved. However, the diffraction intensity of d₁₀₀phase is still lower than that of the corresponding siliceous MCM-41, and decreases accordingly from Al to V.

Key words: Siliceous MCM-41, Metal substituted MCM-41, Purity