关键词: 中孔六角MCM-41, 中孔层状M41S, 微孔ZSM-5沸石, 结构表征

Abstract: For the synthesis system containing cetyltrimethylammonium bromide and sodiumsilicate at low surfactant concentrations and low Sur/Si ratio, the pore and local unit structures of mesoporous M4lSand microporous zeolite ZSM-5, which are obtained in the samesystem at different synthesis temperatures, have been characterized by means 0f N, adsorption-desorption measurments, FTIR, ²⁹Si and ²⁷Al MAS NMRand DTG-The experimentalresults indicate that when synthesis temperature increases from 100℃ to 135℃, the sizes ofmaterials are governed by small crystallites, the pore wall thickness increases but the mesoporous surface areas as well as the volume of materials decrease.When synthesis temperature increases from 135℃ to 150℃, the layers of lamellar M4lSmaterial, obtained fromhexagonal MCM-41 collapse and mesoporous structure disappears due to the removal of thesurfactants by calcination, which are in agreement with experimental findings of XRD.Meanwhile, the double ring vibration band near 598 cm^-1 appears in the FTIRspectra.Thesilanols between layers are condensed, resulting in the loss of fine structure in₂₉Si MASNMRspectra.When further increasing synthesis temperature to 165℃, the silanols of framework are highly condensed, resulting in the decrease of Q3/Q4 ratlo greatly.The intensity of double ring vibration band increases and its vibration position shifts to 548 cm^-1.Thus, the lamellar M4lSis transformed to zeolite ZSM-5.The DTGresults suggest that theformations of different materials result from the different interactions between surfactantsand silicate species under different temperatures.

Key words: Mesoporous hexagonal MCM-41, Mesoporous lamellar M41S, Microporous zeolite ZSM-5, Structural characterization