The Mesoporous Function Of Amphiphilic Molecules Of The Liquid Crystal Template Synthesis Of Rare Earth Materials

This thesis reported the research work on the synthesis and characterization of a series of rare earth incorporated cubic mesoporous silica, and the synthesis of a cubic lanthanum mesoporous oxide has been investigated.Using cethyltrimethylammonium bromide as template under low molar ratio of surfactant to inorganic precursor, we synthesized and characterized a series of highly quality rare earth modified cubic MCM-48 molecular sieves (La-MCM-48, Ce(III)-MCM-48, Ce(IV)-MCM-48, Nd-MCM-48, Y-MCM-48) with different Ln/Si molar ration. The X-ray diffraction and TEM results show that the well-ordered cubic mesostructure was obtained when the Ln/Si molar ratio is less than 0.05. With the increase of Ln/Si molar ratio, the increase of unit cell parameters and the change of FTIR provide powerful evidences for the incorporation of rare earth atom in the framework of mesoporous molecular sieves. Nitrogen sorption data indicates that the BET surface area and the average pore diameter of La-MCM-48, Ce(III)-MCM-48, Ce(IV)-MCM-48, Nd-MCM-48 and Y-MCM-48 are 1149.55 m2/g, 3.3 nm; 1287.67 m2/g, 4.2 nm; 1227.72 m2/g, 3.7 nm; 1195.51 m2/g, 3.6 nm and 1179.61 m2/g, 3.4 nm, respectively. Diffuse reflectance UV-visible spectroscopy reveals the coordination state of rare earth atom. X-ray photoelectron spectroscopy studies indicate the valency of each kind of rare earth atom in the structure of molecular sieves.A cubic mesoporous lanthanum oxide was synthesized by using a kind of laurate possessed ligand-assisted function as template. It was revealed that the laurate has double effect of a coordinated agent and templating agent. The X-ray diffraction indicates the lauric-lanthanum-based cubic mesophase can be obtained at certain molar ratio of initial mixture. The N2 sorption date shows the product is a kind of typical mesophase.