Study On The Preparation Of Mesoporous Molecular Sieves With Ionic Liquid As Template And The Evaluation Of Catalytic Activity

Mesoporous molecular sieves M41S, which are synthesized under hydrothermal crystallization with quaternary ammonium surfactants self-assembled by silicate, are one kind of porous materials. MCM-41 are a typical one. They have a dimension of hexagon structure, regularly ranking, average pore diameter(1.5-10nm), large surface area(≥900m²/g) and adsorbent volume(≥0.73m³/g). It is gradually exhibiting a promosing future in catalyst on the base of easily diffusing of organic molecule and acidity adjustable.Ionic liquid has the same structure with surfactant and molecular directional assembly function. In the hydrothermal synthesis of MCM-41, ionic liquid and compound template of ionic liquid and CTAB were employed as novel template in the preparation of MCM-41 to improve the ordering of molecular directional assembly.In my paper, our research includes following: (1) the synthesis and characterization of ionic liquid [C_nmim]Br (n=12,14,16,18,20); discussing the influence of ionic liquid template on preparation of MCM-41; obtained the best MCM-41 via the characterization of XRD and N₂ adsorption-desorption, then to expand the pore size; (2) discussing the effect of ionic liquid and CTAB as co-templates to the synthesis of MCM-41; synthesizing a series of MCM-41 under different crystal time, crystal time and calcined temperature, find an optimal preparory conditions; (3) discussing the influence of CTAB and PVA as co-templates on preparation of MCM-41; synthesizing a series of MCM-41 under different crystal temperature and calcined temperature, find an optimal preparory conditions; (4) immobilizing Al into surface of MCM-41 via doping to get Al-MCM-41, then impregnating in sulfuric acid solution to synthesize catalyst Al-MCM-41; (5) examining the catalytic activity of Al-MCM-41 prepared above via the synthesis of acetyl salicylic acid, finding the condition of the one that has the highest yield.We can conclude from the experiments that when using [C₁₆mim]Br as single template, we can get the best quality MCM-41; The result showed that the mixture(1:1) of decane and 1,3,5-tri-methybenzene(TMB) had a beneficial effect on the pore diameter, which was increased to 4.5 nm. We can conclude that the optimal synthesis technology of the mixture(decne/TMB=1) as swelling agent : swelling agent/template=1; the largest pore size can be obtained if the swelling agents were introduced during the preparation of micellar solution before introduction of sodium silicate; crystal temperature was 120℃. MCM-41 synthesized with [C₁₆mim]Br-CTAB as co-template, crystal temperature 80℃, crystal time 40h and calcined temperature 540℃have better crystal structure, larger surface area, narrower pore distribution than others; we introduced Al into MCM-41 and adjusted acidity of Al-MCM-41 by immerging in a series concentration of sulfuric acid for different time and calcined at different temperatures. The SO₄^2-/Al-MCM-41 was characterized by X-ray Powder Diffraction and N₂ adsorption-desorption analysis technique. The results showed the SO₄^2-/Al-MCM-41 had uniform pore diameter and stable framework. The catalytic activity of the SO₄^2-/Al-MCM-41 was investigated by the synthesis of acetyl salicylic acid, and we found its catalytic activity was three-time higher than concentrated sulfuric acid as catalyst in the reaction.