Kinetics and Synthesis Control of Mesoporous Molecular Sieves

• Main Authors: Chia-Pei Kao, 高嘉珮
• Other Authors: Chung-Yang Mou
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/45793813052569450615

碩士 === 國立臺灣大學 === 化學研究所 === 88 === Mesoporous silica can be synthesized in either the alkaline route or the acidic route. Up to now, we have not found any detailed kinetic studies on the formation mechanism of mesoporous materials yet. To further realize the formation mechanism under acidic or alkaline conditions, we varied many chemical and physical factors, including the nature and concentration of the acid sources, changing temperature, adding the sodium salts and polar solvent to the CnTMAX-TEOS-acids-H2O or CnTMAX-TEOS-NaOH-H2O components, respectively. Based on the results, we can understand the role of counterion in the formation mechanism in acid and basic routes through. In the acidic route, the order of counterions on the rate of mesoporous materials formation the order followed : ClO3->NO3->Br->SO42-, SO32->Cl->F-. To investigate the mesoporous silica synthesis, we use two different surfactants as template to prepare mesoporous materials under acid conditions. In CnTMAB-TEOS-HNO3-H2O composites, the hierarchically structured mesoporous materials of millimeter-sized silica ropes can be successfully obtained by applying the shearing flow. But, the gyroidal spheres were obtained without shearing flow. Besides, the influence factors on the meso-structure formation kinetics also affect the morphologies and structures of mesoporous materials. Using block copolymer systems, hexagonal mesostructure samples can be synthesized with large pore diameter by using EO17PO85EO17 as template, cubic structures were synthesized from EO106PO70EO106, and lamellar structures were prepared from EO4PO56EO4. Especially in EO20PO70EO20 system, we can synthesize centimeter-sized mesoporous organic-inorganic composite spheres in certain proper synthetic compositions, possessing a uniquely elastic property, large pore size, and surface area.