計算化学によるゼオライト研究の新展開Novel impact of computational chemistry to zeolite research
東北大学大学院工学研究科材料化学専攻Department of Materials Chemistry, Graduate School of Engineering, Tohoku University
東北大学大学院工学研究科材料化学専攻Department of Materials Chemistry, Graduate School of Engineering, Tohoku University
ゼオライトは特異的な固体酸性,分子ふるい作用,イオン交換能を有するため,触媒,吸着剤など広範囲な分野で活用されている。さらに最近では,ゼオライト中で起こる触媒反応機構,ゼオライトへの吸着や拡散現象の解明に,量子化学,分子動力学法,モンテカルロ法などの計算化学手法のゼオライト研究への活用が期待されている。本解説ではゼオライトの計算化学手法に関して,1)結晶構造解明への適用,2)吸着,分子ふるい機能への適用,3)合成プロセス過程の再現,4)ゼオライト中での触媒反応の活性種と反応機構の解明について,我々の最近の成果を中心に現状と今後の展望について概説する。具体的には,メタロシリケートの同形置換による構造変化,NaYゼオライトのAlおよびNa位置の決定,フロンの吸着等温線の再現,ゼオライト分離膜の透過過程,ZSM-5 (010)面上でのCVD成長過程,GaZSM-5のメタン活性化機構について紹介する。
Zeolites are well known for their properties like solid acidity, shape selectivity and ion exchange capability. These materials are widely used as catalysts, adsorbent of pollutants, molecular sieves, etc. Moreover recently zeolites find its way in important application areas like solid support of molecular catalyst, inorganic membrane, inorganic template for making carbon materials. As zeolite structures are well-defined, computer simulation studies e.g. quantum chemistry, molecular dynamics and monte carlo methods can be applied to rationalize reaction mechanism, adsorption and diffusion mechanism and so on.
In this review, we summarize an update of the recent application of computer simulation techniques to zeolite study: 1) application in defining zeolite structure, 2) application in explaining adsorption and diffusion mechanism of zeolite, 3) application in understanding the synthesis mechanism of zeolite, 4) application in determining active site and reaction mechanism in catalytic reaction. We introduced a few of our computer simulation results for example, the change of MFI structure due to the substitution of silicon by titanium, the identification of position of aluminum and sodium in NaY, reproduction of adsorption isotherm for chloroflurocarbon molecules, permeation mechanism of zeolite membrane, intergrowth of zeolite by chamical vapor deposition and activation mechanism of methane on GaZSM-5.
Key words: Reaction mechanism; Adsorption; Diffusion; Quantum chemistry; Molecular dynamics; Monte Carlo method
© 1997 ゼオライト学会© 1997 Japan Association of Zeolite
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