Molecular Interaction of Amino Acids with Acidic Zeolite BEA: The Effect of Water

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• 作者：Kai St眉ckenschneider ; Juliane Merz ; Gerhard Schembecker
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 20, 2014
• 年：2014
• 卷：118
• 期：11
• 页码：5810-5819
• 全文大小：506K
• 年卷期：v.118,no.11(March 20, 2014)
• ISSN：1932-7455

文摘

Experimentally, zeolites were shown to adsorb amino acids from the aqueous phase. However, there has not been a satisfactory theoretical explanation on the effect of water on the underlying adsorption mechanisms yet. In this study, the effect of water on the pH-dependent adsorption behavior of glycine and alanine in zeolite BEA was investigated using density functional theory (DFT). Using a microsolvation model, the coadsorption and formation of an intermolecular H-bond system between water molecules, amino acid, and zeolite was shown. In addition, different pH values were modeled by varying the amino acids protonation states with the protonated states being significantly more stable in the BEA pores than the net neutral ones. This behavior was experimentally approved by isothermal titration calorimetry (ITC) and adsorption isotherm measurements. These results provide new molecular level information on the adsorption of amino acids in zeolites from the aqueous phase and could be used to support the experimental side of adsorption process design in industrial biotechnology by qualitatively predicting binding behavior by means of DFT calculations and simplified model systems.