Structure of the Hydroxyl Groups and Adsorbed D2O Sites in the DX Zeolite: DFT and Experimental NMR Data

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• 作者：Piotr B艂o艅ski ; Artur Birczy艅ski ; Zdzis艂aw T. Lalowicz ; Jerzy Datka ; Zbigniew 艁odziana
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：19548-19557
• 全文大小：490K
• ISSN：1932-7455

文摘

We report on density functional theory computations combined with the results of measurements of the quadrupole coupling constants for ¹⁷O, hydroxyl deuterons, and adsorbed water deuterons in DX zeolite (n(Si)/n(Al) = 1). Calculations are performed for the crystalline periodic model of the DX zeolite. The local structural parameters are found for various oxygen positions at equilibrium. The quadrupole coupling constants for ¹⁷O are in the range C_Q(¹⁷O) = 7.75 卤 0.5 and 3.75 卤 0.5 MHz for (Si鈥揙D鈥揂l) and (Si鈥揙鈥揂l) substructures, respectively. Related values of the asymmetry parameter 畏 fall in the ranges of 0.9 卤 0.5 and 0.15 卤 0.1, respectively. The quadrupole coupling constant for deuterons depends on the OD distance according to the relation C_Q(D)[MHz] = 鈭?.732d_OD[MHz/脜] + 2.938 MHz. Deuterons are assigned to labeled oxygen positions according to the decreasinng quadrupole coupling constant C_Q(D) as O1 鈮?O4 > O2 > O3, with their relative abundances of 54.4, 7.6, 26.6, and 11.4%, respectively. The binding energy of deuteron in hydroxyl groups and for adsorbed water molecules is analyzed. Formation of the water hexamer in the plane of the 12-ring window was confirmed. Results of the calculations are compared with NMR experimental data for ¹⁷O and D.