Distribution of Fe and adsorption of NH3 in mordenite: a computational study

GUO Hai-yan1，REN Jun1，FENG Gang2, CAO Duan-lin1

(1. School of Chemical Engineering and Environment, North University of China, Taiyuan 030051, China;2. SINOPEC Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China)

Abstract： The distribution of Fe and the adsorption of NH3 in H-[Fe]MOR (mordenite) were investigated using dispersion corrected density functional theory (DFT-D2). Based on the results, it can be found that the most favorable site for the distribution of Fe is T1O6, followed by T2O5, T4O2 and T3O1, and energy differences for Fe in different T sites are less than 0.09 eV, indicating that Fe atoms may distribute in all kinds of T sites in MOR. In addition, the adsorption energies for NH3 at each crystallographic position of H-[Fe]MOR were also determined. Finally, it can be concluded that the Brnsted acid site at T2O5 is stronger than the other acid sites, and the adsorption of NH3 on Brnsted acid sites is more stable than on Lewis acid sites.

Key words： mordenite (MOR); distribution of Fe; adsorption of NH3; dispersion corrected density functional theory (DFT-D2) calculations

CLD number： O647.3 Document code： A

Article ID： 1674-8042(2014)01-0080-08  doi： 10.3969/j.issn.1674-8042.2014.01.017

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Fe 在丝光沸石骨架中的取代位置及 NH3 吸附的理论研究

郭海燕1， 任君1， 冯刚2， 曹端林1

(1. 中北大学 化工与环境学院，山西 太原 030051； 2. 中国石化上海石油化工研究院，上海 201208)

摘要:采用色散校正密度泛函方法(DFT-D2)研究了 Fe 同晶取代进入丝光沸石骨架中的可能位置及其对 NH3 分子的吸附。 结果表明， Fe 优先取代位是 T1O6 位， 然后依次是 T2O5, T4O2 和 T3O1位， 且能量差小于 0.09 eV， 说明Fe可能分布在四种非等价晶体T位， 而且电荷平衡质子的位置影响Fe取代位的稳定性。 本文还采用DFT和DFT-D2方法计算了NH3分子在每一个Fe取代的T位的吸附能。 通过比较发现， DFT 低估了 NH3 的吸附能约 0.53 eV, 这表明 DFT-D2 方法对于 NH3 吸附是很有必要的， 且结果与文献相符， T2O5 位的 Brnsted 酸性最强， NH3 在 Brnsted 酸位的吸附比在 Lewis 酸位的吸附更稳定。

关键词:丝光沸石； Fe同晶取代； NH3 吸附； DFT-D2 计算

引用格式：GUO Hai-yan， REN Jun， FENG Gang, et al. Distribution of Fe and adsorption of NH3 in mordenite: a computational study. Journal of Measurement Science and Instrumentation, 2014, 5(1): 80-87. [doi: 10.3969/j.issn.1674-8042.2014.01.017]

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