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过程工程学报 ›› 2022, Vol. 22 ›› Issue (6): 764-773.DOI: 10.12034/j.issn.1009-606X.221184

• 研究论文 • 上一篇    下一篇

密度泛函理论研究金属镧离子的水合团簇

巨朝阳1, 余梦婷1, 雷庭俞2, 程海翔1, 任兰会3*, 葛承胜1*   

  1. 1. 衢州学院化学与材料工程学院,浙江 衢州 324000 2. 中国科学院山西煤炭化学研究所煤转化国家重点实验室,山西 太原 030001 3. 浙江大学衢州研究院特种聚合物研究所,浙江 衢州 324003
  • 收稿日期:2021-06-11 修回日期:2021-08-29 出版日期:2022-06-28 发布日期:2022-06-28
  • 通讯作者: 葛承胜 gechengsheng@qzc.edu.cn
  • 作者简介:巨朝阳(1991-),男,河北省石家庄市人,博士,讲师,农业工程专业,E-mail: jzy@qzc.edu.cn;通讯联系人,任兰会,E-mail: ren_lanhui@163.com;葛承胜,E-mail: gechengsheng@qzc.edu.cn.
  • 基金资助:
    国家自然科学基金资助项目

Hydration of lanthanum ions clusters in aqueous solution: a DFT study

Zhaoyang JU1,  Mengting YU1,  Tingyu LEI2,  Haixiang CHENG1,  Lanhui REN3*,  Chengsheng GE1*   

  1. 1. College of Chemical & Material Engineering, Quzhou University, Quzhou, Zhejiang 324000, China 2. Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, China 3. Institute of Special Polymers, Institute of Zhejiang University-Quzhou, Quzhou, Zhejiang 324003, China
  • Received:2021-06-11 Revised:2021-08-29 Online:2022-06-28 Published:2022-06-28

摘要: Y型分子筛具有许多工整均匀的孔道结构,经常作为酸催化剂、双功能助推剂和择形催化剂,被广泛应用于干燥、洁净过滤、吸附分离和催化等领域。工业生产中稀土Y型分子筛的制备一般选用稀土离子水溶液与NaY型分子筛通过离子交换置换制取,但稀土离子水合结构以及通过分子筛孔的微观机理仍不清楚。本工作采用密度泛函理论(DFT)在M06-2X-D3/def2-SVP计算水平下,La3+采用LANL2DZ赝势基组,采用SMD=water隐式溶剂模型研究了La3+水合团簇及其不同价态时的结构性质,对水合团簇结构尺寸、Mulliken电荷、结合能以及能量分解进行了分析。结果表明,La3+水合团簇结构柔性较大,并非大于某个水合数无法通过分子筛孔;随水合数目的增大,La-O(H2O)平均半径有着增大的趋势,La3+在水溶液中总是趋于更稳定的多水合团簇结构;La-O(OH-)形成的键能比La-O(H2O)强;在[La(H2O)n]3+水合数目小于等于9时,团簇结构中以静电为主导作用,其次是诱导作用和交换互斥作用,色散作用所占比例最小;当水合数目大于9时,诱导作用所占比例升高,静电作用所占比例降低。研究结果对于深入认识稀土水合结构和分子筛制备机理具有重要理论指导意义。

关键词: 分子筛, 密度泛函理论计算, 镧离子, 离子水合, 团簇

Abstract: As one kind of acid and shape-selective catalyst, zeolites Y have been widely used in the fields of drying and clean filtration, adsorption and separation because of its neat and uniform pore structures. The production of rare earth (RE) zeolites generally utilized RE ion aqueous to replace in NaY zeolites by Na-RE ion exchange reaction. However, the structures of RE ion hydration and the microscopic mechanism of the clusters crossing the pores of zeolites were still unclear. This work mainly focused on the structural prosperities of La3+ hydration and different valent hydration clusters based on density functional theory (DFT) calculations at M06-2X-D3/def2-SVP (LANL2DZ for La3+) and SMD=water implicit solvent level. The dimensions of the clusters, Mulliken charges, binding energies, and energy decomposition had been analyzed in this work. It could be found that the structures of clusters were flexible, it was not greater than a certain hydration number of the clusters to pass through the pores of zeolites. With the expanding number of hydration in clusters, the average radius of La-O(H2O) would increase. From the analysis of binding energy, the La3+ tended to be a more stable structure with high hydration in aqueous solution. In addition, the binding energies of La-O(OH-) were stronger than that of La-O(H2O). When n≤9 in the [La(H2O)n]3+ clusters, the electrostatic interaction occupied the dominant proportion, and the following items were induction, exchange repulsion and dispersion energy in the system based on the energy decomposition. When n>9 in the [La(H2O)n]3+ clusters, the proportion of electrostatic interaction would decrease, the induction item would increase at the same time. The proportion changes of exchange repulsion and dispersion energy were not obvious with the increasing numbers of hydration. This work would provide some guidance for understanding the structure of La3+ hydration and basic aid for production of the RE zeolites.

Key words: molecular sieve, DFT calculations, lanthanum ion, ion hydration, clusters