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化学学报
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化学学报 ›› 2009, Vol. 67 ›› Issue (22): 2549-2553. 上一篇    下一篇

研究论文

β分子筛中Brønsted酸分布及酸性强度的量子化学ONIOM 理论计算研究

孙秀良，黄崇品*，陈标华   

  1. (北京化工大学化工资源有效利用国家重点实验室 北京 100029)
  • 投稿日期:2009-01-12 修回日期:2009-05-10 发布日期:2009-07-04
  • 通讯作者: 黄崇品 E-mail:2006080019@grad.buct.edu.cn
  • 基金资助:

    国家重点基础研究发展规划“973”项目资助(2004CB217804)，国家杰出青年科学基金资助。

Location and Acid Strength of Brønsted Acid Sites in β-Zeolite: a Quantum Chemical ONIOM Study

Sun, Xiuliang，Huang, Chongpin*，Chen, Biaohua   

  1. (State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029)
  • Received:2009-01-12 Revised:2009-05-10 Published:2009-07-04

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基于量子化学ONIOM [B3LYP/6-31G(d,p):UFF]计算方法, 研究了β分子筛中Brønsted酸的落位及其酸性强度. 计算采用22T簇模型, 得到了不同酸性位的(Al, H)/Si替代能和质子亲和势. 研究结果表明, Brønsted酸最有可能落位在Al(8)-O(11)-Si(4), Al(8)-O(4)-Si(1), Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置. 根据去质化能的计算, Al(7)-O(7)-Si(2)位置的酸性最强, Al(8)-O(11)-Si(4)的酸性最弱. 酸性的强弱顺序为Al(7)-O(7)-Si(2)＞Al(9)-O(6)-Si(3)＞Al(8)-O(4)-Si(1)＞Al(8)-O(11)-Si(4).

关键词: β分子筛, Br?nsted酸, ONIOM

A quantum chemical ONIOM [B3LYP/6-31G(d,p):UFF] method has been applied to study the distribution of Brønsted acid at nine inequivalent T sites and the acidity of Brønsted acid in β-zeolite. In the calculation, the structure of β-zeolite is represented by 22T cluster model. According to the calculated (Al, H)/Si substitution and proton affinity, it was proposed that most favorable sites for Brønsted acid are Al(8)-O(11)-Si(4), Al(8)-O(4)-Si(1), Al(7)-O(7)-Si(2), and Al(9)-O(6)-Si(3). The acidity of Al(7)-O(7)-Si(2) is the most highest in the preferable Brønsted acid sites, and Al(8)-O(11)-Si(4) site is the lowest. The order of acidity is Al(7)-O(7)-Si(2)＞Al(9)-O(6)-Si(3)＞Al(8)-O(4)-Si(1)＞Al(8)-O(11)-Si(4).

Key words: β-zeolite, Br?nsted acid, ONIOM