Influence of Brønsted acid strength on conversion of carbenium ion by molecular simulation

FU Jia; FENG Xiang; LIU Yibin; YANG Chaohe

doi:10.11949/j.issn.0438-1157.20170962

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Influence of Brønsted acid strength on conversion of carbenium ion by molecular simulation

更新时间：2025-12-10

- Influence of Brønsted acid strength on conversion of carbenium ion by molecular simulation
- CIESC Journal Issue 2, Pages: 725-732(2018)
- 作者机构：
  
  中国石油大学重质油国家重点实验室,山东,青岛,266580
- 作者简介：
- 基金信息：
- DOI：10.11949/j.issn.0438-1157.20170962
  CLC： Q461.1
- Online First：05 February 2018，
  
  Published：05 February 2018
- 稿件说明：
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FU Jia, FENG Xiang, LIU Yibin, et al. Influence of Brønsted acid strength on conversion of carbenium ion by molecular simulation[J]. CIESC Journal, 2018, (2): 725-732.
DOI：

FU Jia, FENG Xiang, LIU Yibin, et al. Influence of Brønsted acid strength on conversion of carbenium ion by molecular simulation[J]. CIESC Journal, 2018, (2): 725-732. DOI： 10.11949/j.issn.0438-1157.20170962.

摘要

采用密度泛函理论（DFT）系统地研究了Brønsted酸强度与催化反应过程中正碳离子转化活性之间的关系。通过调整B酸模型电子分布构建5种酸强度模型，其酸强度范围覆盖弱酸、强酸以及超强酸。将C4正碳离子作为模型化合物，计算其氢转移、异构化、脱氢、β断裂4种反应。计算结果表明氢转移的反应能垒与酸强度呈指数关系，其他3个反应能垒与酸强度呈线性关系。在弱酸范围内各反应对酸的敏感度由高到低排列如下：氢转移反应 > 异构化反应 > β断裂反应 > 脱氢反应，而在强酸范围内氢转移的酸敏感度最低。通过计算过渡态离子携带的电荷可知，反应活性对酸的敏感度与过渡态离子携带的Mulliken电荷有关。过渡态离子携带电荷越多，与酸性位的相互作用越强，所以提高酸强度时能更有效地降低反应能垒。该反应规律与实验结论相匹配，并且从原子层面解释了不同酸强度时实验产率变化的原因，对开发新型催化材料或者催化剂改性有重要意义。

Abstract

The influence of Brønsted acid strength on catalytic reactivity of carbenium ion was systematically studied by density functional theory (DFT) calculations. Four typical reactions of C4 carbenium ion as model compound

including hydrogen transfer

isomerization

β scission

and dehydrogenation

were simulated in five solid acid models with various acid strengths from weak-

strong-

even close to super-acid. The calculation results revealed that the reaction energy barrier decreased exponentially for hydrogen transfer reaction but decreased linearly for other three reactions with the increase of Brønsted acid strength. In weak-acid range

the sensitivities of reactions to acid strength from high to low was:hydrogen transfer > isomerization > β scission > dehydrogenation. Hydrogen transfer reaction had the lowest sensitivity in the strong-acid range. Calculation on ionic character of the organic fragments in transition states showed that reaction sensitivity to acid strength could be related to Mulliken charges of the transition state. The transition state with more Mulliken charge lead to stronger interaction with acid such that the activation energy barrier could be effectively reduced by increasing acid strength. The calculation was consistent with experimental conclusion and explained acid strength on production yield at the atomic level

which is of great significance to the development of new catalytic materials and modification of current catalysts.

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