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化学学报
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化学学报 ›› 2012, Vol. 70 ›› Issue (19): 2091-2096.DOI: 10.6023/A12050182 上一篇    

研究论文

酸性条件下正钛酸钛(IV)中心与过氧化氢反应机理的第一性原理研究

唐侃a, 陶辉锦a,b,d, 蒋新宇c   

  1. a 中南大学材料科学与工程学院 长沙 410083;
    b 中南大学有色金属材料科学与工程教育部重点实验室 长沙 410083;
    c 中南大学化学化工学院 长沙 410083;
    d 中南大学粉末冶金国家重点实验室 长沙 410083
  • 投稿日期:2012-05-07 发布日期:2012-08-07
  • 通讯作者: 陶辉锦 E-mail:thj@csu.edu.cn
  • 基金资助:

    项目受国家自然科学基金(No. 50871124);中南大学贵重仪器使用开放基金(CSUZC2012023)和中南大学粉末冶金国家重点实验室开放基金资助.

Possible Reaction between Titanium(IV) and Hydrogen Peroxide in Acidic Condition: An ab-initio Study on Its Mechanism

Tang Kana, Tao Huijina,b,d, Jiang Xinyuc   

  1. a School of Material Science and Engineering, Central South University, Changsha 410083;
    b Key Lab of Nonferrous Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083;
    c School of Chemistry and Chemical Engineering, Central South University, Changsha 410083;
    d State Key Laboratory For Power Metallurgy, Central South University, Changsha 410083
  • Received:2012-05-07 Published:2012-08-07
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 50871124), the Open-End Fund for the Valuable and Precision Instruments of Central South University (CSUZC2012023) and the Open Fund of State Key Laboratory of Powder Metallurgy.

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正钛酸钛(IV)中心与过氧化氢的溶液反应很早就已经开始被加以关注和研究, 因其在化学催化、分析化学以及精细陶瓷方面具有重要用途. 尽管如此, 其不同条件下的反应机理以及产物长期以来没有得到共识. 本文主要希望通过对特定条件下(pH<1), 对这一反应进行第一性计算研究. 其中计算主要采用B3LYP泛函和6-311G+(3df,2p)基组的组合, 对可能的反应路径进行分步以及总反应热的计算, 其结果(27 kJ/mol)与实验值较为接近. 通过仔细研究反应中分子轨道的变化, 指出成环反应和氢转移反应是整体反应的关键步骤, 采用单向连串反应假设对实验现象进行分析, 并决定其宏观反应动力学“准一级”的特征, 获得了对特定及一般实验条件下的结果的合理解释. 通过对这一反应机理的研究, 我们希望能够将其推广至其他过渡族金属中心与过氧化物结合的反应中, 得以指导高效环氧化催化剂及精细陶瓷的合成与制备.

关键词: titanium(IV), 过氧化氢, B3LYP, 分子轨道, 反应动力学

The reaction between titanyl hydroxy and titanium(IV) has long been interested in and studied as its value in catalysts, analytic chemistry and synthesis of novel ceramic materials. Nevertheless, the possible reaction mechanism and its final products have never been concluded under different experimental conditions. Even in some particular condition i.e. pH<1, different products had been proposed such as Ti(O2)2+ and Ti(O2)(OH). In this article, a possible reaction mecha-nism has been proposed based on first-principles calculations in order to explain its experimental phenomenon under specific condition(s) (pH<1). The calculation is carried out by the combination of B3LYP functional and 6-311G+(3df,2p) basis set. As to estimate the solvent effect, the IEF-PCM model was also introduced in the calculation. Based on the calculation level mentioned above, the reaction profile and heat were figured out, and heat of reaction is comparable to the experimental data (27 kJ/mol vs. 24 kJ/mol). The rate limiting steps are also identified by checking the transformation of molecular orbitals before and after triatomic ring annulation reaction and hydrogen (H+) transfer reaction. In the annulation reaction, the complicated interaction between Ti's 3d orbitals and O's 2p orbitals acts crucial role in the transformation of bonding types into triatomic ring. In the hydrogen (H+) transfer reaction, the vacant orbital 1s of hydrogen (H+) attacks the HOMO of the titanyl peroxo complex to form new O—H bond while breaking the old O—H bond in the complex. The two steps reaction model fits well with pseudo-first-order hypothesis of the general dynamics of the reaction and the deviation of the general reaction dynamics as well, which supports the thermochemistry results made by first principles calculation. We hope this possible mechanism not only explains the reaction products under the specific condition, but also can be extended to other transition metals' reactions with peroxo complex and find its value in the synthesis of epoxidation catalysts and ceramics.

Key words: titanium(IV), hydrogen peroxide, B3LYP, molecular orbital, reaction dynamics