School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai Coal Gasification Engineering Technology Research Center
Shanghai Huanqiu Engineering Co., Ltd
School of Chemical Engineering, Xinjiang University

含HCN的废弃物在气化炉内的高温转化是其绿色处理的方法之一，其中，HCN与H2/H2O的反应是其在气化炉内的主要转化过程。本工作基于密度泛函理论，采用Gaussian及其配套软件对HCN与H2/H2O的反应机理进行了研究。通过分子成键、断键角度提出HCN与H2/H2O的各两种反应路径，结合能垒和热力学分析确定了相对最优路径，并计算了相对最优反应路径的速率常数。结果表明，HCN与H2反应相对最优路径为：三个H2分子在C≡N上分三步进行加成得到产物CH4+NH3；HCN与H2O反应相对最优路径为：H2O分子进攻C原子，O原子和C原子的H先后转移至N原子得到产物CO+NH3。两条相对最优路径在1473 K以上有明显反应速率，分别为9.57×10−4和1.71 mol/(L·s)。研究结果为高温下HCN与H2/H2O反应的工艺和设备开发提供了理论数据支撑。

HCN is a highly toxic substance that can enter the human body through the skin and respiratory system, and in severe cases, cause death. HCN can achieve partial conversion under high-temperature gasification conditions, mainly by reacting with H2 and H2O. In order to further explore the micro reaction mechanism of HCN with H2 and H2O during gasification, and to investigate the effects of temperature and pressure changes on the reaction, this paper uses quantum chemical simulation methods to study the reaction path, reaction thermodynamics, and kinetics of the above reactions, and quantitatively analyzes the changes in thermodynamic parameters and reaction rate constants with temperature, fitting the Arrhenius equation related to the reaction. Calculate the distribution of Fukui functions for various reactants and intermediates in the reaction process of HCN with H2 and H2O using Multiwfn, and speculate on possible reaction pathways. The transition state search and single point energy calculation of the reaction process between HCN and H2 and H2O were carried out using Gaussian & Gaussian View. Similarly, using the wave function program Multiwfn to calculate the Mayer bond order. The analysis of the bond order curve during the reaction process can reveal the changes in the strength of chemical bonds and the situation of bond formation and breaking. Use the Shermo program to calculate the thermodynamic parameters of each stagnation point at different temperatures, including enthalpy, entropy, Gibbs free energy, and partition function. Finally, the KiSThelP program was used to calculate the reaction rate constants for each step of the reaction based on classical transition state theory at different temperatures. The results show that the relatively optimal path for the reaction between HCN and H2 is as follows: three H2 molecules are added in three steps on C≡N to obtain the product CH4+NH3; The relatively optimal path for the reaction between HCN and H2O is as follows: H2O molecules attack C atoms, and the H of O and C atoms are transferred to N atoms to obtain the product CO+NH3. The first step of reaction between HCN and H2 is R1→IM1 which is below 534 K with ΔG<0. After exceeding this temperature, ΔG>0 becomes a reverse spontaneous reaction. It can be considered that an increase in temperature is not conducive to the electrophilic addition reaction of the first H2 on C≡N. The second step is IM1→IM2, with ΔG below 1103 K less than 0 and above greater than 0, indicates that the spontaneity of the second step H2 addition reaction is inhibited as the temperature gradually increases. The third step is IM2→P1. Within the set temperature range, its ΔG is always less than 0, and the reaction can always proceed spontaneously. The ΔG of the first step reaction R2→IM5 in Path 3 is only less than 0 at room temperature, indicating that this step is difficult to occur spontaneously at high temperatures. Path 3 second step reaction IM5→IM6 ΔG is always less than 0 within the set temperature range. The third step of the reaction is IM6→P2, and the temperature of ΔG below 958 K is greater than 0, making it difficult to occur spontaneously. The research results on changes in pressure and free energy show that pressure can increase the upper temperature limit for spontaneous reaction.The reaction rates of HCN with H2 and HCN with H2O are relatively fast at high temperatures. The rate determining steps for Path 1 and Path 3 at high temperatures are R1 → IM1, R2 → IM5, respectively. The rate constants for the two reaction steps above 1473 K are 9.57×10−4 and 1.71 mol/(L·s), respectively. The pre-exponential factors for these two reactions were calculated to be 4.45×109 and 4.68×108 s−1, and the activation energies were 357.62 and 239.30 kJ/mol, respectively.

国家重点研发计划（2022YFB4101500），新疆自治区自然科学基金重点项目（2023D01D02）和上海市2021年科技创新行动计划课题（21DZ1209003）资助

孙明哲, 许建良, 侯秋实, 代正华, 王辅臣. 基于密度泛函理论的HCN与H2/H2O气相反应机理研究[J]. 燃料化学学报（中英文）, 2024, 52(6): 850-863.

SUN Mingzhe, XU Jianliang, HOU Qiushi, DAI Zhenghua, WANG Fuchen. Study on gas phase reaction mechanism of HCN and H2/H2O based on density functional theory[J]. Journal of Fuel Chemistry and Technology, 2024, 52(6): 850-863.