The homogeneous phosphotungstic acid catalyzed N‐oxidation of alkylpyridines by hydrogen peroxide has important applications in pharmaceutical and fine chemical industries. Current industry practice is to employ a semibatch reactor with gradual dosing of hydrogen peroxide into an alkylpyridine/catalyst solution under isothermal conditions. However, due to lack of understanding of reaction mechanism and thermodynamic behavior, this system is subject to significant risk of flammability, fires and explosions due to hydrogen peroxide decomposition. In this study, we conducted semibatch N‐oxidation process in an isothermal reaction calorimeter (RC1) over a wide range of temperature, catalyst amount and oxidizer dosing rates. Reactor pressure, reaction heat generation rate and in situ FTIR spectra of liquid phase species were recorded in real‐time during experiments, and final product was quantified using HPLC and GC–MS analytical tools. We developed an integrated thermodynamic and kinetics model of homogeneous N‐oxidation reaction based on experimental results and past literature findings. More specifically, Wilson excess Gibbs model was employed to estimate activity coefficients of highly nonideal liquid mixture. We found ideal gas law was satisfactory in calculating incondensable oxygen pressure. First principle reaction mechanism and kinetics parameters of (a) catalytic N‐oxidation reaction; (b) catalytic hydrogen peroxide decomposition reaction; (c) noncatalytic N‐oxidation reaction; (d) noncatalytic hydrogen peroxide decomposition reaction was derived based on experimental findings of this study and past literature. The proposed integrated thermodynamic model and kinetics model successfully predicted highly nonlinear reactor pressure, species concentration and reaction enthalpy generation rate profile of homogenous catalytic N‐oxidation and H₂O₂ decomposition reaction. The optimal reactions conditions with maximum N‐oxide product yield and minimum reactor pressure and catalyst usage was theoretically identified and further verified by experiments. The obtained model can be used for inherently safer reactor design and applied to other homogeneous tungstic acid catalytic hydrogen peroxide oxidation processes.

中文翻译：

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均相催化N氧化过程的综合热力学和动力学模型

过氧化氢的均相磷钨酸催化烷基吡啶的N-氧化在制药和精细化工行业中具有重要的应用。当前的工业实践是使用半间歇反应器，其中在等温条件下将过氧化氢逐步加料到烷基吡啶/催化剂溶液中。然而，由于缺乏对反应机理和热力学行为的理解，该系统由于过氧化氢的分解而具有明显的易燃，着火和爆炸的危险。在这项研究中，我们进行了半批N等温反应量热仪（RC1）中的氧化过程，可在很宽的温度，催化剂量和氧化剂投加速率范围内进行。在实验过程中实时记录反应堆压力，反应热生成速率和液相物种的原位FTIR光谱，并使用HPLC和GC-MS分析工具对最终产物进行定量。我们根据实验结果和以往的文献发现，开发了一个均相N氧化反应的综合热力学和动力学模型。更具体地，使用威尔逊过量吉布斯模型来估计高度非理想液体混合物的活度系数。我们发现理想气体定律在计算不可冷凝的氧气压力方面令人满意。（a）催化氮的第一原理反应机理和动力学参数氧化反应 （b）催化过氧化氢分解反应；（c）非催化氮氧化反应；（d）基于本研究的实验结果和以往的文献得出了非催化的过氧化氢分解反应。提出的综合热力学模型和动力学模型成功地预测了均相催化N氧化和H ₂ O ₂分解反应的高度非线性反应堆压力，物质浓度和反应焓生成速率曲线。最大N的最佳反应条件从理论上确定了氧化产物的收率，最小反应器压力和催化剂的使用量，并通过实验进行了进一步验证。所获得的模型可用于本质上更安全的反应堆设计，并可应用于其他均相钨酸催化过氧化氢氧化工艺。