Glycidol (GL) and epichlorohydrin (EPI) are two widely used molecules in chemical, pharmaceutical and food industry applications. However, their use in aqueous environments causes the formation of compounds, like monochloropropanediol (MCPD) and dichloropropanol (DCP), reported as dangerous for human health and therefore regulated by severe law restrictions. To identify the conditions leading to such species and design the corresponding processes in order to prevent their formation, hydrolysis and chlorination of EPI and GL, together with dehydrohalogenation of DCP and MCPD, have been systematically analysed. Different reaction conditions in terms of temperature, pH and chloride ion concentration have been experimentally investigated and the concentration of the involved species was tracked over time by gas chromatography and high-performance liquid chromatography. These experimental data were fitted through a kinetic model, which allowed a general expression of the observed rate constant of each reaction as a function of temperature and pH to be quantified. In particular, the reaction rates are conveniently expressed as combinations of three contributions: alkaline, neutral and acid. The corresponding rate laws explicitly account for the critical role of pH. The developed mechanistic model exhibits good prediction ability and may represent the basis for optimising processes employing EPI and GL.

中文翻译：

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pH 值对水解反应动力学的影响：以环氧氯丙烷和缩水甘油为例

缩水甘油 (GL) 和表氯醇 (EPI) 是化学、制药和食品工业应用中广泛使用的两种分子。然而，它们在水环境中的使用会导致形成化合物，如一氯丙二醇 (MCPD) 和二氯丙醇 (DCP)，据报道它们对人类健康有害，因此受到严格的法律限制。为了确定导致这些物种的条件并设计相应的工艺以防止它们的形成，EPI 和 GL 的水解和氯化，以及 DCP 和 MCPD 的脱卤化氢，已经进行了系统分析。在温度方面的不同反应条件，已经通过实验研究了 pH 值和氯离子浓度，并通过气相色谱法和高效液相色谱法随时间跟踪了相关物质的浓度。这些实验数据是通过动力学模型拟合的，该模型允许将观察到的每个反应的速率常数作为温度和 pH 值的函数的一般表达式进行量化。特别地，反应速率方便地表示为三种贡献的组合：碱性、中性和酸性。相应的速率定律明确说明了 pH 值的关键作用。所开发的机械模型表现出良好的预测能力，可以代表采用 EPI 和 GL 优化工艺的基础。这允许将观察到的每个反应的速率常数作为温度和 pH 值的函数的一般表达式进行量化。特别地，反应速率方便地表示为三种贡献的组合：碱性、中性和酸性。相应的速率定律明确说明了 pH 值的关键作用。所开发的机械模型表现出良好的预测能力，可以代表采用 EPI 和 GL 优化工艺的基础。这允许将观察到的每个反应的速率常数作为温度和 pH 值的函数的一般表达式进行量化。特别地，反应速率方便地表示为三种贡献的组合：碱性、中性和酸性。相应的速率定律明确说明了 pH 值的关键作用。所开发的机械模型表现出良好的预测能力，可以代表采用 EPI 和 GL 优化工艺的基础。