NMR Spectroscopic Study of Reaction Kinetics in Mixtures of Formaldehyde, Water, and Butynediol

Butynediol is an important intermediate in the chemical industry and is produced from acetylene and aqueous formaldehyde. Mixtures of formaldehyde + water + butynediol are complex reacting multicomponent systems in which oligomerization reactions of formaldehyde with both water and butynediol occur. The chemical equilibria of the reactions of formaldehyde with butynediol were studied recently by quantitative NMR spectroscopy (Berje et al., DOI: 10.1002/AIC.15788). The present work complements this by a kinetic study of these reactions. Aqueous formaldehyde solutions were diluted with aqueous butynediol solutions, and the kinetic response was monitored by 1H NMR spectroscopy. Most of the experiments were carried out in NMR sample tubes; additional experiments were carried out with a micromixer NMR probe to extend the studied range to kinetics with time constants well below 1 min. The new reaction kinetic data cover temperatures between 293.15 and 328.15 K and pH values between 3 and 6. A reaction kinetic model was developed based on the equilibrium model from the previous study, and the reaction kinetic constants were determined from the new data. Furthermore, new reaction kinetic data for the system formaldehyde + water were measured, which extend the available data on that system to faster kinetics. These new data confirm the mole fraction-based reaction kinetic model of Hahnenstein et al. (DOI: 10.1021/ie00041a003).

丁炔二醇（Butynediol）是化学工业中的重要中间体，可由乙炔与甲醛水溶液反应制得。甲醛-水-丁炔二醇混合体系属于复杂的反应性多组分系统，其中甲醛可分别与水和丁炔二醇发生低聚反应。近期已有研究通过定量核磁共振波谱（NMR）对甲醛与丁炔二醇的反应化学平衡进行了探究（Berje等人，DOI: 10.1002/AIC.15788）。本研究通过对上述反应开展动力学研究，对前述工作进行了补充。实验中，我们用丁炔二醇水溶液对甲醛水溶液进行稀释，并通过1H核磁共振波谱（1H NMR）监测反应动力学过程。大部分实验在核磁共振样品管中完成；为将研究范围拓展至时间常数远小于1分钟的动力学过程，我们额外采用了微混合器核磁共振探头开展实验。本次获取的全新反应动力学数据覆盖的温度范围为293.15 K至328.15 K，pH范围为3至6。本研究基于前述工作中的平衡模型构建了反应动力学模型，并通过全新实验数据拟合得到了反应动力学常数。此外，我们还测定了甲醛-水体系的全新反应动力学数据，将该体系已有动力学数据的覆盖范围拓展至更快的反应过程。上述全新实验数据验证了Hahnenstein等人基于摩尔分数构建的反应动力学模型（DOI: 10.1021/ie00041a003）。