Budroni M A, Thomas C, De Wit A
Université libre de Bruxelles (ULB), Nonlinear Physical Chemistry Unit, Faculté des Sciences, CP231, 1050 Brussels, Belgium.
Phys Chem Chem Phys. 2017 Mar 15;19(11):7936-7946. doi: 10.1039/c6cp08434f.
Chemical reactions can impact mixing in partially miscible stratifications by affecting buoyancy-driven convection developing when one phase dissolves into the other one in the gravity field. By means of combined nonlinear simulations and experiments, we explore the power of an A + B → C type of reaction to either enhance or refrain convective dissolution with respect to the nonreactive system depending on the relative contribution to density of the dissolving species A, of the reactant B initially dissolved in the host phase and of the product C. Nonlinear simulations are performed by solving reaction-diffusion-convection equations describing the dissolution and reactive dynamics when a less dense phase of A is layered on top of a reactive denser solution of B, in which A is partially miscible with a given solubility. The spatio-temporal dynamics and convective patterns observed in the numerical study compare favorably with experiments carried out with (i) a liquid alkyl-formate stratified on top of an aqueous solution in which the ester dissolves and undergoes a hydrolysis reaction and (ii) gaseous CO dissolving into an aqueous solution of NaOH. We show that the same reaction type can induce a different effect on the convective dynamics depending on the reactant in the host phase. The efficiency of convective dissolution in partially miscible systems can hence be controlled by the chemicals present in the host fluid and their concentration. The direct comparison between the convective dynamics observed during CO dissolution in an aqueous phase and in the ester/water stratification validates the latter as a convenient liquid-liquid model system for the interpretation of the impact of chemical reactivity in geological CO sequestration.
化学反应可以通过影响浮力驱动的对流来影响部分互溶分层中的混合，当一相在重力场中溶解到另一相中时，浮力驱动的对流就会产生。通过结合非线性模拟和实验，我们研究了A + B → C型反应的作用，即根据溶解物种A、最初溶解在主体相中且为反应物的B以及产物C对密度的相对贡献，相对于非反应系统，该反应是增强还是抑制对流溶解。当较低密度的A相层叠在B的反应性较高密度溶液之上时，通过求解描述溶解和反应动力学的反应-扩散-对流方程来进行非线性模拟，其中A与给定溶解度部分互溶。数值研究中观察到的时空动力学和对流模式与以下实验结果相当吻合：（i）液体甲酸烷基酯层叠在酯溶解并发生水解反应的水溶液之上；（ii）气态CO溶解到NaOH水溶液中。我们表明，相同的反应类型根据主体相中的反应物对对流动力学可产生不同的影响。因此，部分互溶系统中对流溶解的效率可以通过主体流体中存在的化学物质及其浓度来控制。在水相中CO溶解过程与酯/水层叠过程中观察到的对流动力学之间的直接比较，证实了后者作为一种方便的液-液模型系统，可用于解释地质CO封存中化学反应性的影响。
