Kinetic Reactive Thin Layer Extraction

When the separation of two closely related compounds by liquidliquid extraction is necessary, conventional wisdom indicates that a selective extractant must be found that will discern between the two by associating with each to different equilibrium compositions. Kinetic reactive thin layer extraction (KRTLX) offers an alternative route that does not rely on finding such a particularly selective host, provided the rates of the chemical reactions between each of the two components and the host are sufficiently differentiated. The optimal design of a KRTLX application requires kinetic data pertaining to the reactions between the components to be separated and the active host in the extractant. The actual implementation of a KRTLX application requires the availability of extraction equipment that allows control of the time span of the reactions, such as is availed by the TLX extractor. KRTLX is modeled and explored numerically on the basis of published kinetic data. A calculated example, concerning the separation of two carboxylic acids, is evaluated, and compared to a conventional equilibrium reactive liquid extraction scheme. In this example, KRTLX yields two distinct streams of substantial purity at high yield in relatively few stages, thus turning out to be both superior in performance and economically advantageous.