Recovery of short‐lived chemical species in a Couette flow reactor

Abstract

AbstractA new technique for studying and recovering short‐lived chemical intermediate species has been developed using a Couette reactor, which is an open one‐dimensional reaction‐diffusion system. Reaction occurs in the annulus between concentric cylinders with the inner one rotating and the outer one at rest. Fresh reagents are in contact with the ends of the annulus, but there is no net axial flow. The axial transport arising from the hydrodynamic motion is effectively diffusive, but has a diffusion coefficient 3 to 5 orders of magnitude larger than that of molecular diffusion. The oxidant (ClO2−) and reductant (I−) of an autocatalytic reaction are fed at opposite ends of the reactor. The reactants diffuse toward each other and react, forming a steady, sharp chemical front and a stable spatial concentration band of unstable intermediate species (HOCl) in the front region. Unstable intermediate species are thus stabilized at a well‐defined spatial position where they can be recovered and studied. The experiments and numerical simulations demonstrate that the faster the reaction rate, the stabler the chemical front and the more effective the recovery of unstable intermediate species.