Shining Light on the Coiled-Flow Inverter—Continuous-Flow Photochemistry in a Static Mixer

Abstract

We present the use of a coiled-flow inverter (CFI) for continuous-flow photochemistry at competitive photon efficiencies. The static mixer is placed inside a reaction chamber, whereas a dark adjacent chamber allows for orthogonal online reaction monitoring via fluorescence spectroscopy. The study of the aqueous visible-light induced degradation of fluorescein with ZnO-APTMS-Au photocatalyst showcases the challenge of uniformly irradiating photoreactors with nonplanar surfaces. Fluorescence imaging is introduced as a simple method to visualize spatial gradients in the irradiance at the outer surface of such complex photoreactor geometries, allowing the analysis of photoreactor efficiency as a function of lighting configuration. We compared uniaxial and multiaxial lighting configurations and discuss the challenges associated with attaining uniform irradiance distribution of incident light on coiled-flow inverters, where chaotic advection combats light attenuation. A first calculation of the photochemical space-time yield (PSTY) for a "photo-CFI" indicates that a competitive photon efficiency can be reached as compared to other photoreactor designs.

Coiled flow inverter mediated synthesis of activated carbon fiber-supported Ni nanoparticles

“…Owing to their tremendous advantages over other continuous flow devices, CFIs have been used in various domains such as multiphase flows, 34,35 heat exchangers, 30 inline mixers, 28 and liquid–liquid extractors. 36,37 CFIs have also been successfully used as reactors for continuous protein refolding, 38 polymerization reactions, 39 photocatalytic degradation, 40 and the two-phase reactions of gas–liquid and liquid–liquid systems. 41–43…”

Catalytic reduction of in-flow aqueous Cr(vi) using a slurry of activated carbon fiber-supported Ni nanoparticles in a coiled flow inverter

“…[7][8][9][10][11][12] Recently, its utility has been extended to a wider domain of polymerization reactions, synthesis of nanoparticles, and photocatalytic reactions. 6,[13][14][15][16] Mechanistically, the curvature-induced secondary flow and flow inversions occur in the laminar flow regime, with a delayed onset of the turbulent flow. The effective mixing and uniformity in the flow can promote the CFI technology for performing heterogeneous catalytic reactions under flow conditions, with an aqueous slurry or suspension of catalytic particles dispersed in reaction media.…”

Process intensification through staggered herringbone micro-channels: Mass transfer enhancement to a reactive wall

“…For these applications flow inverter structures (FIS) can give a better performance because they maximize the driving force by bringing material from the wall to the bulk and vice versa [36,37]. Flow inversion for process intensification was explored by Saxena and Nigam (1984) [38] and later by others for a vast range of application [37,[39][40][41][42][43][44][45][46].…”