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A novel ultrasonic microreactor is demonstrated for the heterogeneous silyl radical-mediated metallaphotoredox cross-electrophile coupling.

Nucleation kinetics play a fundamental role in the design and control of crystallization processes. Understanding how crystallization conditions impact different nucleation mechanisms and the overall nucleation kinetics will lead to improved control over the nucleation process. Herein, a comparative study of the nucleation kinetics for primary, secondary and ultrasound-induced paracetamol crystallization in stirred microvials is presented. The results are evaluated using the classical nucleation theory by assessing the influence of the nucleation mechanism on the kinetic and thermodynamic nucleation parameter. Primary nucleation is promoted by the presence of impurities and exogeneous surfaces. It is also shown that seeding a single crystal into the solution lowers the thermodynamic threshold for nucleation, even without fragmentation of the parental crystal. The addition of ultrasound to the crystallization process on the other hand affects the kinetic part of the nucleation process.

Computer-aided fabrication technologies combined with simulation and data processing approaches are changing our way of manufacturing and designing functional objects. Also in the field of catalytic technology and chemical engineering the impact of additive manufacturing, also referred to as 3D printing, is steadily increasing thanks to a rapidly decreasing equipment threshold. Although still in an early stage, the rapid and seamless transition between digital data and physical objects enabled by these fabrication tools will benefit both research and manufacture of reactors and structured catalysts. Additive manufacturing closes the gap between theory and experiment, by enabling accurate fabrication of geometries optimized through computational fluid dynamics and the experimental evaluation of their properties. This review highlights the research using 3D printing and computational modeling as digital tools for the design and fabrication of reactors and structured catalysts. The goal of this contribution is to stimulate interactions at the crossroads of chemistry and materials science on the one hand and digital fabrication and computational modeling on the other. ispartof: Chemical Society Reviews vol:47 issue:1 pages:209-230 ispartof: location:England status: published

The hydrodynamics and mass transfer characteristics in liquid-liquid flow through various structured and well-defined porous reactors are characterized using laser based optical measurements (PIV and PLIF) in combination with chemical extraction methods. We investigate both high and low interfacial tension fluid systems (toluene-water and n-butanol-water), and we have identified that depending on the fluid properties different design parameters of the porous structures play a crucial role in determining the overall mass transfer performance. In general, the porous reactors enhance slug breakup, resulting in lower mean slug lengths for both phases compared to an empty tube and an associated enhancement in surface renewal velocities. The designed porous milli-scale reactors provide enhanced mass transfer performance, with an order of magnitude reduced energy dissipation compared to conventional milli-scale packed bed reactors. We thank Adriaan Spierings (inspire AG - innovation center for additive manufacturing, Switzerland) for manufacturing the custom designed porous reactors. S. K. acknowledges funding from Marie Curie CIG and FWO-Odysseus II.

We present a novel technique to quantify interfacial mass transfer in gas–liquid flows in capillaries. A model was developed which allowed the relationship between absorption fluxes and bubble size changes to be established. Depending on the observed absorption rate, two limiting and simplifying cases for low and high absorption rates were suggested. For both cases, the flux was viewed as an input function which optimally tracked the observed bubble velocity, bubble volume, and unit cell volume change. For the case of low absorption rates, the mass transfer coefficient can be assumed to be constant and the model was fitted to experimental data by adjusting the value of this mass transfer coefficient. The bubble velocities were extracted from flow images using the cross-correlation between measured signal intensities for nearby pixels. Bubble and unit cell volumes were not determined by individual tracking, but a probability density function was estimated for each location in the capillary which contains the bubble and unit cell sizes of all bubbles passed. This allows the model to be fitted to an ensemble of bubbles making the procedure more robust. The developed model was validated for CO2 absorption in a buffer solution, and then applied to CO2 absorption using the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]), which exhibits high absorption rates and less known thermophysical properties. The developed technique is able to quantify interfacial fluxes for a wide range of gas and liquid flow rates.