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

The migration of non-Brownian particles inside a droplet subjected to shear flow is investigated. The viscosity ratio, particle concentration, particle to droplet size ratio and capillary number are systematically varied. It was observed that particles migrate in the vorticity direction either towards or away from the equatorial plane. The main factor determining the migration direction is the viscosity ratio. The particle concentration and applied capillary number have no influence on the equilibrium distribution and only affect the time necessary to reach this distribution. In order to identify the flow profile, both velocity and shear rate magnitudes to which the particles inside the droplet are subjected, are numerically simulated using the Volume-of-Fluid method in a particle-free droplet/matrix system. The numerical predictions of the flow are used to evaluate the presence of possible driving mechanisms for cross-streamline particle motion, such as particle inertia and shear rate gradients. Depending on the conditions, the simulations reveal significant differences in the streamline profiles and shear rate gradients within the droplet. The observed steady state particle distributions can partially be explained by shear-induced migration towards zones of low shear rates and/or low streamline curvature. However, in complex flows, such as inside a deformed droplet, different migration mechanisms can occur simultaneously. Hence, confinement inside the droplet and potential secondary flows may also play a role.

Common cross-currently illuminated photochemical reactors lack energy efficiency to make them competitive in industry. The use of co- and counter-current illumination was previously proven to increase reactor performance, but these approaches made use of a collimated LED module whereby the used LED module itself having a lower than typical optical efficiency. In this paper, we study the use of non-collimated LEDs for the use in co- and counter-currently illuminated reactors. A ray tracing model was implemented in COMSOL and was validated using experimental data. Via these experimental data, the regime of no kinetic limitations was observed as conversion is not hampered by increasing light flux. Via the model results, it was determined that the most suitable light source for optimal light absorption by the reagent was the most collimated LED possible, in this case with a total viewing angle of 10°. The optimal reactor set-up uses the most reflective material, preferably aluminium or silver, to recuperate diverging light rays of the used wavelength. Furthermore, the wall thickness of the glass reactor must not be excessively thick, with an optimum at 1.5 mm wall thickness for this case. Regarding reagents and absorbance, it is best to use a higher concentration and reduce reactor length as this increases reactor performance under the condition that quantum yield is stable. Via the use of non-collimated light, it was determined that the entrance efficiency can be increased compared to a fully collimated light source, at the cost of reflection losses that increase with path length.

Determination of the experimental nucleation rate for crystallization in solution has been acknowledged as an important topic for a long time, as it improves the design and control of industrial cr...

The introduction of patterns on a membrane-solute interface has been suggested as an effective method to tackle the reduced flux and fouling issues. Herein, the effectiveness of using spray-modified non-solvent induced phase separation (s-NIPS) to create a variety of micrometer-level structured interfaces is now studied. Circular, triangular and rectangular patterns with different dimensions were successfully created on polyacrylonitrile membranes. The rectangular pattern height was varied from 500 to 1500 µm, which resulted in a proportional increase in clean water permeance from 590 ± 47 L m−2 h−1 bar−1 to 1345 ± 108 L m−2 h−1 bar−1 respectively. This coincided with some BSA rejection loss for the highest patterns, indicating the fragile nature of these tall features. No significant rejection losses were found for the smaller pattern heights (145–250 µm) as compared to flat membranes, while fluxes more than doubled still. The critical pressure was also increased substantially for patterned membranes and showed a proportionality with the pattern height. These experimental findings were correlated with the reduced foulant adhesion due to a shear-induced slip boundary layer at the membrane-solution interface. Computational fluid dynamics simulations further showed higher shear stress values due to flow constriction within the membrane’s valley regions. These findings indicate the high potential of s-NIPS patterned membranes in long-term industrial applications by requiring less membrane area for a given application and reducing cleaning interventions.

The energy transition is one of the main challenges of our society and therefore a major driver for the scientific community. To ensure a smart transition to a sustainable future energy scenario different technologies such as energy harvesting using solar cells or windmills and chemical storage in batteries, super-capacitors or hydrogen have to be developed and ultimately deployed. New fabrication approaches based on additive manufacturing and the digitalization of the industrial processes increase the potential to achieve highly efficient and smart technologies required to increase the competitiveness of clean energy technologies against fossil fuels. In this frame, the present roadmap highlights the tremendous potential of 3D printing as a new route to fully automate the manufacturing of energy devices designed as digital files. This article gives numerous guidelines to maximize the performance and efficiency of the next generation of 3D printed devices for the energy transition while reducing the waste of critical raw materials. In particular, the paper is focused on the current status, present challenges and the expected and required advances of 3D printing for the fabrication of the most relevant energy technologies such as fuel cells and electrolysers, batteries, solar cells, super-capacitors, thermoelectric generators, chemical reactors and turbomachinery.

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.

ispartof: JOURNAL OF CRYSTAL GROWTH vol:582 status: published

We systematically study the field equations of f (Q) gravity for spherically symmetric and stationary metric-affine spacetimes. Such spacetimes are described by a metric as well as a flat and torsionless affine connection. In the symmetric teleparallel equivalent of general relativity (STEGR), the connection is pure gauge and hence unphysical. However, in the nonlinear extension f (Q), it is promoted to a dynamical field which changes the physics. Starting from a general metric-affine geometry, we construct the most general static and spherically symmetric forms of the metric and the affine connection. We then use these symmetry reduced geometric objects to prove that the field equations of f (Q) gravity admit general relativity (GR) solutions as well as beyond-GR solutions, contrary to what has been claimed in the literature. We formulate precise criteria, under which conditions it is possible to obtain GR solutions and under which conditions it is possible to obtain beyond-GR solutions. We subsequently construct several perturbative corrections to the Schwarzschild solution for different choices of f(Q), which in particular include a hair stemming from the now dynamical affine connection. We also present an exact beyond-GR vacuum solution. Lastly, we apply this method of constructing spherically symmetric and stationary solutions to f(T) gravity, which reproduces similar solutions but without a dynamical connection. ISSN:1550-7998 ISSN:0556-2821 ISSN:1550-2368

Continuous-flow simplified electrochemically mediated atom transfer radical polymerization (seATRP) was achieved for the first time without supporting electrolytes (self-supported) using a novel sonicated tubular microreactor. Polymerizations of different acrylic monomers were carried out under different applied currents. The reaction was fast with 75% conversion achieved at ambient temperature in less than 27 minutes. Results also showed good evolution of molecular weight and maintained narrow molecular weight distribution. The reaction rate can be further manipulated by tuning the applied current. Sonication under proper conditions was found to be able to significantly improve both reaction rate and controllability. Self-supported reactions also enable more environmentally friendly and cost-effective operations. ispartof: CHEMICAL SCIENCE vol:13 issue:42 pages:12326-12331 ispartof: location:England status: published

The equivalence principle and its universality enables the geometrical formulation of gravity. In the standard formulation of General Relativity (GR) a la Einstein, the gravitational interaction is geometrized in terms of the spacetime curvature. However, if we embrace the geometrical character of gravity, two alternative, though equivalent, formulations of GR emerge in flat spacetimes, in which gravity is fully ascribed either to torsion or to non-metricity. The latter allows a much simpler formulation of GR oblivious to the affine spacetime structure, the Coincident General Relativity (CGR). The entropy of a black hole can be computed using the Euclidean path integral approach, which strongly relies on the addition of boundary or regulating terms in the standard formulation of GR. A more fundamental derivation can be performed using Wald's formula, in which the entropy is directly related to Noether charges and is applicable to general theories with diffeomorphism invariance. In this work we extend Wald's Noether charge method for calculating black hole entropy to spacetimes endowed with non-metricity. Using this method, we show that CGR with an improved action principle gives the same entropy as the well-known entropy in standard GR. Furthermore the first law of black hole thermodynamics holds and an explicit expression for the energy appearing in the first law is obtained., Classical and Quantum Gravity, 39 (23), ISSN:0264-9381, ISSN:1361-6382

ispartof: Chemical Engineering And Processing-Process Intensification vol:181 status: accepted

A modular multiphase flow crystallizer set-up for the continuous crystallization of paracetamol with an in-line nuclei generator has been developed. Gas bubbles are introduced in a capillary to provide heterogeneous nucleation sites and enhance the nucleation rate. Taking advantage of the separate nucleation and growth sections, control over crystal size distribution is achieved without compromising its span. Comparison with batch growth showed smaller crystal sizes as well as narrower span for the continuous growth. Different configurations of the setup were investigated with regard to the presence of the gas in nucleation and growth sections. Reproducible results were only obtained when gas is present both in the nucleation section (as microbubbles) and in the growth section (as gas slugs). Yields of up to 71% were obtained. Taking the growth time and temperature as varying parameters, the mean crystal size could be manipulated.

This study addresses the scalability of in-house designed, and 3D printed structured porous reactors for liquid-liquid reactions. The base structure of these porous reactors consists of cylindrical fibres in defined geometrical arrangements. Their scale-up was realized by increasing the reactor diameter by a factor of 1.5 and 2 respectively while keeping the fibre dimensions constant. Also, the effect of altering the fibre dimensions in proportion to the scale-up factor was assessed. The reactors were characterized in terms of their biphasic heat and mass transfer properties. In stratified flow, the scaled-up structured porous reactors exhibited high interfacial mass transfer coefficients (kLa) at residence times

Continuous-flow microreactor technology has been embraced by researchers in academia and industry due to its excellent transport properties and the increased safety and control over challenging chemical transformations. Despite its popularity, scaling the benefits associated with the microenvironment has proven to be a daunting challenge. This review provides an up-to-date overview concerning the different scale-up approaches of micro/milli-reactors, including numbering up (both internal and external), sizing up (increasing length, geometry similarity and constant pressure drop strategies) and a combination of numbering up and sizing up. The strategies, design principles and applications of each approach have been discussed in detail. Each scale-up approach has its merits and limitations. However, scale-up factors, that are required in the fine chemical and pharmaceutical industry, are within reach when different scale-up approaches are combined.

Summarization: Ultrasound-assisted crystallization is a promising process for the production of crystals within a size distribution width. Toward the direction of attaining high-quality crystals, this article proposes and assesses a theoretical feedback control scheme that can be applied in a continuous tubular crystallizer. In this crystallizer, the antisolvent crystallization of aspirin (a pharmaceutical ingredient) in water (an antisolvent) and ethanol (a solvent) takes place under ultrasound. Initially, a dynamic model is developed and includes the aspirin concentration variations while also taking into account temperature modifications in the inlet. After model validation, a PI control scheme is finely tuned, implemented theoretically, and critically assessed at the (i) trajectory control of the crystal length (average size), (ii) alleviation of suddenly emerged disturbances (e.g., solvent flow rate, inlet temperature), and (iii) a combination of worst-case operating scenarios. As identified, the proposed controller can offer a practical platform that can be readily applied to different scales and geometries in continuous tubular crystallizers operating with ultrasound. During all simulations, the produced crystals maintained high quality. Presented on: Industrial & Engineering Chemistry Research

We discuss the most general field equations for cosmological spacetimes for theories of gravity based on non-linear extensions of the non-metricity scalar and the torsion scalar. Our approach is based on a systematic symmetry-reduction of the metric-affine geometry which underlies these theories. While for the simplest conceivable case the connection disappears from the field equations and one obtains the Friedmann equations of General Relativity, we show that in $f(\mathbb{Q})$ cosmology the connection generically modifies the metric field equations and that some of the connection components become dynamical. We show that $f(\mathbb{Q})$ cosmology contains the exact General Relativity solutions and also exact solutions which go beyond. In $f(\mathbb{T})$~cosmology, however, the connection is completely fixed and not dynamical., Comment: 17 pages, no figures

Ultrasound is frequently applied in crystallization to enhance nucleation and achieve crystal sizes within a narrow range. In this work, a mathematical model is developed, which couples the acousti...

Ultrasonic microreactors are increasingly applied to particle synthesis, crystallization processes, or organic synthesis involving solids because of the clogging prevention offered by ultrasound ir...

Continuous flow reactor technology has a proven track record in enabling photochemical transformations. However, transfer of a photochemical batch process to a flow protocol often remains elusive, ...

ispartof: CHEMPHOTOCHEM vol:4 issue:10 pages:5181-5192 status: published

ispartof: CHEMPHOTOCHEM vol:4 issue:10 pages:5193-5200 status: published

Herein, the control of enhanced protein nucleation in microdroplets under high supersaturation ratios is discussed, where lysozyme is used as a model protein. This study is conducted to evaluate the influence of droplet volume on the size and number of crystals through isothermal and double-pulse temperature experiments performed in a droplet-based microreactor. Lysozyme concentration is estimated during and at the end of the crystallization experiments, based on analytical and experimental results, respectively. Furthermore, nucleation rate in microdroplets is calculated following a Poisson distribution, and crystal growth is assumed to be diffusion-controlled. Controlled and enhanced lysozyme nucleation is achieved in smaller droplet volumes and under certain double-pulse temperature conditions. The droplet volume effect becomes more important at lower supersaturation ratios as the crystal number follows the droplet volume increase, while at higher supersaturation ratios, the crystal number does not considerably vary with the droplet volume. Finally, the proposed analysis can be adopted as an experimental design tool and extended to the crystallization of other macromolecules.

The objective of this work is to establish an experimental approach to scale-up the production of melamine formaldehyde (MF) microcapsules from a batch lab-scale to a pilot-scale inline rotor stator mixer (RSM). The inline RSM is operated in a continuous recycle mode, allowing multiple passes of the emulsion through the intensive mixing zone during continuous production. The liquid is continuously recirculated directly to the RSM, without a holding vessel, as is the case in conventional batch recirculation emulsification. The setup is operated at feed flow rates of 0.24 kg/h - 20 kg/h. Parameters including the Weber number, tip speed and energy density are investigated to correlate the mean capsule size of the batch and flow process. Rotational speeds range from 3000 to 26,000 rpm. The dimensionless maximum diameter correlated well with the Weber number to the power -0.4, for both devices operated at the same residence time. Volume and number based mean diameters showed little influence of the feed flow rate in the continuous recycle mode of operation. This inline RSM setup is therefore an ideal tool to optimize emulsification processes at lab scale and increase production by increasing the feed flow rate, while maintaining rotor-stator geometry.

We propose a new non-perturbative method for studying UV complete unitary quantum field theories (QFTs) with a mass gap in general number of spacetime dimensions. The method relies on unitarity formulated as positive semi-definiteness of the matrix of inner products between asymptotic states (in and out) and states created by the action of local operators on the vacuum. The corresponding matrix elements involve scattering amplitudes, form factors and spectral densities of local operators. We test this method in two-dimensional QFTs by setting up a linear optimization problem that gives a lower bound on the central charge of the UV CFT associated to a QFT with a given mass spectrum of stable particles (and couplings between them). Some of our numerical bounds are saturated by known form factors in integrable theories like the sine-Gordon, E8 and O(N) models., 57 pages, 12 figures. In v3 typos corrected, references added