Flow Setup Research Articles

Experimental study and kinetic modeling of continuous flow conversion of fructose to 5-(chloromethyl)furfural using micro- and millistructured coiled flow inverter

5-(chloromethyl)furfural (CMF) can be derived from renewable feedstocks and is considered as potentially biorenewable platform chemical. Experimental investigations and kinetic modeling of the conversion of d-fructose with aqueous HCl to CMF by a reactive extraction was undertaken with a continuous flow setup. Experiments were performed under variation of extraction solvents, reaction temperatures, fructose concentrations, and reactor diameters for various residence times so that time evolution of species concentration allowed for detailed kinetic analysis. Anisole, a solvent ranked as “recommended” by the CHEM21 selection guide was found to be an environmentally more benign alternative to the typically employed chlorinated extraction solvents. A maximum CMF yield of 79 % was obtained at 90 °C within a residence time of 265 s. Kinetic modeling under non-limiting mass transfer conditions showed general consistency of experimental data with the view that the reactions take place solely in the aqueous phase and that CMF is formed consecutively via 5-(hydroxymethyl)furfural (HMF) from fructose. Under these conditions no side-product formation from CMF and HMF was discernible. Activation energies for conversion of fructose to HMF of 94 ± 8 kJ/mol, of HMF to CMF of 85 ± 6 kJ/mol, and for conversion of CMF to HMF of 74 ± 25 kJ/mol were observed. To the best of our knowledge this study provides the first detailed kinetic investigation of biphasic CMF synthesis under variation of several experimental parameters in continuous flow.

Cost-effective, scalable and smartphone-controlled 3D-Printed syringe pump - From lab bench to point of care biosensing applications

Laboratories all over the word use syringe pumps every day for a multitude of purposes. The market of syringe pumps is limited, as it does not consider the broad range of specifications required by different researchers. In this work, we present a 3D printed syringe pump designed to be affordable, customizable, and extremely user friendly while still maintaining reliability and precision. The pump, thanks to its flexible design and smartphone-controlled interface, can be used in educational settings as well as in biological and chemical laboratories. The presented syringe-pump is used in this work to run a light catalyzed polymerization of butyl methacrylate using visible light, in a continuous flow setup.

Open-source finite volume solvers for multiphase (n-phase) flows involving either Newtonian or non-Newtonian complex fluids

Two new control volume solvers multiFluidInterFoam and rheoMultiFluidInterFoam are presented for the simulation of Newtonian and non-Newtonian n-phase flows (n≥2), respectively, fully accounting for interfacial tension and contact-angle effects for each phase. The multiFluidInterFoam solver modifies certain crucial aspects of the regular multiphaseInterFoam solver provided by OpenFOAM for Newtonian flows, improving its efficiency and robustness, but most importantly improving considerably its accuracy for surface tension driven flows. The new solver uses the volume-of-fluid (VOF) method based on the MULES method and artificial interface compression for the interface capturing, in combination with a suitable continuum surface force model; i.e. the interfacial tension coefficient decomposition method is employed to treat pairings of interfacial tension between the phases. VOF smoothing is also implemented by applying a Laplacian filter on the distribution of volume fractions, and the SIMPLEC algorithm is employed for the velocity–pressure coupling. The above algorithm has also been extended with the development of the rheoMultiFluidInterFoam solver which is capable of fully taking into account complex non-Newtonian effects (e.g. yield stress, viscoelasticity, etc.) of the involved liquids. To this end, the developed solver incorporates the RheoTool toolbox (Pimenta and Alves, 2017), utilizing a wealth of constitutive equations suitable for modeling different types of fluids with complex rheology. Our solvers are tested for both the implementation of the surface tension and of the constitutive equations in a wide range of different flow setups, considering typical benchmark two-phase and three-phase flows, such as the cases of dam break with an obstacle, spreading of a floating lens, a levitating drop, and a bubble rising in an ambient fluid; flows involving Newtonian, viscoplastic and viscoelastic liquids have been considered. Comparisons against analytical solutions or previously published numerical data are performed clearly demonstrating the capability of the new solvers to efficiently and accurately simulate interfacial tension dominated three-phase flows (and n-phase flows in general) for both simple and complex liquids.

Water Oxidation to Hydrogen Peroxide on Carbonaceous Materials

Hydrogen peroxide (H2O2) is one of the most important chemicals used in the chemical industry. It has been widely utilized in pulp and paper manufacturing, chemical synthesis, wastewater management, and disinfection.1 The primary industrial approach to producing H2O2 is via the fossil-based anthraquinone process - an energy-demanding multi-step process requiring high-cost catalysts and generating substantial volumes of waste. Another route to the classic anthraquinone process is the electrochemical production of H2O2 from oxygen (O2) and water (H2O). This electrochemical route based on renewable energy is an appealing “green” alternative.Our research group has been extensively working on the electrochemical production of H2O2 through anodic water oxidation using various electrode materials, including metal oxides, commercial carbon materials, and boron-doped diamond (BDD). Besides the electrode material, a suitable electrolyte is equally essential to achieve high H2O2 concentrations and production rates. The role of carbonate ions (HCO3 - and CO3 2-) for producing H2O2 has been investigated using commercial carbon fiber paper (CFP). The electrolyte pH was correlated with the activity of CO3 2- ions in enhancing H2O2 production. Thereby, a cyclic mechanism of H2O2 generation involving the oxidation of CO3 2- ions to peroxodicarbonate (C2O6 2-) species has been proposed.2 The role of the CO3 2- ions in enhancing the anodic H2O2 production was further studied in a continuous flow reactor using BDD anodes. The flow rate and setup configuration for 2e- water oxidation to H2O2 have been optimized at current densities up to 700 mA cm-2, with an impressive H2O2 production rate and faradaic efficiency. Additionally, the role of a chemical stabilizer in avoiding the H2O2 decomposition in the flow system has been addressed. The importance of electrolyte composition, pH, operating parameters, and cell setup to enhance the production of H2O2 at the anode was shown. Finally, outstanding H2O2 yields were obtained in continuous flow for at least 30 hours. References Perry, S. C.; Pangotra, D.; Vieira, L.; Csepei, L.-I.; Sieber, V.; Wang, L.; Ponce de León, C.; Walsh, F. C., Electrochemical synthesis of hydrogen peroxide from water and oxygen. Nat. Rev. Chem. 2019, 3 (7), 442-458.Pangotra, D.; Csepei, L.-I.; Roth, A.; Ponce de León, C.; Sieber, V.; Vieira, L., Anodic production of hydrogen peroxide using commercial carbon materials. Appl. Catal. B Environ. 2022, 303, 120848.

Continuous flow synthesis of azobenzenes via Baeyer-Mills reaction.

Azobenzene, as one of the most prominent molecular switches, is featured in many applications ranging from photopharmacology to information or energy storage. In order to easily and reproducibly synthesize non-symmetric substituted azobenzenes in an efficient way, especially on a large scale, the commonly used Baeyer–Mills coupling reaction was adopted to a continuous flow setup. The versatility was demonstrated with a scope of 20 substances and the scalability of this method exemplified by the synthesis of >70 g of an azobenzene derivative applied in molecular solar thermal storage (MOST) systems.

Thermofluidics and entropy analysis of couple stress Casson fluid in a channel with stretching walls

The paper investigates thermo-fluidics and entropy generation for a couple stress Casson fluid flow in a porous medium channel composed of two parallel stretching walls. Both the walls maintained at different temperatures stretch linearly in their own planes. The flow set-up caused by the entrainment of the fluid by the stretching walls and temperature difference constitutes a sixth-order nonlinear boundary value problem after similarity transformation. Two different methods viz. Differential Transform Method and Runge–Kutta Fehlberg Method are exploited to treat the system analytically as well as numerically. The effects of pertinent parameters on coefficient of skin friction, Nusselt number, velocity, temperature and inherent thermodynamic irreversibility are shown by tables and graphs and discussed. It is found that the skin friction and Nusselt number increase substantially with increasing values of characteristic length and couple stress parameter and decrease with the increasing values of permeability and Casson parameter, respectively. The computations have been carried out on the MAPLE programming language.

Stress modelling using cellular automata for block caving applications

In underground mining, rock mass stress is commonly modeled as a continuum. However, in block cave mining discrete modelling should be used to properly represent the stress over the extraction level in the broken column where there are high rock columns of large rock fragments. Unfortunately, we lack methods that use discrete modelling of stress in the broken column at block caving scale. In this work, we propose a vertical stress model of granular material to simulate static and dynamic flow conditions. The model is developed within a gravity flow simulator based on cellular automata to simulate the scale of the problem and flow conditions. The vertical stress model proposed is calibrated through four experimental models for the static condition. Then, based on the results from experimental testing, the dynamic condition is calibrated and compared with different flow scenarios. The results show that the proposed model can correctly simulate the vertical stresses in static conditions as well as dynamic conditions under the different flow setups tested. This vertical stress model with its flow simulator based on cellular automata has the potential to be applied at block caving scale once calibration parameters are defined.

Detachable all-carbon-linked 3D covalent organic framework films for semiconductor/COF heterojunctions by continuous flow synthesis

Detachable all-carbon-linked 3D covalent organic framework films for semiconductor/COF heterojunctions by continuous flow synthesis

A Fruitful Decade of Organofluorine Chemistry: New Reagents and Reactions

A Fruitful Decade of Organofluorine Chemistry: New Reagents and Reactions

Catalytic Synthesis of Methyl 9,10‐dihydroxystearate from Technical Feedstocks in Continuous Flow via Epoxidation and Hydrolysis

AbstractThe sequence of the homogeneously Ru‐catalyzed epoxidation of methyl oleate and acid‐catalyzed hydrolysis of the corresponding epoxide methyl 9,10‐epoxy stearate is successfully transferred from batch into flow mode, allowing for the continuous production of methyl 9,10‐dihydroxystearate. Thereby, methyl oleate is first converted up to 97% within 14 min at excellent selectivity in the epoxidation using aqueous hydrogen peroxide as the sole oxidant. In the subsequent hydrolysis, a residence time of 10 min is sufficient for quantitative conversion of the epoxide. The desired, pure vicinal diol is isolated upon crystallization from the crude reaction mixture in an integrated process starting from technical grade (91.5%) substrate. The isolated yield is increased upon the addition of water as a green antisolvent from 75% up to 97%. Finally, the concept is transferred to methyl oleate of even lower purity (76%), still obtaining an isolated yield of 66% of the vicinal diol. Thus, the integration of sequential epoxidation and hydrolysis into continuous flow and subsequent crystallization allows for high conversion and selectivities within a total residence time of 27 min, corresponding to a space–time yield of 190 g h−1 L−1 in the epoxidation and 164 g h−1 L−1 in the hydrolysis, respectively.Practical applications: The modular flow setup enables the targeted functionalization toward the epoxide intermediate or the vicinal diol. Both offer versatile applications for the production of polymers, surfactants, or toward further conversion as in oxidative cleavage starting from methyl oleate. The application of flow chemistry offers advantages for the safe handling of hydrogen peroxide even at high temperatures. With fats and oils being natural substances, oleochemicals such as fatty acid methyl esters are typically available in technical purity so that efficient strategies for the isolation of pure products are of need. Crystallization of the product is promising, as additional organic solvents are not required. Thus, using the difference in melting point and solubility behavior of the desired product compared to other compounds is a promising method for the applicability of renewable resource‐based substrate mixtures.

Front Cover: Electrochemical Hydroxylation of Electron‐Rich Arenes in Continuous Flow (Eur. J. Org. Chem. 20/2022)

The Front Cover demonstrates that electrochemistry in continuous flow is so convenient and reliable that even kids could do it. Electrochemical hydroxylation of sensitive electron-rich arenes was achieved by the implementation of a flow setup. Our goal is to motivate organic chemists, who tend to be quite conservative, to apply the modern techniques in their everyday research and explore new reaction pathways. Cover artwork by Alina Andreyenka. More information can be found in the Research Article by M. Ošeka et al.

Stability of flow in a channel with repeated flow-facing wedge-shaped protrusions

Motivated by an interest in inciting instabilities and mixing for heat transfer enhancement in ducts, flow in a channel with repeated wedge-shaped protrusions is considered for various blockage ratios (wedge height to duct height), pitch (distance between wedges) and wedge angles. The stability of the two-dimensional base flow and its dependence on the geometric parameters is elucidated through a global linear stability analysis. A linearly unstable two-dimensional mode was found, contrasting similar confined flow set-ups. However, the primary instability is a three-dimensional mode manifesting as counter-rotating streamwise vortices over the wedge tip. Analysis of the kinetic energy budget indicates a lift-up mechanism leading to instability, with the dominant energy gain of the global three-dimensional mode due to shear in the base flow. Structural sensitivity and receptivity of the instability to momentum forcing identifies the core of the instability and locations important for flow control. An endogeneity approach is used to show that the local perturbation pressure gradient component dominates the distribution of the local contribution to the growth rate of the linear global eigenmode in most cases considered, despite its net contribution being identically zero. Weakly nonlinear Stuart–Landau analysis reveals that the primary bifurcation is supercritical across all tested geometric parameter combinations. This is consistent with the finding of low linear transient growth amplifications at subcritical Reynolds numbers, being orders of magnitude lower than in similar channel flow set-ups.

Real-time monitoring of Metridia luciferase release from cells upon interaction with model toxic substances by a fully automatic flow setup – A proof of concept

This manuscript reports on a fully automatic sequential injection system incorporating a 3D printed module for real-time monitoring of the release of Metridia luciferase from a modified liver epithelial cell line. To this end, a simple and effective approach for the automation of flash-type chemiluminescence assays was developed. The 3D printed module comprised an apical and a basal compartment that enabled monitoring membrane processes on both sides of the cell monolayer aimed at elucidating the direction of luciferase release. A natural release was observed after transfection with the luciferase plasmid by online measurement of the elicited light from the reaction of the synthesized luciferase with the coelenterazine substrate. Model substances for acute toxicity from the group of cholic acids – chenodeoxycholic and deoxycholic acids – were applied at the 1.0 and 0.5 mmol L−1 levels. The tested cholic acids caused changes in cell membrane permeability that was accompanied by an increased luciferase release. The obtained kinetic profiles were evaluated based on the delay between the addition of the toxic substance and the increase of the chemiluminescence signal. All experiments were carried out in a fully automatic system in ca. 5 min per sample in 30 min intervals and no manual interventions were needed for a sampling period of at least 6 h.

Aminopolycarboxylic Acids-Functionalized Chitosan-Based Composite Cryogels as Valuable Heavy Metal Ions Sorbents: Fixed-Bed Column Studies and Theoretical Analysis.

Over the years, a large number of sorption experiments using the aminopolycarboxylic acid (APCA)-functionalized adsorbents were carried out in batch conditions, but prospective research should also be directed towards column studies to check their industrial/commercial feasibility. In this context, sorption studies of five-component heavy metal ion (HMI) solutions containing Zn2+, Pb2+, Cd2+, Ni2+, and Co2+ in equimolar concentrations were assessed in fixed-bed columns using some APCA-functionalized chitosan-clinoptilolite (CS-CPL) cryogel sorbents in comparison to unmodified composite materials. The overall sorption tendency of the APCA-functionalized composite sorbents followed the sequence Co2+ < Zn2+ < Cd2+ ≤ Pb2+ < Ni2+, meaning that Co2+ ions had the lowest affinity for the sorbent’s functional groups, whereas the Ni2+ ions were strongly and preferentially adsorbed. To get more insights into the application of the composite microbeads into continuous flow set-up, the kinetic data were described by Thomas and Yoon–Nelson models. A maximum theoretical HMI sorption capacity of 145.55 mg/g and a 50% breakthrough time of 121.5 min were estimated for the column containing CSEDTA-CPL cryogel sorbents; both values were much higher than those obtained for the column filled with pristine CS-CPL sorbents. In addition, desorption of HMIs from the composite microbeads in dynamic conditions was successfully achieved using 0.1 M HCl aqueous solution. Moreover, a theoretical analysis of APCA structures attached to composite adsorbents and their spatial structures within the complex combinations with transition metals was systematically performed. Starting from the most stable conformer of EDTA, coordinative combinations with HMIs can be obtained with an energy consumption of only 1 kcal/mole, which is enough to shift the spatial structure into a favorable conformation for HMI chelation.

Electrochemical Hydroxylation of Electron‐Rich Arenes in Continuous Flow

AbstractElectrochemical hydroxylation of arenes by trifluoroacetic acid provides a straightforward access to aryl oxygen compounds under the mild and environmental benign reaction conditions. Harmful and pollutant stoichiometric amounts of oxidation reagents and the use of metal‐catalysts can be avoided. Herein, we present a novel method for the synthesis of hydroxylated products from electron‐rich arenes that was achieved by the implementation of a continuous‐flow setup. The continuous nature of the process allowed to fine‐tune the reactions conditions in order to prevent the decomposition of the sensitive products expanding the reaction scope beyond electron‐poor and neutral arenes that were previously reported in the batch processes. Thus, synthetically valuable hydroxylated arenes were obtained in good yields with the residence time just over a minute. In order to demonstrate the reliability and the efficiency of the electrochemical flow setup, a scale up experiment was also performed.

The Supera Interwoven Nitinol Stent as a Flow Diverting Device in Popliteal Aneurysms

PurposeThe feasibility of using a compressed interwoven Supera stent as a flow diverting device for popliteal aneurysms was recently demonstrated in patients. It is unclear, however, what the optimal flow diverting strategy is, because of the fusiform shape of popliteal aneurysms and their exposure to triphasic flow. To assess this flow diverting strategy for popliteal aneurysms, flow profiles and thrombus formation likelihood were investigated in popliteal aneurysm models.Materials and MethodsSix popliteal aneurysm models were created and integrated into a pulsatile flow set-up. These models covered a bent and a straight anatomy in three configurations: control, single-lined and dual-lined Supera stents. Two-dimensional flow velocities were visualized by laser particle image velocimetry. In addition, the efficacy of the stent configurations for promoting aneurysm thrombosis was assessed by simulations of residence time and platelet activation.ResultsOn average for the two anatomies, the Supera stent led to a twofold reduction of velocities in the aneurysm for single-lined stents, and a fourfold reduction for dual-lined stents. Forward flow was optimally diverted, whereas backward flow was generally deflected into the aneurysm. The dual-lined configuration led to residence times of 15–20 s, compared to 5–15 s for the single stent configurations. Platelet activation potential was not increased by the flow diverting stents.ConclusionA compressed Supera stent was successfully able to divert flow in a popliteal aneurysm phantom. A dual-lined configuration demonstrated superior hemodynamic characteristics compared to its single-lined counterpart.

Roadside units plane optimization scheme in software‐defined vehicular networks

AbstractAs a new research field, software‐defined vehicular networks (SDVN) provide a novel idea for the network management of the internet of vehicles. Due to the time‐sensitivity of vehicle edge networks, time delay optimization for flow rule management is of great significance to improve system performance. Some existing SDVN architectures select part of the underlying roadside units (RSUs) as underlying controllers to assist the upper control plane. There is no mention of how to optimize the state switching between the RSU controller and the common RSU, which may increase the delay and communication overhead. This paper proposes an RSU plane optimization scheme to reduce the state fluctuation between RSUs with control functions. Firstly, we propose a state fluctuation optimization model of the RSU plane. Secondly, the division method and dynamic adjustment strategy of the RSU plane are designed. Finally, a position prediction method is utilized to realize the pre‐installation of flow rules. We use two common methods (greedy and dynamic schemes) to compare with the minimum state fluctuation approach. The simulation analyzes the performance using four parameters. Under the same conditions, the proposed scheme can reduce the flow setup delay and end‐to‐end delay, while reducing the number of controllers and overhead.

A Legendre spectral viscosity (LSV) method applied to shock capturing for high-order flux reconstruction schemes

A novel approach to shock capturing for high-order flux reconstruction schemes is derived based on the mathematical formalism of the filtered governing equations. While the latter perspective is only typically used for turbulence modeling in the context of Large-Eddy Simulations (LES), the novel Legendre Spectral Viscosity (LSV) subfilter scale (SFS) closure model is capable of performing simulations in the presence of shock-discontinuities. The LSV method exploits the set of hierarchical basis functions formed by the Legendre polynomials to extract the information on the energy content near the resolution limit and estimate the overall magnitude of the required SFS dissipative terms, resulting in a scheme that dynamically activates only in cells where nonlinear behavior is important. Additionally, the modulation of such terms in the Legendre spectral space allows for the concentration of the dissipative action at small scales. The proposed method is tested in canonical shock-dominated flow setups in both one and two dimensions. These include the 1D Burgers' problem, a 1D shock tube, a 1D shock-entropy wave interaction, a 2D inviscid shock-vortex interaction and a 2D double Mach reflection. Results showcase a high-degree of resolution power, achieving accurate results with a small number of degrees of freedom, and robustness, being able to capture shocks associated with the Burgers' equation and the 1D shock tube within a single cell with orders 120 and higher.

Retro-aza-Michael reaction in continuous flow. Approaches to synthesis of adaline and euphococcinine related products

A retro-aza-Michael ring opening reaction of tropinone and granatanone (pseudopelletierine) in flow setup was investigated and the resulting products were utilized as key intermediates in approaches to adaline and its analogues. The enantioselective flow-reaction gave products of ring opening of granatanone with enantiopurity up to 98% ee. Attempts to elaborate the retro-aza-Michael product to alkaloids are described. Lithiated carbamate derivative of tropane was converted to a tropane analogue of euphococcinine, an adaline related alkaloid (a methyl and tropane homologue of adaline 19). Reactivity of the retro-aza-Michael product under Morita-Baylis-Hillman conditions was also briefly investigated.

Photochemical Csp2-H bond thiocyanation and selenocyanation of activated arenes, batch and continuous-flow approaches.

Herein, we report an eco-friendly photochemical oxidative Csp2-H thiocyanation and selenocyanation of activated arenes. The reaction proceeds under Violet LED irradiation in the presence of K2S2O8, which quickly oxidizes KSCN and KSeCN, finally producing arylthio/selenocyanates. Using this benign, atom-economic protocol, the desired chalcogenide products were obtained regioselectively, with isolated yields that range from very good to excellent. Although, mechanistic study indicates that it is difficult to distinguish between a radical to a SEAr reaction mechanism between the photo-induced formed •SCN, for the former, or NCSSCN, for the latter, to the aromatic heterocycles. The inhibition experiment together with the observed reactivity and regioselectivity, would be in agreement with the latter. The synthetic methodology designed could be successfully adapted to continuous-flow systems in a segmented-flow regime, employing the organic phase as the product reservoir. Using this setup, the advantage of the latter can be demonstrated by reducing the reaction time and improving the product yields. Similarly, the scaling up of the reaction to gram scale resulted in favorable outcomes by the flow setup, which installs the photo-flow chemistry as a powerful tool to be included into routine reaction procedures, which have great relevance for the pharmaceutical industry.