Mass transfer intensification and kinetics of o-xylene nitration in the microreactor

Rotating foam reactors: Mass transfer and reaction rate

Intensification and kinetic study of trifluoromethylbenzen nitration with mixed acid in the microreactor

This study aims to model the coupled phenomena of photocatalytic reaction and mass transfer in the degradation of Amoxicillin (AMX) and Doxycycline (DOX) using Zinc oxide (ZnO) nanoparticles within microreactor systems. The objective is to gain a comprehensive understanding of the dynamic interaction between the photocatalytic degradation kinetics and the mass transfer processes to optimize the conditions for efficient antibiotic removal from contaminated water. This involves characterizing the reaction kinetics via the Langmuir-Hinshelwood model, estimating the mass transfer coefficients, and analyzing the effects of axial dispersion to ensure the accurate determination of intrinsic kinetic constants and minimize mass transfer limitations. This study used a syringe pump to ensure a consistent flow of antibiotic solution into the microreactor. The results indicate that AMX reaches adsorption equilibrium more rapidly than DOX, corresponding to its faster photocatalytic degradation kinetics and higher final conversion rate (89% for AMX, 86% for DOX). The mass transfer coefficient (kd) was estimated using the Sherwood number, derived from three different models, with the constant Sherwood model best fitting the R1 microreactor data. An analysis of the Damköhler number (DaII) indicates that high flow rates minimize mass transfer limitations in the R1 microreactor, allowing the determination of near-intrinsic kinetic constants. On the contrary, at low flow rates, kinetic constants are apparent as a result of mass-transfer limitations. The study concludes that higher flow rates (≥ 10 mL/h) in the R1 microreactor are preferable to approach intrinsic kinetics and reduce mass transfer limitations during photocatalytic degradation of antibiotics. These findings underscore the potential of ZnO-based oxidation processes in treating antibiotic-contaminated water with optimized conditions, providing a pathway for efficient and sustainable wastewater treatment.

The sulfonation of naphthalene with sulfuric acid to produce naphthalene sulfonic acid was carried out in capillary microreactors as a model liquid–liquid heterogeneous reaction to study droplet coalescence phenomena. The effects of various factors associated with droplet coalescence or the reaction kinetics, such as capillary length (residence time), reaction temperature, molar ratio of reactants, and capillary wall wetting properties, on the reaction performance were investigated. In particular, the influence of droplet coalescence on the specific interfacial area, the mass transfer rate, and the reaction performance was evaluated in detail. Surprisingly, the specific interfacial area could decrease up to 93% along the flow direction in the capillary microreactor with the droplet coalescence. Interestingly, the microreactor wall surface properties were found to affect the reaction performance significantly. Moreover, the Hatta number was evaluated, which reflected the competition between the mass transfer and the reaction during the sulfonation in the capillary microreactors with droplet coalescence.

Part 1 - Systems with Intensive Interphase Mass Transfer

Synthesis of biodiesel through transesterification of vegetable oil with methanol has been experimentally studied in different types of microreactors though detailed numerical simulation has not yet been presented. The capillary microreactor has the potential to greatly intensify mass transfer between immiscible fluids that would result in higher chemical reaction rates. A segmented flow pattern of oil and methanol forms within the reactor. It has been shown experimentally that the two phase flow has dramatic benefits on the intensification of mass transfer and heat transfer. Such reactors have been proposed for the synthesis of biodiesel and detailed understanding of flow dynamics and chemical kinetics would be useful for process optimization. This paper presents a mathematical model and numerical solution for the synthesis of biodiesel in a capillary reactor. The model represents the unsteady incompressible viscous non-equilibrium chemically reacting flow. The equations are discretized with the finite element method (FEM) and solved to demonstrate the flow behavior and concentration distribution of each chemical species within two phases; different residence time will be obtained with different volume flow rate as well. Information about efficient computational treatment of the model will also be presented.

Heterogeneous toluene nitration with mixed acid in microreactors: Reaction regime, characteristics and kinetic models

Intensification of mass transfer in a pulsed bubble column

Heat/mass transfer analogy in the case of convective fluid flow through minichannels

Hydrodynamics and mass transfer performance during the chemical oxidative polymerization of aniline in microreactors

Experimental and kinetic study of the nitration of 2-ethylhexanol in capillary microreactors

Kinetics of glyoxal oxidation by nitric acid in a capillary microreactor

Effect of deviations from concentration equilibrium at phase interfaces, hydrodynamic conditions, surfactants, and interfacial tension on interfacial mass transfer

A convenient strategy to intensify the liquid–liquid mass transfer performance in a capillary microreactor system was developed by narrowing the inlet channel of T‐micromixer or adding baffles into the capillary. Various geometrical parameters such as the inlet mode and diameter of the modified T‐micromixer, the number of baffles and interval distance between baffles in the modified capillary were investigated to elaborate the mass transfer intensification mechanism. The liquid–liquid two‐phase flow patterns in new capillary microreactors were captured by a high‐speed camera. Moreover, pressure drops and specific energy dissipation of these modified microreactor systems were studied and a new parameter indicating the ratio of the mass transfer coefficient to the energy dissipation was proposed. This work highlights the modified capillary microreactor systems with embedding baffle units for achieving high mass transfer rates with its advantages over other types of reactors or microreactors considering specific energy dissipation and effective energy utilization efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 65: 334–346, 2019

This work investigates the mass transfer process with and without first order chemical reaction by direct numerical simulation of two-fluid flows within mini-channels. The large potential of two-fluid flows for mass and heat transfer processes, operated in mini- and micro-systems such as micro bubble columns and monolithic catalyst reactors, motivated the present research. The study is based on the implementation of the species conservation equation in computer code TURBIT-VoF. The implementation of the equation is validated against different solutions of simplified mass transfer problems. The demanding treatment of the interfacial concentration jump described by Henry's law is examined with great concern. The diffusive term is successfully compared against one- and two-dimensional theoretical solutions of diffusion problems in two-phase systems. The numerical simulation of mass transfer during the rise of a 4mm air bubble in aqueous glycerol is performed and compared against another numerical simulation in order to test the convective term. The implementation of the source term for homogeneous and heterogeneous chemical reaction is successfully validated against theoretical solutions of mass transfer with chemical reaction in single-phase flows. The numerical simulations are focused on bubble train-flows flowing co-currently in mini-channels. Taking advantage of the periodic flow conditions exhibited in axial direction, the analysis is restricted to a flow unit cell, which consists of one bubble and one liquid slug. As concerns the hydrodynamics of all simulations performed, good agreement is obtained for the non-dimensional bubble diameter, the ratio of bubble velocity to the total superficial velocity and for the relative velocity in comparison with experimental data. The influence of the unit cell length on mass transfer from the bubble into the liquid phase of an arbitrary species is investigated in square channels having the hydraulic diameter D* h = 2mm. Short unit cells are found more effective than long unit cells for mass transfer, in agreement with published investigations performed for circular channels. This is related to the length of the liquid film between bubble and wall which becomes rapidly saturated due to short diffusion lengths and long contact time and leads to a decrease of the local concentration gradient. The major contribution to mass transfer occurs through the cap and the bottom of the bubbles, as reported also in experimental investigations. For mass transfer with heterogeneous chemical reaction more mass is consumed at the wall for systems having long unit cells, as a consequence of the increased lateral surface and more vigorous recirculation in the liquid slug. For species having a large solubility in the continuous phase, diffusion dominates over reaction allowing short unit cells to be more effective for mass transfer with heterogeneous reaction. A formulation of the mass transfer coefficient based on averaged concentrations is proposed for mass transfer processes and successfully compared against another approach based on the mass balance at interface. In complete agreement with experimental and theoretical studies, the study reveals that long liquid slugs and short bubbles are more efficient than short liquid slugs and long bubbles, respectively.