Microreactor Research Articles

Investigation of CO methanation activities of ZSM-5 supported Ni catalysts using microchannel and conventional reactor

Investigation of CO methanation activities of ZSM-5 supported Ni catalysts using microchannel and conventional reactor

Interiorly Hydrophobic Modification of Electrodeposited Self-supported ZnAg Foam Electrodes for CO2 Electroreduction in a Microchannel Reactor

Interiorly Hydrophobic Modification of Electrodeposited Self-supported ZnAg Foam Electrodes for CO₂ Electroreduction in a Microchannel Reactor

Direct energy deposition for smart micro reactor

ABSTRACT Nuclear microreactors (MRs) have attracted significant attention for their versatility in installation locations, especially with the growing demand for sustainable green energy in large data processing facilities. However, ensuring their safe operation necessitates frequent inspections, which can be challenging for practical efficient management. This study proposes a novel approach using direct energy deposition to incorporate an optical fiber sensor into MR components, enabling real-time monitoring with artificial intelligence. The embedded optical fiber generates real-time data that allows for AI-driven in-vivo thermal deformation analysis. Our smart MR component can detect structural anomalies, identify abnormal operations, and assess operational conditions through augmented reality interfaces and AI technology.

CFD simulation of liquid-liquid extraction mechanism and enhancement schemes in microchannels based on three mass transfer models

Microreactors are highly efficient devices with a large specific surface area to improve the mass transfer efficiency. In this paper, a comprehensive three-dimensional CFD model was constructed based on three mass transfer theories to simulate the liquid-liquid two-phase flow and mass transfer process in a microchannel reactor, and two enhancement schemes were proposed. The multiphase flow and mass transfer characteristics were investigated by visualization and extraction experiments. The results indicated that the extraction efficiencies (E) and overall mass transfer coefficients (KLa) calculated by the penetration model and surface renewal model were within ±15 % errors compared to the experimental values. Moreover, E primarily increases with the increase of fluid residence time, while KLa increases with increasing flow rate. As the flow rate increases from 0.3 ml/min to 1.5 ml/min, E decreases by 15 %, and KLa rises from 0.78 s⁻¹ to 2.65 s⁻¹. Whereas the channel width decreases from 0.8 mm to 0.3 mm, E decreases by 3 %, and KLa rises from 0.44 s⁻¹ to 2.77 s⁻¹. Finally, microchannel with necked structure and baffles in mixing zone both improve the mass transfer efficient to some extent.

Numerical Simulation and Response Surface Analysis of Esterification of Monobutyl Chlorophosphate with n-Butanol in a Microchannel Reactor

Microreactors are essential for microchemical reactions owing to their high mass transfer efficiency, precise control of reaction time, easy amplification, and good safety performance. These characteristics provide several advantages, including shortened reaction times and enhanced chemical reaction conversion rates, rendering microreactors particularly significant in chemical production. In this study, a finite-rate model was developed for the esterification of monobutyl chlorophosphate (MCP) and n-butanol in a microchannel reactor. This study investigates the impact of the microchannel’s length-to-diameter ratio, the mass ratio of n-butanol to MCP at the inlet, and the inlet flow ratio on the entire reaction system through numerical simulations. The findings indicate that increasing the length-to-diameter ratio and reducing the inlet flow rate effectively prolongs the residence time of materials in the microreactor, thereby enhancing the conversion rate of the reactants. Optimal results are achieved with a moderate n-butanol/MCP mass ratio, which facilitates MCP transformation. Moreover, this study employs response surface analysis to investigate the influence of independent factors, such as the microchannel’s length-to-diameter ratio, component ratio, and inlet velocity ratio, on MCP conversion rates. A prediction formula with conversion rate as the dependent variable and microchannel length-to-diameter ratio, component ratio, and inlet velocity ratio as independent variables was established.

Study of the N2O formation mechanism in NOx-assisted heterogeneous catalytic combustion of soot in CeO2-based catalytic microchannel reactor

A CeO2-based catalytic microchannel reactor fixed-bed experiment was carried out to investigate the N2O formation in NOx-assisted catalytic combustion with fresh and hydrothermally aging catalysts during NOx-assisted heterogeneous catalytic combustion of soot. An evolved NOx-assisted soot catalytic combustion reaction mechanism was built to investigate N2O formation and key reaction pathways based on in situ Fourier Transform Infrared Spectroscopy (FTIR) diagnostics and destiny functional theory (DFT) computations. It was found that the temperature range of N2O formation was the same as the initiation temperature of soot catalytic combustion, while the significant catalytic activity of CeO2 catalyst induced a decrease in the temperature range of N2O formation. The CeO2 catalyst inhibited N2O formations from NOx-assisted soot catalytic combustion, while its inhibition effect was gradually weakened with the decrease of catalyst activities. The inhibitory effect of CeO2 on N2O was revealed in the reduction of CN formation rate in high temperatures. Fresh CeO2 catalyst increased the dominance in the CN formation reaction, reduced the CN production rate, and contributed to the decrease in the reaction rate of CNO oxidation by NO and NO2. The increase in the ratio of NOx to soot (β) was more sensitive to N2O formation than the ratio α (NO2 to NOx) and γ (O2 to NOx), led to a stronger inhibition of N2O formation.

An experimental investigation on characteristics of liquid film thickness of gas-liquid Taylor flow in square/rectangular microchannel applied in microreactor

Microchannel reactors employing Taylor flow is 1 – 3 orders of magnitude higher than traditional reactor in handling gas-liquid reaction processes, which has found important applications in oxidation, hydrogenation, chlorination, fluorination and absorption involved in chemical industry. Liquid film thickness of gas-liquid Taylor flow in circular microchannel has been widely investigated, whereas the variation and distribution of liquid film thickness in square/rectangular microchannel are lack of comprehension. In the present work, experiments were conducted to investigate the variation of liquid film thickness in square channels with hydraulic diameter Dh = 0.3, 0.5, 0.7, 1.0 mm, and rectangular channels with a depth of 0.5 mm and widths of 0.3, 0.5, 0.7, 1.0 mm under the condition of air-water and the addition of surfactant Tween-20. The liquid film thicknesses were measured using a laser focus displacement meter (LFDM), the bubble shapes and velocities were compared using high speed photography. The experimental results illustrate that the dimensionless bubble diameter in square/rectangular microchannels can be divided into initial stage, reduction stage and stable stage with the increasing of capillary number Ca. The initial, reduction and stable stage of the dimensionless bubble diameter are all influenced by the channel hydraulic diameter, aspect ratio, asymmetry effects and surface tension coefficient of working fluid. In square channels with Dh = 0.3, 0.5, 0.7, and 1.0 mm, the dimensionless bubble diameter enters the reduction stage at Ca = 0.019, 0.015, 0.011, and 0.009, respectively. Besides, an empirical formula of dimensionless bubble diameter was developed using the dimensionless groups Ca, Re, Bo, and Li/Dh to describe the characteristics of liquid film thickness in square/rectangular microchannel.

Process optimization and scale-up of toluene nitration in a microchannel reactor using HNO3-AC2O as nitrating agent

Aromatic nitro compounds are an important class of basic chemical raw materials, while traditional nitration methods may cause safety accidents and environmental pollution due to strong exothermicity and presence of sulfuric acid. In this work, aiming to alleviate these issues, the nitration of toluene was conducted in a microchannel reactor with nitric acid and acetic anhydride. The effect of temperature, molar ratio of nitric acid to toluene, mass fraction of acetic anhydride, and residence time on the conversion and selectivity of reaction were systematically investigated, and response surface methodology was used to optimize the process. A mononitrotoluene yield of 99.21 % can be achieved under optimum condition. Meanwhile, in order to better understand the exothermic behavior, toluene nitration by HNO3-AC2O was investigated in the semi-batch calorimeter. Finally, the optimized process was scaled up and effect of volumetric flow rate was investigated. At the selected maximum volumetric flow rate, the overtemperature of the system was 10.9 °C with a 98.3 % yield of mononitrotoluene. Continuous flow mode had a space-time yield nearly two orders of magnitude greater than semi-batch mode. This work can provide guidance for safe, efficient and green synthesis of mononitrotoluene.

Influence of Complex Multiphasic Flow on the Thiuram Electrosynthesis in a Microchannel Reactor.

As an important sustainable method for chemical synthesis, organic electrosynthesis experienced a renaissance in recent years for its excellent atom economy. Although microchannel reactors have been proposed to advanced electrosynthesis devices to obtain low energy cost and high reaction performance, the complex multiphasic flow in the electrochemical microchannels are very less reported and the effects of flow condition on the electrosynthesis reaction are less reported. Taking the electrosynthesis of tetraethyl thiuram disulfide (TETD) as a typical case, we developed a visualized electrochemical microchannel reactor equipped with fluorine-doped tin oxide (FTO) loaded glass electrode to investigate the gas-liquid-liquid triple phase flow pattern and the main factors influenced the response current at certain applied cell voltage. The gas-liquid-liquid hybrid flow with low gas hold-up and high liquid flow rate was found crucial for preventing coverage of TETD on the electrode, which provided 23.1 % low current attenuation ratio at 3.0 V cell voltage. The research not only exhibited the complex evolution mechanism of the response current, but also showed the importance of flow condition control for balancing the work efficiency and energy consumption of electrosynthesis process.

Kinetic Aspects of Esterification and Transesterification in Microstructured Reactors.

Microstructured reactors offer fast chemical engineering transfer and precise microfluidic control, enabling the determination of reactions' kinetic parameters. This review examines recent advancements in measuring microreaction kinetics. It explores kinetic modeling, reaction mechanisms, and intrinsic kinetic equations pertaining to two types of microreaction: esterification and transesterification reactions involving acids, bases, or biocatalysts. The utilization of a micro packed-bed reactor successfully achieves a harmonious combination of the micro-dispersion state and the reaction kinetic characteristics. Additionally, this review presents micro-process simulation software and explores the advanced integration of microreactors with spectroscopic analyses for reaction monitoring and data acquisition. Furthermore, it elaborates on the control principles of the micro platform. The superiority of online measurement, automation, and the digitalization of the microreaction process for kinetic measurements is highlighted, showcasing the vast prospects of artificial intelligence applications.

Mixing behavior and mass transfer of liquid–liquid two-phase flow in an annular microchannel with helical wires

Combining the advantages of high efficiency, low-pressure drop, and large throughput, the pore array-enhanced tube-in-tube microchannel (PA-TMC) is a promising microreactor for industrial applications. However, most of the mass transfer takes place in the upstream pore region, while the contribution of the downstream annulus is limited. In this work, helical wires were introduced into the annulus by adhering to the outer surface of the inner tube. Mixing behavior and mass transfer of liquid–liquid two-phase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid (VOF) method. The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%. The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area, while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate. Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed. This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.

Assessment of Technoeconomic Opportunities in Automation for Nuclear Microreactors

Achieving full decarbonization of all economic sectors remains a challenge, especially in niche markets. For example, remote communities and industrial or mining activities detached from the main electric grid heavily rely on fossil fuels, similar to urban and industrial microgrids with combined heat and power needs. A combination of renewables and energy storage is often not suitable due to cost, reliability, intermittency, and large storage requirements. Small nuclear reactors with a flexible purpose could serve these applications. Microreactors (MR) are a class of reactors that are compact, factory manufactured, transportable, and self-regulating. Typically, they generate much less power than their large reactor counterparts. The main advantages of microreactors include the versatile nature of the energy produced, the reliability of supply, and freedom from having to transport and store large quantities of fuels on-site, coupled with the absence of dependence on an electrical grid. A strong business case is needed to move from the microreactor prototype to the commercialization phase. In fact, fossil fuels are still relatively inexpensive, and in the near term, carbon credits will be available to virtually compensate for emissions. For microreactors, one of the main costs in operation and maintenance (O&M) is their staffing levels. In this study, we investigate how to optimize the number (and thus the cost) of workers, moving from a traditional, fully manned, on-site personnel approach to an unmanned, remote personnel approach. We examine four different staffing models that can be implemented as the technology matures and evolves. We estimate the staffing needs of each model and build a business case to justify the substitution of on-site personnel with adequate technologies. To do so, we propose a cost model to quantify potential cost reductions from automating O&M activities. The model accounts for both the reduction in cost derived from the reduced number of full-time-equivalent (FTE) employees and the increase in cost derived from the need to buy new control hardware as needed. Applying the cost model that we created to different scenarios, an on-site O&M cost reduction exceeding 80% can be expected. Additionally, we found that it is more impactful to focus on automating routine O&M tasks rather than attempting to automate transient management (shutdowns, restarts, monitoring condition deviations). In fact, transients typically account for less than 1% of the total FTE time spent on the reactors.

Exploring the performance of Co/Al2O3–ZrO2 nanocatalysts developed through the thermal evaporation method in dry reforming of methane

Abstract This study aimed to investigate the performance of the thin layer nanostructures of Co/Al2O3–ZrO2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al2O3–ZrO2, the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H2/CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition (P = 1 atm, T = 800 °C, t = 4 min deposition time, CH4/CO2 = 1, and GHSV = 48,000 mL g−1 h−1) showed that the catalysts prepared by this method had a good stability.

Bimetallic ZnFe–NC prepared using microchannel reactor for oxygen reduction reaction and mechanism research

Bimetallic ZnFe–NC prepared using microchannel reactor for oxygen reduction reaction and mechanism research

Modelling and optimization of fenton process for decolorization of azo dye (DR16) at microreactor using artificial neural network and genetic algorithm

The Fenton process is widely employed for decolorizing industrial wastewater. Therefore, it is imperative to construct a model for optimizing the operational parameters and estimating the efficiency of decolorization within this process. In this study, an artificial neural network (ANN) model was created based on experimental data provided by a previous researcher who examined the decolorization of Direct Red 16 dye (DR16) using a heterogeneous Fenton process within a microchannel reactor. This model was utilized to optimize and forecast the efficiency of decolorization in the Fenton process. The accuracy of the model was validated by comparing its outcomes with actual experimental data. To further improve the efficiency of decolorization, optimal operational parameters were ascertained utilizing the genetic algorithm method. The study revealed that as dye concentrations increased from 10 to 40 mg/l, decolorization efficiencies improved proportionately, peaking at 89.78 %. Optimal operational parameters for maximizing efficiency were identified as a feed flow rate of 1 ml/min, H2O2 concentration at 500 mg/l, Fe2+ concentration of 4 mg/l, and maintaining pH between 2.6 and 2.8. Insights derived from both experimental and model-generated data were used to analyze the impact of operational parameters on decolorization efficiency.

Effect of catalyst distribution in the combustion catalytic layer on heat and mass transport characteristics of the microchannel reactor

PurposeThe purpose of this study is to investigate the effect of catalyst distribution in the combustion catalytic layer on heat and mass transport characteristics of the auto-thermal methanol steam reforming microchannel reactor.Design/methodology/approachComputational fluid dynamics (CFD) method is used to study four different gradient designs. The corresponding distributions of temperature, species and chemical reaction rate are provided and compared.FindingsThe distributions of species, temperature and chemical reaction rate are significantly affected by the catalyst distribution in the combustion catalytic layer. A more uniform temperature distribution can be observed when the gradient design is used. Meanwhile, the methanol conversion rate is also improved.Practical implicationsThis work reveals the effect of catalyst distribution in the combustion catalytic layer on heat and mass transport characteristics of the auto-thermal methanol steam reforming microchannel reactor and provides guidance for the design of reactors.Originality/valueThe temperature uniformity and hydrogen production performance can be improved by the gradient design in the combustion catalytic layer.

Catalytic biodiesel production from Jatropha curcas oil: A comparative analysis of microchannel, fixed bed, and microwave reactor systems with recycled ZSM-5 catalyst

In this study, we studied the conversion of Jatropha curcas oil to biodiesel by using three distinct reactor systems: microchannel, fixed bed, and microwave reactors. ZSM-5 was used as the catalyst for this conversion and was thoroughly characterized. X-ray diffraction was used to identify the crystalline structure, Brunauer–Emmett–Teller analysis to determine surface area, and temperature-programmed desorption to evaluate thermal stability and acidic properties. These characterizations provided crucial insights into the catalyst's structural integrity and performance under reaction conditions. The microchannel reactor exhibited superior biodiesel yield compared to the fixed bed and microwave reactors, and achieved peak efficiency at 60 °C, delivering high FAEE yield (99.7%) and conversion rates (99.92%). Ethanol catalyst volume at 1% was optimal, while varying flow rates exhibited trade-offs, emphasizing the need for nuanced control. Comparative studies against microwave and fixed-bed reactors consistently favored the microchannel reactor, emphasizing its remarkable FAME percentages, high conversion rates, and adaptability to diverse operating conditions. The zig-zag configuration enhances its efficiency, making it the optimal choice for biodiesel production and showcasing promising prospects for advancing sustainable biofuel synthesis technologies.

Design and study of the flow section of a variable microchannel reformer based on the coupling law of reforming with flow, heat and mass transfer

In the amplification mode, microscale reforming reactions are controlled by the transfer rate. To avoid the amplification effect, the process coupling mechanism in the microchannel reactor must be studied to take full advantage of its precise control. This paper studies the coupling effect between the flow process and the reforming process in the microchannel and constructs a computational model of the flow coupling. A study was conducted on the influence of the coupling effect on the conversion rate, based on a combination of reliability verification and experiments. The following conclusions were obtained: the coupling effect in the reactive flow field was quantified based on the characteristic time of the flow process and the reaction process (Da number), and the microchannel was divided into three parts. The methanol conversion rate of the burst-expansion scheme was increased to more than 6%, and the USAER (unit surface area enhancement rate) reached 7.7. The USAER of the protrusion-expansion scheme can reach 8.342, with a potential for an 10% increase in conversion rate. The distribution of the three-segmented variable cross-section has the most effective regulation effect. The USAER of the protrusion-expansion scheme reaches 9.11, with a conversion rate that can be increased by 7%.

Study on CO2 absorption by EmimCl-MEA deep eutectic solvent in microchannel

Carbon dioxide (CO2) is widely acknowledged as the primary contributor to the greenhouse effect. Microchannel reactors can be used for enhancing chemical processes, solving the problems of limited gas-liquid mass transfer, and have significant advantages in CO2 capture. In this study, the deep eutectic solvent (DES) prepared by mixing ionic liquid (1-ethyl-3-methylimidazolium chloride, EmimCl) and Ethanolamine (MEA) in a molar ratio of 1:1 was selected for CO2 capture in a microchannel. The structure and physical properties of the DES were investigated, and the effects of gas and liquid flow rates, water content, and CO2 concentration on the CO2 absorption properties were analyzed. The increase of the water content not only significantly reduces the viscosity of DES, but also improves the CO2 absorption performance. In addition, the CO2 absorption mechanism of this DES has been obtained by the NMR spectrum, showing that the absorption process is a rapid chemical absorption process between CO2 and MEA. The Cl- of EmimCl could stabilize the protonated amine and prevent it from further reacting with MEACO2-, furthermore increasing the CO2 absorption rate.

Polygonal mesopores microflower catalysts for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene to 2-nitro-4-methylsulfonylbenzoic acid in a continuous-flow microreactor

The development of efficient systems for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene (NMST) to 2-nitro-4-methylsulfonyl benzoic acid (NMSBA) with atmospheric air or molecular oxygen in alkaline medium presents a significant challenge for the chemical industry. Here, we report the synthesis of FeOOH/Fe3O4/MOF polygonal mesopores microflower templated from a MIL-88B(Fe) at room temperature, which exposes polygonal mesopores with atomistic edge steps and lattice defects. The obtained FeOOH/Fe3O4/MOF catalyst was adsorbed onto glass beads and then introduced into the microchannel reactor. In the alkaline environment, oxygen was used as oxidant to catalyze the oxidation of NMST to NMSBA, showing impressive performance. This sustainable system utilizes oxygen as a clean oxidant in an inexpensive and environmentally friendly NaOH/methanol mixture. The position and type of substituent critically affect the products. Additionally, this sustainable protocol enabled gram-scale preparation of carboxylic acid and benzyl alcohol derivatives with high chemoselectivities. Finally, the reactions can be conducted in a pressure reactor, which can conserve oxygen and prevent solvent loss. Moreover, compared with the traditional batch reactor, the self-built microchannel reactor can accelerate the reaction rate, shorten the reaction time and enhance the selectivity of catalytic oxidation reactions. This approach contributes to environmental protection and holds potential for industrial applications.