Flow Microchannel Reactor Research Articles

Highly selective oxidation of glucose to formic acid and exploring reaction pathways using continuous flow microreactors

The process of converting glucose into formic acid (FA) has been explored as a promising route for using biomass as a renewable feedstock for green chemical manufacturing. However, the most commonly used batch-tank reactor systems currently suffer from several drawbacks, including extended processing time, limited product selectivity, and high energy consumption, while the underlying reaction paths have been poorly understood. In this work, a continuous flow microchannel reactor was employed for the glucose conversion catalyzed by H5PV2Mo10O40 with O2 as an oxidant. The influence of various parameters on the conversion rate of glucose and the FA yield was characterized. Experimental results indicated that with a residence time of less than 3 min, the glucose was completely converted, and the highest FA yield reached 82.40 %. Extensive examination on the apparent by-products revealed that most of them acted as intermediates to produce FA through various pathways, including glyoxal, glyceraldehyde and glycolaldehyde as key intermediates for the oxidation of glucose to FA. Furthermore, the density functional theory (DFT) method was used to determine the bond energies of different C–C bond cleavage modes of substrate glucose and fructose produced by the isomerization of glucose. Experimentally, the conversion of three main intermediates and some other possible intermediates and their FA yield were measured with different residence time. It was also found that the CO2 was produced through the decarboxylation of α-hydroxy and α-carbonyl carboxylic acid compounds, while the aldehyde groups in the compounds were more likely converted to FA by the α-carbon bond cleavage. Finally, plausible reaction pathways were proposed for the process of glucose-to-FA catalyzed by HPA-2, providing useful guidance for the identification of side reaction pathways and further improvement of FA yield.

Efficient synthesis of high vinyl polybutadiene based on continuous flow microchannel reactor

AbstractThe traditional batch synthesis of liquid rubber faces issues such as low monomer polymerization concentration, poor uniformity of the reaction system, and inadequate heat dissipation, resulting in an unsatisfactory synthesis efficiency. This study presents a method for the rapid and efficient synthesis of high vinyl 1,2‐polybutadiene liquid rubber using butadiene as the monomer and n‐butyllithium as the initiator. By applying continuous flow microchannel reactors, the limitation of traditional synthesis method can be overcome. The addition of a modifier in the raw material promotes the formation of high vinyl structure. The preparation of liquid rubber requires the addition of a large amount of metal lithium initiator. However, for aerospace sealants, there is a requirement for low metal ion content. To address this, we employed different methods to reduce the metal ion content in the liquid rubber and increase its purity. Ultimately, we achieved the synthesis of high‐purity polybutadiene liquid rubber with 1,2‐vinyl content exceeding 88%, narrow molecular weight distribution, and tunable molecular weights. This research will provide technical guidance for the industrial application of polybutadiene synthesis in continuous flow microchannel reactors.

Fatty acid chain modification of loxenatide and its kinetics in a continuous flow microchannel reactor

In this study, a continuous flow microchannel reactor was designed and constructed for continuous and efficient fatty acid chain modification (FACylation) of polypeptides to achieve higher production capacity than that obtained in a batch reactor. In this microreactor, loxenatide (LOX) was site-specifically modified by N-tetradecylmaleimide (C14-MAL) to continuously synthesize the target product, N-tetradecyl-loxenatide (C14-LOX). Based on the experimental data under different conditions, a kinetic model of FACylation was established to describe the initial stage of the continuous reaction in the microreactor. Under the optimal conditions obtained by the kinetic model, the reaction time in the microreactor could be reduced to 1/3 that of the batch reactor at the same yield, and the production capacity of the microreactor was at least 3.78 times that of the batch reactor within the same time (40 h). These results would contribute to the development of microreactors in the biopharmaceutical industry.

Dehydrogenation of perhydro-dibenzyltoluene for hydrogen production in a microchannel reactor

A preliminary study regarding the dehydrogenation of perhydro-dibenzyltoluene as a liquid organic hydrogen carrier with switching from a stirred tank reactor to a continuous flow microchannel reactor is presented. The hydrogen production percentage in the case of a continuous flow microchannel reactor was found greater when compared to that of a stirred tank reactor. The hydrogen production was increased from 64.1% to 82.2% with the increase in bottom plate temperature from 260 to 320 °C for 0.01 mL/min flow rate. A maximum of 88% of hydrogen was generated for a 40 hours of operation, at a bottom wall temperature of 290 °C. The kinetic model for the microchannel reactor dehydrogenation was presented with a pre-exponential factor of 3.272 s−1 and activation energy of 13.79 kJ/mol. The results revealed that a continuous microchannel reactor can be an appropriate technology for the dehydrogenation of perhydro-dibenzyltoluene.

Using a Microchannel Reactor to Optimize the Production of 1-Alkyl-3-Methylimidazolium Chlorides

The possibility of using microchannel flow reactors to obtain the kinetic and technological parameters of the synthesis of 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid is demonstrated for the reaction of 1-methylimidazole (MIm) with 1-chlorobutane with no solvents. BMIMCl is produced with high selectivity and specific output in a microchannel flow reactor at temperatures of 120–180°C a contact time of 2–45 min, and a pressure of 20 bar. A positive result is obtained, due to the laminar profile of the flow and a uniform distribution of the reagents concentration over the microchannel cross section. Studying the kinetics of the process in a microchannel flow reactor reveals a shift of the reaction to the mode of diffusive inhibition at temperatures above 150°C. The kinetic data obtained for BMIMCl synthesis are used to develop ways of producing 1-ethyl-3-methylimidazolium and 1-hexyl-3-methylimidazolium chlorides (EMIMCl and HMIMCl, respectively) under the conditions of a microchannel flow reactor. The approach proposed in this work is of interest in developing flow and periodic facilities for the low-tonnage production of dialkylimidazolium, ammonium, and pyridinium salts via quaternization of the corresponding alkyl chlorides and nitrogen-containing bases.

The use of a microchannel reactor for optimizing the production of 1-alkyl-3-methylimidazolium chlorides

The possibility to use microchannel flow reactors for obtaining kinetic and technological parameters of the synthesis of 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid was demonstrated for the reaction of 1-methylimidazole (MIm) with 1-chlorobutane in the absence of solvents. BMIMCl was produced with high selectivity and specific output in a microchannel flow reactor at temperatures 120–180 °C and contact times 2-45 min at a pressure of 20 bar. The positive result is obtained due to the laminar profile of the flow and a uniform distribution of the reagents’ concentration over the microchannel cross-section. Investigation of the process kinetics in a microchannel flow reactor made it possible to reveal that the reaction moves to the diffusion resistance mode at a temperature above 150 °C. The kinetic data obtained for the BMIMCl synthesis were used to develop methods for the production of 1-ethyl-3-methylimidazolium and 1-hexyl-3-methylimidazolium chlorides (EMIMCl and HMIMCl, respectively) under the conditions of a microchannel flow reactor. The approach suggested in this paper is of interest for the development of flow and batch setups for a small-tonnage production of dialkylimidazolium, ammonium and pyridinium salts by quaternization of the corresponding alkyl chlorides and nitrogen-containing bases.

Efficient Electrocatalytic Reduction of Furfural to Furfuryl Alcohol in a Microchannel Flow Reactor.

Furfural is considered to be an essential biobased platform molecule. Recently, its electrocatalytic hydrogenation is regarded as a more environmentally friendly process compared to traditional catalytic hydrogenation. In this study, a new, continuous-flow approach enabling furfural electrocatalytic reduction was developed. In an undivided multichannel electrochemical flow reactor at ambient temperature and pressure in basic reaction conditions, the yield of furfuryl alcohol reached up to 90% in only 10 min residence time. Interestingly, the faradaic efficiency was 90%, showing a good effectiveness of the consumed electrons in the generation of the targeted compound. Furthermore, the innovation lies in the direct electrolysis using the green solvent ethanol without the need for membrane separation or catalyst modification, which offers further proof for continuous and sustainable production in industry.

Catalytic Synthesis of Triethanolamine in a Microchannel Reactor

Experimental studies of ammonia oxyethylation in a flow microchannel reactor are performed in broad ranges of temperatures (70–180°C) and residence times (0.47–3.3 min). The main products of the reaction between ethylene oxide (EO) and ammonia are monoethanolamine (MEA), diethanolamine (DEA), and target triethanolamine (TEA). It is shown that EO conversion grows along with residence time τ and reaches 90% at τ = 3.3 min. The highest selectivity toward MEA and DEA is observed at a temperature of 70°C and τ = 3.3 min. High selectivity toward TEA (84%) is achieved at short τ (0.47 min) and the maximum temperature (180°C). The TEA yield grows along with temperature and the residence time to reach 62% at τ = 3.3 min and temperatures of 155–180°C. Mathematical modeling of the ammonia oxyethylation process allows the kinetic constants of individual stages to be calculated. Differences between the obtained kinetic parameters and the literature data, due probably to using a microchannel reactor that ensures high parameters of heat and mass transfer instead of a traditional bulk triethanolamine synthesis reactor, are revealed.

The effect of operating conditions on acylation of 2-methylnaphthalene in a microchannel reactor

Abstract Acylation of 2-methylnaphthalene (2-MN) is a very important reaction in organic synthesis, and the effiency of the continuous reactor is more than one of the batch reactor. Considering that the Friedel–Crafts acylation is a rapid exothermic reaction, in this study, we perform the acylation of 2-MN in a stainless steel microchannel flow reactor, which is characterized by high mass and heat transfer rates. The effect of reactant ratio, mixing temperature, reaction temperature, and reaction time on product yield and selectivity were investigated. Under the optimal conditions, 2-methyl-6-propionylnaphthalene (2,6-MPN) was obtained in 85.8% yield with 87.5% selectivity. Compared with the conventional batch system, the continuous flow microchannel reactor provides a more efficient method for the synthesis of 2,6-MPN.

Pyrolysis of Palm Oil in a Continuous Flow Microchannel Reactor

Palm oil is considered as a potential feedstock for biofuel production in Thailand due to its property and availability. In recent years, there has been an increased attention on upgrading of palm oil to biofuels using various technologies. One of the most promising technologies is pyrolysis, in which palm oil is heated at the temperature in the range of 400 to 500 °C under oxygen-free atmosphere. In the present study, the uncoated catalyst and coated catalyst pyrolysis processes of palm oil for biofuel production in a continuous flow microchannel reactor were investigated with various catalyst types (MgO, Al2O3) at 400-500 °C, 2 ml/hr palm oil flow rate, and 0.1 g of catalysts. Liquid product yield, solid product yield and gaseous product yield were determined. The obtained results revealed that the high triglyceride conversion could be achieved at a short reaction time in microchannel reactor, which attributed to the enhancement of both heat and mass transfer. The pyrolysis liquid products composed of hydrocarbons, free fatty acids, and other oxygenated compounds which are the results of triglyceride cracking. Furthermore, product selectivity of palm oil pyrolysis depended on temperature and catalyst type.

Iminodiacetic acid synthesis over Cu/ZrO2 catalyst in a microchannel flow reactor

Flow microchannel reactor was used to study the synthesis of iminodiacetic acid (IDA) via the catalytic oxidative dehydrogenation of diethanolamine (DEA) over catalyst Cu/ZrO2 (containing copper in amount of 10mass%) at various residence times, reaction temperature ranging within 160–190°C. IDA was shown to form in the course of two consecutive reactions through intermediate compound N-(2-hydroxyethyl)glycine (HEG). DEA conversion and IDA yield were found to increase as residence time and reaction temperature grow, meanwhile HEG concentration maximum on kinetic curves shifts towards shorter residence times. Effective reaction rate constants were determined according to the suggested scheme of IDA synthesis. Calculated activation energies for two consecutive stages of IDA synthesis were found to be 73.7 and 67.2kJ/mol, respectively.

Triethanolamine synthesis in a continuous flow microchannel reactor

Abstract Triethanolamine synthesis from ammonia and ethylene oxide in a continuous flow microchannel reactor has been studied in a wide range of temperatures and residence times. Microchannel reactor performance has been compared to that of conventional tubular reactor. In the microchannel reactor ethylene oxide conversion and triethanolamine yield appear to be higher due to the more efficient mixing of initial reagents and far more intensive heat transfer.

Combination of bio- and chemocatalysis for dynamic kinetic resolution: The assembly strategies for nanozeolite-modified flow microchannel reactors

The combination of bio- and chemocatalysts in one-pot is regarded as a breakthrough both for development of new catalytic concepts and for preparation of high-value chemicals. Zeolite nanocrystals (nanozeolites) have been proved as the most used chemical catalysts and as promising supports for enzyme immobilization. These capabilities of nanozeolites endow them with new possibilities for constructing desired platforms for the combination of bio- and chemocatalysis. In this article, several strategies are proposed to develop a one-pot flow microchannel reactor (MCR) by combining enzyme and chemocatalysis via a nanozeolite assembly approach, and the compatibilities of different types of active centers in various assembly strategies are systematically discussed on the basis of the catalytic results of dynamic kinetic resolution (DKR) of sec-alcohol. By precisely controlling the spatial distribution and the ratio of acidic and enzymatic active sites, as well as the reaction conditions, nanozeolite-modified MCR can achieve fast and highly selective one-pot DKR of sec-alcohol within 30min.

Modelling and design of microchannel reactor for photocatalysis

Chemical reactions in a microreactor can offer new possibilities for many chemical engineering application fields and have been employed in photocatalysis studies. The purpose of this work is to investigate the photocatalytic degradation of salicylic acid (SA) as a pollutant model, in a continuous flow microchannel reactor in order to evaluate the influence of radial concentration profile on the photocatalytic efficiency. The study has been developed on both experimental and theoretical aspects. Microreactors have been manufactured by stereolithography in epoxy resin (Accura® SI 30) and are composed of a channel with a rectangular cross-section of about 1 mm2 with different aspect ratios defined as width/depth. Photocatalytic experiments have been performed at different flow rates. Results can be predicted by the Langmuir-Hinshelwood (LH) kinetic model coupled with surface diffusion. Computational fluid dynamics (CFD-Comsol Multiphysics) can model phenomena and confirmed the reliability of our experimental results with diffusion limitation at low flow rate.

Dynamic control of gold nanoparticle morphology in a microchannel flow reactor by glucose reduction in aqueous sodium hydroxide solution

Continuous flow synthesis of gold nanoparticles was demonstrated using a microchannel reactor with glucose reduction in aqueous alkaline medium. Particle size, morphology, and visual/optical properties of the dispersion liquid were controlled dynamically by tuning of the rate of NaOH addition. Characteristic star-like nanoparticles formed spontaneously as a quasi-stable state, but they changed the morphology to round shape and showed spectral change over time.

A Gold‐Immobilized Microchannel Flow Reactor for Oxidation of Alcohols with Molecular Oxygen

AbstractGoldene Kapillaren: Mit einem goldimmobilisierten Kapillarsäulenreaktor gelingt die Oxidation von Alkoholen mit molekularem Sauerstoff zu Carbonylverbindungen. Diese Kapillarsäulen (siehe Bild) können mindestens vier Tage ohne Aktivitätsverlust verwendet werden.magnified image

A Gold‐Immobilized Microchannel Flow Reactor for Oxidation of Alcohols with Molecular Oxygen

Golden capillaries: A gold-immobilized capillary column reactor allows oxidation of alcohols to carbonyl compounds using molecular oxygen. These capillary columns (see picture) can be used for at least four days without loss of activity.

Flow Pattern, Pressure Drop, and Mass Transfer in a Gas−Liquid Concurrent Two-Phase Flow Microchannel Reactor

Flow pattern, pressure drop, and mass transfer characteristics have been studied for the gas−liquid two-phase flow in a 1.0 mm inner diameter circular microchannel reactor. A mixture of CO2, N2, and polyethylene glycol dimethyl ether was used to represent the gas and liquid phases, respectively. Bubbly, slug, churn, and slug-annular flow patterns were observed in the present work. A flow pattern map using superficial gas and liquid velocities as coordinates has been developed and compared to the existing flow pattern maps for ∼1 mm diameter channels. The data obtained for the pressure drop of the two-phase flow were analyzed and compared with the homogeneous model and the separate flow model to assess their predictive capabilities. The liquid side volumetric mass transfer coefficient increased with an increase of the superficial gas and liquid velocities, and the influences of the superficial gas and liquid velocities on it were demonstrated. The liquid side mass transfer coefficient, which was as high as...

Investigating the Micro-Channel Flow Reactor Configuration on the Liquid Phase Synthesis of tert-amyl Methyl Ether Catalyzed by Sulfuric Acid

Investigating the Micro-Channel Flow Reactor Configuration on the Liquid Phase Synthesis of tert-amyl Methyl Ether Catalyzed by Sulfuric Acid