Reaction Chemistry & Engineering最新文献

Large-scale synthesis of organic compounds using electrochemistry is an emerging, green, and sustainable approach, as it reduces the need for harsh chemicals, potentially lowers energy consumption, and minimizes waste. The C–H amination reactions are important because of the direct transformation of inert C–H bonds into more efficient and selective C–N bonds. This reaction also helps streamline synthetic routes by reducing the number of steps and the need for protecting groups. For large-scale electrochemical C–H amination reactions, the best way is to increase the electrode surface area. However, this approach is a big challenge with classical electrodes, e.g., glassy carbon electrode (GCE). New-type flexible, rollable, and durable electrodes are required to overcome this challenge. This work reports the production of a flexible graphene-based paper electrode (FGPE) using an economic mold-casting method for large-scale electrochemical C–H amination reactions of various benzoxazole derivatives. For the characterization of FGPEs and products of electroorganic synthesis, we have performed numerous advanced techniques. We have determined that C–H amination reactions occur with yields of at least 95% in 13 h by bending the FGPE. Large-scale electrochemical synthesis applications were applied using 5 times more electrode surface area of the FGPE, leveraging its flexibility and foldability. They exhibited a yield of 90% with a 16.7-fold increase in benzoxazole amount in the cell.

As an important chemical, benzaldehyde (BzH) can be synthesized by oxidizing dibenzyl ether (DBE) with nitric acid (HNO₃). This is an environmentally friendly and chlorine-free production process, but it has problems such as intense in situ gas generation, low space–time yield and safety issues. This study developed a safe and efficient continuous-flow synthesis method using a packed-bed microreactor. Five critical parameters including reaction residence time, glass bead particle size, temperature, oxidant concentration, and initiator dosage were systematically investigated. Under optimal conditions (T = 85 °C, d = 104.5 μm, HNO₃ eq. = 3 and NaNO₂ eq. = 0.009), the conversion of DBE and the yield of BzH reached 80.11% and 96.35% after 17.92 min. The space–time yield was twice that of capillary microreactors and 40 times that of batch reactors. The reasons for in situ gas production in capillary microreactors and its negative impacts were explored. A kinetic model was developed, providing significant theoretical insights and practical value for better understanding the oxidation process and optimizing the process parameters.

Melanoidin (MD), a refractory macromolecule pollutant common in industrial wastewater, presents significant environmental challenges due to its chemical stability and resistance to biodegradation. In this study, a crystalline covalent organic framework (COF) was synthesized using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and triformylbenzene (TFB) as building blocks. The resulting TAPT–TFB COF possessed an ordered mesoporous structure, abundant nitrogen-rich active sites, and an extended π–π conjugated framework. These structures featured enhance molecular adsorption and facilitated efficient separation and transport of photogenerated charge carriers, thereby promoting effective MD removal. Notably, 49.5% of MD removal occurred under dark conditions, highlighting the substantial contribution of adsorption. Under simulated irradiation, the TAPT–TFB COF achieved 90.0% MD removal within 90 min, following pseudo-second-order kinetics with the low activation energy of 17.1 kJ mol⁻¹, indicating an adsorption-assisted photocatalytic process. Furthermore, the roles of key reactive species, the influence of coexisting ions, catalyst stability, and performance in real water matrices were systematically evaluated, confirming the TAPT–TFB COF's robustness and practical applicability. This work highlights nitrogen-rich TAPT–TFB COFs as promising, durable adsorption-assisted photocatalysts for effective remediation of refractory organic pollutants, broadening the scope of advanced wastewater treatment technologies.

The alkylation of the nitrogen atom is a key reaction class for the synthesis of building blocks, APIs and other bioactive compounds. Herein, we report a green N-alkylation methodology that combines a simple continuous-flow protocol using readily accessible reagents and environmentally benign solvents, aiming to improve both efficiency and sustainability. This methodology enabled the synthesis of 15 derivatives, varying both the Michael acceptors and amine substrates, with yields of up to 93%. Transformation of selected APIs were also included to demonstrate the applicability of the process. Green-metric calculations were conducted to further highlight the sustainability potential of the methodology.

This study numerically investigates gas–solid flow behaviour and reactive species transport during the hydrochlorination of aluminium in a fluidized bed reactor (FBR) operating at a temperature of 523 K. The present study reports the first numerical investigation of the aluminium hydrochlorination reaction. The hydrogen chloride (HCl) gas inlet flow rates are varied as 0.1, 0.2, and 0.3 lpm. A coupled Eulerian–Lagrangian approach employing the MP-PIC model is utilized to resolve solid–gas momentum exchange, species consumption, and product formation. In the MP-PIC model, the gas phase is treated as a continuum Eulerian phase and the solid aluminium particles are represented by Lagrangian particles. To perform the simulation, a reactor having a height of 570 mm and a diameter of 12 mm is considered at a temperature of 523 K. The results reveal that the low-velocity regime produces distinct hydrodynamic characteristics when compared to high flow rates. Furthermore, the results showed that decreasing the flow rate enhances the consumption of HCl and increases the production of aluminium chloride (AlCl₃) and hydrogen (H₂) along the reactor height. At a flow rate of 0.1 lpm, the extended residence time enables the highest conversion, while increasing the flow rate to 0.3 lpm leads to an incomplete reaction despite improved mixing and turbulence. The finding highlights the dominant role of residence time in low-flow hydrochlorination and provides insights into the optimal operation of a small-scale fluidized bed reactor for aluminium hydrochlorination.

Aminophenols are versatile intermediates widely utilized in the pharmaceutical, dye and pigment, and materials science industries. Conventional synthetic methods typically involve harsh reaction conditions, use expensive noble metal catalysts, or generate a large amount of environmentally unfriendly “three wastes” (residual solids, off-gas, and wastewater). In this study, we systematically optimized the diazo coupling reduction process and established an efficient and practical synthetic route for aminophenol synthesis. This protocol features a broad substrate scope (20 examples), mild reaction conditions, straightforward post-reaction treatment, and excellent yields (up to 96%). The application of this process was further extended to the development of a kilogram-scale synthesis of the muscle relaxant chlorzoxazone. Notably, the overall three-step yield reached up to 75.6%.

The traditional reaction screening method means testing reagents such as bases, ligands, and catalysts using trial-and-error approaches, which is tedious, and fewer reagents can be evaluated. However, by developing a method that can be used to dispense solid chemical reagents at a nanomole scale for high-throughput reaction screening (HTS), a combination of multiple reagents can be screened rapidly until optimal reagents can be identified. As a proof of principle, a solid dispensing method developed using silica (SiO₂) as an inert carrier of reagents was utilised to screen four bases and twelve ligands for the copper-catalysed oxidative esterification of benzaldehyde and the oxidation reaction of styrene. Using high-throughput screening together with the developed solid dispensing method, about 96 reactions of copper-catalysed oxidative esterification of benzaldehyde with ethyl bromide and benzyl bromide were screened, and one reaction of oxidation of styrene until an optimal combination of reagents was found.

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for safe, efficient, and reversible hydrogen storage and transport. While heterogeneous catalysts have traditionally dominated LOHC hydrogenation and dehydrogenation, homogeneous catalysts present distinct advantages, including high selectivity, tunable active sites, and operation under milder conditions. This review systematically examines recent advances in the design and application of homogeneous catalysts for the hydrogenation and dehydrogenation of both homocyclic LOHCs, such as benzene, toluene, and naphthalene derivatives, and N-heterocyclic LOHCs, including quinolines, carbazoles, and indoles. Emphasis is placed on structure–activity relationships, mechanistic insights, and emerging trends, with a focus on catalysts based on both noble and earth-abundant metals. Beyond catalyst performance, we address key challenges in homogeneous catalyst recovery, recycling, and process integration, all of which are critical for industrial scalability. By identifying current gaps in the literature and outlining future research priorities, this work aims to guide the development of efficient, reversible, and economically viable homogeneous catalytic systems for next-generation hydrogen storage technologies.

In the last years, the use of 3D printing for the preparation of structured materials with catalytic functionalities has attracted considerable interest. In this work, using ZSM-5 zeolite as acidity provider, we explore two routes that employ additive manufacturing to prepare structured catalysts for dimethyl ether production via methanol dehydration. In the first route, ZSM-5-based monoliths are 3D-printed using crystalline ZSM-5 powder and bentonite clay as a binder. In the second route, α-alumina support structures are first fabricated via robocasting, followed by in situ hydrothermal synthesis of ZSM-5 on the printed structures. The structured catalysts along with their starting materials are characterized by N₂ adsorption, XRD, pyridine-FTIR, electron microscopy, while stress–strain curves are also obtained to evaluate the monoliths' mechanical stability. The structured catalyst prepared via the first route adequately retains the physicochemical properties of the ZSM-5 crystallites. Via the second route, ZSM-5 crystallites with good porosity and acidity are grown on the 3D printed α-Al₂O₃ support, achieving a total loading of ca. 4 wt%. When compared on an equivalent ZSM-5 basis, the ZSM-5/α-Al₂O₃ catalyst exhibits up to twice the activity in methanol conversion with 100 C-mol% DME selectivity, while it also outperforms the corresponding hydrothermally prepared ZSM-5 powder. This is possibly linked to the excellent dispersion of the ZSM-5 active sites on the 3D-printed α-Al₂O₃ structure, which provides a unique substrate for the growth of surface ZSM-5 nano-crystallites. This work highlights the great potential of employing 3D printing techniques for catalytic applications.

Lipase immobilization is an effective strategy for enhancing enzyme stability, reusability, and catalytic efficiency in biotechnological processes. This review critically evaluates recent advances in adsorption, embedding, covalent coupling, and cross-linking methods, highlighting their advantages, limitations, and industrial applicability. Emphasis is placed on the design of support materials and their influence on enzyme–support interactions, which govern overall catalytic performance. Applications in pharmaceuticals, food systems, environmental remediation, and biodiesel production are analyzed to identify current trends and technological challenges. Although significant progress has been made, issues such as high production costs, lack of standardization, and limited scalability continue to hinder industrial implementation. Future efforts should focus on developing sustainable support materials and optimizing enzyme–support interactions to enhance immobilization effciency. These innovations will facilitate the development of efficient and environmentally friendly biomanufacturing systems.