Search Results (12)

The chemical industry faces major challenges despite recent progress in the transition to more environmentally friendly processes. Sustainable industrial chemistry relies on the optimization of protocols and downstream processes such as extraction, purification, and drying. Process intensification, which includes non-conventional techniques and continuous manufacturing, has emerged as a key strategy to improve efficiency and environmental impact. Technologies such as ultrasound, microwaves, mechanochemistry, and reactive extrusion offer improved performance but face scalability and proprietary barriers. Flow chemistry offers additional benefits, including smaller reactors, lower energy consumption (from 40 to 90%), and increased safety through continuous, automated reactions. However, implementing these methods requires overcoming engineering, economic, and regulatory hurdles. Biphasic catalysis and sonochemical activation in liquid–liquid systems are promising approaches for scalable reactions under mild conditions. The pharmaceutical industry, a major source of waste, has shown resistance due to high validation costs and complex regulations. Fortunately, international regulatory institutions have introduced programs to facilitate the introduction of advanced technologies. Future perspectives emphasize the integration of modular, intensified processes with digitalization and smart manufacturing. Collaborative, transdisciplinary research will be crucial for accelerating commercialization and addressing sustainability challenges in chemical production. Full article

Microwave electrodeless ultraviolet (MWUV) technology, as an emerging food processing technique, has garnered growing attention in the realm of food science in recent years. Based on different application requirements, MWUV equipment types are categorized as microwave oven reactor, continuous-flow UV-microwave reactor, coaxially driven MWUV reactor, and complete ultraviolet reactor. The luminescence properties of MWUV equipment depend on their filler gas; mercury is commonly used as a filler gas to produce a wavelength at 253.7 nm for food non-thermal sterilization. The microbial sterilization effect of MWUV is primarily attributed to the synergistic action of microwave and ultraviolet (UV): MWUV enhances reactive oxygen species (ROS) production, disrupts the cell membrane structures of bacteria, leads to bacterial endosome leakage, and induces nucleic acid damage. MWUV extends food shelf-life by eliminating microorganisms without significantly altering food quality compared with traditional thermal sterilization methods. Additionally, MWUV, combined with digestion reagents such as HNO₃ and H₂O₂, can effectively enhance the digestion of food samples to detect essential and toxic elements. Studies on MWUV technology hold broad potential in the food industry, with promising implications for food safety and consumer demand for high-quality food. Future research may focus on optimizing the equipment parameters and integrating with other food processing technologies to facilitate further development and application of MWUV. Full article

Microwave continuous-flow heating has been proven to reduce the time of chemical reaction, increase the conversion rate, and improve product purity effectively. However, there are still problems such as relatively low heating efficiency, unideal heating homogeneity, and poor compactness, which brings further drawbacks like difficulty in fabrication and integration. In this study, a compact microwave continuous-flow heater based on six fractal antennas is proposed to address the problems above. First, a multi-physics simulation model is built, while heating efficiency and the volumetric coefficient of variance (COV) are improved through adjusting the geometric structure of this heater and the phase assignment of each radiator. Second, an experiment is conducted to verify the simulation model, which is consistent with the simulation. Third, a method of fast varying phases to achieve greater heating efficiency and heating homogeneity is adopted. The results show that the single-phase radiator improved efficiency by 31.1%, and COV was significantly optimized, reaching 64%. Furthermore, 0–100% ethanol–water solutions are processed by the heater, demonstrating its strong adaptability of vastly changing relative permittivity of liquid load. Moreover, an advance of this microwave continuous-flow heater is observed, compared with conventional multi-mode resonant cavity. Last, the performance of this microwave continuous-flow heater as the chemical reactor for biodiesel production is simulated. This design enables massive chemical production in fields like food industry and biodiesel production, with enhanced compactness, heating efficiency, and heating homogeneity. Full article

Non-isocyanate Polyurethane (NIPU) has been known to result from a thermal-ring-opening reaction between bis-cyclic carbonate (BCC) compounds and polyamines. BCC can be obtained from carbon dioxide capture using an epoxidized compound. Microwave radiation has been found to be an alternative process to conventional heating for synthesizing NIPU on a laboratory scale. The microwave radiation process is far more efficient (>1000 times faster) than using a conventional heating reactor. Now, a flow tube reactor has been designed for a continuous and recirculating microwave radiation system for scaling up NIPU. Furthermore, the TOE (Turn Over Energy) of the microwave for a lab batch (24.61 g) reactor was 24.38 kJ/g. This decreased to 8.89 kJ/g with an increase in reaction size of up to 300 times with this new continuous microwave radiation system. This proves that synthesizing NIPU with this newly-designed continuous and recirculating microwave radiation process is not only a reliable energy-saving method, but is also convenient for scale-up, making it a green process. Full article

This paper proposes a high-efficiency single-mode traveling wave reactor based on a rectangular waveguide and its design method for continuous flow processing. The reactor has a large-capacity reaction chamber (1000 mm × 742.8 mm × 120 mm) that can provide high-energy-efficiency and approximately uniform microwave heating. The microwave heating uniformity is improved by maintaining single-mode microwave transmission and eliminating higher-order modes in such a multi-mode reaction chamber. The high energy efficiency of microwave heating is achieved by adopting impedance matching techniques. The incident microwave in the reactor can remain in a traveling wave state, and the power reflection can be minimized. Several numerical simulations based on multi-physics modeling are conducted to investigate the heating uniformity, the energy efficiency and the flexibility under different operation conditions. The results show the microwave energy efficiency can be higher than 99%, and meanwhile, the coefficient of temperature variation can be lower than 0.4. Furthermore, when the reactor is operated under different flow velocities and with different heating materials, both the energy efficiency and the heating uniformity can also meet the above requirements. The proposed reactor can be used in the applications such as oil processing, wastewater tackling, chemical synthesis, beverage sterilization and other microwave-assisted continuous flow processes that require high heating uniformity, high energy efficiency and good adaptability. Full article

Over the last decade, enabling technologies and sustainable catalysis have become appealing options for biodiesel preparation because of their impressive process intensification and energy savings. The present review will compare the most innovative protocols that have been developed and improved to use non-conventional energy sources and catalysts that are performed, in particular, using continuous-flow methods. Although this account cannot be comprehensive, it will, however, provide a good overview of the reaction-rate improvements and catalyst activation that is provided by microwaves, ultrasound, hydrodynamic cavitation, flow reactors and even hybrid techniques. Advantages and limitations are discussed together with industrial scalability. Full article

A simple and efficient microwave (MW)-assisted method was elaborated for the catalyst-free synthesis of isoindolin-1-one-3-phosphonates by the three-component condensation of 2-formylbenzoic acid, aliphatic primary amines and various dialkyl phosphites. The batch and the continuous flow reactions were optimized in respect of the temperature, the reaction time and the molar ratio of the starting materials. To evaluate the potential of MW irradiation, comparative thermal experiments were also carried out. In order to obtain “real time” information about the condensation, the special Kabachnik–Fields reaction of 2-formylbenzoic acid, butylamine and diethyl phosphite was monitored by in situ FT-IR spectroscopy. The novel title compounds could be prepared in high yields at low temperature under a short reaction time. A suitable method could also be developed for the preparation of the isoindolin-1-one-3-phosphonates at a “few g” scale by using a continuous flow MW reactor. Full article

The microwave (MW) technique is an efficient tool in the realization of organic reactions, as well as in the analytical field and in the food industry. The continuous flow approach is of special interest as a promising way to scale-up MW-assisted syntheses. Besides summarizing the batch precedents, this review focuses on the utilization of the MW technique in the continuous-flow realization of organophosphorus transformations. The advantages of the continuous flow technique against the batch accomplishment are also shown. A few materials chemistry-related applications are also mentioned. Full article

The continuous flow alcoholysis of dialkyl H-phosphonates by aliphatic alcohols in the absence of a catalyst was elaborated using a microwave (MW) reactor equipped with a flow cell. By the precise control of the reaction conditions, the synthesis could be fine-tuned towards dialkyl H-phosphonates with two different and with two identical alkyl groups. In contrast to the “traditional” batch alcoholysis, flow approaches required shorter reaction times, and the products became available at a larger scale. Full article

(E)-3-[4-(Pent-4-en-1-yloxy)phenyl]acetic acid is one of the useful components of liquid crystal materials which can be produced through Williamson ether synthesis by synthesizing 4-hydroxy-cinnamic acid and 5-bromo-1-pentene. Although Williamson ether synthesis is generally slow under conventional external heating conditions, microwave irradiation was effective for significant acceleration of the etherification. Furthermore, we demonstrated the rapid and continuous synthesis of (E)-3-[4-(pent-4-en-1-yloxy)phenyl]acetic acid, using a microwave-assisted flow reactor developed by us, in which the blockage by salt precipitation was suppressed by the continuous addition of an aqueous methanol solution after the reaction cavity. Full article

Viability of the continuous-flow synthesis of rhomboidal copper(II) oxide (CuO) micro- and nanonoparticles was demonstrated. It has been shown that ultrasonic mixing of reactants, in the stage of Cu(OH)₂ synthesis, followed by microwave irradiation of the resulting suspension, gives very fine particles of CuO at high yield and within minutes. Near optimal parameters for the synthesis of fine particles in the continuous reactor were determined. Full article

A controlled radical polymerization process using the Reversible Addition-Fragmentation Chain Transfer (RAFT) approach was scaled up by a factor of 100 from a small laboratory scale of 5 mL to a preparative scale of 500 mL, using batch and continuous flow processing. The batch polymerizations were carried out in a series of different glass vessels, using either magnetic or overhead stirring, and different modes of heating: Microwave irradiation or conductive heating in an oil bath. The continuous process was conducted in a prototype tubular flow reactor, consisting of 6 mm ID stainless steel tubing, fitted with static mixers. Both reactor types were tested for polymerizations of the acid functional monomers acrylic acid and 2-acrylamido-2-methylpropane-1-sulfonic acid in water at 80 °C with reaction times of 30 to 40 min. By monitoring the temperature during the exothermic polymerization process, it was observed that the type and size of reactor had a significant influence on the temperature profile of the reaction. Full article