Reaction Chemistry & Engineering最新文献

A site- and stereoselective deuterium labelling method for carbohydrates has been developed using a Ru/C catalyst under continuous flow conditions. It has been demonstrated that enhancing the void fraction of the catalyst cartridge leads to improved incorporation, while maintaining high selectivity over 150 h. This scalable, sustainable approach has the potential to reduce energy use, waste and Ru consumption, thus broadening continuous flow applications in organic synthesis.

(R)-Citronellal is one of the key chiral intermediates in the synthesis of the isomer (-)-menthol, one of the most commercialised terpenoid flavours worldwide. Enzymatic approaches could represent a less energy-demanding alternative for its synthesis, such as a previously reported bienzymatic cascade starting from inexpensive, commercially available geraniol. A copper radical oxidase (CgrAlcOx) followed by a flavin-dependent ene reductase (OYE2) were used to obtain (R)-citronellal. Here, we used a metal-affinity immobilisation strategy on the His-tagged enzymes for the cascade and studied enzyme recovery and reusability as well as increased solvent tolerance. After screening a panel of resins for enzyme immobilisation and water-immiscible co-solvents, we successfully obtained 95% conversion to (R)-citronellal with 96.9% enantiomeric excess (ee) in a concurrent cascade after 7 h of reaction time, starting from 10 mM of geraniol.

Correction for ‘Intensification of silver nanoparticle synthesis through continuous flow split and recombine microreactors’ by Amritendu Bhuson Ghosh et al., React. Chem. Eng., 2024, 9, 1707–1720, https://doi.org/10.1039/D4RE00025K.

Correction for ‘Rare-earth doped hexagonal NaYbF₄ nanoprobes with size-controlled and NIR-II emission for multifunctional applications’ by Yu Min et al., React. Chem. Eng., 2023, 8, 2258–2269, https://doi.org/10.1039/D3RE00168G.

Coupling fermentation derived oxygenates via Guerbet-type reactions offers a potential route for producing fuels and chemicals from agricultural feedstocks. In this work the vapor phase reactions of n-butanol over a bimetallic PdZn/SiO₂ catalyst and physical mixtures of PdZn/SiO₂ and TiO₂ were studied. The bimetallic catalyst was highly selective for n-butanol dehydrogenation without the subsequent decarbonylation of butanal which is characteristic of monometallic Pd nanoparticles. When combined with TiO₂, a known aldol condensation catalyst, the bifunctional system performs Guerbet-type coupling reactions and produces mixtures of C₈ oxygenates and higher-order products including C₇, C₈, and C₁₂ hydrocarbons. Results show that within the reaction network PdZn/SiO₂ performs dehydrogenation/hydrogenation reactions and decarbonylates C₈ aldehydes to form C₇ hydrocarbons. TiO₂ catalyzes aldol condensation and alcohol dehydration reactions responsible for producing C₈ and C₁₂ hydrocarbons. Based on the developed understanding of the function of each catalyst, it was shown that increasing the Brønsted acidity of the TiO₂ catalyst resulted in an increase in the production of C₈ hydrocarbons relative to C₁₂ hydrocarbons. This work demonstrates the ability of bimetallic Pd-based catalysts that are selective for alcohol dehydrogenation to participate in Guerbet-type coupling reactions and that their combination with an appropriate aldol condensation/dehydration catalyst is an effective strategy to produce higher molecular weight oxygenates and hydrocarbons from renewable resources.

A magnetic photocatalyst based on reduced graphene oxide and semiconducting MnV₂O₆ (rGO/Fe₃O₄/MnV₂O₆) was synthesized by magnetizing the rGO/MnV₂O₆ composite for the efficient degradation of methylene blue (MB), a biodegradation-resistant dye. The prepared magnetic photocatalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer–Emmett–Teller surface area analysis, Barrett–Joyner–Halenda (BET-BJH) pore analysis and vibrating sample magnetometry (VSM). Its photocatalytic properties and activity were investigated using UV–Vis diffuse reflectance spectroscopy (DRS), fluorescence spectroscopy and inductively-coupled plasma analysis. The synthesized rGO/Fe₃O₄/MnV₂O₆ nanocomposite exhibited a bandgap of 2.59 eV and a specific surface area of 201.5 m² g⁻¹. The optimum photocatalytic conditions for efficient MB photodegradation were determined, and the photocatalytic efficiency was investigated under different light irradiations, including blue and yellow light as well as sunlight. The rGO/Fe₃O₄/MnV₂O₆ photocatalyst demonstrated excellent MB degradation efficiency, achieving up to 94% under sunlight irradiation. Additionally, the catalyst exhibited remarkable reusability, maintaining 88% degradation efficiency after the 6th cycle, with negligible structural changes. The magnetic properties of the employed photocatalyst played a key role in facilitating their separation and recycling. The kinetics and mechanism of the photodegradation process were evaluated, revealing a pseudo-first-order rate constant of 0.0882 min⁻¹ for a hydroxyl radical-based mechanism. The MB degradation was driven by the generation of superoxide (O₂˙⁻) and hydroxyl (˙OH) free radicals during the reaction.

This work presents a new approach to recycling silicone waste: depolymerization in ammonia. The optimal depolymerization conditions (150 °C, 0.25 mL H₂O, 24 h) to achieve complete polymer conversion were developed using a model siloxane fluid PMS-200. The method performance was demonstrated on model unfilled silicone rubbers obtained by classical methods of curing silicone elastomers such as hydrosilylation, condensation of functional groups and radical polymerization in the presence of benzoyl peroxide. The versatility of this approach for recycling both linear silicones (fluids and gums) and filled rubbers (fillers of different nature) was demonstrated. The completeness of the depolymerization and the analysis of the low molecular weight products were tested by SEC, GC and ²⁹Si NMR spectroscopy. The scalability of the process has been demonstrated.

In a previous communication, we described a flow chemical microwave implementation, where the reaction mixture is circulated. In this way, the given reactor capacity can be increased by up to ten times without any special modifications. It was investigated how the flow rate affects the required number of cycles, and hence the time required to achieve the maximum conversion. The role of the ionic liquid catalyst, and the effect of the increase in the volume on the outcomes were also studied. In this paper, we analyse further the data obtained from an energetic point of view. It was observed that the power of the magnetron of the microwave reactor is consumed by the sets marked by higher flow rates and by increased volumes. The direct esterification of phenyl-H-phosphinic acid with butyl alcohol, which has been previously reported under microwave conditions, was chosen as a model reaction.

This work investigates the immobilization of laccase obtained from Galactomyces geotrichum onto modified bentonites. The structures of the composites were examined using SEM, FTIR, and BET techniques. Biocatalysts were evaluated in terms of activity, stability and kinetic parameters. Among the immobilized laccases, GDU-bent-lac exhibited the highest efficacy in operational (96% after 10 cycles), thermal (61% within 24 h at 65 °C), and storage (79.69% for 30 days) stabilities. Results suggested that the Langmuir model better correlated with the obtained data than the Freundlich isotherm. Results of the biodegradability study indicated that the increase in the biodegradability index of olive mill wastewater was remarkable when CTAB-bent-lac was used. Additionally, the bulk increase in the biodegradability was related to the support before laccase immobilization (0.43), and moreover, immobilization enhanced the biodegradability to some extent (0.46). In this research, a strong laccase-producing microorganism that was isolated from olive mill wastewater was used for the bioremediation of the same wastewater. To the best of our knowledge, the immobilization of laccase produced by G. geotrichum, isolated from OMW, onto modified bentonites has not been published earlier. Furthermore, the feasibility of using immobilized laccase to increase the biodegradability of OMW was investigated for the first time.

With the growth in importance of H₂ both industrially and as a potential energy vector along the pathway to achieving future environmental sustainability, there is an increasing need for cleaner and more efficient methods of H₂ production. One promising short-term solution is to perform the water-gas shift reaction for H₂ production in a chemical looping reactor to produce separate H₂ and CO₂ streams, thereby reducing equipment size and the cost of downstream CO₂ separation. Non-stoichiometric perovskite oxides have been identified as promising oxygen carrier materials (OCMs) for the chemical looping water-gas shift (CLWGS) process as they can be engineered to allow rapid oxygen uptake kinetics, and also benefit from a thermodynamic advantage allowing higher conversions than that of conventional mixed feed reactor systems at the same temperature. The relationship between the oxygen non-stoichiometry of the solid OCM and the equilibrium oxygen partial pressure of the gas phase streams plays an important role in determining the gas conversions and usable oxygen capacity of the OCM. In this work, an optimal relationship between the two material properties in a thermodynamically limited system is proposed, and an equilibrium packed-bed reactor model is used for validation. The effect on conversions was investigated by varying the thermodynamics of the non-stoichiometric material relative to the proposed optimal case. More generally, an analogue of the pinch analysis can be used to analyse chemical looping water-gas shift reactions and similar processes.