Reaction Chemistry & Engineering最新文献

(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.

An autonomous continuous-flow, hydrothermal synthesis reactor, capable of self-optimising nanoparticle size using an in-line characterisation technique and machine learning is presented. The developed system is used for synthesis of hematite (α-Fe₂O₃) nanoparticles across three process variables, optimising for a target particle size. Optimisation is achieved in under 7 h with only 500 ml of 0.1 M Fe(NO₃)₃·9H₂O aqueous stock solution used, and without human intervention.

Indoxacarb is a novel broad-spectrum oxadiazine insecticide, and only (S)-indoxacarb is the active ingredient. (S)-5-Chloro-2-hydroxy-1-oxo-2,3-dihydro-1H-indene-2-carboxylate is the key intermediate for synthesising (S)-indoxacarb. However, the current process for producing the intermediate is inconvenient and difficult to scale up. Herein, we report an improved protocol for the efficient, highly stereoselective and industrially feasible preparation of the intermediate, which features the use of tert-butyl hydroperoxide (TBHP, 70% in H₂O) as oxidant, purification by filtration and mild conditions.

Light interacts with gas bubbles in various ways, potentially leading to photon losses in gas-liquid photochemical applications. Given that light is a valuable 'reagent', understanding these losses is crucial for optimizing reactor efficiency. In this study, we address the challenge of quantifying these interactions by implementing a method that separately determines the photon flux and utilizes actinometric experiments to determine the effective optical path length, a key descriptor of photon absorption. The results reveal the unexpected impact of gas phase introduction in continuous-flow photoreactors. Notably, photon absorption, and consequently the throughput of a photoreactor, can be increased by the introduction of a gas phase. This enhancement arises from the reflection and refraction effects of gas bubbles, which can intensify light intensity in the liquid volume and thereby offset any loss in residence time. The photon absorption losses that were observed were associated with large bubbles and were less significant than anticipated. In contrast, the introduction of small bubbles was found to increase photon absorption, suggesting it is a potential strategy to optimize photoreactor performance.

Excess fluoride in drinking water can cause poisoning. To solve this problem, a porous metal–organic framework (MOF) was fabricated via the solvothermal approach and employed for the removal of fluoride ions from water. ZrAl-MOF was fabricated by self-assembly of polyvalent Zr⁴⁺, Al³⁺metal ions and 4,4-biphenyldicarboxylic acid (BPDC). The developed metal-based ZrAl-MOF was used to remove fluoride ions from water and could remove fluoride ions to a maximum of 109.2 mg g⁻¹ (308 K). ZrAl-MOF has a special core–shell structure with a layer of small balls stacked outside and cobweb-like structure inside. The properties of the bimetallic MOF can be adjusted by Zr⁴⁺, Al³⁺ metal ions and BPDC to meet the demand for maximum adsorption performance. Bimetallic MOFs commonly have a substantial specific surface area, capable of providing numerous active sites and being favorable for the adsorption reaction of substances. The electronic properties of different metals may lead to stronger electrostatic attraction and enhanced adsorption of fluoride ions. The factors affecting the adsorption effect, such as solution pH, ZrAl-MOF dosage, reaction time, initial fluoride concentration, temperature, and coexisting anions, were optimized. The fluorine adsorption capacity of ZrAl-MOF was less affected by the adsorbent under acidic conditions and by the presence of sulphate and nitrate ions in the water. In addition, the experimental data were fitted with various adsorption kinetic and isotherm models. It is shown that fluorine adsorption is feasible and spontaneous. The fluorine adsorption mechanism of ZrAl-MOF is mainly electrostatic attraction and ion exchange.

To accelerate the energy transition, processes for the production of sustainable fuels are desired such as the conversion of syngas from biogenic residues into liquid fuel by using the Fischer–Tropsch synthesis (FTS). These novel conversion processes are often of smaller scale due to the feedstock for which intensified reactor concepts are required. Structured reactors present viable alternatives to conventional packed bed reactors. Structured reactors can be obtained by e.g. loading a conventional tubular reactor with structured internals. Here, two strategies were followed in an effort to obtain the highest productivity per reactor volume, namely application of 3D-printed catalysts and secondly, thermally conductive aluminium and copper contactors filled with catalyst particles. Superior productivities were obtained by applying Al foam and 3D-printed Cu contactors when packed with FTS catalyst particles, with heat duties of respectively 880 kW m⁻³ and 1238 kW m⁻³ compared with only 185 kW m⁻³ for the 3D-printed catalyst and 218 kW m⁻³ for a conventional packed bed. For the system using the ordered 3D-printed Cu contactors, it presented a productivity of at least 0.85 g_C5+ g_cat⁻¹ h⁻¹. The excellent productivities could be correlated to the high thermal conductivity of the metal contactors facilitating the heat transfer from the bed centreline to the reactor wall as revealed by laser flash analysis (LFA) thermal conductivity measurements.

During the past decade, multicomponent reactions (or MCRs) have become excellent tools for rapidly synthesizing structurally complex and high-value small molecules. In particular, the development of MCRs for building molecules of interest in biology and medicine has been receiving increasing attention due to their simplicity, efficiency, and convergent advantages. They have widespread applications in drug development, materials science, and biomedicine. It is noteworthy that MCRs typically have features such as mild conditions and universal compatibility with green solvents, highlighting their green sustainability. This minireview highlights recent progress in MCRs under different catalytic conditions until 2024. We classify the content of the review according to the type of catalyst in order to offer a better overview and deeper understanding to the readership, hoping this work will exhibit the charm of multicomponent reactions.

Correction for ‘Combination of near-infrared spectroscopy and a transient flow method for efficient kinetic analysis of the Claisen rearrangement’ by Yoshihiro Takebayashi et al., React. Chem. Eng., 2024, 9, 2975–2983, https://doi.org/10.1039/D4RE00301B.