Reaction Chemistry & Engineering最新文献

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.

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.

Two layers of mesoporous silica with orthogonally stacked and oriented mesopore cylinders were observed by transmission electron microscopy. Analysis showed orthogonally stacked mesostructures with different pore sizes depending on the position. Furthermore, the adsorbed dye inside the mesopores suppressed structural collapse, and elution occurred from the top layer.

The global energy crisis highlights the need for sustainable energy solutions. Nitrogen fixation, converting N₂ into valuable products, is gaining attention. In this study, we investigate the effect of water vapor in gas-phase nitrogen fixation via gas–liquid mixed-phase pulsed discharge. Results show that increasing water vapor enhances nitrogen fixation efficiency but introduces a competitive mechanism between NH₄⁺ and NO_x. This study examines the effect of water vapor on nitrogen fixation via pulsed discharge at 20 kV and 10 Hz. When water vapor content reached 100%, NH₄⁺ concentration decreased by 49.2%, while NO₃⁻ concentration increased by 19%. Additionally, raising the liquid temperature from 6 °C to 80 °C reduced NH₄⁺ by 57.6% and increased NO₃⁻ by 54.1%. Spectral diagnostics and radical scavenging experiments confirmed the key role of H and OH radicals in the fixation process. Reaction kinetics analysis further validated the competition between NH₄⁺ and NO_x synthesis. While water as a raw material is critical for green nitrogen fixation, its impact on product distribution must be considered in optimizing future applications.

In this paper, the effect of H₃PO₄-activated biochar on nickel-based catalysts for steam methane reforming (SMR) was explored. FTIR, BET, XRD, Raman, TEM, HRTEM, H₂-TPR and XPS analyses were used to characterize the supports and catalysts. The results showed that the activation of H₃PO₄ regulates the pore structure of the support and promotes the development of micropores into mesopores. Meanwhile, H₃PO₄ introduced more functional groups to promote the dispersion of Ni, which reduced the average particle size of the catalyst from 32 nm to 19 nm. In addition, it increased the number of defects of the catalyst and inhibited carbon deposition during the SMR process, which improved the activity and stability. The catalyst shows best performance at 650 °C, and the CH₄ conversion reaches 80.89%. After 80 h, the conversion decreased by only 2%.

In this work, a facile and efficient ultrasound-assisted fast synthesis of quinazolinones from o-aminobenzamides and aldehydes is reported. The reaction proceeds smoothly under ambient temperature and pressure conditions without the need for a metal catalyst in just 15 minutes. In addition, this approach exhibits broad substrate tolerance and provides a series of quinazolinones with moderate to excellent yields. The results reported here reveal an important new application of ultrasound-assisted synthesis in the fast synthesis of valuable organic products.

Covalent linkages between lignin and cellulose/hemicellulose, referred to as lignin carbohydrate complexes (LCCs), have been identified to significantly contribute to the refractory nature of lignocellulosic biomass. However, experimental resolution of LCCs is limited, leading to a very limited knowledge of the chemical and structural details of LCCs. As a result, the present work uses first-principles based computational methods to quantify the reaction mechanisms, kinetics and thermodynamics associated with the formation and deconstruction of the prominent phenyl glycoside (PG) LCC linkage in biomass. The two previously proposed formation mechanisms, hemi-acetal and transglycosylation, are associated with significant activation barriers, suggesting these pathways are kinetically limited. A new mechanism is proposed, the electrophilic addition of hemicellulose to a lignin quinone methide (QM) intermediate, that possesses facile kinetics and is exergonic, suggesting it could be the pathway responsible for the significant fraction of PG linkages observed in the native biomass. Moreover, PG formation showed a composition dependence, suggesting that xylans will have higher fractions of PG linkages compared to mannans, explaining why softwoods and hardwoods have different reported types of LCCs. Additionally, the reaction mechanisms, kinetics and thermodynamics associated with the deconstruction of the PG LCC linkages in biomass under acidic conditions are investigated. The chemical degradation of the hemicellulose moieties is the primary competing reaction; however, the deconstruction energetics demonstrate that breaking PG linkages is kinetically and thermodynamically favored in acid catalyzed deconstruction. This indicates that PG linkages may not significantly contribute to the biomass recalcitrance.

Metallic sealants are widely used with high-temperature membranes. Here we show that their use in supported molten-salt membranes results in order-of-magnitude differences in CO₂ flux and introduces O₂ co-permeation. The ‘short-circuiting’ effect they introduce has important implications for the design of future experiments, and the interpretation of past work.

Most conventional zeolite synthesis takes place in closed batch autoclaves that cannot be monitored or controlled during the process. Moreover, the study of time-dependent parameters of the synthesis with the conventional “cooling-opening” procedure not only reduces accuracy as a series of reactors (never 100% identical) needs to be started in parallel (and stopped at different times), it is also labor intense. Furthermore, the classic batch concept does not permit the intermediate addition of species without disrupting synthesis and the cooling-reheating effects. In this study, we developed a technique for zeolite synthesis monitoring in one-pot experiments using the sampling feature of fed-batch (FB) reactors. These one-pot syntheses can save time and ingredients instead of performing plenty of classic batch experiments. In addition, we could control and manipulate the zeolite synthesis by using the feeding function of the FB reactor and the intermediate addition of precursors at operational temperatures and pressures. Stannosilicate and zincosilicate syntheses were carried out via the FB reactor to investigate the intermediate timed-addition and the possibility of optimizing feeding rates of heteroatoms opposed to a classic synthesis, which faces challenges when a high amount of heteroatom precursor presents at the start. Finally, a modified FB platform was further developed to be able to monitor essential kinetic and synthetic parameters on-line (T, P, and also pH) on-line without intervention. For instance, pH profiles can allow one to estimate key events in zeolite synthesis, but in the art, these profiles are always measured ex situ (including cooling effects etc.).