Reaction Chemistry & Engineering最新文献

Macrocycles are candidates for wide-ranging applications, yet their synthesis can be low-yielding, poorly reproducible, and resource-intensive, limiting their use. Here, we explore the use of Non-Thermal Plasma (NTP) as an efficient method for the synthesis of imine macrocycles at the gram scale. NTP-mediated macrocyclisations consistently achieved high yields of up to 97% in reduced reaction times compared to the standard non-plasma method, and were successfully carried out with a range of different aldehyde substrates. Control experiments were performed to explore the origin of the observed improvements. The results indicate that NTP methods could be advantageous for macrocycle synthesis, particularly for substrates that are sensitive to elevated temperature, and other materials formed via imine condensation.

The effects of Ca and Fe of a bimetallic Ca–Fe catalyst when applied to pine sawdust pyrolysis were investigated by thermogravimetry-mass spectrometry. Trials were also performed using heterotopic Ca–Fe and HZSM-5 to catalyse the degradation of pine sawdust to produce aromatic hydrocarbons, employing a fixed bed reactor and gas chromatography-mass spectrometry. The presence of CaO was found to promote deoxygenation while Fe enhanced in situ hydrogen supply, whereas the Ca–Fe catalyst combined these effects. This material promoted the formation of low-oxygen compounds to generate precursors that were transformed into aromatics via HZSM-5. Up to 90.47% aromatic proportion and a 31.02 mg g⁻¹ benzene/toluene/ethylbenzene/xylene yield were obtained at 600 °C using a 1 : 1 mass ratio of Ca–Fe to HZSM-5 and a 2 : 1 mass ratio of catalysts to pine sawdust. This combination of catalysts is evidently an effective means of strengthening the pyrolysis of pine sawdust to produce aromatic hydrocarbons.

Measuring the thermokinetic data of chemical reactions is an important part for chemical process development. However, some reactions are very sensitive to the presence of metals, limiting the use of standard materials for calorimeters. In this work we present a flow calorimeter employing a 3D printed ceramic reactor plate for the measurement of metal-sensitive reactions. The calorimeter was characterized by residence time measurements aided by mixing simulations, and was validated via a standard neutralization reaction, an aggressive nitration reaction, and a binary solvent system for mixing enthalpy, before being used for a nitrosylation reaction featuring a metal sensitive product.

Indonesia, renowned for its tropical marine environments, boasts a rich diversity of macroalgae, with Sargassum being a major contributor. Currently, the primary application of Sargassum revolves around alginate extraction, prompting a systematic exploration of alternative end-products for optimal utilization. Thermochemical conversion of Sargassum into bio-oil, biochar, and gas, particularly through microwave-assisted pyrolysis (MAP), emerges as a promising avenue. MAP, distinguished by its energy-efficient process and high heating rate, stands as a viable alternative to conventional pyrolysis. A thorough feasibility analysis of MAP, incorporating kinetic studies and bio-oil characterization, revealed that particle sizes of 40–70 mesh exhibited the highest reaction rates. Sensitivity tests validated the reliability of kinetic parameters (A and E_a) obtained from MATLAB 2016b, confirming their suitability for scaling-up purposes. These findings underscore the potential of MAP compared to conventional pyrolysis, driven by its rapid heating rates. The resulting bio-oil, with a pH of 8, comprised carboxylic acids and aliphatic, cyclic aliphatic, and aromatic compounds, along with sterols and polyaromatic derivatives that can be further utilized particularly as building blocks and end-products in chemical industries. However, it is crucial to note that the bio-oil poses challenges in the upgrading process to transform it into fuel.

C–N bond formation plays a crucial role in various chemical synthesis processes in both the chemical industry and nature. While numerous methods have been developed for the formation of C–N bonds, only a few meet the criteria of “green chemistry”. In this study, we present a continuous-flow procedure for the decyanative N-heteroarylation of anilines and secondary alicyclic amines using a photoorganocatalytic reaction. Through the synergistic combination of photochemistry, organocatalysis, and continuous-flow technology, we were able to achieve high and close to quantitative yields, while significantly reducing the reaction time from 12 hours in batch procedures to just 1 hour in continuous-flow conditions.

The conversion of biomass-derived furfuryl alcohol into 1,2-pentanediol, a high-value fine chemical with wide applications, is of high research and commercial value. In this study, Ce-doped CuCeMgAl mixed metal oxide catalysts were synthesized using layered double hydroxides as the precursor. Characterization techniques including BET, XRD, XPS, TPR and TPD were used to study the structure and physiochemical properties of synthesized catalysts. In furfuryl alcohol hydrogenolysis, CuCeMgAl catalysts showed higher furfuryl alcohol conversion and higher 1,2-pentanediol yield than the CuMgAl sample, likely due to more metal active sites and higher concentration of basic sites. Furthermore, reduction temperature, an important parameter for MMO-type catalysts, was studied for its effect on catalyst activity. It is found that basic site concentration is affected by reduction temperatures, leading to distinct activity for CuCeMgAl catalysts. With lower reduction temperatures, the activity of CuCeMgAl catalysts could be further increased, demonstrating the importance of reduction parameters for Cu-based mixed metal oxide catalysts.

The reaction pathway of hydrolysis of UF₆ to form UO₂F₂ particles is an essential insight in nuclear fuel processing; however, it is still limited to theoretical calculations. Herein, we present the identification of the intermediates and products using various gas precursor concentrations and molecular beam mass spectrometer (MBMS). Compounds containing different uranium atom counts were identified by exposing 300 and 2323 ppm water to 200 ppm UF₆. Non-uranium compounds (e.g., (HF)₃(H₂O)H, (HF)₄H, and (H₂O)₂(HF)₃) dominate the mass spectra in terms of absolute signal intensity. These compounds were dependent on the initial concentration of UF₆ based on the linear relationship observed between products and gas reactant. Uranium compounds were characterized by UF₆, UO₃, and UO₂F₂ core molecules, with each species existing predominantly in a certain water concentration. Monomeric compounds (e.g., UF₆(HF)₂(H₂O)₇, UO₂F₂(HF)₇H, and UO₂F₂(HF)₅(H₂O)₃) or species with one uranium atom had high fluorine to uranium ratio (F/U) due to several HF units bonded with the uranium core. Dimeric (e.g. (UO₂F₂)₂(H₂O) and (UF₆)₂(H₂O)4(HF)₃H) and trimeric (e.g., (UO₃)(UO₂F₂)₂(HF)(H₂O)₃ and (UO₂F₂)₂UF₆H₂F) compounds persisted in high masses with low F/U and H/U ratios. Moreover, ramping of UF₆ concentration (50–231 ppm) at fixed water content (1.3% Rh or 300 ppm) showed different trends among 949 ions, with some following consistently with molecular identification (e.g., (UO₃)₃(HF)₂(H₂O)H). Overall, this study provided important information regarding the formation pathway of UO₂F₂