Reaction Chemistry & Engineering最新文献

In the recycling of waste lubricating oil, the rapid deactivation of catalysts during the hydrotreating process limits their industrial application. In this paper, a three-reactor process is proposed for the refining of waste lubricating oil, which is compared with the conventional two-reactor process. Experimental results reveal that the three-reactor technique demonstrates enhanced performance in hydrodesulfurization (HDS), hydrodechlorination (HDCl), hydrodenitrogenation (HDN), hydro-decolorization, and demetallization, effectively doubling the service life of the catalysts. Characterization of the deactivated catalysts identifies carbon deposition, silicon (Si) poisoning, and boron (B) poisoning as the primary factors contributing to catalyst deactivation. The presence of a protective agent (the second catalyst) within the three-reactor process effectively removes Si and B, thereby mitigating the Si and B poisoning of the primary hydrogenation catalyst, and extending the catalyst's lifespan. This approach offers a viable solution to the challenge of frequent catalyst deactivation encountered during the high-value utilization of waste lubricating oils, thereby providing an effective pathway for overcoming this issue in the chemical industry.

Fabrication of high-performance microwave absorbers by assembling multi-dimensional nanocomponents into core–shell electromagnetic structures has been shown to be a new manufacturing strategy. In this work, a novel core–shell carbon-fibres@ZIF-67@NiMn-layered double hydroxide (NiMn-LDH) film with excellent electromagnetic wave absorption was obtained by electrospinning ZIF-67 inside carbon fibres and subsequent solvothermal process with NiMn-LDH. With the synergistic effects of Co particles in ZIF-67 increasing magnetic loss, the appropriate proportion of the carbon fibres as a carbon source improves dielectric loss and provides a carrier for NiMn-LDH. Furthermore, NiMn-LDH at the outer shell improves impendence matching. Co/carbon fibres@NiMn-LDH (Co/CF@NiMn-LDH) was composited at a thickness of 2.8 mm with minimum reflection loss (R of −53 dB), and it also has good flexibility. The EAB of the obtained CF@NiMn-LDH composite reaches 6.7 GHz. This work provides a reference for the application of flexible carbon matrix composites in the electromagnetic wave absorption field.

The development of high performing and stable energetic materials (EMs) is a focus for a variety of applications including explosives, propellants, and pyrotechnics. To enhance stability, energetic crystals are often interfaced with materials such as chemical binders, which can introduce a variety of physiochemical phenomena ultimately leading to unpredictable stability and performance within the composite. Therefore, a thorough understanding of how energetic crystals behave when interfaced with various chemical functionalities is crucial for designing safer, high performing energetic formulations. This work provides a fundamental insight into interactions between a high performing energetic material, CL-20 (hexanitrohexaazaisowurtzitane), and other materials' surfaces. Highly controlled, tunable 2D metal-halide perovskite (2D MHP) templates with tunable periodicity and chemistry were created and used as a template layer to influence nucleation and growth of CL-20 crystals. All MHP/CL-20 bilayer films exhibit small, nonuniform crystalline deposit morphology for the CL-20 crystals with β-CL-20 polymorphic structure. While most MHP films template the formation of β-CL-20 crystals with a (111) preferential orientation, PbPMA₂Cl₄/β-CL-20 films crystallize with a (020) preferential orientation. The results presented herein suggest interfacial energy minimization between the two bilayer components is the dominant driving force behind the CL-20 preferential orientations. This methodology can potentially be used for developing techniques for growing energetic crystals with desired morphology, packing density and crystallographic orientation.

Flow chemistry has greatly expanded the reaction toolbox by demonstrating a wide range of individual chemical transformations. For commercial scale processes, it provides an appealing alternative to batch reactors by reducing production costs, increasing product yield and overall process robustness. We describe an approach for continuous processing of a specialty chemical manufactured using a batch process with a typical yield of 150 kg per hour and concomitant adiabatic temperature increase of up to 250 °C. This necessitates controlled feed addition causing longer processing time, lower productivity, and undesirable polymerization reactions. We present a continuous process that addresses the challenges of thermal management and reaction selectivity using flow chemistry thereby enabling up to 12-fold reduction in residence time with a comparable product profile. Fundamental reactor engineering and design principles and associated safety considerations used for designing the reactor and continuous process are described. Guided by this analysis, a continuous process using a ¼ inch tubular reactor is investigated. The results indicate residence time reduction from 6 hours to 30 minutes for comparable feed conversion of 87% and similar product composition. Greater than 90% conversion could not be achieved in the current reactor configuration and associated reactor runaway analysis suggests feed decomposition due to pressure fluctuations or insufficient reactants in the reactor. The analysis highlights the need for designing a reactor with better pressure control using a back pressure regulator and choosing a smaller diameter tube. These insights underscore the importance of applying fundamental reactor engineering principles for designing safe and efficient processes at an industrial scale.

In this paper, we have demonstrated radio frequency (RF) heating of susceptor nanomaterials coupled with conventional catalysts to enable a new class of heterogeneous catalytic reactors with localized, volumetric heating. The recent emphasis on industrial decarbonization has highlighted the need to reduce greenhouse gas emissions from chemical process heating. Existing industrial scale catalytic reactors use fuel-fired furnaces to achieve high temperatures which contributes to CO₂ emissions and requires on-site infrastructure. Compared to conventional heating, this work uses a power-to-chemicals route, where RF fields (1–200 MHz) are utilized to volumetrically heat RF-responsive carbon nanomaterials integrated with the catalyst. With the option of using renewable electricity sources, the greenhouse gas emissions associated with the process can be reduced, thereby contributing to industrial decarbonization. We demonstrate the use of an RF applicator to drive the highly endothermic propane dehydrogenation reaction on a Pt/alumina catalyst using carbon nanotubes as the RF susceptors. The propane conversion and propylene yield using RF heating were similar to those obtained when the reactor was heated externally in an oven (conventional heating (CH)) at 500 °C. After each reaction cycle, the catalyst was successfully regenerated by RF heating in air to remove deposited carbon.

Transition metal chalcogenides (TMCs), such as FeSe₂, FeS₂, and CuS, have attracted considerable attention for energy storage due to their multi-electron transfer capabilities and high capacities. This study presents the synthesis of spherical CuFeS₂ through a binder-free hydrothermal process, incorporating selenium powder to form hollow spheres of CuFeS₂ encapsulated by FeSe₂ nano-planes (CuFeS₂@FeSe₂). Utilizing a modified electrode without a binder and adopting a spherical CuFeS₂@FeSe₂ structure significantly enhance the performance of asymmetric supercapacitors. The absence of a binder eliminates potential issues associated with binding agents, ensuring a more efficient charge transfer. The spherical configuration, with FeSe₂ layers surrounding and encapsulating the CuFeS₂ core, contributes to improved capacitance and stability. The unique structure allows for better utilization of active materials, enhancing the specific capacitance of the electrode. This modified electrode demonstrates remarkable cyclic stability, indicating its potential for long-term practical applications. This unique nanostructure was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), demonstrating enhanced nanomaterial conductivity. Electrochemical performance analyses, including cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS), reveal a specific capacity of 1306 A g⁻¹ at a current density of 2 A g⁻¹ in a three-electrode system. Furthermore, as a positive electrode in an asymmetric supercapacitor device (CuFeS₂@FeSe₂||AC), paired with activated carbon@NF (AC) as a negative electrode, the system achieves an efficient energy density of 152.01 W h kg⁻¹ with superior durability, retaining 91.03% capacity after 3000 cycles.

Methyl benzoate (MB) is a chemical raw material used in various fields. However, the conventional approach to synthesizing MB is characterized by difficulties such as equipment corrosion, by-product generation, and recycling challenges. In light of these challenges, this work proposes the utilization of deep eutectic solvents (DESs) as both extractants and catalysts in a reactive extraction process. In particular, p-toluenesulfonic acid-based deep eutectic solvents (PTSA-based DESs) were tested as potential candidates, with choline chloride (ChCl) and imidazole (Im) chosen as hydrogen bonding acceptors (HBAs). The feasibility of DESs consisting of ChCl and PTSA was assessed using the COSMO-RS theory. The optimal process conditions were determined. Under the optimal conditions, the yield of MB reached 93.46%, and the performance of [ChCl–PTSA] remained stable after five cycles. We also used the group contribution method and COSMO-RS to derive separate kinetic models, with activation energies of 43.71 kJ mol⁻¹ and 38.71 kJ mol⁻¹. Our work highlights the potential of [ChCl : PTSA] in the industrial production of MB.

Polyurethanes represent a class of highly versatile synthetic polymers, suitable for a wide range of applications. Their biological degradation is of great interest since it can allow the design of specific formulations by selecting suitable building blocks and it can contribute to the development of sustainable recycling processes. In the current study, a commercial hydrolytic enzyme (cutinase from Humicola insolens, HiC) was investigated for its ability to degrade various polyurethane adhesive formulations, by focusing first on macrodiols, then on specific polyurethanes. The aim was to identify solvent-based polyurethane formulations susceptible to enzymatic hydrolysis. First, a semi-quantitative assay, namely the emulsion turbidity test, was carried out on some macrodiols. Then, weight loss tests were carried out on specific solvent-based polyurethane formulations, and three promising formulations have shown 90, 60 and 40% degradation, after 96 h of incubation with HiC. A study of the enzymatic degradation mechanism of macrodiols and the most degradable polyurethanes was also carried out, through the characterization of the solid residues after the enzymatic degradation by infrared spectroscopy, calorimetric and thermogravimetric analysis, and the identification and/or quantification of the monomers released during the hydrolysis of macrodiols within the liquid fraction (by high-performance liquid chromatography). According to the results, a prevalent exo-type action mode for HiC against some macrodiols was found under the conditions tested, while, from a chemical point of view, the degradation seems to determine, on the polyurethane residues, a general increase in crosslinking.

The synthesis of potentially biologically active phosphinoyl functionalized N-(2-(phenylethynyl)benzyl)amine, 1,2-dihydro-isoquinoline and 2H-isoindoline via a multicomponent reaction of 2-(phenylethynyl)benzaldehyde, amine and diphenylphosphine oxide is described for the first time. Depending on the catalyst and the conditions used, the same one-pot three-component reaction can selectively lead to the mentioned three different products. The formation of the cyclic products was investigated by a comprehensive catalyst screening, as well as by quantum chemical calculations. It was found that for the synthesis of phosphinoyl functionalized N-(2-(phenylethynyl)benzyl)amine, there is no need to use any catalyst. For the complete formation of isoquinoline ring containing phosphine oxide, zirconium(IV) chloride was the most efficient catalyst and 2H-isoindol-1-ylphosphine oxide was synthesized selectively by a silver acetate catalyst. Furthermore, dihydro-isoquinolin-1-ylphosphine oxide was converted into the thermodynamically more stable 2H-isoindol-1-ylphosphine oxide.

Ammonia (NH₃) is emerging as a promising fuel due to its high energy density, high hydrogen content, and zero carbon emissions from combustion. The study of chemical kinetics in NH₃ combustion offers theoretical approaches to address its low reactivity and high nitrogen oxide (NO_x) emissions, especially in binary fuels with hydrogen (H₂), which have been shown to positively affect NH₃ combustion systems. However, existing NH₃/H₂ models have various defects under different conditions. In this study, we develop a simplified NH₃/H₂ chemical kinetics model that is comprehensively validated using a large amount of representative experimental literature data, including ignition delay time, laminar flame speeds, and species concentration profiles. The model is analyzed using an innovative multidimensional average error iteration method, ensuring that the overall average error remains within 5%. Subsequently, the model is simplified by removing unnecessary components and reaction steps through the direct relation graph with error propagation method, reducing computational consumption. The combustion results of the pure NH₃ and NH₃/H₂ mixtures under most conditions are highly consistent with those of the new model. By conducting sensitivity and productivity analyses, we determined the key reactions controlling fuel reactivity under different H₂ ratios and the important interactions between intermediate products are described in detail. Additionally, the different reaction directions of NH₃ and the principle of NO_x generation under high H₂ conditions are elucidated through these analyses and reaction pathway diagrams.