Search Results (117)

Fluid mechanical conditions are crucial for cavitation formation, and significantly influence chemical reactivity. This study investigates process conditions such as pressure, degassing, cavitation and reaction volume, and the sound emission of oxidative dye degradation by cavitation. For ensuring comparability and scalability, dimensionless similarity numbers aligned to the process were introduced. A further focus of the paper is reproducibility with corresponding guidelines. Measurements of dye degradation were carried out without additional chemicals. The oxidation process was assessed by the chemiluminescence of luminol. For this purpose, configurations with three nozzle sizes at different pressure differences were investigated. The generated cavitating jet was captured by imaging techniques and correlated to degradation. The most energy-efficient configuration was obtained by the smallest nozzle diameter of 0.6 mm at a pressure difference of 40 bar. Significant degassing occurred during cavitation. It was more pronounced with smaller nozzle diameters, correlating with higher degradation. Furthermore, discontinuous treatment methods can improve efficiency. Scaling to higher flow rates through multiple reactors in parallel proved more effective, compared to increasing the nozzle diameter or the pressure difference. For the same treated volume, two parallel reactors increased degradation by a factor of 1.35. The insights provide perspectives for optimizing jet cavitation reactors for water treatment. Full article

Discovering stable polymeric nitrogen phases and exploring their properties are crucial for energy storage and conversion, garnering significant attention. In this study, we investigate the formation possibility of a stable compound between Ar and N₂ through ab initio calculations under low-pressure conditions (0–100 GPa). The novel super nitride, Imm2 ArN_10, is designed to demonstrate robust thermodynamic stability under high pressures (91 GPa) and showcase the unique host–guest structure, in which guest atoms (Ar) are trapped inside the host polymeric N₁₀. Significantly, given the weak interaction between Ar and N atoms and a channel parallel to the c-crystallographic axis in ArN₁₀, we propose a novel method to stabilize the previously unknown polymeric nitrogen structure, Imm2-N₁₀, by removing the guest argon atoms from the natural channels of ArN₁₀. Imm2 ArN₁₀ and N₁₀ are thermodynamically and dynamically stable, with energy densities of 9.1 kJ g⁻¹ and 12.3 kJ g⁻¹, respectively—more than twice that of TNT. Additionally, ArN₁₀ and N₁₀ stand out as leading green energetic materials, boasting a superior explosion velocity of 17.56 km s⁻¹ and a detonation pressure of 1712 kbar, surpassing that of TNT. These findings significantly impact on the creation of pure nitrogen frameworks through chemical reactions involving inert elements under high pressure. Full article

Polygonatum cyrtonema Hua (PCH) belongs to the genus Polygonatum Mill of the Liliaceae family. As a traditional tonic herb, the rhizome of PCH has been widely used as a functional food and traditional Chinese medicine, mainly for the treatment of spleen and lung Qi deficiency, essence and blood deficiency, internal heat, and thirst. To further elucidate the unknown chemical composition of PCH, this study presents an analytical strategy using macroporous resin (D101) column chromatography combined with ultra-high-performance liquid chromatography-Q-Exactive Orbitrap mass spectrometry (UHPLC-Q-Exactive Orbitrap MS) for the characterization of PCH’s chemical composition. The PCH extracts were separated via D101 resin column chromatography in conjunction with reverse phase liquid chromatography (C18 column). They were then analyzed by Q-Exactive Orbitrap mass spectrometry utilizing parallel reaction monitoring (PRM) mode, diagnostic fragment ions (DFIs), and neutral loss (NL). A total of 153 compounds were identified through comparing the mass spectrometry data with standard references, the published literature, and public databases, including 40 alkaloids, 43 organic acids, 30 flavonoids, 17 saponins, and 23 other compounds; The result expands PCH’s chemical composition, enhancing our understanding of its therapeutic effects and quality assurance. At the same time, the strategy has the potential to show a wide range of applications in the chemical characterization of different samples. Full article

Nonlinear equations are essential in research and engineering because they simulate complicated processes such as fluid dynamics, chemical reactions, and population growth. The development of advanced methods to address them becomes essential for scientific and applied research enhancements, as their resolution influences innovations by aiding in the proper prediction or optimization of the system. In this research, we develop a novel biparametric family of inverse parallel techniques designed to improve stability and accelerate convergence in parallel iterative algorithm. Bifurcation and chaos theory were used to find the best parameter regions that increase the parallel method’s effectiveness and stability. Our newly developed biparametric family of parallel techniques is more computationally efficient than current approaches, as evidenced by significant reductions in the number of iterations and basic operations each iterations step for solving nonlinear equations. Engineering applications examined with rough beginning data demonstrate high accuracy and superior convergence compared to existing classical parallel schemes. Analysis of global convergence further shows that the proposed methods outperform current methods in terms of error control, computational time, percentage convergence, number of basic operations per iteration, and computational order. These findings indicate broad usage potential in engineering and scientific computation. Full article

Reaction system (RS) belongs to a type of qualitative computing model inspired by biochemical reactions taking place inside biological cells. It concerns more the interactions and causality among reactions rather than concrete concentrations of chemical entities. Many biochemical processes and models can be represented in the form of reaction systems so that complex relations and ultimate products of a variety of reactions can be revealed qualitatively. The reaction system works in parallel mode. Software simulation of this kind of model may suffer from the penalty of inefficient parallelism for the limited performance of CPU/GPU, especially for the simulation of large-scale models. Considering potential applications of reaction systems in disease diagnoses and in drug developments, hardware implementation of reaction systems provides a better way to accelerate computations involved. In this paper, an FPGA implementation method of a reaction system called RSFIM is proposed. Two small-scale models, i.e., the reaction system of intermediate filaments self-assembly and heat shock response, are implemented on FPGA, achieving a computing speed of $2\times {10}^8$ steps per second. For large-scale models, the ErbB reaction system is implemented, obtaining a speedup of $7.649\times {10}^4$ compared with its highest performance GPU simulation so far. The reaction system binary counter, which is a quantitative model, is also implemented by the Boolean explanation of the qualitative character of the reaction system. FPGA implementation of reaction systems opens a novel research line to speed up the simulations of reaction systems and other biological models in the perspective of parallel digital circuits. Full article

A microreactor is a chemical reaction device that mixes liquids in a very narrow channel and continuously generates reactions. They are attracting attention as next-generation chemical reaction devices because of their ability to achieve small-scale and highly efficient reactions compared to the conventional badge method. However, the challenge is to design a control system that is tolerant of faults in some of the enormous number of sensors in order to achieve parallel production by numbering up. In a previous study, a simultaneous control system for two different temperatures was proposed in an experimental system that imitated the microreactor cooled by Peltier devices. In addition, a fault-tolerant control system for one area has also been proposed. However, the fault-tolerant control system could not be applied to the control system of two temperatures in the previous study. In this paper, we extend it to a two-input, two-output fault-tolerant control system. We also use a fault detection system that combines ChangeFinder, a time-series data analysis method, and One-Class SVM, an unsupervised learning method. Finally, the effectiveness of the proposed method is confirmed by experiments. Full article

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane. Full article

Single crystals of the new modification of copper pyrovanadate, δ-Cu₂V₂O₇, were prepared using the chemical vapor transport reaction method. The crystal structure (monoclinic, P2₁/n, a = 5.0679(3), b = 11.4222(7), c = 9.4462(6) Å, β = 97.100(6)°, V = 542.61(6) ų, Z = 4) was solved by direct methods and refined to R₁ = 0.029 for 1818 independent observed reflections. The crystal structure contains two Cu sites: the Cu1 site in [4 + 2]-octahedral coordination and the Cu2 site in [4 + 1]-tetragonal pyramidal coordination. There are two V⁵⁺ sites, both tetrahedrally coordinated by O atoms. Two adjacent V1O₄ and V2O₄ tetrahedra share the O4 atom to form a V₂O₇ dimer. The crystal structure of δ-Cu₂V₂O₇ can be described as based upon layers of V₂O₇ dimers of tetrahedra parallel to the (001) plane and interlined by chains of the edge-sharing Cu1O₆ and Cu2O₅ polyhedra running parallel to the a axis and arranged in the layers parallel to the (001) plane. The crystal chemical analysis of the three other known Cu₂V₂O₇ polymorphs indicates that, by analogy with δ-Cu₂V₂O₇, they are based upon layers of V₂O₇ groups interlinked by layers consisting of chains of CuO_n coordination polyhedra (n = 5, 6). The crystal structures of the Cu₂V₂O₇ polymorphs can be classified according to the mutual relations between the Cu-O chains, on the one hand, and the V₂O₇ groups, on the other hand. The analysis of the literature data and physical density values suggests that, at ambient pressure, α- and β-Cu₂V₂O₇ are the low- and high-temperature polymorphs, respectively, with the phase transition point at 706–710 °C. The β-phase (ziesite) may form metastably under temperatures below 560 °C and, under heating, transform into the stable α-phase (blossite) at 605 °C. The δ- and γ-polymorphs have the highest densities and most probably are the high-pressure phases. The structural complexity relations among the polymorphs correspond to the sequence α = β < γ < δ; i.e., the δ phase described herein possesses the highest complexity, which supports the hypothesis about its stability under high-pressure conditions. Full article

According to the green growth and carbon-neutral policy in Korea, the installation of large-capacity ESSs is rapidly being increased, but a total number of 50 ESS fire cases have occurred since the end of 2023. ESSs are typically composed of series-parallel connections with numerous Li-ion batteries, and when the temperature of a deteriorated cell increases due to thermal, electrical, and mechanical stress, thermal runaway can occur due to additional heat generated by an internal chemical reaction. Here, an internal chemical reaction in a Li-ion battery results in the different characteristics on the decomposition reaction and heat release depending on the operation conditions in the ESS, such as the rising temperature rate, convective heat transfer coefficient, and C-rate of charging and discharging. Therefore, this paper presents mathematical equations and modeling of thermal runaway, composed of the heating device section, heat release section by chemical reaction, chemical reaction section at the SEI layer, chemical reaction section between the negative and positive electrodes and solvents, and chemical reaction section at the electrolyte by itself, based on MATLAB/SIMULINK (2022), which were validated by a thermal runaway test device. From the simulation and test results based on the proposed simulation modeling and test device according to the operation conditions in ESSs, it was found that the proposed modeling is an effective and reliable tool to evaluate the processing characteristics of thermal runaway because the occurrence time intervals and maximum temperatures had almost the same values in both the test device and simulation modeling. Accordingly, it was confirmed that the rising temperature rate and the convective heat transfer coefficient were more critical in the thermal runaway than the C-rate of charging and discharging. Full article

The traditional Mongolian medicine Erdun-Uril is a conventional combination of 29 herbs commonly used for the treatment of cerebrovascular ailments. It has the effects of reducing inflammation, counteracting oxidative stress, and averting strokes caused by persistent cerebral hypoperfusion. Prior research on Erdun-Uril has predominantly concentrated on its pharmacodynamics and mechanism of action; however, there has been a lack of systematic and comprehensive investigation into its chemical constituents. Therefore, it is crucial to establish an efficient and rapid method for evaluating the chemical constituents of Erdun-Uril. In this study, Erdun-Uril was investigated using UHPLC-Q-Exactive Orbitrap MS combined with parallel reaction monitoring for the first time. Eventually, a total of 237 compounds, including 76 flavonoids, 68 phenolic compounds, 19 alkaloids, 7 amino acids, etc., were identified based on the chromatographic retention time, bibliography data, MS/MS² information, neutral loss fragments (NLFs), and diagnostic fragment ions (DFIs). And of these, 225 were reported for the first time in this study. This new discovery of these complex components would provide a reliable theoretical basis for the development of pharmacodynamics and quality standards of the Mongolian medicine Erdun-Uril. Full article

Nanotechnology, a rapidly growing field, holds tremendous promise as it harnesses the unique properties and applications of nanoparticulate materials on a nanoscale. In parallel, the pressing global environmental concerns call for the development of sustainable chemical processes and the creation of new materials through eco-friendly synthesis methods. In this work, zero-valent iron nanoparticles (nZVI) were synthesized using an innovative and environmentally friendly approach as an alternative to conventional methods. This method leverages the antioxidant capacity of natural plant extracts to effectively reduce dissolved metals and produce nZVI. The chosen extract of green tea plays a pivotal role in this process. With the extract in focus, this study delves into the remarkable capability of nZVI in degrading two dyes commonly used in medicine, chrysoidine G and methylene blue, in aqueous solutions. Additionally, Fenton-type oxidation processes are explored by incorporating hydrogen peroxide into the nanoparticle mixture. By applying the statistical design of experiments and Response Surface Methodology, the influence of four key parameters—initial concentrations of Fe²⁺, Fe³⁺, H₂O₂, and polyphenols—on dye elimination efficiency in aqueous solutions is thoroughly analyzed. The obtained results demonstrate that advanced oxidation technologies, such as Fenton-type reactions in conjunction with nanoparticles, achieve an excellent efficiency of nearly 100% in eliminating the dyes. Moreover, this study reveals the synergistic effect achieved by simultaneously employing nZVI and the Fenton process, showcasing the potential for further advancements in the field. Full article

Tetroxane derivatives are interesting drugs for antileishmaniasis and antimalaric treatments. The gas-phase thermal decomposition of 3,6,-dimethyl-1,2,4,5-tetroxane (DMT) and 3,3,6,6,-tetramethyl-1,2,4,5-tetroxane (acetone diperoxide (ACDP)) was studied at 493–543 K by direct gas chromatography by means of a flow reactor. The reaction is produced in the injector chamber at different temperatures. The resulting kinetics Arrhenius equations were calculated for both tetroxanes. Including the parent compound of the series 1,2,4,5-tetroxane (formaldehyde diperoxide (FDP)), the activation energy and frequency factors decrease linearly with the number of methyl groups. The reaction mechanisms of ACDP and 3,6,6-trimethyl-1,2,4,5-tetroxane (TMT) decomposition have been studied by means of the DFT method with the BHANDHLYP functional. Our calculations confirm that the concerted mechanism should be discarded and that only the stepwise mechanism occurs. The critical points of the singlet and triplet state potential energy surfaces (S- and T-PES) of the thermolysis reaction of both compounds have been determined. The calculated activation energies of the different steps vary linearly with the number of methyl groups of the methyl-tetroxanes series. The mechanism for the S-PES leads to a diradical O···O open structure, which leads to a C···O dissociation in the second step and the production of the first acetaldehyde/acetone molecule. This last one yields a second C···O dissociation, producing O₂ and another acetone/acetaldehyde molecule. The O₂ molecule is in the singlet state. A quasi-parallel mechanism for the T-PES from the open diradical to products is also found. Most of the critical points of both PES are linear with the number of methyl groups. Reaction in the triplet state is much more exothermic than the singlet state mechanism. Transitions from the singlet ground state, S₀ and low-lying singlet states S_1–3, to the low-lying triplet excited states, T_1–4, (chemical excitation) in the family of methyl tetroxanes are also studied at the CASSCF/CASPT2 level. Two possible mechanisms are possible here: (i) from S₀ to T₃ by strong spin orbit coupling (SOC) and subsequent fast internal conversion to the excited T₁ state and (ii) from S₀ to S₂ from internal conversion and subsequent S₂ to T₁ by SOC. From these experimental and theoretical results, the additivity effect of the methyl groups in the thermolysis reaction of the methyl tetroxane derivatives is clearly highlighted. This information will have a great impact for controlling these processes in the laboratory and chemical industries. Full article

The zeolite-catalyzed conversion of DME into chemicals is considered environmentally friendly in industry. The periodic density functional theory, statistical thermodynamics, and the transition state theory are used to study some possible parallel reactions about the hydrogen-bonded DME over zeolite ferrierite. The following are the key findings: (1) the charge separation probably leads to the conversion of a hydrogen-bonded DME into a dimethyl oxonium ion (i.e., DMO⁺ or (CH₃)₂OH⁺) with a positive charge of about 0.804 e; (2) the methylation of DME, CH₃OH, H₂O, and CO by DMO⁺ at the T2O6 site of zeolite ferrierite shows the different activated internal energy (∆E^≠) ranging from 18.47 to 30.06 kcal/mol, implying the strong methylation ability of DMO⁺; (3) H-abstraction by DMO⁺ is about 3.94–15.53 or 6.57–18.16 kcal/mol higher than DMO⁺ methylation in the activation internal energy; (4) six DMO⁺-mediated reactions are more likely to occur due to the lower barriers, compared to the experimental barrier (i.e., 39.87 kcal/mol) for methyl acetate synthesis; (5) active intermediates, such as (CH₃)₃O⁺, (CH₃)₂OH⁺, CH₃CO⁺, CH₃OH₂⁺, and CH₂=OH⁺, are expected to appear; (6) DMO⁺ is slightly weaker than the well-known surface methoxy species (ZO-CH₃) in methylation; and (7) the methylated activity declines in the order of DME, CH₃OH, H₂O, and CO, with corresponding rate constants at 463.15 K of about 3.4 × 10⁴, 1.1 × 10², 0.18, and 8.2 × 10⁻² s⁻¹, respectively. Full article

Ni–Cu alloys are suitable candidates as catalysts in hydrogen evolution reaction. Because of the different magnetic properties of Ni and Cu, the influence of an applied external magnetic field on the synthesis Ni–Cu alloys was studied. The coatings were prepared with visible changes in their appearance. The differences between the observed regions were studied in terms of morphology and chemical composition. In addition, the overall chemical and phase compositions were determined using X-ray fluorescence and X-ray diffraction methods, respectively. The catalytic activity was measured in 1 M NaOH using linear sweep voltammetry. The contact angle was determined using contour analysis. All samples were hydrophilic. Hydrogen evolution started at different times depending on the area on the surface. It started earliest on the coating obtained in parallel to the electrode magnetic field at 250 mT. We found that when the Lorenz force is maximal, Cu deposition is preferred because of the enhancement of mass transport. Full article

Carveol is a rare fine chemical with specific biological activities and functions in nature. The artificial synthesis of carveol from plentiful and cheap turpentine is expected to further improve development of pharmaceutical and industrial applications. A new green catalytic system for the preparation of high-value carveol from α-epoxypinane is presented. A novel ammonium salt solid acid (AC-COIMI-NH₄PW) was obtained from phosphotungstic acid bonded with imidazole basic site on nitrogen-doped activated carbon which, after ammonia fumigation, presented an excellent catalytic performance for the selective rearrangement of α-epoxypinane to carveol in DMF as solvent under mild reaction conditions. At 90 °C for 2 h, the conversion of α-epoxypinane could reach 98.9% and the selectivity of carveol was 50.6%. The acidic catalytic sites exhibited superior durability and the catalytic performance can be restored by supplementing the lost catalyst. Based on the investigation of catalytic processes, a parallel catalytic mechanism for the main product was proposed from the rearrangement of α-epoxypinane on AC-COIMI-NH₄PW. Full article