Detailed Oxidation Mechanism Research Articles

A Detailed Reaction Mechanism for Thiosulfate Oxidation by Ozone in Aqueous Environments.

The ozone oxidation, or ozonation, of thiosulfate is an important reaction for wastewater processing, where it is used for remediation of mining effluents, and for studying aerosol chemistry, where its fast reaction rate makes it an excellent model reaction. Although thiosulfate ozonation has been studied since the 1950s, challenges remain in developing a realistic reaction mechanism that can satisfactorily account for all observed products with a sequence of elementary reaction steps. Here, we present novel measurements using trapped microdroplets to study the pH-dependent thiosulfate ozonation kinetics. We detect known products and intermediates, including SO32-, SO42-, S3O62-, and S4O62-, establishing agreement with the literature. However, we identify S2O42- as a new reaction intermediate and find that the currently accepted mechanism does not directly explain observed pH effects. Thus, we develop a new mechanism, which incorporates S2O42- as an intermediate and uses elementary steps to explain the pH dependence of thiosulfate ozonation. The proposed mechanism is tested using a kinetic model benchmarked to the experiments presented here, then compared to literature data. We demonstrate good agreement between the proposed thiosulfate ozonation mechanism and experiments, suggesting that the insights in this paper can be leveraged in wastewater treatment and in understanding potential climate impacts.

Ab initio chemical kinetics and shock-tube experimental study on nitrocyclohexane pyrolysis and combustion

Nitrocyclohexane (NCH) is a model nitroalkane compound with naphthenic structural groups for studying the combustion properties of nitro-based energetic fuels, and also demonstrates significant potential applications for advanced engines. However, accurate description of the detailed kinetic mechanisms for pyrolysis and combustion of NCH receives little attentions. Herein, the detailed pyrolysis and oxidation mechanism of NCH is studied by using quantum chemistry calculations and chemical kinetic theory. The potential energy surfaces of the CN bond dissociation reaction, HONO elimination reaction, abstraction reactions of NCH as well as the subsequent β-scission reactions are calculated using G4//M06–2X/6–311++G(d, p) method, which are subsequently employed for reaction rate constant computations via transition state theory (TST) and RRKM/master-equation (RRKM/ME) method. The ab initio chemical kinetic study results are used to develop a detailed kinetic mechanism to predict the pyrolysis experimental results of NCH, which are performed using a single-pulse shock tube (SPST). The SPST experiment is performed at pressure of 10 bar, temperature ranging from 1070 to 1560 K, reaction time of around 1.77 microsecond with fuel concentrations of 0.5 % diluted by Argon gas. The developed detailed kinetic mechanism exhibits reasonable prediction results of the pyrolysis product distributions together with literature ignition delay times across a wide range of temperature, pressure, and equivalence ratio conditions. Rate-of-production analysis is conducted to gain insight into the pyrolysis chemical kinetics of NCH. The present work should be valuable for the study of the combustion chemistry of nitro-alkane energetic fuels.

Numerical study of the combustion process and NOx evolution mechanism of ammonia-hydrogen compound fuel engine under different intake conditions

To explore the distinction between generation atmosphere of fuel NOx and thermal NOx in an ammonia-hydrogen compound fuel engine, a numerical calculation model was established based on a detailed ammonia-hydrogen oxidation mechanism. The combustion process and NOx evolution mechanism of the ammonia-hydrogen compound fuel engine under different intake conditions were studied. The researchresults for different equivalence ratios show that the in-cylinder hydrogen volume is the primary factor influencing the initial heat release. When the equivalence ratio is between 0.89 and 1.14, the mixture exhibits a higher combustion rate, leading to a shorter CD and an earlier CA50. At this point, the heat release process closer to TDC contributes improving engine combustion efficiency and indicated efficiency. Therefore, when the equivalence ratio is between 0.89 and 1.00, combustion efficiency is higher than 98 % and indicated efficiency is higher than 43 %, the ammonia-hydrogen compound fuel engine achieves relatively higher economy. Both over-rich and over-dilute mixtures induce an enhancement of fuel NOx, while the higher in-cylinder temperature caused by stoichiometric combustion leads to a boom of thermal NOx. Consequently, the total NOx emission from the ammonia-hydrogen compound fuel engine is higher at equivalence ratios between 0.80 and 1.00, and the NOx emission reaches its peak at an equivalence ratio of 0.89. Analysis of the evolution process of key N components in the cylinder shows that incomplete combustion plays a significant role in fuel NOx emissions, while thermal NOx emissions are mainly influenced by the distribution of in-cylinder components and combustion temperature. Specifically, thermal NOx emissions primarily depend on the in-cylinder components distribution in the narrow equivalence ratio range around stoichiometric ratio, and are significantly affected by in-cylinder temperature under other conditions. The in-cylinder oxygen concentration significantly affects fuel NOx emissions under most operating conditions. Further optimization of intake temperature shows that combustion efficiency exceeds 90 % when the intake temperature is above 280 K. When the intake temperature reaches 310 K, the combustion efficiency reaches up to 98 %, thus an intake temperature of about 310 K is sufficient to meet the need for improving the combustion efficiency of ammonia-hydrogen compound fuel engine. To achieve high efficiency and lower NOx emissions, appropriate lean combustion combined with an intake temperature slightly above room temperature is recommended.

Towards a uniform description of recombiners performance by a consistent CFD approach with the use of a detailed mechanism of hydrogen oxidation

For a consistent CFD substantiation of the recombiner performance, a detailed mechanism of hydrogen and oxygen recombination is used. The detailed mechanism of chemical kinetics (multi-step recombination reaction) makes it possible to claim universality, both in the numerical justification of the recombiner performance and in the justification of the flameless recombination threshold and makes it possible to justify the method for optimizing the recombiner to improve its characteristics. The models developed based on this approach were applied to both flat and cylindrical catalytic elements, which are used in FR and RVK recombiners, respectively. As part of the numerical studies, the detailed recombination mechanism was verified, namely the temperature distribution along the catalytic elements was compared and the performance of catalytic elements was compared as well. Good agreement was obtained between the calculated and experimental data. The approach considers not only the mechanism of surface recombination of hydrogen and oxygen on platinum, but also the mechanism of recombination in the gas phase. This makes it possible to calculate the onset of intense combustion outside the catalytic plates, which is a sign of volumetric ignition of the hydrogen-air environment. The concentrations at which such ignition is possible were obtained at different contents of water vapor in the medium. Thus, the proposed approach and the created models make it possible to fully describe the performance of recombiners of distinct designs without the use of additional experimental data, which is extremely necessary when justifying the hydrogen explosion safety of nuclear power plants.

Protein oxidation in dairy products and effects on intestinal health

Lipid oxidation and microbial action have long been attributed to reduced food quality, but the effect on quality has only been gradually noticed in recent years. In food systems, protein oxidation can occur naturally and can also be triggered by processing. Therefore, the oxidation phenomenon is very common in the processing process of protein food. It is very important to study the detailed oxidation mechanism of protein. The new problem is the intake of oxidized protein impacts the health of the human body and intestinal microorganisms in its role, microorganisms in the human body intake of oxidized protein's detailed role is not clear. However, it is undeniable that the gut microbiota plays a vital role in human gut health, and it is very important to study the detailed function of the human gut microbiota after ingestion of oxidized proteins. This study conducted a detailed analysis of food processing to create a protein oxidation environment, protein oxidation mechanism, protein oxidation modification on human intestinal health, and digestion characteristics. Besides, the study also analyzes the role of microorganisms and puts forward the insufficiency. The paper also provides references and help for protein oxidation research.

Synthesis of a trivalent copper complex for efficient degradation of antibiotic ofloxacin

Copper-based catalysts have been widely used in heterogeneous advanced oxidation processes (AOPs) to degrade emerging contaminants, with trivalent copper species (Cu(III)) often identified as crucial intermediates. However, the current understanding of the reactivity and potential oxidation mechanism associated with such reactive species remains quite limited. In the present study, a stable Cu(III) complex was synthesized, and its reactivity towards a typical fluoroquinolone antibiotic, ofloxacin (OFX), was comprehensively investigated. The results revealed that Cu(III) itself functioned as the primary oxidizing agent instead of secondary hydroxyl radicals generated during OFX decomposition, which exhibited high reactivity over a wide pH range (3.0–9.0) with molar ratio of Cu(III) to OFX between 1:2 and 3:1. Interestingly, prevalent constituents of natural water, including (bi)carbonate (0–10 mM), chloride (0–10 mM), nitrate (0–10 mM) and humic acid (0–30 mg/L), displayed minimal influence on the oxidation efficiency of Cu(III). Piperazine moiety was identified as the primary reaction site, and three different pathways including tertiary amine oxidation, hydroxylation, and N-demethylation process were proposed. The detailed oxidation mechanisms were further illustrated by density functional theory (DFT) calculations. This study contributes to the theoretical foundation for investigating the mechanism of Cu(III)-mediated oxidation of antibiotics.

Gas–particle partitioning of toluene oxidation products: an experimental and modeling study

Abstract. Toluene represents a large fraction of anthropogenic emissions and significantly contributes to tropospheric ozone and secondary organic aerosol (SOA) formation. Despite the fact that toluene is one of the most studied aromatic compounds, detailed chemical mechanisms still fail to correctly reproduce the speciation of toluene gaseous and condensed oxidation products. This study aims to elucidate the role of initial experimental conditions in toluene SOA mass loadings and to investigate gas–particle partitioning of its reaction products at different relevant temperatures. Gaseous and particulate reaction products were identified and quantified using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHemical Analysis of aeRosol ONline (CHARON) inlet. The chemical system exhibited a volatility distribution mostly in the semi-volatile regime. Temperature decrease caused a shift of saturation concentration towards lower values. The CHARON–PTR-ToF-MS instrument identified and quantified approximately 60 %–80 % of the total organic mass measured by an aerosol mass spectrometer. A detailed mechanism for toluene gaseous oxidation was developed based on the Master Chemical Mechanism (MCM) and Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) deterministic mechanisms, modified following the literature. The new mechanism showed improvements in modeling oxidation product speciation with more observed species represented and more representative concentrations compared to the MCM–GECKO-A reference. Tests on partitioning processes, nonideality, and wall losses highlighted the high dependency of SOA formation on the considered processes. Our results underline the fact that volatility is not sufficient to explain the gas–particle partitioning: the organic and the aqueous phases need to be considered as well as the interactions between compounds in the particle phase.

Molar ratio of (-)-epicatechin and (-)-epigallocatechin gallate determined their enzymatic oxidation products and color characteristics

Catechins are the primary polyphenols in tea. Enzymatic oxidation models of (-)-epicatechin (EC) and (-)-epigallocatechin gallate (EGCG) with different proportions were established to investigate the formation mechanism of oxidation products and their relationship to color characteristics. Their oxidation products were analyzed by liquid chromatography tandem mass spectrometry (LC-MS) combined with UV-visible spectrometry. These products were quantified by LC-MS and performed correlation coefficient analysis of color. The results indicated that single oxidation of EGCG dominated the whole reaction when EGCG had high proportions in the reaction mixture, promoting the formation of red pigments such as dehydrotheasinensin AQ and theacitrinin B. When EC with high ratios, the oxidation pathways preferred utilizing both EC and EGCG, promoting the formation of yellow pigments such as theaflavin and theadibenzotropolone A. This study provided the detailed oxidation mechanism of EC and EGCG mixture, suggesting that the proportions of catechol-type and pyrogallol-type catechins markedly affected the direction of enzymatic oxidation reaction and further influenced the color formation.

Insights into long-term environmental oxidation of recycled high-viscosity modified asphalt toward durable and sustainable pavement infrastructure

The investigation of long-term environmental oxidation resistance of rejuvenated high-viscosity modified asphalt (HVMA) is of great significance as it unlocks its full potential for recycled utilization, offering improved solutions for sustainable and cost-effective pavement infrastructure. This study aims to comprehensively investigate the long-term environmental oxidation resistance and mechanisms of various oil-based and polymer-based rejuvenated HVMAs. Firstly, the long-term oxidation process of oil-based and polymer-based rejuvenated HVMAs was simulated using the indoor accelerated environmental aging test. Subsequently, a series of rheological tests and X-ray photoelectron spectroscopy (XPS) test were employed to examine the environmental oxidation characterization of rejuvenated HVMAs. Finally, a radar chart was proposed to rank the anti-oxidation capabilities of various rejuvenated HVMAs, accompanied by a detailed oxidation mechanism analysis. The results indicate that polymer-based rejuvenated HVMA exhibits superior environmental oxidation resistance compared to oil-based rejuvenated HVMA. The addition of polymer-based rejuvenators effectively retards the phase angle plateau disappearance and rheological performance deterioration of rejuvenated HVMA during environmental aging. Polymer-based rejuvenators significantly slow down the oxidation rates of carbon and sulfur elements in rejuvenated HVMA. Although the addition of oil-based rejuvenators may not enhance the anti-oxidation capability, the restructuring of the polymer phase structure plays a crucial role in improving the anti-oxidation performance. The ranking of anti-oxidation capabilities among the four polymer-based rejuvenated HVMAs is as follows: SBS-based waste furfural oil (SFO) > SBS-based waste rubber oil (SRO) > SBS-based aromatic oil (SR) > SBS-based waste cooking oil (SWCO). SFO demonstrates the highest resistance to environmental oxidation, primarily attributed to the inherent UV absorption and free radical scavenging capability of furfural oil (FO). SRO exhibits favorable anti-aging performance due to the chemical composition resembling asphalt, which provides enhanced chemical stability. Conversely, waste cooking oil (WCO) contains a significant amount of unsaturated fatty acid esters, which is susceptible to oxidation due to oxygen attack, resulting in the lowest anti-aging capability of SWCO.

Antioxidant performance and oxidation mechanism of a liquid silicon infiltration (LSI) SiC–Si coating at an ultra-high temperature of 1873 K

A novel SiC–Si coating with a high amount of net-like distributed Si was fabricated on the graphite substrate by liquid silicon infiltration (LSI) method to improve the oxidation-resistant performance. The mass gain of this LSI coating after 300 h oxidation at 1873 K was only 3.018%, suggesting an excellent static antioxidant property at 1873 K. The detailed oxidation mechanism of this LSI coating was explored in this work. It was found that the high amount of Si with the net-like distribution in this LSI coating promoted the passivation growth of SiO2 glass layer and prevented the SiO2 glass from crystallizing into cristobalite. In addition, the Si in this coating retarded the active oxidation and enhanced the coating stability. In contrast, the infiltration (VSI) SiC–Si coating presented an apparent mass loss, and the pack cementation (PC) SiC coating showed the catastrophic failure. The oxidation mechanisms of these two coatings were also discussed against the backdrop of the LSI coating with high antioxidant performance.

An Experimental and Kinetic Study of Phenylacetylene Ignition at High Temperatures

ABSTRACT Phenylacetylene plays a critical role as an intermediate in PAH formation in hydrocarbon flames. In this work, the autoignition characteristics of phenylacetylene were investigated behind reflected shock waves. Ignition delay times were measured at temperatures ranging from 1228 to 1813 K, pressures of 2, 4, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, as well as fuel mole fractions of 0.1% and 0.2%. The effects of temperature, pressure, equivalence ratio, and mole fractions on ignition delay time were investigated, and quantitative relationships were obtained by regression analysis of the experimental data. A detailed oxidation mechanism of phenylacetylene based on NUIGMech1.1 was proposed and verified using ignition data. Reaction pathway and sensitivity analyses have been carried out to investigate the significant reaction pathways in the ignition process and key reactions that affect the ignition delay time. The addition reactions by O and OH species contribute significantly to phenylacetylene consumption and promote fuel ignition. Finally, a comparison of the ignition delay times of ethylbenzene, styrene, and phenylacetylene was conducted in this study, and kinetic analyses have been conducted to investigate the impact of different side chains attached to aromatic rings on the ignition of these C8 aromatics.

Butyl Acetate Pyrolysis and Combustion Chemistry: Mechanism Generation and Shock Tube Experiments.

The combustion and pyrolysis behaviors of light esters and fatty acid methyl esters have been widely studied due to their relevance as biofuel and fuel additives. However, a knowledge gap exists for midsize alkyl acetates, especially ones with long alkoxyl groups. Butyl acetate, in particular, is a promising biofuel with its economic and robust production possibilities and ability to enhance blendstock performance and reduce soot formation. However, it is little studied from both experimental and modeling aspects. This work created detailed oxidation mechanisms for the four butyl acetate isomers (normal-, sec-, tert-, and iso-butyl acetate) at temperatures varying from 650 to 2000 K and pressures up to 100 atm using the Reaction Mechanism Generator. About 60% of species in each model have thermochemical parameters from published data or in-house quantum calculations, including fuel molecules and intermediate combustion products. Kinetics of essential primary reactions, retro-ene and hydrogen atom abstraction by OH or HO2, governing the fuel oxidation pathways, were also calculated quantum-mechanically. Simulation of the developed mechanisms indicates that the majority of the fuel will decompose into acetic acid and relevant butenes at elevated temperatures, making their ignition behaviors similar to butenes. The adaptability of the developed models to high-temperature pyrolysis systems was tested against newly collected high-pressure shock experiments; the simulated CO mole fraction time histories have a reasonable agreement with the laser measurement in the shock tube. This work reveals the high-temperature oxidation chemistry of butyl acetates and demonstrates the validity of predictive models for biofuel chemistry established on accurate thermochemical and kinetic parameters.

A novel object-oriented directed path screening method for reduction of detailed chemical kinetic mechanism

Numerical simulation is widely recognized as an efficient means of developing high-performance combustors. However, its efficiency is limited by the growing size of chemical kinetic mechanisms, which increases computation costs. To substantially reduce the size of mechanism while retaining the accuracy, an object-oriented directed path screening (OoDPS) method is proposed in this study. In this methodology, species are ranked according to the order in which they are generated in flame, then reactions are ranked according to the generation of the species in the left hand side of each reaction. A set of important species codetermining the accurate prediction of concerned combustion characteristics are predefined as the "Object". Calibration databases are extracted from laminar premixed flames simulated using the detailed mechanism with equivalence ratio varying from 0.7 to 1.5. The contributions of each reaction in the detailed mechanism to the production/consumption of each species in the Object are evaluated. The size of the reduced mechanism depends on the user-defined contribution coefficient threshold. In this study, a detailed mechanism for methane-ammonia oxidation, consisted of 84 species and 703 reactions, is applied to demonstrate the reliability of the OoDPS method. Several derived skeletal mechanisms are validated against the detailed mechanism. OoDPS method shows a better performance than DRGEP in predicting the laminar burning velocity and ignition delay time at the same level of reaction number. For diffusion flames, OoDPS remains superior to DRGEP in predicting the concentration profiles of H, O and OH, and this superiority becomes more significant for reduced mechanism with less reactions. Unfortunately, as the size of reaction decreases from 703 to 109, the accuracy of OoDPS-generated skeletal mechanism decreases as the increase of ammonia in the fuel, which can be restrained by extending the calibration databases.

A detailed surface reaction mechanism to investigate oxidation of methane over nickel catalyst

AbstractWe have developed a kinetically consistent detailed surface reaction mechanism for modeling the oxidation of methane over a nickel‐based catalyst. A one‐dimensional model, LOGEcat based on the single‐channel 1D catalyst model, is used to perform the simulations. The original multi‐step reaction mechanism is thermodynamically consistent and consists of 52 reactions. By thermodynamic consistency, we mean that the equilibrium is achieved with the support of the Arrhenius parameters and does not depend on the thermochemistry of the species involved in the considered reactions. The detailed mechanism developed in this investigation contains 26 reversible reactions. These reactions are obtained with the use of the thermochemistry of the species. The study focuses on ensuring kinetic consistency and this is done with the help of thermodynamic analysis by bringing the thermochemistry of the species in play in order to develop a surface reaction mechanism. The new mechanism can be used to understand the other processes, for example, steam‐ and dry‐reforming of methane over nickel, however, the main focus of the paper is to check the performance of the detailed mechanism for catalytic partial oxidation of methane. The applicability of the mechanism is checked for various reactor conditions in terms of parameters such as temperature and pressure by comparing the results with the available reference data. The detailed mechanism developed in this study is able to accurately express oxidation of methane over the nickel catalyst for the considered reactor conditions.

High-Temperature Autoignition of Propylene Glycol: An Experimental and Kinetic Study

ABSTRACT Propylene glycol is a potential fuel additive with high oxygen-contained. Propylene glycol has two isomers, 1,2-propylene glycol and 1,3-propylene glycol. In order to comprehend the combustion behavior of propylene glycol, the autoignition properties were investigated experimentally behind reflected shock waves. The Ignition delay times were obtained at the temperature range of 1100–1550 K, pressures of 2, 4 and 10 atm, equivalence ratios of 0.5, 1.0 and 2.0, as well as fuel concentrations of 1.0% and 1.5%. The effects of temperature, pressure, fuel and oxygen concentrations on the ignition delay time were studied, and the corresponding quantitative relationships were obtained through linear regression analysis. A detailed oxidation mechanism of propylene glycol was proposed and verified by ignition data and species profiles. Kinetic analyses were carried out to investigate the propylene glycol oxidation. Pathway analysis indicated that H-abstraction reactions are the main consumption channels of propylene glycol. Rate of production analysis illustrated that H-abstraction reactions by H and OH radicals dominate the fuel consumption. Sensitivity analysis confirmed that besides H-abstraction reactions, C–C bond dissociation reactions express strong promoting effects on fuel ignition. Comparisons of the ignition delay time of propylene glycol, ethylene glycol and propanol were conducted.

Numerical analysis of ammonia HCCI combustion in a free piston engine through trajectory-based combustion control

Ammonia is a promising carbon–neutral fuel, able to power heavy-duty vehicles, non-road machineries and ocean ships with zero CO2 emission. However, practical challenges still exist when applying ammonia in traditional internal combustion engines (ICEs) due to its high ignition energy, slow flame propagation and significant NOx emissions. Free piston engine (FPE) is a flexible alternative to ICE whose piston can move freely without the constraints of crankshaft. Therefore, its piston trajectory can be leveraged as a new control means to facilitate ammonia combustion. In this paper, a numerical analysis investigating ammonia HCCI combustion in FPE was presented. A physical-based model was developed at first, including a unique trajectory synthesizing mechanism and a detailed reaction mechanism of ammonia oxidation. Various asymmetric piston trajectories were then employed into the model and the simulated HCCI combustion were analyzed through six characteristics, namely indicated thermal efficiency, location of peak pressure, exhaust gas temperature, combustion duration, ignition delay, and NOx emissions. This investigation not only determines the best compression ratio (CR = 25) for ammonia ignition, but also shape the optimal piston trajectory (symmetric trajectory with Ω = 0.5) for ammonia HCCI combustion to enhance thermal efficiency and reduce NOx emission simultaneously.

Oxidation behavior of a cathodic arc evaporated Cr0.69Ta0.20B0.11N coating

CrTaBN hard coatings deposited by cathodic arc evaporation are a promising new material class for use in demanding applications, due to their high hardness and good thermal stability in protective atmosphere. Up to now however, studies on the detailed oxidation mechanism of quaternary CrTaBN coatings are lacking in the literature. Thus, within this work, the oxidation behavior of a Cr0.69Ta0.20B0.11N coating grown by cathodic arc evaporation was studied in a combinatorial approach of advanced characterization techniques. In situ high-energy x-ray diffraction at a synchrotron radiation facility showed that up to ∼1100 °C, only the face-centered cubic (fcc) CrxTayB1−x−yN solid solution of powdered CrTaBN contributes to the crystalline phase composition. As the temperature is further increased, tetragonal CrTaO4 and rhombohedral Cr2O3 form. In situ high-temperature Raman spectroscopy evidenced that B2O3 contributes to the phase composition of the material in the temperature regime from ∼600 to 1000 °C. Applying high-resolution transmission electron microscopy allowed to identify the presence of four discrete zones in a partly oxidized CrTaBN coating on sapphire: intact fcc-CrTaBN at the interface to the substrate, followed by a Cr-deficient and Cr-enriched layer, respectively, and a porous layer with small grains at the surface.

Application of Screen Printed Diamond Electrode, Coupled with “Point-of-Care” Platform, for Nanomolar Quantification of Phytonutrient Pterostilbene in Dietary Supplements: An Experimental Study Supported by Theory

Herein, a screen–printed diamond electrode (SPDE) coupled with a “point-of-care” platform (30 µL-drop concepts, single-drop-detection approach) was successfully applied for the electrochemical determination of pterostilbene (PTS). Cyclic voltammetry identified irreversible oxidation of PTS, where oxidation peak was shown to be strongly dependent on the pH of the working environmental. Although the proposition of the detailed electrochemical oxidation mechanism of PTS goes out of the scope of the present research, we have determined the most probable reactive site of our analyte, by utilizing DFT-based reactivity descriptors (Fukui functions). For electrochemical quantification of PTS, oxidation peak at 0.32 V (vs. Ag/AgCl) was followed in presence of 0.5 mol L−1 of Briton–Robinson buffer solution (pH = 9). Coupled with the optimized parameters of differential pulse voltammetry (DPV), SPDE detected PTS in two linear ranges (first range was from 0.011 to 0.912 µmol L−1; second range was from 0.912 to 4.420 µmol L−1), providing the LOD and LOQ on a nanomolar level (3.1 nmol L−1 and 10.0 nmol L−1, respectively). The selectivity of the optimized DPV method was found to be excellent, with the current changes of less than 7%, in the presence of ten times higher concentrations of the certain interferences. The practical applicability of the SPDE and single-drop-detection approach in dietary supplements (with a declared PTS content of 50 mg/tablet), with the recovery values ranging from 95 to 102%, shows that the developed method has high potential for precise and accurate PTS detection, as well as exceptional miniaturization possibilities of relevant equipment for on-site sensing.

Detailed mechanism of organic pollutant oxidation via the heterogeneous Fenton reaction requires using at least two substrates, e.g.: DMSO and EtOH

Heterogeneous catalysts hold immense potential applicability in batch-advanced oxidation technologies. The present study examined LaFeO3 Fenton-like catalyzed oxidation of EtOH and DMSO. LaFeO3 is used to catalyze many processes, including an advanced oxidation process (AOP). Less is known about its role in Fenton-like reactions for AOPs. The results point out that two short-lived oxidizing intermediates are formed. Based on oxidation products analysis, it is tentatively proposed that the two short-lived oxidizing intermediates are [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] and [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. Both substrates are oxidized by [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2], the oxidation of DMSO by this intermediate is considerably faster than that of ethanol. [(LaFeIVO3)2(LaFeIIIO3)n-2]2+ oxidizes only EtOH. The yield of [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] is larger than that of [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. The knowledge gained in this study will help elucidate the detailed mechanisms of perovskite catalyzed Fenton-like processes and thus facilitate the development of efficient AOPs. The involvement of two short-lived intermediates was shown only by studying the oxidation of two very different substrates, a novel approach whose groundbreaking results are important for catalytic processes that will advance environmental strategies.

Diffusion combustion of n-decane with unpassivated aluminum nanoparticles additives: Аnalysis of mechanism and numerical simulation

Possible mechanisms of the increase in the flame front temperature, observed in experiments with diffusion combustion of n-decane with the addition of unoxidized aluminum nanoparticles with a diameter of 20 nm, were analyzed numerically. It was shown that at nanoparticle concentrations of 0.5 and 2.5 wt%, which were considered in the experiment, the heat release caused by the oxidation of aluminum can induce only a slight (up to 10 K) increase in the temperature of the front. Numerical modeling of a laminar diffusion flame allowed us to establish that the most probable cause of an increase in the temperature of the flame front is the acceleration of gas-phase reactions of n-decane oxidation. A detailed kinetic mechanism of ignition and oxidation of n-decane in the presence of aluminum vapor was developed to test the previously proposed hypothesis of promoting the n-decane combustion with aluminum vapor. Numerical calculations using the developed kinetic mechanism have shown that gaseous aluminum as a combustion promoter does not allow achieving the same increase in the flame front temperature as in the experiment. It makes the development of alternative mechanisms for promoting the combustion of n-decane by aluminum nanoparticles urgent.