Synthesis, characterization and antimicrobial effect of Cu(ii) and Zn(ii) compounds derived from 1,2,4-triazoles

Compounds of Cu(II) and Zn(II) with 3-R-1H-1,2,4-triazole-5-amine {R = methyl (mta), phenyl (pta)} were prepared and characterized by infrared spectroscopy (IR), multinuclear NMR (1H, 13C), electronic spectroscopy (UV-VIS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), microanalyses and melting point. Dimeric, monomeric, and polymeric materials were synthesized in this work. The Zn(II)-1,2,4-triazole derivatives have the metal ion at the center of two geometric arrangements, being a tetrahedron for the complex-7 and 9, and an octahedron for the complex-8. The only polymeric material, complex-7, was characterized by the DSC analytical data. The Decomposition reaction of complex-8 in chloroform produced the complex-9, a aminoguanidine derivative, and the Zn(II)-benzoate compound. The IR and UV-VIS of Cu(II)-mta derivatives revealed two possible geometric patterns for the metallic ion; a distorted bipyramidal trigonal geometry for compounds 10 and 11 in solution, and in the solid state, the same geometry for complex-10, but for complex-11, the IR data suggest a distorted octahedral geometry. The biological assay of the 1,2,4-triazole compounds and their metal derivatives against Gram-positive and Gram-negative bacteria shown the compounds of Zn(II) as the only active materials with values of MIC within the range of 133.5 µM (83.3 µg / mL) to 360.7 µM (166.6 µg / mL).

Catalytic properties of a composite material based on belarusian dolomites in relation to the decomposition of pyrolysis tar

The paper discusses results of an experimental study of the thermal decomposition of pyrolysis tar in a homogeneous process and in the presence of a catalyst. Experiments on thermal decomposition of pyrolysis tar were carried out under isothermal conditions in a laboratory setup at temperatures of 300, 400, 450 and 500 °C. The rate of the homogeneous process of thermal decomposition of tar and maximal degrees of decomposition were determined. According to the data of this work, the activation energy of the homogeneous process was 320 kJ/mol. It was found that the rate of thermal decomposition of the tar increases in the case of introducing samples of natural dolomites into the reaction zone, as well as a composite material based on them. This increase is due to the occurrence of a heterogeneous catalytic decomposition reaction of the pyrolysis tar. The apparent activation energy of this process was 210 kJ/mol (when using dolomites) and 202 kJ/mol (when using composites). It was noted that the composite material has significantly more favorable mechanical properties than dolomite. Based on the established data, it was concluded that the creation of composite catalysts for the thermal decomposition of heavy hydrocarbons formed in the processes of thermochemical conversion of biomass is promising.

NON-ISOTHERMAL KINETICS OF SOLID-PHASE DECOMPOSITION OF MIXTURES OF OCTOGEN WITH NITRO-NITROZOAMINES

Определены формально-кинетические характеристики термораспада нитро-нитрозоаминов и их смесей с октогеном. Реакция разложения нитрозоаналогов октогена и нитро-нитрозопроизводных тетраазадекалина характеризуется меньшей энергией активации по сравнению с октогеном, и протекает с большей скоростью. Проведен анализ активационных параметров термораспада смесей, установлено активирующее влияние нитрозопроизводных тетраазадекалина на разложение октогена. The formal-kinetic characteristics of the thermal decomposition of nitro-nitrosoamines and their mixtures with HMX have been determined. The decomposition reaction of nitroso analogs of HMX and nitro-nitroso derivatives of tetraazadecalin is characterized by a lower activation energy compared to HMX, and proceeds at a higher rate. The analysis of the activation parameters of the thermal decomposition of the mixtures was carried out, the activating effect of the nitroso derivatives of tetraazadecalin on the decomposition of HMX was established.

Hydrogen Production through Catalytic Water Splitting Using Liquid-Phase Plasma over Bismuth Ferrite Catalyst

This study examined the H2 production characteristics from a decomposition reaction using liquid-phase plasma with a bismuth ferrite catalyst. The catalyst was prepared using a sol–gel reaction method. The physicochemical and optical properties of bismuth ferrite were analyzed. H2 production was carried out from a distilled water and aqueous methanol solution by direct irradiation via liquid-phase plasma. The catalyst absorbed visible-light over 610 nm. The measured bandgap of the bismuth ferrite was approximately 2.0 eV. The liquid-phase plasma emitted UV and visible-light simultaneously according to optical emission spectrometry. Bismuth ferrite induced a higher H2 production rate than the TiO2 photocatalyst because it responds to both UV and visible light generated from the liquid-phase plasma.

Catalytic and Sulfur-Tolerant Performance of Bimetallic Ni–Ru Catalysts on HI Decomposition in the Sulfur-Iodine Cycle for Hydrogen Production

The sulfur-iodine (SI) cycle holds great promise as an alternative large-scale process for converting water into hydrogen without CO2 emissions. A major issue regarding the long-term stability and activity of the catalysts is their poor sulfur deactivation resistance in the HI feeding process. In this work, the effect of Ru addition for enhancing the activity and sulfur resistance of SiO2-supported Ni catalysts in the HI decomposition reaction has been investigated. The presence of H2SO4 molecules in the HI results in severe sulfur deactivation of the Ru-free Ni/SiO2 catalysts by blocking the active sites. However, Ni–Ru/SiO2 catalysts show higher catalytic activity without sulfur-poisoning by 25% and exhibit more superior catalytic performance than the Ru-free catalyst. The addition of Ru to the Ni/SiO2 catalyst promotes the stability and activity of the catalysts. The experimental trends in activity and sulfur tolerance are consistent with the theoretical modeling, with the catalytic activities existing in the order Ni/SiO2 < Ni–Ru/SiO2. The effect of Ru on the improvement in sulfur resistance over Ni-based catalysts is attributed to electronic factors, as evidenced by theory modeling analysis and detailed characterizations.

Synthesis of Refractory Metal Carbides on Carbon Fibers in Molten Salts and Their Electrocatalytic Properties

Coatings of TaC and NbC and Mo2C crystals on carbon fibers were obtained by currentless transfer in molten salts. Investigation of electrocatalytic properties of these compositions in the reaction of the hydrogen peroxide decomposition was carried out. It was determined that the hydrogen peroxide decomposition reaction has a zero order for all refractory metal carbides. Using the values of the rate constants at different temperatures the activation energies for the reaction of the hydrogen peroxide decomposition on refractory metal carbides were calculated using the Arrhenius equation. It has been established that coating of NbC on carbon fibers has a higher electrocatalytical properties in comparison with other carbides. The electrocatalytic properties of NbC/C, TaC/C and Mo2C/C composites were studied also by cyclic voltammetry.

Effect of Lanthanum Cerium Cysteine on Cure Characteristics, Mechanical Properties, and Thermooxidative Aging for Natural Rubber

In this work, a novel additive lanthanum cerium cysteine (LC-Cys), with the molecular formula La0.35Ce0.65(Cys)3Cl3·3H2O, was successfully synthesized through complex decomposition reaction of L-Cysteine and chlorinated rare earths. The effects of additive LC-Cys on cure characteristics, mechanical properties, and thermooxidative aging were investigated. LC-Cys as a multifunctional additive was applied to increase the curing rate and reduce the content of zinc oxide in the presence of the sulfur vulcanization system. It was found that the vulcanizates filled with (5ZnO/2LC-Cys) exhibited the highest modulus, which indirectly indicated the high crosslink and stiffness of the vulcanizates. Moreover, the vulcanizates with LC-Cys showed excellent mechanical properties and resistance to thermooxidative aging. Compared to NR composites filled with normal ZnO, LC-Cys even enhanced the mechanical strength and thermooxidative aging properties with 40% lower ZnO addition.

Pyrolysis kinetic analysis of sequential extract residues from Hefeng sub-bituminous coal based on Coats-Redfern method

Sequential extract residues (Ri, i=1, 2, 3, 4, 5) were obtained from Hefeng acid-washing coal (HFAC) by petroleum ether, carbon disulfide, methanol, acetone and isometric carbon disulfide/acetone mixture, sequentially. Pyrolysis behavior of the samples was carried out using thermogravimetry analysis. Coats-Redfern method with different reaction order was used to analyze the pyrolysis kinetic of each sample, and the kinetic parameters, including correlation coefficient (R2), activation energy (E), pre-exponential factor (A), were calculated. Results showed that the weight loss of extract residues was higher than HFAC, and pyrolysis behavior varies greatly for residues, which may be due to unstable structure after extraction. From conversion-temperature (α-T) curves, pyrolysis process was divided into three stages: low-temperature stage (150-350 oC), medium temperature stage (350-550 oC) and high temperature stage (550-950 oC). And the medium temperature stage made great contribution to the process of pyrolysis, which was dominated by depolymerization and decomposition reaction, and the effect of kinetic fitting to this stage is better, with R2 higher than 0.95. Relationship between kinetic parameters and reaction order showed that swelling effect might be an important reason for the discrepancy of E for each sample in the process of pyrolysis. And Ln(A)-E relationship has a great significance to predict E and the A under higher reaction order.

Coupling Effect of Metals and Oxides on the Oxygen Supply Performance of Sodium Chlorate Oxygen Candle

In this study, to explore the influence of metals and oxides on the oxygen production rate and stability of sodium chlorate oxygen candles, 28 experimental samples were investigated. The effects of Co2O3, Co3O4, and Fe2O3 with different mass fractions on the thermal decomposition temperature and thermal decomposition rate of sodium chlorate were compared and analyzed. Co3O4 (5%) was obtained to reduce the thermal decomposition range to 260–450°C and reduce the pyrolysis interval ∆T to 46.2°C. Through the development of three metals (Fe, Mg, and Mn), under four mass fractions (2%, 4%, 6%, and 8%) mixed with Co3O4 (5%), the results of the effective oxygen production efficiency test for the thermal decomposition reaction of sodium chlorate demonstrated that Mn (6%)–Co3O4 (5%) exhibited the best catalytic and heat coupling effect; the effective oxygen production efficiency of 97.8% was achieved. Oxygen candle oxygen supply experiment was conducted; the oxygen candle composition for the test was determined to be NaClO3 (86%), Mn (6%), Co3O4 (5%), and kaolin (3%); in the four stages of the oxygen candle oxygen supply reaction test, the average oxygen supply rate reached 1.647 L/min, actual oxygen production was 28 L, and effective oxygen production rate of the oxygen candle was 53.6%. An increase of 9% was observed compared to the previous similar studies. The results of this study present a formula to optimize the oxygen supply of the oxygen candle, which is crucial for improving the oxygen supply performance of the oxygen candle.

Comment on “Isotopic evidence for dominant secondary production of HONO in near-ground wildfire plumes” by Chai et al. (2021)

Chai et al. (2021) recently published measurements of wildfire-derived (WF) oxides of nitrogen (NOx) and nitrous acid (HONO) and their isotopic composition. The method used to sample NOx, collection in alkaline solution, has a known 1:1 interference from another reactive nitrogen compound, acetyl peroxynitrate (PAN). Although PAN is thermally unstable, subsequent reactions with nitrogen dioxide (NO2) in effect extend the lifetime of PAN many times longer than the initial decomposition reaction would indicate. This, coupled with the rapid and efficient formation of PAN in WF plumes, means the NOx measurements reported by Chai et al.​​​​​​​ were severely impacted by PAN. In addition, the model reactions in the original paper included neither the reactions of NO2 with hydroxyl radical (OH) to form nitric acid nor the efficient reaction of larger organic radicals with nitric oxide to form organic nitrates (RONO2).