Layered perovskite-like Sr2TiO4 is a promising catalyst for oxidative coupling of methane (OCM)—a potential direct route to produce C2 (ethane + ethylene) hydrocarbons, especially, ethylene. In this work, Sr2 – хLnxTi1 – yFeyO4 (Ln = La, Pr, х = 0, 0.1; y = 0–0.3) layered perovskites with partially substituted positions of Sr (La, Pr) or Ti (Fe), were synthesized by sol–gel method using polymeric precursors and wetness impregnation followed with calcination at 900–1000°C. The samples were characterized by X‑ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), adsorption and temperature-programmed hydrogen reduction (H2-TPR). It was revealed that Sr2TiO4 doping with La leads to formation of nanocomposite material containing Sr2TiO4, La‑doped SrTiO3 and La2O3 while Sr2TiO4, Sr3Ti2O7 and Pr6O11 are observed in the case of Pr. Fe–doped samples with x = 0.1–0.2 are the single-phase systems. Testing of the obtained doped materials in oxidative coupling of methane has shown the correlation of their catalytic activity with H2-TPR data and also with the ratio O_2^2 - /O2– (the surface adsorbed and surface lattice oxygen, correspondingly) and peculiarities of O2–. The higher СН4 conversion and C2 selectivity for the La-doped catalyst is due to appearance of O2– reduced at medium temperature. The low activity of Pr and Fe doped samples is conditioned by the presence of a large amount of surface adsorbed oxygen O_2^2 - facilitating COx formation and decreasing C2 selectivity.
The Diels–Alder (DA) reaction between 3-methyl-3-penten-2-one (MP) and myrcene is experimentally examined and theoretically modeled as part of the Iso E Super synthesis process. The results reveal that the DA reaction between MP and myrcene follows a typical electron-demand mechanism, and the para-product (2) is the most stable structure. With the addition of the AlCl3 catalyst, the reaction energy barrier drops significantly from 132.85 to 61.38 kJ/mol, easing the reaction conditions. The AlCl3 catalyst exhibits the highest catalytic activity among the catalysts tested, especially in isooctane solvent, of which the conversion of myrcene reaches 88.51
Anderson-type sodium hexamolybdoaluminate(III) is used for the synthesis of quinoxaline derivatives using 1,2-diketone and 1,2-diamine in aqueous medium at room temperature. This catalyst is characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA). The Al(III) catalyst is a heterogeneous catalyst that was successfully recovered and recycled four times without major loss of activity. The methodology is environmentally benign and offers excellent product yields. The (Na3[AlMo6O24H6]·8H2O) is biologically evaluated for its cytotoxic activity against human breast adenocarcinoma cell lines. This catalyst exhibited moderate cytotoxic activity compared to the standard drug 5‑fluorouracil (5-FU), with a cell viability of 62.48
Al1 – xMgxCr2O4 nanochromites, where x = 0, 0.02, 0.04, 0.06, 0.08, and 0.10, were synthesized by citrate gel auto combustion technique. The X-ray diffraction study confirms the synthesized nanochromites belong to the spinel structure with the FD3M space group, and the average crystallite size was 20 to 24 nm, which was calculated from the Debye–Scherrer formula. The distribution of these sizes would be seen in the SEM pictures, providing light on the uniformity. About 550 and 625 cm–1 wavenumber domain FTIR bands are present in the FTIR spectrum, which correlate to the metal-oxygen bonds stretching vibrations of the octahedral (Mg–O bond linkage) and tetrahedral (Cr–O or Al–O bond linkage) sites. Using Tauc plots, the bandgap energy of the material was calculated, i.e., in between 2.21–3.26 eV. Fluorescence (FL) emission in the 400 nm region was seen in the PL spectra. Two organic industrial pollutants, such as Methylene Blue (MB) and Acid Red 18 (AR18), were utilized to examine the photocatalytic activity under visible light. Anticancer activity of Al1 – xMgxCr2O4 nanochromites tested with HeLa CCL2 cells. Antibacterial activity is carried out by two gram-positive and two gram-negative bacterial agents, namely Staphylococcus aureus (ATCC6538), Bacillus subtilis (ATCC11774), Escherichia coli (ATCC8739), and Klebsiella pneumoniae (ATCC10031). Antifungal activity is investigated by two fungal pathogens (candida albicans (ATCC10231) and Aspergillus niger (ATCC1015)) by a pour plate method.
Alkyl furfuryl ethers are promising additives to motor fuels, which can be produced by reductive etherification of furfural with alkyl alcohol. The Cu/Al2O3 catalyst was prepared using a copper ammonia complex as the precursor of active component. The catalytic behavior of the physical mixture of the Cu/Al2O3 catalyst and ZSM-5-Al2O3 composite was studied in the reductive etherification of furfural in a flow reactor using H2 as a reducing agent. This process involves the sequential hydrogenation of furfural on the Cu0 sites of the Cu/Al2O3 catalyst, followed by the etherification of the resulting furfuryl alcohol on the acid sites of zeolite. The highest yield of 2‑(isopropoxymethyl)furan (IMF) of 85
Using the activated chemiluminescence method, it was found that in the presence of monosaccharide additives, the antiradical activity of phenolic carboxylic and hydroxycinnamic acids in the reaction with 2-amidinoisopropane-2-peroxyls in an aqueous medium at pH 2 increases significantly. The found synergistic effect is most pronounced (over 90
This paper is devoted to a review and analysis of the authors’ (Kovalenko and her colleagues) results published in the journal Kinetics and Catalysis in 2007–2018. This article briefly describes the results on obtaining composite carbon–mineral supports, which were an inorganic matrix (IM) with a synthesized surface layer of catalytic filamentous carbon (CFC). This surface CFC layer, 10–50 μm thick, was formed by chaotically interlaced carbon nanofibers (CNFs) or multiwalled carbon nanotubes (MWCNTs) with a diameter of ≥20 nm and a length of ≥1 μm synthesized on supported Ni or Co catalysts, respectively. We used various methods, such as impregnation, homogeneous precipitation, and inclusion, to apply metal (Me) catalysts; we also studied inorganic matrices that differed in their chemical nature (aluminosilicates; aluminum, titanium, and silicon oxides; and carbon), textural characteristics (meso- and macroporous matrices), and macrostructures (honeycomb monoliths, foams, and granules of various shapes). The resulting composite adsorbents with a CFC layer (CFC/Me/IM) combined the mechanical strength and macrostructure of inorganic matrices with the unique adsorption properties of nanostructured carbon filaments. The adsorptive immobilization of industrially significant enzymes (glucose isomerase, glucoamylase, nitrile hydratase, and lipase) on the CFC/Me/IM composites made it possible to prepare active and stable heterogeneous biocatalysts (BCs) for the bioconversion of vegetable resources into marketable, valuable products, including various esters. The objectives of this mini review were as follows: (1) a thorough analysis of our own data on the preparation of highly active Me (Ni, Co) catalysts supported on inorganic matrices for high-temperature pyrolysis of hydrocarbons and intended for the synthesis of carbon deposits with a pronounced filamentary nanostructure (nanofibers or nanotubes) and, as a result, the synthesis of a surface CFC-layer; (2) a comparative analysis of the adsorption properties of CFC/Me/IM composites for the immobilization of various commercially attractive enzymes, mainly, microbial hydrolases (lipase); (3) an analysis of the results of a systematic study of biocatalytic properties, such as enzymatic activity and stability, of heterogeneous BCs prepared by adsorptive immobilization of enzymes on the CFC/Me/IM composites, with the main focus on heterogeneous BCs with the activity of recombinant lipase from Thermomyces lanuginosus (rec-Lip) in the low-temperature synthesis of various esters in anhydrous media of nonpolar organic solvents; and (4) a description of the initial results of studies of a new inorganic matrix for supporting a Ni catalyst and synthesizing a CFC layer, namely, a carbon xerogel (CX) obtained from graphitized resorcinol–formaldehyde precursors and a study of the properties of BCs prepared by adsorption immobilization of rec-Lip on the CFC/Ni/CX composites. One of the key findings from a comparative analysis of the results of developing the scientific basis for the preparation of active and stable heterogeneous BCs based on CFC/Me/IM composites was that the catalytic properties of the BCs were provided first and foremost by the morphology and textural characteristics of the mesoporous CFC layer synthesized on the surface of the CFC/Me/IM composites. For example, the enzymatic activity and operational stability of the composite BCs were many times (by orders of magnitude) higher than those of BCs prepared by immobilizing rec-Lip on the original inorganic matrices (without the CFC layer).
The reactivity of pyrazolone derivatives towards secondary peroxyl radicals was studied in a model system of radical chain oxidation of 1,4-dioxane. The objects of study were 3-methyl-1-phenyl-2-pyrazolin-5-one (1), 5-amino-1,2-dihydro-1-phenyl-3H-pyrazol-3-ol (2) and 3-amino-1-phenyl-2-pyrazolin-5-one (3). The reaction kinetics were monitored by measuring the rate of oxygen uptake at 333 K. 1,4-Dioxane acted as a solvent and a source of peroxyl radicals. Compounds 1, 2, 3 were found to interact with peroxyl radicals with a rate constant (fk7 × 10–4, L mol–1 s–1) of 6.1 ± 0.3, 17.8 ± 1.7, and 3.7 ± 0.4, respectively. The stoichiometric inhibition coefficient f was found to be 2.
The use of natural gas as a motor fuel in distributed energy systems and transport requires a clear understanding of the kinetics of the effect of methane homologs on its ignition. The results of kinetic modeling of the ignition of methane mixtures with air and a small admixture of light hydrocarbons presented in this paper help explain the reasons for such unexpected experimental results as the similar effects of C2–C6 methane homologs on ignition, despite their significantly different reactivity. The significantly higher reactivity of methane homologs leads to their rapid thermal decomposition, the main product of which is ethylene, even before methane ignition. Methane ignition is directly affected by ethylene oxidation, which is independent of its source.
The Pd–S-containing samples prepared using elemental sulfur were tested in the hydrogenation of representatives of various classes of unsaturated compounds (acetylenic hydrocarbons, alcohols, and alkylanthraquinones). It was shown that the hydrogenation of acetylenic derivatives catalyzed by Pd–nS/NaZSM-5 catalysts was characterized by a sigmoidal profile of kinetic curves with an induction period, which increased as the [S] : [Pd] ratio raised from 0.25 to 1.0. Using phenylacetylene hydrogenation as a model reaction, various origins of the S-shaped kinetic dependence and competing hypotheses were discriminated. A method for enhancing the activity of Pd–S-containing samples in the hydrogenation of unsaturated compounds under mild conditions was proposed.
Methane, a potent greenhouse gas, poses a significant risk when released into the environment. In this work, a Pd/SiO2@CeO2 catalyst was developed and evaluated for its methane oxidation performance under oxygen-rich environments. The 2.5 wt
This research aims to develop a PdAg/TiO2 catalytic film enriched with palladium on the surface of nanoparticles for selective semihydrogenation of 2-methyl-3-butyn-2-ol (MBY) in microcapillary reactor. Here we report an effective and versatile synthesis of colloidal core-PdAg/open shell-Pd NPs (PdAg4@Pd) by using a facile successive reduction method. Coating the core-PdAg4 with shell-Pd NPs enables a significant improvement in the activity of PdAg2/TiO2 (up to 24 times) for the selective semihydrogenation of a MBY. High-angle annular dark-field scanning transmission electron microscopy analysis reveal the presence of Ag atoms on Pd shell which is responsible for the suppression of MBY full hydrogenation by the Pd NPs. The as-fabricated on inner surface of microcapillary reactor film with PdAg4@Pd/TiO2 nanocomposites produces a 2-methyl-3-buten-2-ol (MBE) with selectivity 96 at 97
Natural gas is routinely odorized with trace sulfur compounds, such as methanethiol (CH3SH), to enable leak detection. Although methane, the primary component of natural gas, is commonly used as the reference fuel in combustion studies, the oxidation behavior of CH3SH in premixed methane flames remains poorly characterized, despite its presence in natural gas, biogas, and refinery streams. This study presents a detailed kinetic mechanism for simulating CH3SH-doped premixed CH4 flames across a broad equivalence ratio range (Φ = 0.7–1.3). Results reveal a strong stoichiometric dependence: lean flames (Φ = 0.7) promote complete oxidation, yielding high concentrations of SO2 and SO3, which pose risks of acid deposition and corrosion. In contrast, rich flames (Φ = 1.3) suppress SOx formation but significantly enhance the production of reduced sulfur species (H2S and CS2) by up to an order of magnitude. Stoichiometric conditions (Φ = 1.0) yield a mixed speciation profile. These findings underscore the critical need for precise equivalence ratio control. We propose staged combustion strategies; employing slightly rich primary zones followed by oxidizing post-treatment as a promising approach for cleaner utilization of odorized natural gas.
The paper presents the results of a kinetic study of the thermal decomposition of calcium carbonate under conditions of continuous heating to a temperature of 1273 K at a constant rate of 1.25, 2.5, 5, 10, and 20 K/min. The integral method and the Coats–Redfern method were used to describe the reaction mechanism and determine the macrokinetic parameters. Experimental dependences of the logarithm of the preexponential factor on the activation energy were obtained. The dependences of the activation energy and preexponential factor on the heating rate are shown. The effect of the heating rate of calcium carbonate on the activation energy can be explained by the relationship between the heating rate and the concentration of CO2. Equations are proposed for calculating the reaction rate constant using the integral data processing method and the Coats–Redfern method. It has been demonstrated that the integral method and the Coats–Redfern method allow one to calculate the macrokinetic parameters of the thermal decomposition of calcite with comparable accuracy and taking into account the heating rate in these calculations makes it possible to obtain calculated values of the degree of conversion, the standard deviation of which from the experimental data is <4.1
This paper considers the photocatalytic activity of silicon nitride–based composites in the degradation of the pharmaceutical pollutant ketoprofen (KTF). The composites were obtained by nitriding ferrosilicon with various Eu2O3 additives (0–7 wt
A formal kinetic study of 2-ethyl-9,10-anthraquinone hydrogenation was carried out over 3
An Erratum to this paper has been published: https://doi.org/10.1134/S0023158426010015
Widespread application of any catalyst requires rigorous testing in the reaction of interest. Hydrogen-peroxide-based advanced oxidation processes (AOPs) are attracting growing attention because they oxidize pollutants rapidly, completely, and with minimal formation of by-products. Here we report the performance of a porous M3O4–poly(dicyclopentadiene) nanocomposite (Mn3O4/p(DCPD)) as a heterogeneous Fenton-like catalyst for the decolorization of methylene blue (MB), a dye that is toxic to humans and aquatic ecosystems. The influence of key operating variables—reaction time, initial dye concentration, H2O2 dosage, temperature, and catalyst loading—was examined systematically. Under the optimum conditions (0.25 g/L catalyst, 20 mg/L MB, ambient temperature), the dye was fully degraded within 120 min. The catalyst is easily processed, separated, and reused, making Mn3O4/p(DCPD) a promising candidate for sustainable AOP treatment of dye-contaminated water.
Supported LaFe1 – xNixO3/α-Al2O3 (x = 0, 0.6, 1) perovskite containing catalysts are prepared by impregnation of a high-temperature block carrier based on α-Al2O3 with a suspension of the active component followed by heat treatment at 900°C. The catalysts were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and temperature-programmed reduction with H2 (H2-TPR) methods and studied in the reaction of high-temperature decomposition of nitrous oxide. It is shown that all the supported catalysts are two-phase and contain only corundum and perovskite phases. The parameters of the crystal structure and the X-ray size of the corundum phase in the supported catalysts do not differ from the carrier. The observed slight increase in the cell volume for nickel-containing perovskites in supported catalysts may be due to an increase in the vacancy content in them. According to H2-TPR data, the temperatures of the reduction peaks of the supported catalysts do not differ from the reduction peaks of the unsupported perovskites, which indicates that the active component is not modified by the carrier. In terms of activity, the supported catalysts can be arranged in a row LaNiO3/α-Al2O3 > LaFe1 – xNixO3/α-Al2O3 > LaFeO3/α-Al2O3, which corresponds to the row activity of unsupported perovskites. Catalyst LaNiO3/α-Al2O3 with LaNiO3 content 7
