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Vol 64, No 2 (2023)
ОБЗОРЫ
Catalytic Methods for Producing Higher 2-Ketones: Prospects for the Wacker System in the Oxidation of α-Olefins
Abstract
Abstract—
Methods developed over the past 60 years for the preparation of unbranched С6–С14 2-ketones by catalytic oxidation of linear α-olefins have been analyzed and summarized. Particular attention has been paid to the consideration of the catalytic Wacker system, which is important for industrial organic synthesis, and the proposed ways for its modification. Methods for controlling the reaction selectivity have been discussed, and the role of co-catalysts, oxidizing agents, and ligands has been considered.
121-138
Machine Learning and Big Data Analysis in the Catalysis Field
Abstract
Recently, there has been a rapid development of experimental methods in the field of catalytic research, an increase in the amount of data that is difficult to process and objectively interpret. These methods will allow you to obtain the necessary information from experimental data using statistical approaches such as PCA, MCR, ALS. The use of new statistical and computational data processing methods will accelerate the development and implementation of catalytic technologies. At the same time, machine learning algorithms are beginning to be actively used to interpret and build descriptive models. This article will discuss the main methods of machine learning and their successful application for the analysis of infrared and X-ray absorption spectroscopy data.
139-152
ARTICLES
Effect of CO2 Additives on the Non-Catalytic Conversion of Natural Gas into Syngas and Hydrogen
Abstract
Abstract—
A kinetic analysis of the non-catalytic carbon dioxide reforming of CH4 has been carried out in the temperature range of 1500–1800 K under conditions of variable temperature behind the reflected shock wave. The stages of conversion of methane into synthesis gas, the characteristic time intervals corresponding to these stages, and the most important elementary reactions have been established. At the first stage, as a result of thermal pyrolysis, methane molecules are sequentially converted into ethane, ethylene, and then acetylene, the most stable hydrocarbon in this temperature range. At the second stage, acetylene is normally converted into CO and H2, being accompanied by the formation soot particles in the case of rich mixtures. The conversion of CO2 proceeds at the second and third stages, when CH4 conversion is almost complete. It occurs as a result of the interaction of CO2 molecules with H● atoms arising in the reacting system and leads to the formation of CO molecules and OH● radicals. Acetylene is predominantly consumed in the reaction with OH radicals. A high concentration of acetylene during methane reforming promotes the intensive formation of soot nuclei, for which acetylene makes the highest contribution to the rate of their surface growth. At the same time, acetylene itself is not a precursor of soot particle nuclei, which are mainly formed from \({{{\text{C}}}_{{\text{3}}}}{\text{H}}_{3}^{\centerdot }\) radicals.
153-172
Kinetics of the Tetrahydrofuran Oxidation Initiated by 2,2'-Azo-bis-Isobutyronitrile
Abstract
The kinetic of the tetrahydrofuran oxidation initiated by 2,2'-azo-bis-isobutyronitrile in the temperature range 303–323 K are studied. The process rate was been monitored by oxygen absorption. It has shown that the tetrahydrofuran oxidation rate depends linearly on his concentration and proportional to the square root of the initiator concentration. The oxidizability parameter of tetrahydrofuran and the initiation rate constant by 2,2'-azo-bis-isobutyronitrile of the tetrahydrofuran oxidation are found: lg(k2(2k6)–0.5) = 4.3 – 44.1/θ [L0.5 mol–0.5 s–0.5], lg ki = 13.9 − 120.4/θ [s–1], where θ = 2.303 × 10–3RT kJ/mol. The rate constant (k7) of the reaction of the tetrahydrofuran peroxyl radical with α-tocopherol at temperature of 303 K is (4.0 ± 1.1) × 105 L mol–1 s–1.
173-180
Kinetic Peculiarities of Nucleic Acid Elongation as a Multistage Cosequent Enzymatic Reaction
Abstract
The article investigates kinetics of nucleic acid elongation as a multistage consequent reaction curling up to cycle. There is represented a matematically precise proof of empiric formulae used to estimate elongation time depending on nucleotide chain length. There are given some estimations of characteristic elongation time for typical chain lengths, for example for new coronavirus (SARS-nCoV-2). There is also investigated stability of elongation kinetics and at typical chain lenghts is shown an existance of instable oscillating solution component in addition to main exponential component.
181-188
Research of Kinetic Features of Hydrodesulfurization, Hydrodenitrogenation, and Hydrogenation of Heavy Petroleum Compounds on Sulphide Ni6PMonW(12 – n)/Al2O3 Hydrotreating Catalysts
Abstract
Kinetic studies of hydrodesulfurization and hydrodenitrogenation reactions were carried out, as well as a comparison of the hydrogenating activity of the synthesized Ni6PMonW(12 – n)/Al2O3 catalysts and an industrial reference catalyst in the process of hydrotreating of heavy mixed oil feedstock. As it was shown, the HDS reaction is described by a pseudosecond order equation, while the HDN reaction is described by a pseudofirst order. The obtained hydrogenates meet the requirements for the quality of feedstock of catalytic cracking plants in terms of coking capacity, sulfur and nitrogen content.
189-202
Ammonia Decomposition Over Cobalt-Based Silica-Supported Fischer-Tropsch Synthesis Catalysts
Abstract
Decomposition of ammonia over silica-supported cobalt catalysts for Fischer–Tropsch synthesis has been studied at a pressure of 0.1 MPa, a gas hourly space velocity range of 1000–6000 h–1 and a temperature range of 400–650°C in a tubular fixed bed reactor in a flow-through mode. It was found that silica-supported cobalt catalysts for hydrocarbons synthesis via the Fischer–Tropsch protocol also exhibit high activity in ammonia decomposition. Both activity and hydrogen productivity decrease in the series: Co–Ru/SiO2 > > Co–Al2O3/SiO2 > Ru/SiO2 > Co–Al2O3/SiO2(35%)/ZSM-5(30%)/Al2O3(35%). The relatively low values of effective activation energies estimated for all catalysts indicate that the reaction can proceed with a high conversion at moderate temperatures.
203-215
Effect of the Hydride and Carbide Phases of Palladium Nanoparticles on the Vibration Frequencies of Adsorbed Surface Molecules
Abstract
Palladium-based materials, including nanoparticles, are widely used in the petrochemical, pharmaceutical, automotive, and other industries. The hydride, carbide, and oxide phases of palladium formed during the hydrogenation or oxidation reactions of hydrocarbons significantly affect the catalytic properties of the catalyst. Based on theoretical calculations performed by the density functional theory (DFT) method, the effect of Pd–Pd interatomic distances and the presence of carbon atoms occupying octahedral voids in the fcc lattice of palladium on the vibrational frequencies of adsorbed hydrocarbons represented by ethylidene is shown. Theoretical research is supported by experimental data of infrared (IR) diffuse reflectance spectroscopy (DRIFTS) collected in situ during the formation of carbide and hydride phases of palladium in commercial Pd/Al2O3 nanocatalysts under the influence of ethylene and hydrogen. The proposed approach can be used to develop new methods for IR spectra analysis leading to the quantitative diagnostics of structural changes in palladium during various catalytic reactions in the in situ mode.
216-226
Delopment of Composite Carbon–Silicate Materials, Their Research and Testing for the Preparation of Heterogeneous Biocatalysts for Low-Temperature Synthesis of Esters
Abstract
Composite carbon–silica materials (CCSM), differing in the content of carbon and silica components, were obtained using two silicon dioxide precursors (silica sol and silane) and multi-walled carbon nanotubes (MWNTs). At the initial stage of obtaining CCSM by method 1, impregnation of finely dispersed MWCNT powder with silica sol was used, method 2 was carried out using treatment of MWCNTs with tetraethoxysilane followed by hydrolysis and polycondensation. The content of silica (SiO2) in the composites varied from 3 to 60 wt %. After drying and appropriate heat treatment at 250–350°C, the composite materials were studied by various physicochemical methods: nitrogen porosimetry, electron microscopy, X-ray fluorescence analysis, and synchronous thermal analysis. Significant differences in parameters were found depending on the chemical composition of CСSM, including textural characteristics. Thus, with an increase in the SiO2 content, the specific surface area of composite materials increased (by a factor of 2), and maxima were observed on the distribution curves over pore diameters (at 20–40 nm).The composite carbon–silica materials were tested as adsorbent for the preparation of heterogeneous biocatalysts (BC) for the low-temperature synthesis of esters; the active component of these BC was lipase immobilized exclusively on the carbon surface of nanotubes. With a decrease in the content of MWCNTs in the composite materials, the enzymatic activity and operational stability of biocatalysts, measured in the reaction of esterification of heptanoic acid (C7) with butanol (C4), decreased monotonically, reaching a 2–8-fold drop in activity at the maximum content of SiO2 (58 wt %).
227-242
Study of Rh/Ce0.75Zr0.25O2 – δ/θ-Al2O3/FeCrAl Catalyst Regeneration after Diesel Fuel Autothermal Reforming
Abstract
A study of soot (coke) formation on the surface of a structured Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl catalyst during autothermal reforming of diesel fuel into synthesis gas was performed. The SEM studies revealed the formation of fibrous carbon particles of 5–50 µm in size on the catalyst surface. It was found that the process of coke formation occurs on the catalytic coating surface, causes no exfoliation and/or damage of the catalytic layer, and the carbon deposits are readily oxidized during catalyst regeneration by oxygen or water vapor. Intensive oxidation of soot with oxygen begins at a temperature of 450°C; a major part of carbon deposits is oxidized even before the reactor furnace reaches the operating temperature of diesel fuel autothermal reforming (750°C). Water vapor oxidizes carbon deposits as well, but less efficiently than oxygen. The catalyst regeneration with water vapor proceeds actively at a temperature of 750°C that proves the possibility of catalyst self-regeneration in the process of diesel fuel autothermal reforming, which is performed with water excess.
243-248