Catalysis in Industry最新文献

The main patterns of oxidative chlorination (oxychlorination) with such unsaturated hydrocarbons as propylene, acetylene, 1,3-butadiene, and benzene are considered. It is shown that when the processes are conducted in the gas phase, having heterogeneous copper or palladium based catalysts in the system is preferable. It is shown that palladium in a catalyst promotes processes of substitutive oxychlorination. Stagewise schemes of reactions are given for processes of propylene, acetylene, and benzene oxychlorination along with corresponding kinetic equations. Applied aspects of the above processes are discussed.

The author considers the main patterns characteristic of the processes of hydrogen chloride oxidation (the Deacon reaction) and oxidative methane and ethane chlorination. It is shown that the most widely recognized and best studied catalysts of these processes are copper chloride systems that are based on different supports and contain alkali and rare-earth metal chlorides, which reduce the entrainment of an active phase from the surface of a catalyst with a simultaneous increase in its activity. The prospects for using ruthenium catalysts are also noted. The main kinetic and technological patterns of oxychlorination are considered. Conditions are described that allow the yield of target products (lower methane chlorides) to be increased in the oxychlorination of methane and vinyl chloride during the oxychlorination of ethane. Variants of reactor units for oxychlorination are proposed.

The effect of Na⁺, ({text{NO}}_{2}^{ - }), and ({text{NO}}_{3}^{ - }) ion concentration on the photocatalytic oxidation rates of model organic dyes, namely, cationic dye methylene blue (MB) and anionic dye methyl orange (MO), is studied. Based on studies of the hydrochemical characteristics of polluted rivers in urban areas (Khabarovsk, Russia) in the period from 1999 to 2019, it is shown that the ion concentration varies in a range of 0.005–0.7, 0.05–15, and 13–180 mg/L for ({text{NO}}_{2}^{ - }), ({text{NO}}_{3}^{ - }), and Na⁺, respectively. The kinetics of photooxidation of MB and MO is studied by optical spectrophotometry in a concentration ranges of the studied ions of 0–1–10–100–1000–10 000 mg/L using P25 titania as a photocatalyst. Photooxidation time (t) at different conversions (α) of the dyes at the initial (^10%t), middle (^50%t), and final stages (^90%t) of the photocatalytic process is assessed. The effect of absorption of light quanta at wavelengths of 200–350 nm by Na⁺/({text{NO}}_{2}^{ - }) and Na⁺/({text{NO}}_{3}^{ - }) ions as a function of the concentration of these ions in a photocatalytic solution is shown. Recommendations for practical applications of the photocatalytic treatment of real contaminated water are given, while showing the necessity to take into account the concentration of the studied ions. A description of the observed effect of ions on the rate of photocatalytic oxidation of model organic dyes in terms of the band structure of semiconductors, elements of the theory of electrolytic dissociation, and recombination of free radicals in photocatalytic processes is proposed.

Published data on salicylic acid synthesis methods based on the use of phenol, ortho-cresol, and benzoic acid are reviewed and analyzed. Current trends in the development of a technology based on the Kolbe–Schmitt process (production of aromatic and heteroaromatic hydroxy acids by treating alkali metal phenolates with CO₂) are shown. Data on the effect of the catalyst system composition and benzoic acid hydroxylation process conditions on the achieved conversion and selectivity values and purity of the product are described. The review can be useful for choosing a suitable raw material base and a precursor conversion method for the development of domestic production of salicylic acid, which is a high-demand compound used in various industries.

The efficiency of trapping of solid microparticles contained in diesel fuel by a package loading of catalysts, which is a counterpart of an industrial package of guard bed hydroprocessing catalysts, is studied. The package of catalysts consists of catalyst pellets graded with respect to shape and size: segmented rings, hollow cylinders of two standard sizes, and pellets with a trilobe-shaped cross section. The tests are conducted in a trickle flow mode using a constant ensemble of microparticles—iron scale with a size of 5–150 µm—at the inlet of the package loading. It is found that the penetration coefficient of the package loading of guard bed catalysts does not change significantly (K ≈ 0.985) during the test. At the same time, the pressure drop across the 17-cm-high guard bed catalyst package linearly increases from 220 to 408 Pa due to the trapping of solid microparticles by the catalyst pellets. The theoretical estimate of the initial pressure drop (228 Pa) agrees with the test data (220 Pa) with fairly high accuracy.

Features of the catalytic action of Pd–Ag, Pd–Cu, Pd–Au, Pd–Ga, and Pd–Zn bimetallic systems on the acetylene conversion to ethylene are discussed taking into account two factors that determine the effect of the second metal on palladium, namely, the “ensemble effect” (geometric effect) and the “ligand effect” (electronic effect). The relationship between the calculated thermodynamic and kinetic parameters of the adsorption interaction of major reaction medium components and intermediates with the catalyst surface, the structure of active ensembles, and characteristics determined in tests, such as the structural parameters of bimetallic phases, the electronic state of their components, and catalytic properties, is shown. Some examples are given to show that the modifier atoms can be incorporated into active ensembles and the sites formed by the modifier atoms can be involved in the catalysis of individual elementary steps.

The authors reveal aspects of the formation of platinum nanoparticles and chemical coating of carbon support surfaces when preparing model (0.5%Pt/Sibunite) and industrial (0.5%Pt/Graphite) catalysts for synthesizing hydroxylamine sulfate via the hydrogenation of NO in a solution of H₂SO₄. It is shown that functionalizing the surfaces of supports with nitrogen-containing groups while depositing platinum ensures not only the dispersion of metal but a strong increase in its selectivity toward hydroxylamine sulfate. It is assumed that maximum selectivity is characteristic of active sites being single atoms or small platinum clusters bound to the nitrogen-containing ligands of a carbon surface.

The results of testing the technology of preparing a bifunctional cobalt catalyst used to synthesize hydrocarbons from CO and H₂, obtained by extruding a mixture of Co-Al₂O₃/SiO₂ catalyst and HZSM-5 zeolite powders with a binder (boehmite) under industrial conditions (two batches of 50 kg each) are presented. The catalyst technology is tested on equipment at the Ishimbay Specialized Chemical Catalyst Plant (Russia). The resulting samples of industrial catalyst are studied via XRF, H₂-TPR, and DTG, and tested in the synthesis of hydrocarbons from CO and H₂ at 250°C, a pressure of 2.0 MPa, and a gas hourly space velocity of 1000 h⁻¹. It is shown that the bifunctional cobalt catalyst for producing low pour-point diesel fuel under industrial conditions allows properties of the catalyst obtained under laboratory conditions to be reproduced. The technology for obtaining the catalyst can be recommended for the production of industrial batches. It is found that changing the conditions of the catalyst’s heat treatment and the presence/absence of a peptizer and pore former do not appreciably reduce the productivity of C₅₊ hydrocarbons. The amount of the diesel fraction in C₅₊ products obtained on industrial catalyst samples remains at the same level as on the laboratory catalyst sample. At the same time, the low-temperature properties of diesel fuel obtained on all catalyst samples have similar values. The best low-temperature properties of diesel fuel are obtained on an industrial sample synthesized without a peptizer and a pore-forming component. The cloud point and the point of liquid loss are −16 and −24, respectively.

The review discusses the latest advances in the study of heterogeneous metal-containing catalysts for the production of an environmentally friendly energy carrier—hydrogen—by the dehydrogenation of formic acid (FA), which is an available and low-toxic substance. Although the activity of homogeneous catalysts in the FA dehydrogenation reaction is higher than that of heterogeneous catalysts, the use of the latter makes it possible to simplify the technology and improve the environmental safety of hydrogen production from FA. An increase in the efficiency of heterogeneous FA dehydrogenation catalysts based on noble metals (Pd, Au, Ag) is achieved by developing novel methods for synthesizing monometallic, bimetallic, and trimetallic nanoparticles on various supports. The review compares the efficiency of various heterogeneous nanocatalysts in the FA dehydrogenation reaction and discusses various factors (metal nature, nanoperticle size and composition, support nature) that affect the activity and hydrogen selectivity of the catalysts. A significant increase in activity in the FA dehydrogenation reaction is achieved by intensifying the interaction of metal nanoparticles with the surface of a chemically modified support, which contributes to a decrease in the size of nanoparticles, an increase in the uniformity of their distribution on the support, and a change in the electronic state of the metal. Advances in the development of industrial heterogeneous catalysts for the production of pure hydrogen from FA will provide a significant contribution to the development of hydrogen power engineering.

The authors study the effect of the content of zeolite ZSM-22 (15–70 wt %) in a support on the physicochemical properties of Pt/ZSM-22–Al₂O₃ catalysts. The dependence of the yield and composition of sunflower oil hydrodeoxygenation products on these catalysts on the temperature (310–340°C), pressure (3‒5 MPa), and weight hourly space velocity (WHSV) (0.8–3 h⁻¹) is determined. The possibility is shown of the full hydrodeoxygenation of sunflower oil with the formation of C₅₊ hydrocarbons containing up to 72% of iso-paraffins with yields of 75–79 wt %.