Catalysis in Industry最新文献

Products from the thermal conversion of heavy crude oil in the presence of Ni- and Co-containing catalysts formed in situ from a mixture of appropriate salts with ethanol have been studied. In the catalytic process, the light fraction yield increases from 51 to 63% and the coke yield decreases from 3 to 2 wt % compared with the respective parameters of thermal cracking. In the case of a mixed Ni+Co catalyst, the lowest yields of gas (5 wt %) and coke (0.1 wt %) are observed. The decrease in sulfur content in both the thermal cracking (by 17%) and catalytic cracking products (by 12–32 rel %) occurs primarily due to the removal of sulfur in the form of gaseous products. The structural group characteristics of average asphaltene molecules before and after heavy crude oil cracking have been studied. Using X-ray diffraction analysis, Ni_0.96S, Ni₉S₈, and Co₉S₈ phases have been identified in the solid cracking products.

Nanoscale oxides of copper and nickel, with diameter 17 and 25 nm respectively, have been synthesized via an easy sol-gel method using polyvinyl alcohol. The method involves the simple dispersion of metal ions (M²⁺ = Cu or Ni) into the PVA gel and subsequent calcination of the dried gel at 400°C for 3 h. The synthesized oxide materials are characterized by different physical tools like TGA, powder XRD, SEM, TEM and DRS UV-visible spectroscopic technique. The oxides are found to be very efficient catalysts in the epoxidation of styrene. CuO gives 87% styrene conversion and 88% SO selectivity while, NiO gives 69% styrene conversion and 80% with TBHP as an oxidant at the end of 6 h. Both the catalysts can suitably be reused for several successive runs without appreciable loss in activity and selectivity. The cost–effective synthesis, excellent catalytic performance and reusability make these oxides promising catalysts for the industrial use.

The steam reforming and autothermal reforming of methyl oleate (model compound simulating biodiesel fuel) to synthesis gas in the presence of a structured Rh-containing catalyst have been studied. It has been shown that methyl oleate conversion occurs through a thermal cracking stage and the subsequent conversion of the resulting organic compounds with a shorter carbon skeleton. Based on test results, a mathematical model that takes into account the radial temperature gradient and represents an effective tool for the quantitative description and optimization of the biodiesel conversion process has been developed.

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.