Catalysis in Industry最新文献

The influence of the diesel fuel hydrotreating temperature on the regularities of silicon sorption on grains of a NiMo/Al₂O₃ guard bed catalyst with a diameter of 2.5 mm was studied. The tests were carried out on a laboratory stand with a reactor in which the catalyst layer was divided (sectioned) into five parts along the height by metal perforated partitions that are permeable to the feedstock. This made it possible to obtain silicon concentration profiles along the height of the catalyst layer. Decamethylcyclopentasiloxane was used as silicon compound in the diesel fraction, the content of which was 200 ppm. Three series of experiments were conducted for 200 h at temperatures of 315, 340, and 365°C. The feedstock was straight-run diesel fraction containing decamethylcyclopentasiloxane additive as an additional source of silicon. It has been established that with an increase in the process temperature, the ability of the catalyst to absorb silicon increases.

Ni_xCo_{1 – x}Al₂O₄ (x = 0−0.5) catalysts were prepared by coprecipitation of Ni, Co, and Al nitrate salt solutions. Heat treatment of the resulting xerogel at 700°C in air resulted in aluminum oxide with a spinel structure, in which nickel and cobalt ions were stabilized. Studying in situ reduction of these precursors in a hydrogen-containing gas mixture at 700°C by X-ray diffraction analysis and ex situ after preliminary reduction in a hydrogen-containing gas mixture and further operation under reaction conditions showed that 3–4 mm ensembles of Ni–Co alloy particles are formed on the surface of the spinel. The influence of catalyst composition and duration of their testing on catalytic properties in the reaction of dry methane reforming (DMR) was investigated. The Ni_0.35Co_0.65Al₂O₄ catalyst showed stable performance in the DMR reaction for 20 h with a CH₄ conversion of 76% and a H₂ yield of 42% (T = 700°C, τ = 30 ms). The high catalytic activity of the obtained catalysts in DMR is due to the formation of highly dispersed alloy Ni–Co nanoparticles of the active phase in an amount of 17–18 wt % on an initially large specific surface area of spinel, which is by nickel and cobalt ions and has mobile bulk oxygen in a reduced state.

Recently, due to the depletion of hydrocarbon fuel reserves against the background of high rates of decline in their reserves, considerable attention has been paid to the development of effective methods for synthesizing biofuels and biodiesel fuels, including from renewable sources of raw materials. However, a high cost price of biodiesel production requires the development of new technological approaches. Therefore, the direction of using microchannel (microfluidic) technologies for the synthesis of biodiesel fuel has begun to actively develop in chemistry and chemical technology. The use of microchannel (MC) reactors facilitates the intensification and safety of chemical processes, resulting in economic and environmental benefits for the chemical industry. The miniature dimensions of MC reactors allow for savings in materials during their manufacture, as well as resources during operation. Increased heat and mass transfer values in MC reactors contribute to a significant increase in the productivity of installations, exceeding the productivity of classical reactors in industry by 1–2 orders of magnitude. This review analyzes literature data for 2020–2024 devoted to the application of microchannel technologies for the synthesis of biodiesel fuel. Particular attention is paid to the advantages and disadvantages of MC reactors, as well as the main trends in their development.

The kinetics of the formation of methane condensation products in the absence of oxygen at 600°C was studied on 1% Pt/γ-Al₂O₃ and 1% Pt/MgAlO_x samples with similar platinum cluster sizes. In contrast to the reference sample 1% Pt/γ-Al₂O₃, removal of strongly adsorbed carbon-containing compounds accumulated during the reaction by oxidation at the same temperature completely restored the catalytic characteristics of 1% Pt/MgAlO_x systems. The possibility of increasing the operation time of such catalysts in a cyclic mode with maximum productivity in terms of C₂–C₃-hydrocarbons and minimal formation of CO and CO₂ at the regeneration stage was demonstrated.

The structure of 10%Ni/LaCeY(n)O_x catalysts containing different amounts of yttrium (0.5–10 mol %) and their catalytic activity in dry methane reforming (DMR) have been studied. The phase composition of the support and catalyst samples has been characterized using a set of physicochemical methods; the effect of yttrium introduction method on the formation of the active surface of the catalysts has been studied. Varying the yttrium content in the support, it has been found that 1 mol % is the optimum amount of the introduced additive to provide minimum changes in the initial conversions of the reactants (methane and CO₂) and the H₂/CO ratio at 650°C for 6 h as compared to the respective parameters of the unmodified catalyst. An increase in the modifier content to 10 mol % leads to an increase in the deactivation rate due to more vigorous carbon deposition and the formation of encapsulating carbon species (amorphous carbon and onion-like carbon). The Ni/LaCeY(1)O_x sample exhibiting the highest stability under DMR conditions is characterized by the dominant content of multiwalled carbon nanotubes with uncapped end Ni nanoparticles.

An approach to conditioning associated petroleum or natural gas has been described. The method is based on the catalytic pyrolysis of C₁–C₄ light hydrocarbons in the presence of multicomponent alloy particles. In this process, the C₂–C₄ hydrocarbon fraction undergoes pyrolysis to form hydrogen and carbon nanofibers (CNFs) that accumulate on the catalyst. The highest activity in the decomposition of a C₂–C₄ mixture is exhibited by an equiatomic [CoFeNi] alloy promoted with 7 at % of copper ([CoFeNi]Cu₇). The maximum CNF yield at 650°C is 106 g/g_cat within 30 min. It has been shown that this alloy can be effectively used for the catalytic decomposition of the C₂–C₄ fraction mixed with methane. The dependence of the CNF yield on the C₂–C₄ fraction concentration in the model mixture has been determined. It has been found that during the pyrolysis of a mixture with a volume ratio of C₂–C₄/СH₄ = 10/90, the catalyst does not undergo any significant deactivation within 30–180 min. The CNF yield after 180 min of reaction is 160 g/g_cat. The average conversion of the C₂–C₄ fraction per pass is 20%. The morphology and structure of the synthesized CNFs have been studied by scanning and transmission electron microscopy and low-temperature nitrogen adsorption methods.

The formation of a Winsor III microemulsion is detected for the first time in a system of concentrated H₂SO₄ + C₄–C₆ alkanes with added quaternary ammonium salt dimethyldioctadecylammonium chloride (C₁₈H₃₇)₂N⁺(CH₃)₂Cl^– acting as a surfactant. The effect this microemulsion has on parameters of the sulfuric acid alkylation of isobutane (iB) with 1-butene (1b) and 1-pentene (1p) is studied. Adding only 0.03 wt % of surfactant relative to H₂SO₄ sharply alters many parameters of the process, relative to using pure H₂SO₄. The conversion of isobutane rises by 1.5–2 times. The yield of C8 products produced by the olefin can double, with the research octane number reaching 100 points. NMR shows that relative to unmodified acid, the number of resulting acid-soluble oils (ASOs) falls by 15–20 times after using the microemulsion in the alkylation of isobutane with 1-butene.

The possibility of hydroprocessing the plastic waste pyrolysis product to produce valuable hydrocarbons was investigated. Catalytic tests were conducted in a flow mode at T = 310°C, P_H2 = 80 bar, and LHSV = 1 h^–1 over a fixed bed of a macro–mesoporous CoMoNi/Al₂O₃ catalyst using a pyrolysis oil fraction (polyethylene–polypropylene mixture) with T_boil < 360°C as the feedstock. The hydroprocessing led to the formation of a product exhibiting the properties of kerosene, except for boiling point and cloud point. It was found that acidic additives (zeolite or zeolite-like materials) should be introduced into the catalyst for the implementation of isomerization and cracking processes.

This paper reports the results of ethylene trimerization to hexene-1 on a chromium–pyrrole catalytic system in semiperiodic and continuous regimes under varied reaction conditions. The effect of the catalyst concentration, temperature, and ethylene pressure on the kinetic profile of reaction rate–time curves is demonstrated. A generalized scheme is proposed for the process of ethylene trimerization to hexene-1. At the same time, it is shown that the kinetic data on the formation of reaction products are insufficient for the trimerization process to be completely described within the framework of a universal kinetic model due to a multistage character of this process, the experimental establishment of dependence for each stage (formation of catalytic intermediates, initiation, the occurrence of side reactions with participation of catalytic system components, tri-, oligo-, and polymerization reactions) and, thereby, due to variability in the catalytic behavior of the system.

Experiments on the decomposition of formic acid on carbon nanofibers (CNF) to obtain pure hydrogen were conducted. It has been shown that carbon nanofibers are capable of decomposing formic acid primarily with the formation of hydrogen and carbon dioxide. Alkaline treatment of CNF results in a sharp increase in the catalytic activity in the decomposition of formic acid. Treatment of CNF with alkali slightly increases the selectivity of the formic acid decomposition reaction to hydrogen and CO₂. It was found that alkaline treatment leads to modification of the CNF surface with sodium ions, which are uniformly distributed over the carbon surface; in addition, sodium carbonate nanoparticles and sodium ions intercalated into the CNF structure are present. It was shown that the activity of the 0.2%Pt/CNF catalyst slightly exceeds the activity and selectivity of the 6% NaOH/CNF catalyst.