Catalysis in Industry最新文献

A study on the efficiency of glass fiber catalysts (GFCs) in the oxidation of hydrogen in a carbon dioxide medium at elevated pressure is performed. Catalyst samples were synthesized from platinum, palladium (as active metals), and heat-resistant high-silica glass fibers, both unmodified and modified with Zr. Catalysts are prepared via surface thermal synthesis and leaching with impregnation. All three tested samples show approximately the same activity, but Pt-based STS is preferred because it uses a much cheaper and widely available glass fibers instead of rare and expensive Zr-modified materials. More than 200 h of life tests for this catalyst show its high stability. The rate of hydrogen oxidation on this catalyst can be described by a kinetic equation corresponding to the law of mass action with a linear dependence on the pressure in the reaction system. The studied GFC can be made in the form of structured cartridges with a small drop in pressure and high intensity of heat and mass transfer under the conditions of the industrial technological process, so its future practical application seems promising.

The possibility of obtaining sorbitol from potato starch via one-pot hydrolysis-hydrogenation is demonstrated using bifunctional catalysts 0.3–3 wt % Ru/Cs₃HSiW₁₂O₄₀ (Ru/Cs-HPA). It is found that a catalyst with 1 wt % Ru is the one most effective, since it has the optimum ratio of the concentrations of Brønsted and Lewis acid sites on the support’s surface and a large specific surface area. The kinetics of the reaction with 1% Ru/Cs-HPA is studied and the observed energy of activation of the hydrolysis-hydrogenation of starch to sorbitol is found to be 80 ± 8 kJ/mol. A kinetic model is proposed on the basis of experimental and published data. The model accurately describes the hydrolysis-hydrogenation of starch. The yield of sorbitol was 88 mol % (99 wt %) after 3 hours of the reaction using a catalyst with the optimum composition (1% Ru/Cs-HPA) at the optimum temperature (150°C).

The activity and selectivity of sulfidized and non- sulfidized palladium alumina supported catalysts in the hydrogenation of 1,3-pentadiene to pentenes is studied. Preliminary sulfidation of palladium catalysts substantially improves their selectivity toward olefins in a broad range of Н₂ : diene ratios (from 2.5 to 10). Samples activated in Н₂ at elevated temperatures display higher activity in diene hydrogenation. Palladium catalysts are more active at low temperatures of the reaction, but sulfidized Ni catalysts studied earlier are competitive with palladium ones in selectivity toward olefins and productivity, and are more selective in an excess of hydrogen. The modification of palladium with chromium, silver, or lithium improves the selectivity toward olefin.

The effect of the type of polysaccharide support for immobilization and encapsulation on the stability of chymotrypsin was studied. The synthesized biocatalysts were compared according to their proteolytic activity. The cellulose–chitosan composite was found to have the highest proteolytic activity equal to 192 units/g. Immobilization was found to slightly change the optimum temperature and pH of chymotrypsin, but they substantially grew toward higher temperatures and alkaline pH values. The greatest relative increase in the activity of immobilized chymotrypsin was observed when using the cellulose–chitosan composite. The activity of chymotrypsin changed by no more than 45–50% during storage of the cellulose–chitosan and cellulose–alginate composites for 24 months. According to the results of our study, the cellulose–chitosan composite was the optimum support for immobilization of chymotrypsin.

The in situ formation of a catalytic heterohomogeneous system containing Al–M alloy (M is Ni, Co, Cu) and Al(M)/Cl complex in a benzene–ethylene medium at a temperature of 80°C and a pressure of 0.2–0.3 MPa is studied. The characteristic patterns of interaction between Al–M alloys activated with a liquid metal Ga–In eutectic and a chlorinating agent (CCl₄) with the formation of catalytically active metal–aluminum chloride Al(M)/Cl complexes are established. Results from spectrokinetic measurements show the order of the reactivity of activated alloys with respect to excess CCl₄ is Al–Cu ≈ Al–Ni > Al > Al–Co. The highest catalytic activity is displayed by nickel–aluminum chloride complexes whose selectivity toward ethylbenzene is 48%. Data from IR and UV-VIS spectroscopy show that the structure and composition of metal chloride complexes formed in situ in the aromatic reaction medium is determined by a combination of coupled ionic pairs ([{text{AlC}}{{{text{l}}}_{4}}]_{{{text{tetr}}}}^{ - }{text{/[NiC}}{{{text{l}}}_{{text{6}}}}]_{{{text{oct}}}}^{{4-}}) and (left[ {{text{AlC}}{{{text{l}}}_{{text{4}}}}} right]_{{{text{tetr}}}}^{ - }/left[ {{text{CuC}}{{{text{l}}}_{{text{2}}}}} right]_{{{text{lin}}}}^{ - }), which are stabilized by (C₆H₅)₃C⁺ carbocation.

The reactivity of adsorbed acetic acid forms on the Pt–ReO_x/TiO₂ catalyst has been studied. Three adsorbed acetic acid forms were identified by in situ Fourier IR spectroscopy at 200°С: bidentate acetates and two forms of molecularly adsorbed acetic acid. The consumption rate constants two forms of molecularly adsorbed acetic acid (0.02 and 0.029 s^–1, respectively) were found to be close in magnitude to the catalytic reaction constant rate (0.034 s^–1) measured at 200°С. It was concluded that these two forms of molecularly adsorbed acetic acid are key intermediates in acetic acid hydrogenation on the Pt–ReO_x/TiO₂ catalyst.

The processes for the production of basic monomers at Nizhnekamskneftekhim via dehydrogenation are described. The cooperative development of modern domestic catalysts with the Kazan Federal University is emphasized. The disadvantages of existing catalytic systems are considered, and the possivle ways of their elimination are presented.

The technical feasibility of the direct monetization of associated petroleum gas currently burned is considered. The proposed approach is based on the low-temperature steam reforming of hydrocarbons, with which flare gases can be brought to meet the requirements for fuel used in gas piston and turbine power plants. The preparation and catalytic properties of new rhodium-based catalysts for low-temperature steam reforming of flare gas are discussed. Mixed cerium zirconium oxides are the most promising catalyst supports. Such catalysts have a number of advantages over the known nickel catalysts in the low-temperature steam reforming of hydrocarbons.

A study of original iron–potassium catalysts of ethylbenzene (EB) dehydrogenation to styrene and industrially used catalysts: Cat-1 (imported), Cat-2 and Cat-3 (domestic) is performed. Initial samples are multiphase systems consisting of potassium ferrites, hematite, and cerianite (CeO₂). The phase composition of the catalysts after two years of operation consists mainly of magnetite and cerianite, while the amount of potassium (K⁺) in Cat-1, Cat-2, and Cat-3 samples falls by 40, 20, and 26%, respectively. At the same time, K⁺ for the Cat-2 sample is distributed uniformly in granules of the waste catalyst. XRD data indicate the CSR size of its CeO₂ crystals does not change appreciably. The CSR size of CeO₂ crystals in the Cat-3 sample falls from 302 to 110 Å, while it grows from 284 to 419 Å in the Cat-1 sample. After two years of operation, the greatest conversion of EB (72.1%) was observed for the Cat-2 sample, and it fell from 72.3 to 57.4% on the Cat-3 sample. There is a 600–1100% drop in the waste samples’ resistance to crushing, making them unsuitable for further use.

Results of studying the sorption-enhanced water gas shift reaction over a mechanical mixture of grains of 5 wt % Pt/Ce_0.75Zr_0.25O₂ catalyst and 10 wt % NaNO₃/MgO sorbent are presented. It is shown that pure magnesium oxide sorbs virtually no СО₂ under model conditions, while its promotion with NaNO₃ substantially improves the dynamic sorption capacity in the 300–350°C range of temperatures with a maximum at 320°C. The catalyst shows high activity and selectivity in the water gas shift reaction for a model mixture (CO, 11.6; H₂, 61; H₂O, 27.4 vol %). The concentration of CO at the outlet from the reactor is less than 1 vol % in the 220–400°C range of temperatures (the minimum is 0.3 vol % at 240°C) with СН₄ at the temperatures below 320°C (0.61 vol % at this point). Using this sorbent in mixtures with a catalyst in the sorption-enhanced water gas shift reaction at 320°C substantially reduces its sorption capacity, due probably to the full conversion of NaNO₃ into Na₂CO₃ that is not completely decomposed at the stage of regeneration. This nevertheless allows the outlet СО and СН₄ concentrations to be halved, relative to values observed at this temperature in experiments with no sorbent: 6.1 × 10⁻⁴ and 8.2 × 10⁻² vol % per dry gas basis at the middle of the first adsorption cycle. Prospects for using this approach in the sorption-enhanced water gas shift reaction and the need for further studies on improving the capacity and stability of the presented sorbents are described.