Catalysis and petrochemistry

Oxidative dehydrogenation of propane with the participation of mild oxidants (N2O and СО2) on metal(oxide)-zeolite catalysts

2024-12-19T10:36:26+00:00

The paper presents the results of the study of textural and acidic characteristics of metal (oxide)-zeolite compositions M-BEA (MTW, MOR, ZSM-5) (М = Ga, Fe, Co, In) and their influence on catalytic properties in the oxidative dehydrogenation of propane to propylene with the participation of CO₂and N₂O/ODP-СО₂ (N₂O). The ODP-N₂O process was investigated on indium-, cobalt-, and iron-oxide compositions based on zeolites of structural types BEA, MOR, and ZSM-5 (H-form). The best indices of propylene production were achieved on the sample 10 %Fe₂O₃/HZSM-5 at the temperature 400 °С: the selectivity of formation and yield of propylene are S_С3Н6 = 40 % and Y_С3Н6 = 21 % at the conversion of С₃Н₈ – 53 % and N₂O – 85 %. In the ODP-СО₂ process, among the samples of gallium-containing zeolites of the MTW, BEA, and MOR structure (for the Si/Ga ratio = 15-24), higher indices of selectivity are 70 % and propylene yield – 26 % (at X_C₃_H₈ = 37.5 %, 600 °С), were achieved on the Ga_5.0MTW catalyst (Si/Ga = 24), which is characterized by a developed mesoporous structure, the largest surface (S_BET = 585 m²/g) and the highest concentration of weak, medium and strong acid Lewis sites (according to the FTIR-Py data).

Vapour-phase condensation of methyl glycolate into glycolide over oxide catalysts at lowered pressure

2024-12-19T10:36:27+00:00

Glycolide is now considered as a promising monomer for production of biodegradable polyglycolate. Due to its high gas impermeability, mechanical strength and thermal stability, this polymer can be used in oil and gas industry, in medicine as biocompatible implants and surgical suture material, and as an ecological packaging material. Traditionally, glycolide is produced from glycolic acid. First, it is polycondensed into a low-molecular-weight oligomer, which is then depolymerized into a monomer. In this work, the vapor-phase conversion of methyl glycolate over several supported oxides without the use of an inert carrier gas under lowered pressure was studied. Condensation occurs according to the reaction 2С₃H₆O₃ → C₄H₄O₄ + 2CH₃OH. First, methyl glycolyl glycolate is formed from two molecules of methyl glycolate, which is further condensed into glycolide. The reaction was carried out at 250-300 °C, a pressure of 25-150 mbar and loads on a catalyst of 7-25 mmol MG/g_cat/h at a contact time of less than 1 sec. It was shown that more effective is supported TiO₂/SiO₂ catalyst, which provides 44 % methyl glycolate conversion with a selectivity towards glycolide of 64 % at 270 °C/25 mbar. Glycolide productivity of this catalyst achives to 4.9 mmol/g_cat/h. The main by-products are methanol, methyl glycolyl glycolate, methyl methoxyacetate and methoxymethanol.

Activation of the industrial copper-zinc-aluminum catalyst for the production of methanol

2024-12-19T10:36:28+00:00

It was first established the influence of mechanochemical activation of copper-zinc-alumina oxide catalyst on the structure and morphology of its surface, mechanism, and principles of carbon oxides hydrogenation reaction within a wide temperature range at atmospheric pressure. Catalytic investigations were carried out in the laboratory unit with a gradient-free catalytic vibroreactor. It was revealed that mechanochemical treatment of copper-zinc-aluminum oxide catalyst before catalysis can reduce reaction initiation temperature and optimum temperature synthesis by 20-30 °C. At the same time, pre-machining of the catalyst provides increase its productivity by 50 % in comparison with the granulated catalyst. It was established that only effective additive of the powdered catalyst can be subjected to in situ mechanochemical activated. Investigation of the in situ catalyst’s activity depending on the frequency of physical percussion showed that an optimal vibration of reactor corresponded to the frequency 5 Hz. At this frequency, the catalyst productivity per mass unit of the effective catalyst addition introduced into the reactor was 47 mmol СН₃ОН/(g_cat·h) at temperature 220 °C and under the pressure 0.1 MPa. This two and a half times more than the value obtained at the industrial conditions at 240 °C and 9.0 MPa (January – May 2001, “Alvigo” company, Severodonetsk city, Ukraine). Total catalyst’s productivity under the frequency of vibration reactor 5 Hz is 4.5 mg СН₃ОН/(g_cаt·h). This is 2-3 times greater than the corresponding data for the granulated catalyst in a static mode. The increase of the catalyst activity under mechanical stress is explored by the increase of concentration defects of a crystal lattice of the catalyst. A new effective method for synthesis gas conversion into the methanol under conditions of mechanochemical activation of the catalyst can be used in industry as an alternative to methanol production at high pressures.

Catalytic Oxidation of Aromatic Aldehydes on Se-Modified Microgels

2024-12-19T10:36:28+00:00

The aim of this work is to investigate the catalytic activity of Se-modified microgels in the heterogeneous oxidation of aromatic aldehydes. The study tested heterogeneous systems with organic solvent-to-water volume ratios of 1 : 4, 1 : 1, and 4 : 1. The dependence of benzoic acid yield on reaction temperature was examined across a range from 20 °C to 60 °C. It was established that the synthesized selenium-modified microgel catalysts with a 3D polymer structure enable a benzoic acid yield of 87.0 % (with selectivity of 89.4 %) in the heterogeneous oxidation of benzaldehyde with hydrogen peroxide, at a benzene-to-water ratio of 1 : 1 and a reaction temperature of 50 °C. The catalytic oxidation processes of several aromatic aldehydes – benzaldehyde, cinnamaldehyde, anisaldehyde, and veratraldehyde – were studied in a biphasic organic solvent/water system. The oxidation of aromatic aldehydes resulted in valuable products for the pharmaceutical and cosmetic industries, including aromatic acids, mequinol, hydrocoumarin, and 3,4-dimethoxyphenol. The synthesized Se-containing microgel catalysts enable mild process conditions, high yields, and high selectivity, which enhance process efficiency, reduce environmental impact, and improve the quality of the final product.

Nonmetal doped TiO2 nanostructures: preparation, chemical states of dopants, properties

2024-12-19T10:36:29+00:00

In this work, hydrofluoric acid and ammonium hydrofluoride were used as fluorine precursors, and thiourea and sulfuric acid - as sulfur precursors, and the phase composition, morphology, texture, and electronic structure of non-metals doped TiO₂ nanostructures compared, the chemical state of dopants in the obtained materials was examined, and the influence of the specified factors on photocatalytic activity in the processes of photodegradation of complex organic compounds, for example on antibiotic of the tetracycline series – doxycycline, was stadied. It is shown that hydrofluoric acid and thiourea lead to the formation of anatase, while at low ratios of ammonium hydrofluoride to titanium butoxide, anatase heterostructures with brukite are formed, and at high ratios of sulfuric acid to titanium butoxide, the formation of the crystalline phase of titanyl sulfate is observed. It was determined that hydrofluoric acid causes the formation Sheet-like morphology, and the presence of sulfuric acid in the sol-gel reaction mixture leads to the formation of spheroidal particles, which at small ratios of sulfuric acid to titanium butoxide form loosely agglomerated particles of spheroidal morphology, which are formed from anatase crystallites. The photocatalytic activity of codoped TiO₂ nanostructures in the doxycycline photodegradation process under UV and visible light irradiation was investigated and it was established that under UV light irradiation the activity mainly depends on the phase composition and crystallite sizes, while under visible light irradiation the activity depends from the interstitual dopants content that increase the materials sensitivity to visible light. It was established that nitrogen, carbon and fluorine co-doped TiO₂ nanostructures obtained in the presence of ammonium hydrofluoride are characterized by the presence of surface Ti-F groups and interstitual carbon and surface carbonate, while carbon and sulfur co-doped TiO₂ nanostructures obtained in the presence of thiourea after hydrothermal treatment contain Ti-SH groups, which are oxidized as a result of calcination at 450 °C are oxidized with the formation of interstitual sulfur (S⁶⁺) and surface sulfate.

Regularities of epoxidized alkyl oleates ring-opening reactions with alcohols, water and organic acids in the presence of commercial sulfonated resins as catalysts

2024-12-19T10:36:30+00:00

Current paper deals with the use of sulfonated resins, distinguished by the porous structure (macroreticular Purolite CT275 and gel-type CU-2-8ChS), as solid acid catalysts for syntheses of perspective components of biolubricants via oxirane ring-opening reactions of fatty epoxides with water (hydrolysis), ethanol and i-propanol (alkoxylation), and levulinic and oleic acids (acylation). Epoxidized ethyl and i-propyl oleates as ring opening substrates were synthesized from used cooking oil. Reactions were carried out in batch reactor for 3 h at 100 °C under stirring with epoxide: resin acid sides molar ratio 1 : 0.05. Reagent to epoxide ratio was 10 : 1 (alkoxylation, hydrolysis) or 1.5 : 1 (acylation). Products composition was determined by GC, conversion and selectivity were calculated. Number of side ring-opening reaction were revealed, main of which were isomerization to ketone and dimerization. General observation is that porous Purolite CT275 provides higher conversion, but facilitates side processes. Non-porous CU-2-8-CHs provided notably higher selectivity (up to 90 % for hydroxyl esters in ethoxylation), but with many-times slower conversion, especially in case of alkoxylation with secondary alcohol. In hydrolysis, water soaked cationites did not provide any conversion, while epoxide introduction first on catalyst made transformation possible. Acylation proceeded in a great extent without separate catalyst and was accompanied by dimerization, while isomerization was not observed. Gel-type resin provided only negligible growth of conversion and selectivity. Porous resin enhanced the conversion, but mainly by side reactions intensification. Cyclohexane as solvent facilitated slightly selective catalyst-free acylation, but with significant conversion drop. Purolite CT275 in ethyl levulinate media favored the ring opening of epoxide with ketone function, yielding ketal-type product.

Hydrogenolysis of disaccharides into propylene glycol on copper-containing oxides

2024-12-19T10:36:30+00:00

The hydrogenolysis of 10 % methanol-water solutions of sucrose and maltose to propylene glycol on supported copper-containing catalysts in flow reactor was studied. The highest concentration of propylene glycol in the reaction products (0.23 mmol/ml) has been obtained in the hydrogenolysis of sucrose on 23Cu-1Cr₂O₃/Al₂O₃ catalyst with its full conversion at 170 °C/4.0 MPa H₂ and a load on catalyst of 0.8 mmol С₁₂Н₂₂О₁₁/g_cat/h. At that, the catalyst productivity towards propylene glycol consists 0.7 mmol/g_c_at/h. Hydrogenolysis of maltose in these conditions is characterized by 81 % conversion and low (0.04 mmol/ml) concentration of propylene glycol in the reaction products. The main byproducts of sucrose hydrogenolysis are ethylene glycol, hydroxyacetone, 1,2-butanediol, 1,4-butanediol and sorbitol. Concentration of propylene glycol in the reaction products of sucrose hydrogenolysis on 23Cu-1Cr₂O₃/Al₂O₃ does not change significantly (0.23-0.18 mmol/ml) during 18 h of catalyst operation. Сomparison of the productivities of 23Cu-1Cr₂O₃/Al₂O₃ catalyst to propylene glycol in hydrogenolysis of 10 % solutions of sucrose (0.7 mmol/g_c_at/h) and glucose (0.9 mmol/g_cat/h) suggests that glucose is more suitable for the production of propylene glycol than studied disaccharides.

Synthesis of imidazoline derivatives – the active basis of anticorrosion agents

2024-12-19T10:36:31+00:00

Synthesis of the active base of a solid corrosion inhibitor for the protection of underground equipment of gas condensate and oil wells, namely, 1-amido-hydroxystearate-diethylenediamine-2-hydroxystearyl-imidazoline and ethylene-bis-2-hydroxystearyl-imidazoline is described. Imidazoline derivatives have been obtained by condensation of triethyltetramine with 12-hydroxystearic acid at different temperatures. Analysis of the reaction products by ¹H NMR spectroscopy and chromatography-mass spectrometry is presented, with confirmation of the formation of target products at each stage of synthesis. It was found that when the reaction is carried out at 280 ℃, a significant amount of ethylene-bis-2-hydroxystearyl-imidazoline is formed. The perspective of using a technical mixture of 1-amido-hydroxystearate-diethylenediamine-2-hydroxystearyl-imidazoline and ethylene-bis-2-hydroxystearyl-imidazoline for anti-corrosion protection of oil pipelines is demonstrated.

Use of synthesised ultradispersed substances in technological systems

2024-12-19T10:36:31+00:00

Ultrafine calcium carbonate was synthesized by the exchange reaction and carbonation method with crystallite size of 7-44 nm. The size, polymorphic modification, and morphology of the crystallites were confirmed by X-ray diffraction analysis and scanning electron microscopy. The main attention is focused on development of methods for the synthesis of ultrafine calcium carbonate directly at the sites of well depressurization (microcracks) and the basics of technology for eliminating or preventing fluid manifestations in oil and gas wells. Depending on the intensity of gas occurrences, gas migration paths, the size of gas pipeline channels, the location of depressurization areas, thermobaric conditions, as well as the technical and operational condition of wells, it is proposed to perform sealing in one of two effective ways.

The first method involves sealing microscopic gas flow channels by transporting highly mobile low-viscosity solutions containing chemical reagents in a colloidal state to the depressurization sites, followed by creating conditions for their reaction and the formation of solid or gel-like sealants. To implement this method, one inverted microemulsion is prepared, the internal phase of which is an aqueous solution with the ionic reagent CaCl₂, and the second – with the ionic reagent Na₂CO₃, which are injected together under stirring by the “jet to jet” method to form CaCO₃ crystallites and are pressed by carbon dioxide into the depressurized areas. The second method of sealing microscopic gas flow channels involves transporting a low-viscosity solution containing one of the reagents in a colloidal state and the other reagent in a gaseous state to the depressurization sites, followed by creating conditions for their reaction and the formation of solid or gel-like sealants. The technical result of this method is achieved by the interaction of calcium hydroxide contained in the polar phase of the inverted micelle with carbon dioxide, which is pre-filled into the well. The permeability of CO₂ through the membrane-like adsorption-solvent shell of biosynthetic surfactants around the calcium hydroxide facilitates the formation of CaCO₃ and the pushing of ultrafine calcium carbonate by carbon dioxide into the gas-fluid channels. The well is treated using the “sliding tamping” method in the repression-depression mode.

My way in catalysis

2024-12-19T10:36:32+00:00

In this paper, I attempt to summarize my research in heterogeneous, heterogeneous-homogeneous, and homogeneous catalysis and memories of events that have influenced my worldview. Among the reactions that have been investigated are the following: ammonia synthesis and decomposition, hydrogen oxidation, selective oxidation of aromatic hydrocarbons, oxidation of CO and CO-NO mixtures, CO hydrogenation including Fischer-Tropsch synthesis, oxidative coupling of methane, conversion of ethanol to hydrogen and C₂-C₄ olefins. A rapid isotopic exchange between gaseous ammonia and nitrogen adsorbed on an iron catalyst has been established. This is direct evidence of nitrogen adsorption as a limiting stage of the ammonia synthesis reaction. It has been experimentally substantiated that nitrogen adsorption is described by an isotherm known as the Temkin isotherm. Consistent evidence has been obtained that the hydrogen oxidation reaction on the V₂O₅ and V₂O₅-MoO₃ catalysts occurs under certain conditions by a heterogeneous homogeneous mechanism. For the first time, a kinetic model was proposed for this type of catalysis based on a detailed mechanism of heterogeneous oxidation of hydrogen on oxide catalysts. The mechanism and kinetic model of selective oxidation of aromatic hydrocarbons on oxide catalysts are proposed. They have been successfully applied to explain experimental data. A new type of catalyst for the oxidation of o-xylene to phthalic anhydride has been found - activated carbons, which combine high selectivity with significant overall activity. A non-trivial mechanism of the effect of sulfur dioxide on the kinetics of oxidation of CO on platinum metals was proposed. An amazing fact was revealed: in the presence of a platinum or palladium catalyst, due to the transition to a heterogeneous-homogeneous mode, the reaction proceeds at a high speed even at room temperature. To explain the effect found, it was first suggested that the catalyst could not only initiate a chain process, but also participate in the branching of chains. The proposed reaction scheme also made it possible to explain the presence of two stationary process modes under the same external conditions. Various types of kinetic oscillators have been proposed, including the simplest in heterogeneous catalysis oscillators. The foundations of the method of competing reactions in heterogeneous catalysis are significantly developed. It has been shown theoretically and experimentally that under certain conditions one of the reactions can accelerate the other. Another non-trivial effect of the mutual influence of competing reactions was the strong inhibition of one reaction by another, even when the surface coverage of adsorbed compounds is negligible. New competitive catalysts for steam reforming of ethanol (PRE) into hydrogen have been found.

Unconsciously in my work, I tried to follow Albert Einstein’s advice: “We must make things as simple as possible – but not simpler.”

To the 70th anniversary of V.I. Kashkovsky

2024-12-19T10:36:33+00:00

To the 70th anniversary of V.I. Kashkovsky