Oxidative desulfurization technology of petroleum fractions purification is a highly relevant topic. In this study, new molybdate-based catalysts were proven to be highly efficient in the oxidation of model and real diesel fuels. Surface acidification during impregnation of hydroxyapatite promotes the self-assembly of Keggin-type phosphomolybdates alongside with polymolybdate (“molybdenum blue”) clusters and generates a synergistic catalytic system. Controlled thermal treatment preserved polyoxomolybdate structures responsible for enhanced activity. The optimized catalyst demonstrated efficient oxidation of dibenzothiophene over a wide sulfur concentration range (500–8000 ppm). Notably, 99% sulfur removal from straight-run diesel containing 11,700 ppm was achieved at 70 °C within 8 h, confirming applicability to real feedstock. The results highlight hydroxyapatite as a reactive support enabling in situ formation of active polyoxomolybdate species and provide a scalable strategy for deep desulfurization of high sulfur fuels under mild conditions.

Mesoporous nanopowders based on hydroxyapatite (HA) doped with tungstate groups up to 7.5 mol% were synthesized by precipitation. Low tungstate concentrations (from 1 to 2.5 mol%) yielded single-phase apatite, while higher concentrations (>= 5 mol%) led to CaWO4 co-precipitation. The obtained samples exhibited a substantial specific surface area (SSA) ranging from 74 to 88 m2/g and nanoscale particle size (10-25 nm). The 7.5 mol% tungstate-HA catalyst demonstrated high efficiency in the selective oxidative conversion of benzyl alcohol to benzaldehyde at room temperature. Optimal conditions were achieved, resulting in greater than 51 % substrate conversion, 100 % benzaldehyde selectivity, and a turnover frequency (TOF) of up to 180 h- 1. The high catalytic activity was attributed to active peroxo complexes, the large specific surface area, and the achieved porosity of up to 0.355 cm3/g. The findings of this study indicate that room temperature oxidative conversion with water as a coproduct is a promising green chemistry solution.

Aerobic oxidative desulfurization (AODS) of high-sulfur feedstocks is essential for developing efficient, eco-compatible deep-oil refining technologies. However, the influence of the high initial sulfur concentration on AODS efficiency remains poorly understood. This gap is critical, as real feedstocks often contain several thousand parts per million of sulfur. We show that increasing the sulfur content of the model fuel (DBT in dodecane) from 500 to 8000 ppm leads to a pronounced decrease in the oxidation rate: the DBT conversion decreases from 100% to 9% under identical conditions within 60 min at 150 degrees C, indicating a strong inhibitory effect at high sulfur concentrations. A systematic study was performed on a model fuel containing 8000 ppm of S using a series of Fe, Co, Mn, and Bi molybdate catalysts while varying key process parameters (temperature, catalyst dosage, and air flow rate). To overcome the inhibitory effect, an initiator-assisted strategy was proposed. The addition of tert-butyl hydroperoxide (TBHP) as an initiator increased the DBT conversion from 9% to 33% in 60 min, shortening the induction period and increasing the desulfurization efficiency by generating additional alkyl peroxide radicals. For the first time, complete oxidation of high-sulfur fuel (8000 ppm of S) was carried out using a MnMo catalyst combined with TBHP as an initiator in a two-stage process (150 degrees C; 0.22 wt % catalyst; air flow rate 6 L/h; stage 1:0.8 wt % TBHP, 120 min; and stage 2:0.4 wt % TBHP, 150 min). The catalyst maintained high activity and structural stability over five cycles. Proposed reaction pathway involving superoxide (O2 center dot-) radical and alkyl peroxide generated from atmospheric O2 and TBHP is discussed. The suggested approach has also been successfully applied to straight-run diesel fuel (10,208 ppm), where the degree of desulfurization has increased from 20 to 45%.

Our purpose was to develop a highly selective and efficient catalyst based on molybdate-substituted hydroxyapatite for low-temperature liquid-phase oxidation of benzyl alcohol. Catalysts were synthesized by the coprecipitation method while the molybdate anion content was varied from 1 to 10 mol.%. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, N2 surface adsorption/desorption isotherm measurement, electron paramagnetic resonance spectroscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. In contrast to hydrothermal synthesis, the obtained hydroxyapatite samples are characterized by a large specific surface area of 121 m2/g and high catalytic activity in the oxidation of benzyl alcohol with hydrogen peroxide under mild conditions. It was found that the turnover number (426 h- 1) of nanosized mesoporous catalyst HA-2.5%MoO4 (MoHA2) is 5-20 times higher than that of known molybdenum-containing catalysts. In the presence of the obtained nanocatalyst, more than 59 % substrate conversion was achieved with 100 % selectivity at 30 degrees C. It was revealed that the key criteria for a nanocatalyst for this purpose are a highly developed surface with well-dispersed molybdate anions and the presence of the Mo (VI)/Mo(IV) redox couple, which ensure improved catalyst-substrate phase contact, the formation of a peroxo complex, and high selectivity for the formation of benzaldehyde as the target product.

For the first time cobalt-manganese spinel structure catalysts were effectively applied for aerobic oxidation of sulfur-containing compounds. High activity of obtained catalysts is achieved due to the existence of the redox couples Co2+/Co3+ and Mn3+/Mn4+ in the spinel structure. It has been shown that the high mobility of oxygen in the spinel structure contributes to the efficient oxidation of sulfur-containing compounds. The CoMn2O4 and MnCo2O4 spinel-type catalysts were obtained by the hydrothermal method and characterized by a complex of physicochemical methods: XRD, FTIR, nitrogen adsorption-desorption, SEM, TEM, TPR-H2, and XPS. Under optimal conditions (130 degrees C, & omega;(cat.) = 0.034 wt%, 2 h), the complete DBT oxidation was achieved in the presence of CoMn2O4. High stability of catalyst over 5 cycles of oxidation was demonstrated. A possible reaction mechanism has been proposed based on EPR data and catalysts characterization results.

This review provides an analysis of prior research on the oxidation of organic compounds with oxygen as an oxidant in the presence of transition-metal molybdates. The reaction mechanisms suggested for the oxidation of various classes of organic substrates, methods for the synthesis and modification of molybdates, and promising industrial applications of molybdate catalysts are discussed.

Nanosized mixed tungsten-iron carbide (FeWC) was successfully applied in aerobic oxidative desulfurization. The combination of catalytically active centers responsible for the activation of oxygen and the oxidation of sulfur-containing compounds made it possible to obtain a highly efficient catalyst. The catalyst was synthesized by microwave irradiation, allowing to obtain a nanoscale catalyst in just 15 min. The catalyst was characterized in detail by a variety of methods: XRD, HRTEM, EDX, SEM, XPS, and low-temperature nitrogen adsorption/ desorption. The key factors influencing the dibenzothiophene (DBT) oxidation were investigated. Under opti-mized conditions DBT conversion was 100% in 1 h at 130 degrees C, 6 atm. The possible mechanisms including oxygen activation, alkyl peroxide formation, and substrate oxidation by tungsten peroxo-complexes were discussed. The catalyst retains its activity for at least 5 cycles of oxidation-regeneration. Aerobic oxidative desulfurization of straight-run gasoline in the presence of FeWC was performed and sulfur content was reduced from 995 to 6 ppm.

New highly effective heterogeneous catalysts representing immobilized Anderson-type polyoxometalate (POM) supported on the hydrophobic surface of a porous aromatic framework PAF-30 were modified with triethylamine or 1-methylimidazole for the aerobic oxidation of sulfur-containing substrates. The catalysts were characterized using FT-IR, solid-state C-13 NMR, N-2 adsorption-desorption isotherms, BET, SEM, TEM, EDX, TGA, XRF, and XPS analyses. The activity of synthesized catalysts in the aerobic oxidation of a model fuel was investigated. It was shown that the immobilization of POM on the surface of PAF-30 modified with 1-methylimidazole can significantly increase the efficiency of the process of aerobic oxidation of dibenzothiophene (DBT) due to the uniform dispersion of the active phase on the support. The effect of the catalyst dosage, reaction temperature, and the nature of the substrate on the air oxidation process was studied. Optimal reaction conditions were selected, allowing us to achieve 100% DBT conversion: 0.54 mg/mL of PAF-30-Imi-POM catalyst, 130 degrees C, 1 h, 650 rpm, air flow rate 6 L/h. In addition, it has been demonstrated that the catalyst PAF-30-Imi-POM retains high activity for at least 5 cycles of reuse with the use of intermediate regeneration.

New molybdenum-containing catalysts based on PAF-30 mesoporous carbon material for oxidation of sulfur-containing compounds (SCs) in a model fuel were synthesized. The PAF-30 support was modified with functional groups containing a positively charged nitrogen atom with various substituents. The modified supports were studied by the methods of low-temperature nitrogen adsorption/desorption, IR spectroscopy, and elemental analysis. The major factors affecting the oxidation were considered: reaction temperature and time, oxidant amount, catalyst dosage, and kind of sulfur-containing substrate. For the Мо/PAF-30-NEt 3 catalyst, optimum conditions were found for oxidation of various classes of SCs in model mixtures: H 2 O 2 : S molar ratio 6 : 1, 60°С, 60 min. The Мо/PAF-30-NEt 3 catalyst operates in dibenzothiophene (DBT) oxidation during five cycles without appreciable activity loss.

Herein, we present a new type of high-performance catalyst for aerobic oxidation of organosulfur compounds based on tungsten carbide. The synthesis of tungsten carbide was performed via microwave irradiation of the precursors, which makes it possible to obtain a catalyst in just 15 min. The synthesized catalyst was investigated by a variety of physicochemical methods: X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and N2 adsorption/desorption. It was shown that active centers containing tungsten in the transition oxidation state (+4) play a key role in the activation of oxygen. The main factors influencing the conversion of dibenzothiophene (DBT) were investigated. It should be noted that 100% conversion of DBT can be achieved under relatively mild conditions: 120 °C, 3 h, 6 bar, and 0.5% wt catalyst. The catalyst retained its activity for at least six oxidation/regeneration cycles. The simplicity and speed of synthesis of the proposed catalyst in combination with its high activity and stability open broad prospects for its further use both for oxidative desulfurization and for other reactions of aerobic oxidation of organic substrates.

Oxidative desulfurization of straight-run naphtha fraction in the presence of a heterogeneous catalyst containing two active sites was studied. Combination of an acid component and a transition metal ensures high performance of the oxidative desulfurization catalyst HPMo–NA–SBA-15, in which the SBA-15 support is mesoporous ordered silica. The nicotinic acid fragments bound to the SBA-15 support and phosphomolybdic acid anion by covalent and ionic bonds, respectively, prevent the washout of the phosphomolybdate active phase, thus preserving the catalyst performance in at least five oxidation/regeneration cycles. Conditions were found for obtaining a naphtha fraction with ultralow sulfur content (5 ppm).

Methanogenic biotransformation of unusual substrates (sulfur (S)-containing wastes: non-purified vacuum gas oil, straight-run gasoline fraction (Naphtha), gas condensate, and straight-run diesel fraction) coming from oil industry after their oxidative desulfurization was investigated. Nitrogen-containing wastes (hydrolysates of chicken manure and Chlorella vulgaris biomass) were added as co-substrates to mixture with oil industry wastes. The 100 % conversion of S-organic compounds to inorganic sulfide accumulated in the reaction liquid medium was achieved with simultaneous production of biogas containing high methane percent (greater than 70 %). Polishing of effluents from methane tank was carried out by denitrifying oxidation of ammonium (DEAMOX). The high process efficiency was due to use of original immobilized artificial consortia at the stage of meth-anogenesis and DEAMOX. This study reveals the real potential in the processing of very complex mixtures of large-scale wastes, usually inhibiting methanogenesis, by developing biocatalysts based on synthetic biology approaches.

Herein, we present a new approach to the design of the catalysts for aerobic oxidation of sulfur-containing compounds. Iron-containing zeolite-based (ZSM-5, ZSM-12) catalysts were synthesized and successfully tested in oxidation of model mixtures as well as real petroleum fractions. The catalysts were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV/Vis), temperature programmed desorption of ammonia (NH3-TPD), and low-temperature nitrogen adsorption-desorption. Among these catalysts Fe-ZSM-12 demonstrated the best activity: exhaustive oxidation of dibenzothiophene (DBT) in the presence of this catalyst was achieved in 2 h at 150°C. Influence of the reaction conditions (temperature, amount of catalyst, and time) on the conversion of the model substrate was studied. It was shown that in the presence of Fe-ZSM-12 catalyst activation of molecular oxygen proceeds via formation of superoxide radical. Fe-ZSM-12 exhibited an excellent stability and retained its activity after 10 cycles of oxidation. Under optimal reaction conditions sulfur content in straight-run gasoline fraction was reduced from 807 to 43 ppm, in diesel fraction – from 1898 to 150 ppm. Two-dimensional GC-MS analysis of diesel fraction before and after desulfurization indicates high selectivity of the process. Possibility of sulfur dioxide formation during the aerobic oxidative desulfurization process was studied for the first time. The use of zeolite-based catalysts containing transition metals for aerobic oxidation of sulfur-containing compounds is a promising approach for clean fuel production.

Different wastes (ethanol extracts with sulfur-containing organic compounds from petroleum industry obtained after oxidative desulfurization, chicken manure, and Chlorella vulgaris biomass from water waste treatment plants) were used as complex co-substrates for a deep bioconversion in methanogenesis and DEAMOX process. We achieved 100% conversion of S-containing organic compounds to inorganic sulfide accumulated in the reaction liquid medium with simultaneous production of biogas with high methane content (>70%) with this technique. This success was provided by immobilized synthetic consortium consisting of 80% anaerobic methanogenic sludge, 10% Desulfovibrio desulfuricans cells, and 10% Rhodococcus opacus cells. Further anaerobic treatment of the obtained media with immobilized artificial DEAMOX consortium consisting of both denitrifying and methanogenic sludge allowed the conversion of N-NH 4 + (80.5%) and N-NO 3 - (93.4%) into N 2 .

Immobilized ionic liquids with Brønsted acidity containing fragments of nicotinic and phosphomolybdic acids are synthesized by two methods: suspension impregnation and chemical immobilization. The obtained catalysts are characterized by the low-temperature adsorption/desorption of nitrogen, elemental analysis, and transmission electron microscopy. The conditions for exhaustive oxidation of dibeznothiophene are determined: 30 min, the molar ratio of hydrogen peroxide and dibenzothiophene = 6 : 1, the weight fraction of catalyst = 0.5 wt %, and T = 80°C. The catalysts obtained by impregnation lose their activity after regeneration and the catalysts obtained by chemical immobilization retain their activity after at least five oxidation/regeneration cycles.

The paper describes a method developed for the oxidation of organosulfur compounds using organic peroxides generated in situ under the action of atmospheric oxygen on gasoline fraction after reforming. Naphtha reformate that contained dibenzothiophene as a model substrate was subjected to oxidative desulfurization by organic peroxides generated in situ under atmospheric oxygen. The study examined various catalytic systems, including immobilized Anderson-type polyoxometalates, and initiators, which, in combination, provided effective generation of alkyl hydroperoxides, selective oxidation of organosulfur compounds in the hydrocarbon feedstock, and a high conversion rate.

Anderson-type polyoxometalate (POM) catalysts were synthesized and applied for deep oxidative desulfurization of model fuel containing dibenzothiophene. O2 contained in air was used as oxidant under mild conditions. The influence of the nature of central heteroatom and that of the quaternary ammonium cation used on the conversion of DBT was investigated. For the first time to the best of our knowledge, the role of the solvent in aerobic oxidative desulfurization was investigated and the possible mechanism of DBT oxidation was suggested. It was shown that the key stage in the oxidation of the sulfur-containing compound is the generation of alkyl peroxides from the solvent.

New highly efficient heterogeneous catalysts based on an immobilized Anderson-type polyoxometalate supported on the functionalized SBA-15 surface have been successfully synthesized and characterized by FT-IR, XRD, N2 adsorption-desorption isotherms, BET, SEM, TEM, EDX, and XPS analyses. The catalytic activity was investigated in the aerobic oxidative desulfurization of a model fuel. Heterogeneous catalysts were synthesized by various methods of immobilization using organic fragments of different natures. An efficient method of immobilization based on the grafting of N-methylimidazole as a cation-forming agent has been shown. The effect of temperature, dosage, and active phase loading on the conversion of dibenzothiophene (DBT) was studied. The highest activity was shown by the CoMo-0.5IL-SBA catalyst (IL = 1-methyl-3-(trimethoxysilylpropyl)-imidazolium cation), in the presence of which 100% DBT removal is achieved within 90 min at 120 degrees C at a catalyst amount of 0.2 wt %. Moreover, the immobilized catalyst could be recycled 5 times without a significant loss of catalytic activity.