The catalysts of the CaO‒Fe2O3 system with Fe2O3 content in the range of 0‒100 wt.% were synthesized by the solid state method at 900 and 1000 °C. The catalysts were characterized by XRD and SEM‒EDX methods, and their activity in the oxidative conversion of methane at 750 °C was studied. The phase composition of the catalysts corresponds to the CaO‒Ca2Fe2O5, Ca2Fe2O5‒CaFe2O4 and CaFe2O4‒a-Fe2O3 regions of the phase diagram. The specific catalytic activity dependence on the Fe2O3 content has an extremum. The CaO‒Ca2Fe2O5 catalysts have the highest reactivity and the active centers in them are localized at the phase interface. The activity of Ca2Fe2O5–CaFe2O4 samples decreases with an increase in the CaFe2O4 content. The CaFe2O4‒a-Fe2O3 catalysts have a core-shell structure and exhibit the least activity, which is determined by the CaFe2O4 shell.

Using the methods of X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed reduction with hydrogen, the relationship between the phase composition, structural characteristics of the phases, and the reactivity with respect to hydrogen was investigated for calcium ferrites-based catalysts. The catalyst samples were prepared via solid-state synthesis from CaO and Fe2O3 at 900 and 1000°C by varying the Fe2O3 content in the CaO–Fe2O3 system. The phase composition of the resultant samples corresponds to the CaO‒Ca2Fe2O5, Ca2Fe2O5‒CaFe2O4, and CaFe2O4‒α-Fe2O3 regions. In the CaO–Ca2Fe2O5 samples the lattice parameters of Ca2Fe2O5 and its activity with respect to hydrogen depend on the phase ratio. The activity of CaFe2O4 is higher in Ca2Fe2O5‒CaFe2O4 compared to CaFe2O4‒α-Fe2O3 catalysts.

The effect of temperature and duration of calcination of single-phase samples of hematite with the alpha-Fe2O3 structure on the oxidizing ability with respect to hydrogen in the temperature-programmed reaction mode in the temperature range of 40-900 degrees C was studied. It is shown that the calcination temperature is a significant factor affecting the reactivity of lattice oxygen in the oxidation of hydrogen. Samples of alpha-Fe2O3, calcined at 800-900 degrees C, show the highest activity, the process of alpha-Fe2O3 reduction in these samples proceeds through the stage of reduction to magnetite, followed by complete reduction to metal through the combination of reduction stages of oxides. The calcination of alpha-Fe2O3 samples at 1000-1100 degrees C leads to a significant decrease in the oxidizing ability, the alpha-Fe2O3 reduction initiates at temperatures 50-100 degrees C higher, proceeds without separating individual reduction stages of oxide, there is no complete reduction of alpha-Fe2O3 under the studied conditions. It has been established that with an increase in the calcination temperature of the hematite samples, the X-ray density of alpha-Fe2O3 increases, which indicates a decrease in the degree of crystal lattice disorder and an increase in the binding energy of lattice oxygen and manifests itself in a significant decrease in the reactivity of alpha-Fe(2)O(3)in the oxidation of hydrogen.

In this paper, the relationship between the structural features of hematite samples calcined in the interval of 800–1100 °C and their reactivity regarding hydrogen studied in the temperature-programmed reaction (TPR-H2) was studied. The oxygen reactivity of the samples decreases with the increasing calcination temperature. The study of calcined hematite samples used X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Raman spectroscopy, and their textural characteristics were studied also. According to XRD results, hematite samples calcined in the temperature range under study are monophase, represented by the α-Fe2O3 phase, in which crystal density increases with increasing calcination temperature. The Raman spectroscopy results also register only the α-Fe2O3 phase; the samples consist of large, well-crystallized particles with smaller particles on their surface, having a significantly lower degree of crystallinity, and their proportion decreases with increasing calcination temperature. XPS results show the α-Fe2O3 surface enriched with Fe2+ ions, whose proportion increases with increasing calcination temperature, which leads to an increase in the lattice oxygen binding energy and a decrease in the α-Fe2O3 reactivity regarding hydrogen.

The heavy crude oil of the Mordovo-Karmal deposit was cracked in the presence of NiCr/WC catalyst. The catalytic upgrading heavy crude oil was carried out in the batch reactor at 450 degrees C, catalyst content in the range of 0.01-0.20 wt%, and 100 min of residence time. It is shown that the cracking in the presence of a catalyst results in the formation of a light 'synthetic' oil. The viscosity of the liquid products of catalytic cracking decreases by an order of magnitude. The content of the fractions boiling up to 360 degrees C increases to 78 wt%, while the content of resins, asphaltenes, and sulfur decreases. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The effect of the HF modification of ferrospheres separated from fly ash after the combustion of brown coal on their chemical, phase compositions and catalytic properties in the oxidative coupling of methane was studied. The modification led to a change in the phase composition in comparison with that of the initial ferrospheres: a CaF2 phase appeared, the hematite phase content increased, and the ferrospinel content decreased. The yield of C2 hydrocarbons at 750°C increased by a factor of 1.5–2.0, and the fraction of ethylene in them increased to 30 or 65% at 750 or 850°C, respectively. It was assumed that an increase in the efficiency of HF-modified ferrospheres in the formation of ethane and its dehydrogenation into ethylene was due to the formation of oxyfluoride-type active sites. The pyrohydrolysis of fluorine-containing catalyst components at 850°C due to interaction with water vapor in a reaction atmosphere led to the formation of systems active in deep oxidation; this manifested itself in a sharp decrease in selectivity for the formation of C2 hydrocarbons and an increase in selectivity for CO2.

In this paper, α-Fe2O3–CaFe2O4 composite materials obtained by high-temperature solid-phase synthesis from Ca and Fe (III) oxides with varying molar ratio CaO/Fe2O3 in the range 0.15-1.00 were investigated. The materials are characterized by Х-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDS) and simultaneous thermal analysis (STA) in the hydrogen temperature-programmed reduction mode (H2-TPR). SEM-EDS studies of the specimens were revealed a formation of the “core-shell” type complex microstructure of material with the hematite phase as the “core”. H2-TPR of the specimens allowed to establish a decrease of the contribution of low-temperature forms of lattice oxygen in areas of 350-510 °С (up to 2.6 times) and 510-650 °С (up to 1.7 times), and the growth of the contribution of the high-temperature oxygen form in the range of 650-900 °С (up to 2 times) with an increase in the content of the phase CaFe2O4 from 33.4 to 97.5 wt. %. Relying on the assessment of lattice oxygen mobility, it was suggested, that the samples with content of CaFe2O4 phase more than 55.4 wt. % are promising for use as oxygen carriers in chemical looping processes of syngas production.

Методом твердофазного синтеза при температуре 1000 °C получены структурированные композиционные материалы СaFe2O4—α-Fe2O3 (содержание α-Fe2O3 2—82 мас.%). Изучение фазового состава образцов выполнено методом рентгеновской дифракции. Показано, что в зависимости от состава шихты изменение содержания фаз СaFe2O4 и α-Fe2O3 происходит по линейному закону. С помощью сканирующей электронной микроскопии показано формирование двухфазной системы α-Fe2O3—СaFe2O4. Методом мёссбауэровской спектроскопии при комнатной температуре установлено формирование катионных вакансий железа в кристаллической структуре СaFe2O4 при отсутствии структурных дефектов α-Fe2O3. Показано, что катионные вакансии могут формироваться при синтезе образцов в воздушной атмосфере.

Structured composite materials CaFe 2 O 4 -α-Fe 2 O 3 (α-Fe 2 O 3 content is 2–82 wt.%) are obtained with the method of solid-phase synthesis at 1000 °C. The phase composition of the samples is studied using powder X-ray diffraction. It is shown that the content of CaFe 2 O 4 and α-Fe 2 O 3 phases changes linearly, depending on the composition of the starting material. The scanning electron microscopy data indicate the formation of a two-phase system α-Fe 2 O 3 -CaFe 2 O 4 . The Mössbauer spectroscopy data at room temperature testify the formation of cationic iron vacancies in the CaFe 2 O 4 crystal structure in the absence of α-Fe 2 O 3 structural defects. Cationic vacancies can be formed during the synthesis in the atmosphere of air.

Catalytic properties in the reaction of oxidative coupling of methane (OCM) of HF-modified ferrospheres separated from combustion brown coal fly ash are investigated. It is established that the modification of ferrospheres results in a significant increase in the efficiency of C-2-hydrocarbons formation at 750 degrees C, the yield increases by 1.5-2.0 times, the content of ethylene in the C-2-products-up to 30 %, and at 850 degrees C - up to 65 %. It is suggested that the high efficiency of ethylene formation is associated with the formation of oxifluoride centers, which are deactivated at 850 degrees C and converted into oxide centers of deep oxidation.

In processing a heavy oil feedstock, an urgent problem is to find new and less expensive, primarily cracking, catalysts. We have studied the activity of redox catalysts based on ferrospheres from energy ashes in the cracking of two types (paraffinic and asphaltenic) of heavy oil and paraffinic crude oil under autoclave conditions. It was found that at 450 °C and in the presence of 10 wt % of ferrospheres, the selectivity toward liquid products for paraffinic and asphaltenic feedstock achieves 95–96 % and 72 %, respectively. Compared with the thermal cracking, this catalytic system provides the composition of liquid products with the higher content of light products and higher percent of the gasoline fraction. The influence of ferrospheres is most pronounced in the cracking of paraffinic feedstock: compared with thermal cracking, the content of light fractions in the products of petroleum cracking increases by ~20 % and achieves 67 %, while in the products fuel oil cracking, the ratio of the gasoline fraction increases 14-fold. During the cracking, we detected changes in the phase composition and structural characteristics of ferrospheres, formation of surface carbonaceous deposits with different reactivity in the combustion, and accumulation of sulfur compounds from petroleum feedstock.

Finding new low-cost catalysts, especially ones that can be used in cracking, is a problem of great interest in the refining of heavy oils. The activity of redox catalysts based on coal fly ash ferrospheres is examined for the cracking of two types of heavy oils (paraffin and asphaltenic), and for paraffin oil residue under autoclave conditions. It is established that at 450°C and with 10 wt % of ferrospheres, the selectivity of the formation of liquid products can be as high as 95–96% for paraffin oil and 72% for asphaltenic oil. The content of light products and the gasoline fraction increases in liquid products in comparison to thermal cracking. The effect of ferrospheres is most pronounced in the cracking of paraffin oil: the light fraction in the oil cracking products grows by approximately 20% relative to those obtained after thermal cracking, reaching almost 67%; the gasoline fraction in the light products of oil residue cracking grow by 14 times. The phase composition and structural characteristics of ferrospheres change during cracking, carbon compounds with different combustion reactivity are deposited on their surfaces, and concentrated sulfur compounds from heavy oils are observed.

Проведен совместный крекинг бурого угля и мазута, изучен состав полученных продуктов. Исследовано влияние инициирующих добавок (ферросфер летучих зол ТЭЦ) и соотношения уголь/мазут в исходном сырье на выход дистиллятных фракций в ходе крекинга.

The combined cracking of brown coal and petroleum residue was performed, and the composition of the products obtained was studied. The effects of initiating additives (fly ash ferrospheres from heat and power plants) and coal/residue ratios in the source material on the yields of distillate fractions in the course of cracking were examined.

Transformations of high-molecular-mass heteroatomic compounds (resins, asphaltenes) present in atmospheric distillation residue of crude oil from the Usa field (Republic of Komi) by thermal cracking at temperatures of 350–450°C in the presence of fly ash ferrospheres as initiator additives have been studied. The structural group parameters of resin and asphaltene molecules existing in the feedstock and the thermolysis products have been determined using elemental analysis, molecular mass, and proton NMR data.

Исследованы превращения высокомолекулярных гетероатомных соединений (смол, афальтенов) мазута нефти Усинского месторождения (Республика Коми) в процессе термического крекинга при температурах 350–450°С в присутствии инициирующих добавок – ферросфер энергетических зол. Определены структурно-групповые параметры молекул смол и асфальтенов исходного мазута и продуктов термолиза с использованием данных элементного состава, мол. массы, ПМР-спектроскопии.