A FeCo catalyst obtained by thermolysis of double complex salts (DCSs) was used for the selective hydrogenation of CO2 to CH4. The DCS-based catalyst did not require activation, and its structure remained unchanged either during high-temperature treatment with H2 or CO or under the process conditions of CO2 hydrogenation; therefore, the catalyst selectivity was not subject to structural changes.

This study investigates the effects of feed gas composition (CO/H2, CO2/H2, or CO/CO2/H2) on the activity and selectivity of an Fe-based composite catalyst (20Fe/2K–2V/PVA) for the synthesis of oxygenates, specifically higher alcohols. Physicochemical characterization using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis revealed that feed gas composition governs the final phase composition of the active catalyst (χ-Fe5C2, Fe, Fe3O4). The highest yield of higher (C5+) alcohols (up to 3.4 g/m3), with carbon conversion of approximately 46

Background: This study investigates the behavior of nanosized iron-containing dispersions during Fischer-Tropsch synthesis (FTS) in three-phase reactors of different types: CSTR and SBCR. Methods: The catalytic activity of nanosized dispersions was studied in three-phase reactors of different types: CSTR and SBCR. Calculations of the parameters of kinetic models for different reactors were carried out using Excel 2013 spreadsheets, the physical properties of gas mixtures and liquid hydrocarbon media were carried out using built-in models of ASPEN HYSYS v 10. Significant findings: For the first time, the influence of the type of slurry reactor on the catalytic behavior of a nanosized particles during FTS was systematically studied. It has been established that at various temperatures, pressure and GHSV in the presence of a nanosized Fe catalysts, X CO for SBCR in most cases is close to X CO for CSTR, which is not consistent with the literature data for these reactors with micro-sized slurry catalysts. The results of kinetic estimates indicate the presence of inhibition in the liquid/nanoparticle edge, which is hypothetically related to the dynamics of molecules of long-chain alkanes of the dispersion on this edge and may depend on the nature of the mechanical action on such a medium.

The catalytic activity of an iron–containing nanoscale chitosan-based catalyst in the Fischer–Tropsch synthesis (FTS) and the features of the formation of the structure of such a catalyst have been studied. It is shown that the nature of the acids used in the preparation stage—nitric, acetic or citric, has a significant effect on the structure obtained by partial destruction of chitosan and the size of the nanocrystallites of the active phase, which, in turn, leads to significant changes in the activity of the catalyst and productivity for the target products—C5+ hydrocarbons. The best performance of catalyst in FTS observed for the sample, obtained with use of nitric acid: С5+ productivity reached to 2136 g С5+/kgFe/h.

The catalytic performance of iron-based nanodispersions in Fischer–Tropsch synthesis in two different slurry reactor types, specifically a continuous stirred-tank reactor (CSTR) and a slurry bubble column reactor (SBCR), was comparatively investigated. It was found that, at equal process temperatures, the CO conversion in the SBCR using a gas disperser with four equally spaced 1-mm holes was lower than that in the CSTR. However, this observation is inconsistent with other reports in the literature. Replacing this disperser with a plate with a single centered 2-mm hole enhanced the CO conversion up to values close to those obtained in the CSTR. The reaction rate constants were calculated for the different reactor types.

A sample of a catalytic system based on nickel and a carbon-containing material, microcellulose, was obtained using a hydrothermal synthesis method. A catalytic study of the synthesized system in the process of selective hydrogenation of carbon monoxide and carbon dioxide was carried out with calculation of the apparent activation energy. The sample was demonstrated to be highly active in the selective hydrogenation reactions of carbon oxides. A 100

Изучено влияние температуры гидротермальной карбонизации (190-250 °С) гидролизного лигнина на свойства получаемых биоуглей. Биоугли исследованы комплексом физико-химических методов, проведен их элементный, технический и термический анализ. Показано, что повышение температуры гидротермальной обработки лигнина отрицательно влияет на выход биоугля, но позволяет получить термически более стабильный продукт, имеющий топливные характеристики, сопоставимые с бурыми углями. The effect of hydrothermal carbonisation temperature (190-250 °C) on the properties of biochar produced from hydrolytic lignin was studied. Biochar was investigated using a set of physicochemical methods, its elemental, proximate and thermal analysis was carried out. It is shown that an increase in the temperature of hydrothermal treatment has a negative effect on biochar yield but allows obtaining a more thermally stable product with fuel characteristics comparable with those of brown coal.

The homogeneous acetic acid synthesis-type Ru–Co–Li/N-methylpyrrolidone catalyst for CO and H2 transformations has been studied at moderately high pressures. For 1CO:2H2, low acetic acid selectivity has been observed, along with remarkable methyl acetate selectivity, the absence of aldehydes and ethyl acetate and sharp deviations from the Anderson-Schultz-Flory distribution for both alcaohols and long-chain hydrocarbons. For 1CO:1H2 and slightly elevated pressure, acetic acid selectivity slightly increased, notable ethyl acetate formation was detected, and both long-chain hydrocarbons and alcohols disappeared. Hypotheses are discussed about the direct parallel formation of all observed product groups (hydrocarbons, alcohols, esters, and acetic acid) and hydrocarbon chain growth limitations according to the formed Ru–Co cluster size in the presence of the aforementioned catalytic system.

The equilibrium parameters of steam isobutanol reforming were calculated. These include the H 2 yield, selectivity with respect to carbon-containing gases, and feed conversion. The calculated data, on the whole, agree with the published data and experimental values of the isobutanol conversion and yield of isobutyraldehyde and higher alkanes on Ni–Co catalysts supported on biochars prepared by hydrothermal carbonization of cellulose. On the other hand, the calculated yields of H 2 , СО, and СН 4 disagree with the experimental data, which suggests that the equilibrium in the experiments on the steam isobutanol reforming on this catalyst is not attained. Feeding a homogeneous mixture of water, isobutanol, and ethanol into the reactor at 700°С allows the Н 2 yield to be increased from 58 to 66% and the water conversion, from 58 to 76% compared to the steam reforming of isobutanol without ethanol. The addition of ethanol allows the coking to be significantly reduced and the H 2 and СО yield higher than 90% at 900°С to be reached.

The study investigates hydrogenation of CO 2 over mono- and bimetallic catalysts supported on biochar. In this reaction, bimetallic iron–cobalt catalysts were shown to surpass monometallic iron and cobalt catalysts in terms of catalytic performance. The optimal combination of performance parameters was reached at an iron to cobalt ratio of 3 : 1. The composition and genesis of the active phase in the bimetallic Fe–Co catalyst were identified, and the CO 2 hydrogenation mechanism was suggested for an iron-dominated bimetallic catalyst. Using biochar as a support was found to provide an active phase composition favorable for CO 2 hydrogenation.

Описан процесс метанирования - селективного гидрирования оксидов углерода. Рассмотрены химические основы процесса и особенности формирования продуктов реакции в зависимости от используемого катализатора. Оценены преимущества каталитических систем на основе углеродных материалов и недостатки катализаторов на оксидных подложках для получения синтетического метана. Для процесса селективного гидрирования монооксида углерода (СО) предложены никельсодержащие углеродные катализаторы на основе березового активированного угля и микроцеллюлозы, полученные методами пропитки по влагоемкости и гидротермального синтеза. Синтезированные образцы исследованы методами оптико-эмиссионной спектроскопии с индуктивно-связанной плазмой, низкотемпературной адсорбции азота, сканирующей электронной микроскопии, энергодисперсионной спектроскопии, рентгенофазового анализа, термогравиметрического анализа. Изучено влияние подложки и метода синтеза катализатора на конверсию СО и выход метана в ходе реакции селективного гидрирования СО, выявлен оптимальный средний размер кристаллитов NiO и Ni(OH)2 - прекурсоров активной фазы. Показано, что наилучшие показатели конверсии монооксида углерода и выхода метана в реакции метанирования достигнуты в присутствии никельсодержащего углеродного образца на основе микроцеллюлозы, полученного методом гидротермального синтеза. Methanation process, or selective hydrogenation of carbon oxides, is described. The chemical foundations of the process and the features of the formation of reaction products are considered, depending on the catalyst used. The advantages of catalytic systems based on carbon materials and disadvantages of the catalysts on oxide substrates for the production of synthetic methane are evaluated. Nickel-containing carbon catalysts based on birch activated carbon and microcellulose were obtained by incipient wetness impregnation and hydrothermal synthesis, and proposed for the selective hydrogenation of carbon monoxide (CO). The synthesized samples were studied by optical emission spectroscopy with inductively coupled plasma, low-temperature nitrogen adsorption, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, thermogravimetric analysis. The influence of the substrate and the method of catalyst synthesis on CO conversion and methane yield from the selective hydrogenation of CO was studied, and the optimal size of NiO and Ni(OH)2 crystallites, the precursors or the active phase, was determined. It is shown that the best carbon monoxide conversion and methane yield from methanation reaction are achieved in the presence of nickel-containing microcellulose-based carbon sample obtained by hydrothermal synthesis.

Работа посвящена разработке нового типа железосодержащего катализатора (Кт) на основе лигнина для процесса гидрирования монооксида углерода. Каталитические системы получали методом гидротермального синтеза и изучали комплексом физико-химических методов (ИК-Фурье спектроскопия, спектроскопия комбинационного рассеяния, низкотемпературная адсорбция азота, элементный анализ, атомно-абсорбционный анализ, рентгенофазовый анализ, рентгеновская фотоэлектронная спектроскопия, просвечивающая электронная микроскопия). Показано, что сформированные катализаторы представляют собой мелкозернистый непирофорный негигроскопичный порошок черного цвета. Установлено, что каталитические системы проявляют высокую активность в процессе гидрирования монооксида углерода: конверсия близка к 100 %, производительность по углеводородам С5+ достигает 131.6 г/(кг Кт•ч). The work is concerned with the development of a new type of iron-containing catalyst (Ct) based on lignin for the hydrogenation of carbon monoxide. Catalytic systems were obtained by hydrothermal synthesis and studied using a set of physicochemical methods (Fourier transform IR spectroscopy, Raman spectroscopy, low-temperature nitrogen adsorption, elemental analysis, atomic absorption analysis, X-ray phase analysis, X-ray photoelectron spectroscopy, transmission electron microscopy). Brunauer-Emmett-Teller (BET) surface area analysis, elemental analysis, atomic absorption analysis, X-ray fluorescence (XRF), transmission electron microscopy (TEM). It is shown that the formed catalysts are fine-grained, non-pyrophoric, non-hygroscopic, black powders. The catalytic systems are determined to exhibit high activity in carbon monoxide hydrogenation: the conversion is close to 100 %, the productivity with respect to C5+ hydrocarbons reaches 131.6 g/(kg Ct ∙ h).

Torrefaction and hydrothermal carbonization are low-temperature thermochemical procedures for the biomass conversion to biocoal, a carbon-neutral analog of fossil coal. Biocoals, compared to untreated biomass, exhibit hydrophobic properties, increased energy density, and calorific value similar to that of brown coals. The two processing methods differ essentially in that hydrothermal carbonization is performed in the presence of a large amount of water as reaction medium; hence, the biocoal formation mechanisms will be different for each process. Papers dealing with specific features of low-temperature heat treatment of biomass and with regular trends in conversion of biomass structural components (cellulose, hemicellulose, lignin) in the course of torrefaction and hydrothermal carbonization are considered in the review.

Reducing the amount of CO2 in the atmosphere is a very important task. Therefore, the development and search for new approaches to the synthesis of catalytic systems, allowing for the catalytic conversion of CO2 into valuable products, is an urgent task. In this work, the catalyst was obtained by the thermolysis of a double complex compound. In this regard, kinetic studies of the parameters of the thermolysis process of double complex salts-[Co(NH)3]6][Fe(CN)6] were additionally determined using isoconversion and model approaches of non-isothermal kinetics. The catalyst was studied using various physicochemical methods—X-ray diffraction (XRD), infrared (IR)-spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). It was shown that, at the stage of catalyst preparation, the formation of a CoFe alloy occurred, while the surface mainly consisted of carbon in sp2-hybridization, and the metals existed in the form of spinel CoFe2O4. It was shown that catalysts based on bimetallic salts were active in the process of hydrogenation of carbon dioxide without a pre-activation stage (CO2 conversion reached 28%, with a specific activity of 4.0 µmolCO2/gMe·s). It was established that it was possible to change the selectivity of the carbon dioxide hydrogenation process by pre-treating the catalyst with hydrogen (selectivity for methane formation in the presence of an unreduced catalyst is 46.4–68.0%, whereas in the presence of a reduced catalyst it is 5.1–16.5%).

The effect of treatment of a freshly reduced cobalt catalyst with oxygen and ammonia on its properties in the Fischer–Tropsch synthesis was studied. It was shown that treatment with small amounts of catalytic poisons helped to increase the selectivity of the catalyst with respect to the formation of target products, linear C 5+ hydrocarbons. The observed effect can be explained by partial blocking of the sites of direct CO hydrogenation to methane and modification of Lewis acid sites. The data obtained were consistent with the concept of the two-center surface model of Co catalysts for the Fischer–Tropsch synthesis and the theory of astoichiometric components of catalytic reactions.

Supported iron catalysts based on a carbon-containing material, biochar obtained by the hydrothermal carbonization of biopolymers (cellulose and lignin), were studied. The catalytic systems showed high activity in the Fischer–Tropsch synthesis. A composition of C 5+ liquid products, uncharacteristic for iron-containing catalysts, characterized by high isoalkane content (up to 55%) was recorded. This fact was discussed in the context of the theory of bifunctional centers proposed by A.L. Lapidus with coworkers. It was suggested that the active centers of the test catalysts can be considered bifunctional (a carbide phase and an oxide phase). A correlation between the Fischer–Tropsch synthesis data on the test catalysts and the data obtained by Lapidus and coworkers on cobalt-containing catalysts was shown.

Targeted synthesis of C/composite Ni-based material was carried out by the method of matrix isolation. The composite was formed with regard to the features of the reaction of catalytic decomposition of methane. The morphology and physicochemical properties of these materials have been characterized using a number of methods: elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, temperature programmed reduction (TPR-H2), specific surface areas (SSA), thermogravimetric analysis, and differential scanning calorimetry (TGA/DSC). It was shown by FTIR spectroscopy that nickel ions are immobilized on the polymer molecule of polyvinyl alcohol, and during heat treatment, polycondensation sites are formed on the surface of the polymer molecule. By the method of Raman spectroscopy, it was shown that already at a temperature of 250 °C, a developed conjugation system with sp2-hybridized carbon atoms begins to form. The SSA method shows that the formation of the composite material resulted in a matrix with a developed specific surface area of 20 to 214 m2/g. The XRD method shows that nanoparticles are essentially characterized by Ni, NiO reflexes. The composite material was established by microscopy methods to be a layered structure with uniformly distributed nickel-containing particles 5–10 nm in size. The XPS method determined that metallic nickel was present on the surface of the material. A high specific activity was found in the process of catalytic decomposition of methane—from 0.9 to 1.4 gH2/gcat/h, XCH4, from 33 to 45% at a reaction temperature of 750 °C without the stage of catalyst preliminary activation. During the reaction, the formation of multi-walled carbon nanotubes occurs.

This review describes a process for methanation (selective hydrogenation) of carbon oxides with an emphasis on its importance for environmentally friendly and distributed energy generation. The drawbacks of oxide-supported catalysts and the advantages of carbon-based catalysts are assessed in terms of green chemistry principles. Catalysts based on carbon nanotubes, carbon nanofibers, and biomass derivatives are further discussed. Major research approaches are outlined for the implementation of carbon-based catalysts in selective hydrogenation of carbon oxides. This discussion suggests that the most promising catalysts for methanation are those based on biomass-derived carbon materials.

This review provides an analysis of recent scientific and engineering literature on chemical methods for CO2 processing using heterogeneous catalysts. The following major uses of carbon dioxide are discussed: exhaustive hydrogenation; synthesis of hydrocarbons including light olefins; synthesis of oxygenates; and production of cyclic carbonates. Furthermore, the paper highlights the main design approaches for CO2 conversion catalysts and formulates priorities for decarbonization using heterogeneous catalytic reactions .

Carbon materials were formed by the hydrothermal carbonization of cellulose, which were used as support for carbon dioxide hydrogenation catalysts (Fe/C and Fe-Mn/C). In the presence of these catalytic systems, CO2 conversion reached 50%. It is shown that the manganese introduction into the Fe-containing catalytic system significantly affects the distribution of gaseous С1-С4 products and liquid С5+ hydrocarbons. Promotion leads to the suppression of methane formation and an increase in the proportion of C2-C4 light olefins in gaseous products, as well as to intensification of secondary processes with the formation of a significant amount of iso-structures in liquid products. The different distribution of С1-С6 alcohols in the oxygen-containing products on the Fe/C and Fe-Mn/C catalysts indicates the manganese effect on the routes of their formation.