FeCoNiCu(Cr, Mn, La, Ce)-Al high-entropy alloys (HEAs) were prepared via a combined centrifugal casting–self-propagating high-temperature synthesis process to serve as multifunctional catalyst precursors. The findings indicated that even with aluminum content reaching 50 wt %, the typical bcc structure inherent to HEAs was preserved. Doping additions (Cr, Mn, La, and Ce) led to pronounced microstructural changes, including alterations in morphology, porosity, and elemental distribution, while the primary phase constituents of the FeCoNiCuAl-based alloys remained consistent. It was found that La and Ce exhibited poor bulk incorporation into the HEAs, evidenced by a low surface content. Aluminum leaching and hydrogen peroxide stabilization converted these precursors into catalysts. These catalysts demonstrated high activity in the deep oxidation of propane and CO. The FeCoNiCu catalyst achieved the best results for CO oxidation, reaching 100% CO conversion at 250 °C. For propane oxidation, the FeCoNiCuCrMn catalyst was the most active, yielding 100% CO conversion at 300 °C and 97% propane conversion at 400 °C.

High-entropy alloys were produced by centrifugal self-propagating high-temperature synthesis and used as precursors for preparation of catalysts for CO and propane deep oxidation and CO2 hydrogenation. The precursors were converted into catalysts by aluminum leaching and stabilization with hydrogen peroxide solution. Prepared FeCoNiCu, FeCoNiCuMo, FeCoNiCuMn, and FeCoNiCuCr catalysts were characterized by XRD, SEM/EDS, and BET methods and tested in the processes of deep oxidation of CO and propane and methanation of CO2. The highest CO2 conversion, 50.6

NiAl, NiCoAl, and CoCuAl intermetallics on ceramic TiC and TiCrC supports were produced by self-propagating high-temperature synthesis (SHS) from granular mixtures and used as precursors for preparation of catalysts for CO and propane deep oxidation and CO2 hydrogenation. The precursors were converted into catalysts by aluminum leaching and stabilization with hydrogen peroxide solution. Prepared supported catalysts were characterized by XRD, SEM/EDS, and BET methods and tested in the processes of deep oxidation of CO and propane and methanation of CO2. It was revealed that 100 % CO conversion is observed in TiC-supported catalysts at 250 degrees C. Catalysts containing NiCo active phase on both ceramic supports were shown to be the most active in propane oxidation. In CO2 methanation, Ni/TiCrC sample showed the highest CO2 conversion (58.9 % at 350 degrees C) with 100 % methane selectivity.

Ni/TiC catalysts were produced by SHS from granular Ti + C + Ni mixtures and leaching in NaOH solution followed by stabilization with H2O2 solution of intermetallic precursors prepared by SHS from TiC + (Ni + Al) mixtures. Prepared granular and powder catalysts were characterized by XRD, SEM, EDS, and BET method. The catalytic activity of catalysts was determined in the temperature range of 150–400°С using the CO2 + H2 mixtures with different Н2 concentration. It was found that catalyst containing 10 wt % Ni leached from precursor with Ni : Al = 1 : 2 possesses the highest hydrogenating activity at 350°С and 20 vol % H2.

Supported mono- and bimetallic catalysts containing 10 wt

Copper and lanthanum promoted cobalt catalysts for CO2 hydrogenation to higher hydrocarbons are described. The catalysts were prepared by the self-propagating high-temperature synthesis followed by alkaline leaching. They are active in CO2 hydrogenation at 200 °C under 10 bar pressure (CO2 : H2 = 1 : 3) with selectivity to C2+ alkanes up to 39%; no alkenes and alcohols are formed under these experimental conditions.

Co–Ni supported catalysts were prepared by low-temperature combustion of dried mixture of solutions of cobalt and nickel nitrates and urea after impregnation of silica fabric (>97

Co–Al and Co–V–Al intermetallics produced by centrifugal self-propagating high-temperature synthesis (SHS) were used as precursors for preparation of catalysts for deep oxidation and hydrogenation of CO2. Leaching in NaOH solution and stabilization with H2O2 solution of precursors were carried out in permanent magnetic field (MF) (0.24 Т) and alternating magnetic field (0.13 Т, 50 Hz). Prepared Co и Co–V (95Co–5V, 90Co–10V) granular catalysts with size of 100–300 µm were characterized by XRD, SEM, EDS, and BET method and revealed to have a scaly surface structure. It was shown that the type of MF affects phase composition and surface morphology, as well as specific surface and activity in deep oxidation of CO and hydrocarbons as an important part of the neutralization of gas emissions, and hydrogenation of CO2, the processing of which would reduce atmospheric pollution with this greenhouse gas. Catalysts obtained in alternating MF was found to possess higher activity in the process of deep oxidation.

Previously, we suggested a new class of polymetallic catalysts based on SHS-produced intermetallic compounds for environment-friendly deep oxidation of CO and hydrocarbons [1]. Among these, Co–La catalyst showed best catalytic activity in the Fischer– Tropsch synthesis [2]. Since Co is also active in oxidation reactions [3], we made an attempt to further improve the oxidative ability of SHS-produced Co–La catalyst upon its modification with copper [4]. Moreover, Co and Cu catalysts exhibited high activity in the hydrogenation of СО2 [5–7]. Cu-doped Co–La catalysts of nominal composition (95 – x)Co–xCu–5La (x = 10, 30, 50 wt %) were prepared by centrifugal SHS from Co3O4–Cu2O–Al– La powder mixtures. As-prepared intermetallics were leached with NaOH, stabilized by processing in H2O2 solution (for details see [1, 2]), and characterized by SEM/EDS (Zeiss Ultra plus microscope + JCXA-733 Superprobe JEOL accessory) and XRD (DRON-3, Fe-Kα radiation). The 100–300 μm fractions of SHSproduced catalyst were tested for their activity in a flow silica reactor as described in [1, 2]. Gas compositions were determined using an Avtotest 02.03P gas analyzer and a gas-liquid chromatograph Model 3700.

Polymetallic Co90–V10 catalyst was derived from an SHS-produced Co–V–Al precursor and its performance in the deep oxidation of СО, propane and in the СО 2 hydrogenation was determined and compared with that of previously synthesized Co100 and Co95–V5 polymetallic catalysts. The precursor and catalyst were characterized by XRD, SEM, and BET analyses. In the processes of deep oxidation, Co90–V10 catalyst showed the best results. The CO 2 hydrogenation turned independent of V content of catalyst. A maximum of CO 2 conversion (65% at 350°C) was exhibited by Со100 catalyst. The СО 2 conversion over Co100 and Co95–V5 catalysts was found to show a maximum at a gas hour space velocity (GHSV) of 6000 h –1 .

The process of magnetic - field-assisted preparation of ferromagnetic Ni–Co–Mn catalyst for deep oxidation/hydrogenation from a mixture of SHS-produced intermetallics was explored by SEM, XRD, and BET methods. Alkali leaching of precursor powder was carried out in the absence of magnetic field, in permanent magnetic field (240 mT), and in alternating magnetic field (27 mT, f = 50 Hz). The application of MF during the preparation of Ni–Co–Mn catalysts was found to affect (a) their specific surface and morphology and (b) catalytic activity/selectivity in deep oxidation of CO and propane and hydrogenation of СО 2 . The effect of MF was more pronounced in the process of hydrogenation and in case of alternating magnetic field.

A new class of multifunctional polymetallic catalysts was developed, the precursors of which are complex multicomponent intermetallic compounds prepared by self-propagating high-temperature synthesis. The catalysts based on Co and Ni exhibit high activity in the hydrogenation of CO2 to methane. The maximum yield of methane is observed at 250–350 °C with an almost complete conversion of CO2 and 100% selectivity. Hydrocarbons C1-C4, including unsaturated hydrocarbons (propylene and butadiene), were synthesized on the Co-Fe-La catalyst under a pressure to 2 MPa at 250–350 °C and the ratio CO2: H2 = 1: 1. The new class of catalysts is promising for the development of direct CO2 hydrogenation to heavy (liquid) alkanes and unsaturated hydrocarbons.

In the present study, the active phases (AP) of an Fe–Ni–Co–Mn catalyst produced from SHS-intermetallics (a), a catalyst prepared via formation an intermetallic layer on a mesh surface of chromium-nickel stainless steel (b), and of a Co–Mn catalyst prepared via SHS on silica gel support (c), were isolated and characterized by SEM and XRD. The catalysts studied were highly active in the process of deep oxidation and catalysts (b) and (c) were highly active in the process of CO2 methanation as well. All AP had oxo-metallic composition and were formed from nanoscale components, but if the structure of these components for catalyst (a) was the same as on the surface of the catalyst, the structures of AP components for catalyst (b) significantly differed from the surface structures. In addition, AP sediment grain nanostructures of catalyst (c) differed from those of catalysts (a) and (b).

SHS-produced complex intermetallics were used as precursors for preparation of Ni–Fe- and Cobased catalysts for deep oxidation of carbon monoxide, propane, and hydrogen. The catalysts were characterized by XRD, SEM, EDS, and BET method and revealed a developed nanostructured surface, which explains their high activity in the processes of deep oxidation. The catalysts under study look promising for incineration of waste and exhaust gases, safeguarding fire/explosion hazards, as well as for use in flameless heat generation, fuel cells, etc.

Рассматриваются особенности синтеза, физико-химические характеристики и специфика работы в восстановительных процессах предложенных нами ранее новых многофункциональных полиметаллических катализаторов. Предшественниками катализаторов являются сложные интерметаллиды 3d-металлов и редкоземельных элементов, получаемые методом самораспространяющегося высокотемпературного синтеза (СВС). Структура катализатора включает каркас из низших интерметаллидов, покрытый сильно разупорядоченной, в значительной мере аморфной, металл-оксидной активной фазой. Эта фаза образует на поверхности двухуровневые наноструктуры ( 10 100 нм) с характерной формой плоских шестигранников. Катализаторы обладают высокой активностью в реакциях глубокого окисления и восстановления (синтез Фишера–Тропша, гидродесульфирование нефтяных фракций), причем в процессах восстановления не требуют предварительной активации.