Omarov, Shamil O

Matveyeva A.N., Omarov S.O.

Manh Long B., Cam T.S., Omarov S.O., Lebedev L.A., Seroglazova A.S., Stovpiaga E.Y., Gerasimov E.Y., Popkov V.I.

Different ∑REFeO3 catalysts (RE = 16 rare-earth elements) obtained from solution combustion synthesis at different red/Ox ratios with ultra-high entropy can be effectively applied for catalytic hydrogen oxidation, with H2 conversion ∼86% at 500 °C.

Matveyeva A.N., Omarov S.O.

AbstractCO2 is the most cost-effective and abundant carbon resource, while the reverse water–gas reaction (rWGS) is one of the most effective methods of CO2 utilization. This work presents a comparative study of rWGS activity for perovskite systems based on AFeO3 (where A = Ce, La, Y). These systems were synthesized by solution combustion synthesis (SCS) with different ratios of fuel (glycine) and oxidizer (φ), different amounts of NH4NO3, and the addition of alumina or silica as supports. Various techniques, including X-ray diffraction analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, N2-physisorption, H2 temperature-programmed reduction, temperature-programmed desorption of H2 and CO2, Raman spectroscopy, and in situ FTIR, were used to relate the physicochemical properties with the catalytic performance of the obtained composites. Each specific perovskite-containing system (either bulk or supported) has its own optimal φ and NH4NO3 amount to achieve the highest yield and dispersion of the perovskite phase. Among all synthesized systems, bulk SCS-derived La–Fe–O systems showed the highest resistance to reducing environments and the easiest hydrogen desorption, outperforming La–Fe–O produced by solgel combustion (SGC). CO2 conversion into CO at 600 °C for bulk ferrite systems, depending on the A-cation type and preparation method, follows the order La (SGC) < Y < Ce < La (SCS). The differences in properties between La–Fe–O obtained by the SCS and SGC methods can be attributed to different ratios of oxygen and lanthanum vacancy contributions, hydroxyl coverage, morphology, and free iron oxide presence. In situ FTIR data revealed that CO2 hydrogenation occurs through formates generated under reaction conditions on the bulk system based on La–Fe–O, obtained by the SCS method. γ-Al2O3 improves the dispersion of CeFeO3 and LaFeO3 phases, the specific surface area, and the quantity of adsorbed H2 and CO2. This led to a significant increase in CO2 conversion for supported CeFeO3 but not for the La-based system compared to bulk and SiO2-supported perovskite catalysts. However, adding alumina increased the activity per mass for both Ce- and La-based perovskite systems, reducing the amount of rare-earth components in the catalyst and thereby lowering the cost without substantially compromising stability.

Seroglazova A.S., Dmitriev D.S., Omarov S.O., Stovpiaga E.Y., Popkov V.I.

In this research endeavor, we report the successful synthesis of mesoporous and single-phase nanopowders of orthorhombic hafnium titanate, HfTiO4, using a facile solution combustion approach. The direct synthesis yielded an X-ray amorphous product, which was found to crystallize completely into single-phase HfTiO4 upon annealing at 800 °C for 1 hour, marking the first successful synthesis of this material via this method. The synthesized HfTiO4 nanopowders were thoroughly characterized using various techniques. Structural analyses conducted through powder X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed the formation of pure orthorhombic HfTiO4 nanocrystals, exhibiting an average size of 24.6 nm. Moreover, the scanning electron microscopy (SEM) morphological study and adsorption-structural analysis of the HfTiO4 nanopowder revealed a well-developed mesoporous structure with a specific surface area of 17 m2/g and an average pore size of 15 nm. The band gap of the synthesized HfTiO4 was determined to be 3.47 eV, designating it as a potential photoanode material. Photocatalytic applications were evaluated through photoelectrochemical tests, which showcased a high photoresponse in both the UV (365 nm) and visible (450 nm) regions of the spectrum. Importantly, the photoresponse under visible light surpassed that of commercial TiO2 (Sigma-Aldrich), signifying its potential as an efficient photoanode material.

Matveyeva A.N., Omarov S.O., Gavrilova M.A.

Cam T.S., Omarov S., Trofimuk A., Lebedev V., Panchuk V., Semenov V., Nguyen A.T., Popkov V.

Foam-like nanocomposites of the Ce-Fe-O system with two (c-CeO2, am-F2O3), three (c-CeO2, o-CeFeO3, α-F2O3), or four phases (c-CeO2, o-CeFeO3, α-F2O3, am-Fe2O3) were synthesized using the RedOx reaction of glycine-nitrate combustion. The glycine/nitrate ratio (G/N) was varied from deficient (0.2, 0.4) and stoichiometric (0.6) to excess ratios of glycine (0.8, 1.0, 1.2, 1.4). PXRD, 57Fe Mössbauer spectroscopy, N2-physisorption, TEM, H2-TPD, O2-TPD, and H2-TPR were used to examine the characteristics of the obtained samples. The average crystallite size of the obtained composites was in the range of 1.3–31.3 nm, 33.4–50.7 nm, and 10.1–33.9 nm for c-CeO2, o-CeFeO3, and α-Fe2O3, respectively. The lowest SBET (1.5 m2/g) belonged to the case of stoichiometric G/N, while the highest value (49.2 m2/g) was found in the case of the highest amount of glycine (G/N = 1.4); the latter case also had the largest total pore volume (Vp = 0.182 cm3/g) when compared to the others. Moreover, the advanced catalytic performance of foamy Ce-Fe-O-based nanocomposites toward H2 combustion in air was found with t10 = 275 °C, t50 = 345 °C, and Ea = 76.9 kJ/mol for sample G/N = 1.2. The higher activity of sample G/N = 1.2 in catalysis was attributed to different properties of the composite including an appropriate component phase ratio, smaller size of crystallites, higher specific surface area, higher reducibility and oxygen capacity, etc. The findings make it possible to carry out the directed synthesis of catalysts based on the Ce-Fe-O system with specific phases, dispersion, and morphological composition for efficient hydrogen oxidation at moderate temperatures.

Matveyeva A., Omarov S., Gavrilova M., Trofimuk A., Wärnå J., Murzin D.

The impact of the fuel/oxidizer ratio, the fuel type and the oxygen excess in the synthesis of ceria supported Ni and Co catalysts on the physicochemical properties and activity in steam and aqueous-phase reforming of glycerol was studied.

Chebanenko M.I., Omarov S.O., Lobinsky A.A., Nevedomskiy V.N., Popkov V.I.

This study demonstrates the potential of obtaining nanostructured materials based on g-C3N4 with a high specific surface area for use as efficient electrode materials for hydrogen production. The study uses a novel method of g-C3N4 exfoliation that increases the specific surface area of the starting material by a factor of three. Nanocrystalline g-C3N4 is obtained through the thermolysis of urea and treated with steam in a specified temperature range. The resulting series is analyzed using a range of physicochemical methods to determine the optimal temperature for steam exfoliation. Catalytic electrochemical tests are carried out in the electrolytic reforming of ethanol. It has been demonstrated that steam exfoliation can boost the rate of electrocatalytic reforming by 1.3 times while decreasing the amount of hydrogen evolution overpotential. The results of this study demonstrate the potential for the use of steam exfoliation as an effective method for obtaining high-performing electrode materials for hydrogen production.

Matveyeva A.N., Omarov S.O., Gavrilova M.A., Sladkovskiy D.A., Murzin D.Y.

Rare-earth orthoferrites have found wide application in thermocatalytic reduction-oxidation processes. Much less attention has been paid, however, to the production of CeFeO3, as well as to the study of its physicochemical and catalytic properties, in particular, in the promising process of CO2 utilization by hydrogenation to CO and hydrocarbons. This study presents the results of a study on the synthesis of CeFeO3 by solution combustion synthesis (SCS) using various fuels, fuel-to-oxidizer ratios, and additives. The SCS products were characterized by XRD, FTIR, N2-physisorption, SEM, DTA–TGA, and H2-TPR. It has been established that glycine provides the best yield of CeFeO3, while the addition of NH4NO3 promotes an increase in the amount of CeFeO3 by 7–12 wt%. In addition, the synthesis of CeFeO3 with the participation of NH4NO3 makes it possible to surpass the activity of the CeO2–Fe2O3 system at low temperatures (300–400 °C), as well as to increase selectivity to hydrocarbons. The observed effects are due to the increased gas evolution and ejection of reactive FeOx nanoparticles on the surface of crystallites, and an increase in the surface defects. CeFeO3 obtained in this study allows for achieving higher CO2 conversion compared to LaFeO3 at 600 °C.

Omarov S.O., Martinson K.D., Matveyeva A.N., Chebanenko M.I., Nevedomskiy V.N., Popkov V.I.

A series of nanocrystalline Ni/CeO 2 catalysts with various Ni content was prepared by urea-nitrate combustion synthesis and evaluated in glycerol steam reforming for renewable H 2 production. The as-prepared, reduced and spent catalysts were characterized by various analytical techniques such as XRD, N 2 -physisorption, SEM–EDX, TEM–HAADF and SAED, H 2 -TPR, XPS, Raman, and DTA–TGA. NiO is predominantly in the X-ray amorphous state (particle size 2–4 nm regardless of the Ni amount), which is retained for Ni 0 particles after reduction by H 2 . Significant fraction of NiO(Ni 0 ) is localized between CeO 2 aggregates. An increase in the Ni content leads to inhibition of the agglomeration of CeO 2 crystallites and increase in CeO 2 defectiveness up to 6.8 wt% Ni; formation of CeO 2 (Ni 2+ ) solid solution at 8.7 wt% Ni, which decomposes upon reduction. The sample containing 6.8 wt% Ni exhibits the best combination of Ni content and dispersion, CeO 2 defectiveness, glycerol conversion, H 2 yield, selectivity to H 2 and CO 2 and has low selectivity to hydrocarbons. TEM and DTA–TGA revealed the formation of amorphous, graphite-like, and fibrous coke depending on the Ni amount. This formation leads to accelerated deactivation due to partial agglomeration of Ni 0 particles and encapsulation of amorphous nickel. • x Ni/CeO 2 ( x = 0–8.5 wt%) catalysts were synthesized via solution combustion method. • Thermostable amorphous (2–4 nm) NiO and Ni 0 nanoparticles. • Maximum CeO 2 defectiveness at 6.8 wt% Ni due to electronic effect. • 6.8 wt% is the minimal Ni amount for the high hydrogen yield in GSR. • Amorphous, graphitic, and fibrous coke, encapsulation of amorphous Ni.

Matveyeva A.N., Omarov S.O., Nashchekin A.V., Popkov V.I., Murzin D.Y.

Correction for ‘Catalyst supports based on ZnO–ZnAl2O4 nanocomposites with enhanced selectivity and coking resistance in isobutane dehydrogenation’ by Anna N. Matveyeva et al., Dalton Trans., 2022, 51, 12213–12224, https://doi.org/10.1039/d2dt02088b.

Matveyeva A.N., Omarov S.O., Nashchekin A.V., Popkov V.I., Murzin D.Y.

ZnO–ZnAl2O4 obtained by urotropine-nitrate combustion synthesis can be effectively used as dehydrogenation catalyst supports. The ZnO content affects their properties and isobutane conversion, which passes through a maximum for 20 mol% of ZnO.

Cam T.S., Omarov S.O., Chebanenko M.I., Izotova S.G., Popkov V.I.

This review covers recent advances in the synthesis of cerium dioxide, its properties, and potential applications. Cerium dioxide is known for its abilities to form surface vacancies, store and release oxygen, as well as to increase the thermal stability of the material by metal-Ce interactions, etc. The crystallite size, specific surface area, morphology, and dispersion of CeO 2 nanoparticles can be significantly affected by the applied synthetic method, so it is necessary to assess its advantages and disadvantages. Therefore, different synthesis methods of CeO 2 nanoparticles have been reviewed and assessed in the first part of the paper. In the second part of the review, we highlight our new and important findings in this field. In particular, advanced A 2 O/CuO/CeO 2 (A = Li, Na, K, Rb, Cs) nanocatalysts have been prepared and tested towards the low-temperature CO oxidation. Each synthesized composite consists of nanosized CeO 2 crystallites and amorphous incorporated oxides (CuO and A 2 O). The highest catalytic activity has been achieved for the 1Li 2 O/20CuO/80CeO 2 sample with 20% CO conversion at 93 °C. Increasing the Li 2 O loading to 2 and 3 at.% did not enhance the catalytic activity due to the lower specific surface area of the obtained samples. It has been shown that CO adsorption is increased due to synergistic metal oxide-ceria interactions on the catalyst surface and, Li + promotion stabilizing the Cu + species.

Omarov S.O.

Cam T.S., Omarov S.O., Chebanenko M.I., Sklyarova A.S., Nevedomskiy V.N., Popkov V.I.

Concerning the catalytic field of CO oxidation for designing the cost-effective, stable, and highly active catalysts based on CuO/CeO 2 nanocomposites, in this work, the urea-nitrate combustion method was used to synthesize a series of CuO/CeO 2 catalysts with different CuO loadings (at%Cu) to test their catalytic activity in the CO oxidation, to find out the optimum at%Cu which allows the CuO/CeO 2 composite to perform a higher activity in close to room-like temperature. The at%Cu of 0%, 2.5%, 5.0%, 7.5%, 10%, 20%, 30%, 40%, and 50% were set up to obtain a catalyst series. The resulting catalysts were characterized using EDX, PXRD, SEM, and other methods. It was shown that the CuO loading caused changes in the phase composition (crystalline CeO 2 , amorphous or crystalline CuO), the crystallite size (5–10 nm for CeO 2 ; 20–33 nm for CuO), and the specific surface area (12.2–85.8 m 2 /g), as well as in the morphological and pore structure. These factors comprehensively influenced the catalytic performance of the samples. The initial temperature ( t i ) toward CO oxidation for the best catalyst obtained in this study belonged to the low-temperature region ( t i < 50 °C). The temperature for 50% CO conversion ( t 50% ) of the best catalysts was less than 100 °C that was much lower compared to pure CeO 2 ( t 50% ≈ 31 2 °C). For CO oxidation, the active sites on the surface were correlated with the interactions between copper and cerium oxides; the improvement in catalytic activity is also related to the high concentration of oxygen vacancies or high oxygen storage capacity of the catalysts. Besides, the advantage in the specific surface area of the samples played as one of the decisive factors to the higher CO conversion. It was noted that the increase of CuO loading into the CuO/CeO 2 catalysts exceeded 20% doesn’t lead to a further decrease in the temperature of CO oxidation. Thus, the optimum catalyst composition was determined to be the CuO/CeO 2 -20, and its properties were studied by the methods of Raman, XPS, TEM, H 2 -TPR, and EDS in detail. Results proved a strong synergistic effect – the coexistence of redox pairs Ce 4+ /Ce 3+ -Cu 2+ /Cu + , the formation of oxygen vacancies, as well as the presence of superficial lattice oxygen and adsorbed oxygen species leading to improve the catalytic activity of CuO/CeO 2 -20 catalyst. Moreover, the stability of the CuO/CeO 2 -20 catalyst was investigated and excellent results were obtained. We believe that the activity in CO oxidation of the CuO/CeO 2 -20 sample can even be enhanced by doping oxides of the other rare-earth and transition metals, which requires further study. • A series of catalysts based on CuO/CeO 2 composites with different CuO loadings (at%Cu = 0, 2.5, 5.0, 7.5, 10, 20, 30, 40, 50) was successfully synthesized. • Crystalline CeO 2 and CuO with an average crystallite size not exceeding 10 nm for CeO 2 and 33 nm for CuO were obtained. • Specific surface area, CeO 2 crystallite size, amount of amorphous CuO phase, type of morphology, and pore distribution, comprehensively affected the catalytic performance. • The optimum catalyst for CO oxidation was determined as CuO/CeO 2 -20. • The addition of CuO into ceria lattice will not only induce their synergistic interaction with the formation of more Cu + species but will also lead to generating more oxygen vacancies.

Zhang H., Wei J.

Tien N.A., Thanh Uyen T.T., Mittova V.O., Tomina E.V., To Nga T.T., Hien T.C., Ngoc Anh V.T.

Zhang J., Shen Y., Rao Q., Yang T., Pan Y., Jin H.

Khrapova E.K., Omarov S.O., Ivanova A.A., Kirilenko D.A., Kukushkina Y.A., Krasilin A.A.

Al-Yousef H.A., El Maati L.A., Alomar M., Farid H.M., Aman S., Bahlool T.

Sror G., Vradman L., Landau M.V., Herskowitz M.

Dong R., Li W., Yang Q., Li P., Zhang P., Wang L., Fu D.

Kurmashov P.B., Golovakhin V., Ukhina A.V., Ishchenko A.V., Ivanova N.M., Maksimovsky E.A., Bannov A.G.

Wang C., Ren X., Cao H., Zhang D.

Dasari H.P., Patil S.S., Kamath R.S., Kisiela-Czajka A.M.

Ighalo J.O., Paddock M., Almkhelfe H., Nepal A., Lacroix B., He X., Anthony J.L., Amama P.B.

Xiang H., Wang C., Yan Z., Zhang Y., Zhang P., Jing F., Luo S.

Wagay A.A., Shourya A., Patil S.S., Shirasangi R., Dasari H.P.

In this study, the EDTA-Citrate method was employed to synthesize NiO-PDC (NPC) and NiO-YSZ (NYZ) powder catalysts in nanostructured form. Subsequently, the catalysts were slurry dip-coated onto monolith cordierite substrates with alumina, using a one-step coating approach, and their CO oxidation activity was tested. The coating was achieved by first mixing the catalyst with the alumina suspension to prepare a homogeneous slurry, which was then used for dip coating onto the monolith. The adherence test was performed on the coated monolith to evaluate the mechanical stability of the catalyst-alumina composite layer. The coating was visually confirmed through optical imaging. The remaining powders (after coating) were then subjected to BET surface area, XRD, Raman spectroscopy, H2 TPR and O2 TPD analysis for characterization. Raman spectra showed that NPC exhibited higher oxygen vacancies than NYZ. H2 TPR and O2 TPD provided better evidence of the reduction potential and O2 desorption of NPC respectively. NPC/cord demonstrated the highest catalytic activity (T50 = 165 °C) compared to NYZ/cord (T50 = 215 °C) and bare cordierite (T50 = 777 °C), which is attributed to its better redox properties and higher oxygen vacancies. The effect of flow rate and heating rate on CO oxidation was studied on NPC/cord and NYZ/cord. The long-term stability of the NPC/cord and NYZ/cord were tested through 5-h and 50-h isothermal studies.

Chauhan A., Verma R., Alfifi F., Dhiman V.K., Ataya F.S., Rao S.K., Gopalakrishnan C., Rana G.

Shen P., Zhang X., Xu H., Pan B.

Tian G., Li Z., Zhang C., Liu X., Fan X., Shen K., Meng H., Wang N., Xiong H., Zhao M., Liang X., Luo L., Zhang L., Yan B., Chen X., et. al.

AbstractThe directional transformation of carbon dioxide (CO2) with renewable hydrogen into specific carbon-heavy products (C6+) of high value presents a sustainable route for net-zero chemical manufacture. However, it is still challenging to simultaneously achieve high activity and selectivity due to the unbalanced CO2 hydrogenation and C–C coupling rates on complementary active sites in a bifunctional catalyst, thus causing unexpected secondary reaction. Here we report LaFeO3 perovskite-mediated directional tandem conversion of CO2 towards heavy aromatics with high CO2 conversion (> 60%), exceptional aromatics selectivity among hydrocarbons (> 85%), and no obvious deactivation for 1000 hours. This is enabled by disentangling the CO2 hydrogenation domain from the C-C coupling domain in the tandem system for Iron-based catalyst. Unlike other active Fe oxides showing wide hydrocarbon product distribution due to carbide formation, LaFeO3 by design is endowed with superior resistance to carburization, therefore inhibiting uncontrolled C–C coupling on oxide and isolating aromatics formation in the zeolite. In-situ spectroscopic evidence and theoretical calculations reveal an oxygenate-rich surface chemistry of LaFeO3, that easily escape from the oxide surface for further precise C–C coupling inside zeolites, thus steering CO2-HCOOH/H2CO-Aromatics reaction pathway to enable a high yield of aromatics.

Ismail W., Belal A., Abdo W., El-Shaer A.

AbstractA simple technique was utilized to fabricate pure hexagonal La2O3 nanorods by utilizing lanthanum(III) nitrate hexahydrate (La(NO3)3·6H2O) and ammonia (NH4OH). The La2O3 nanoparticles were analyzed using XRD, TGA, Raman, SEM, FTIR, TEM, PL spectroscopy, and Mott–Schottky techniques. The XRD analysis confirmed the production of La(OH)3 nanorods under appropriate conditions, which were then successfully converted into La2O2CO3 and finally into La2O3 nanorods through annealing. The TGA analysis showed that the total weight loss was due to water evaporation and the dissolution of minimal moisture present in the environment. The FTIR analysis confirmed the presence of functional groups. The SEM analysis revealed changes in morphology. The TEM analysis to determine the particle size. The PL findings showed three emission peaks at 390, 520, and 698 nm due to interband transitions and defects in the samples. The Mott–Schottky analysis demonstrated that the flatband potential and acceptor density varied with annealing temperature, ranging from 1 to 1.2 V and 2 × 1018 to 1.4 × 1019 cm−3, respectively. Annealing at 1000 °C resulted in the lowest resistance to charge transfer (Rct).

Manh Long B., Cam T.S., Seroglazova A.S., Lobinsky A.A., Gerasimov E.Y., Popkov V.I.

Using the two-step solution combustion method, nanocrystals of ultra-high-entropy rare-earth orthoferrite (UHE REO) were synthesized and used as effective catalysts for the hydrogen evolution reactions (HER) and oxygen evolutions (OER).

Warsi M.F., Ihsan A., Alzahrani F.M., Tariq M.H., Alrowaili Z.A., Al-Buriahi M.S., Shahid M.

In this study, LaFeO3 perovskite orthorhombic-shaped nanospheres and holmium-doped LaFeO3 nanomaterials were prepared by a simple co-precipitation method. Their composite was made with carbon nanotubes (Ho-LaFeO3/CNTs) via an ultrasonication route. The X-ray Diffraction spectroscopy (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscopic analysis (SEM), Electrochemical Impedance Spectroscopy (EIS), and UV–visible spectroscopy, were done to analyze the prepared nanomaterials. Tauc plot was used to find the bandgap of prepared samples. The photocatalytic efficiency of prepared nanocrystals under visible light irradiation was investigated by degrading Congo red dye (colored pollutant) and Benzoic acid (colorless pollutant). The prepared Ho-LaFeO3/CNTs nanocomposite showed the highest photocatalytic efficiency compared to LaFeO3 and Ho-LaFeO3 samples as it degraded 83% Congo red and 69.5% Benzoic acid in 140 min, respectively. Carbon nanotubes helped in trapping the electrons and lower the recombination rate of e-/h+ pairs and as a result, increase the photocatalytic activity.

Rizzetto A., Piumetti M., Pirone R., Sartoretti E., Bensaid S.

A set of Dual Function Materials (DFMs) was prepared to seize the CO2 from a rich feed gas and to in-situ convert it to methane (synthetic natural gas). Specifically, ruthenium-ceria composite materials were synthesized through successive impregnation depositions on two high surface area supports, namely Al2O3 and ZSM-5. Cerium oxide has both the roles of CO2 adsorbent and promoter support for ruthenium, which represents the active component for methanation. Three different quantities of ceria (10, 20, and 30 wt.%) were dispersed onto the solid supports, and the adsorption capacities of the ceria-based materials were studied at different temperatures (150, 200, and 250 °C) at atmospheric pressure. The samples exhibiting the best results in terms of CO2 adsorption (30 wt.% CeO2/Al2O3 and 30 wt.% CeO2/ZSM-5) were subsequently impregnated to obtain ruthenium-loaded catalysts (2 wt.% Ru). These functionalized materials were characterized by XRD, N2 physisorption at -196 °C, TPDRO, ICP-MS, XPS, FESEM, HRTEM, and FT-IR. Then, cyclic experiments of CO2 adsorption and methanation were performed, simulating a real use of the catalysts at 250 °C and atmospheric pressure. The deposition of ruthenium-ceria on a high surface area support was found to be crucial for maintaining the methanation activity of this catalytic system under cyclic CO2 adsorption-hydrogenation conditions. The Al2O3-supported ruthenium-ceria catalyst adsorbed a lower amount of CO2 (ca. 200 μmol g−1 per each cycle) with respect to the zeolite-supported sample (ca. 300 μmol g−1); nevertheless, the former material presented the best methanation performances, thanks to an intermediate ruthenium-ceria interaction, yielding a maximum of 51% of CO2 converted and producing up to 111 μmol g−1 of CH4.

Dawa T., Sajjadi B.

In light of the increasing concern for sustainable growth and development, there is a rising demand for energy-efficient conversion processes. Chemical Looping (CL) technology has emerged as a promising solution that utilizes chemical intermediates, such as metal oxides or other metal derivatives, to decompose complex reactions into multiple sub-reaction steps. This innovative approach enables the separation of the overall reaction into distinct stages, which can be conducted in separate reactors. Consequently, the direct contact between inert substances present in reactant feedstocks and the desired product can be avoided, leading to reduced purification costs. This state-of-the-art literature review provides an updated overview of the potential of perovskite structures in chemical looping technology. Perovskite materials exhibit desirable properties, including excellent oxygen transport capabilities, high chemical stability, and adjustable redox properties, making them ideal candidates for CL applications. By examining recent advancements and research efforts, this review aims to shed light on the current state of perovskite based CL, its challenges, and future prospects. The findings presented here contribute to the understanding of the potential of perovskite structures in enabling energy-efficient and sustainable chemical conversion processes. This review includes two major parts, the first part is dedicated to the structure of the perovskites and the corresponding classifications based on the cell structure, ionic size cation phase, and dimension, while the second part of the work focuses on the applications of those structures in seven different chemical looping technologies, including chemical looping combustion (CLC), chemical looping reforming (CLR), chemical looping gasification (CLG), chemical looping oxygen uncoupling (CLOU), chemical looping air separation (CLAS), chemical looping dehydrogenation (CLDH), and chemical looping epoxidation (CLEPOX).

Yarbaş T., Ayas N.

Evaluation of CO2, which is harmful to the environment, as an alternative energy source in CH4 production was investigated from a thermodynamic point of view. The methanation of CO2 is exothermic, however it does not occur at low temperatures due to the kinetic barrier. Thermodynamic modeling studies were carried out to determine the appropriate parameters in the reaction using the Gaseq software according to the Gibbs free energy minimization approach. For this purpose, the effects of H2/CO2 molar feed ratio (2, 3, 4 and 5), temperature (100–1100 °C) and pressure (1, 3, 5 and 10 atm) on CO2 conversion (XCO2) and CH4 selectivity (SCH4) were investigated. As a result, 99.87% XCO2 and 99.99% SCH4 were reached using the molar ratio of H2/CO2 = 4 at 1 at m and 100 °C. The CO2 methanation modeling study at low pressure range was studied in detail and low operating pressure proved to be appropriate.

Matveyeva A.N., Omarov S.O., Gavrilova M.A.

Yu Y., Bian Z., Wang J., Wang Z., Tan W., Zhong Q., Kawi S.

• Ce-Ni catalyst prepared with modified hydrothermal method by adjusting the proportion of solvents. • The adsorbed CO is a side product. • Formate and methoxy species are important intermediates. • The oxygen vacancies, nickel dispersion are critical to the improvement of catalytic performance. A series of nickel-ceria catalysts were prepared with the hydrothermal method and the composition of solvents was adjusted. The performance of the catalysts on CO 2 methanation varied greatly with the volume ratio of ethylene glycol/water in the hydrothermal process. Among them, the catalyst denoted as CN-70-70EG exhibited the highest catalytic activity with a CO 2 conversion of 67.8 % at 375 °C. Catalysts were characterized by XRD, BET, H 2 -TPR, CO 2 -TPD, XPS, Raman, UV–vis DRS, SEM mapping and in-situ DRIFTS. It was revealed that the catalytic performance was dependent on the nickel dispersion, the number of surface oxygen vacancies and the ability of the catalysts to be activated at low temperatures. In-situ DRIFTS experiments showed that CO 2 was initially adsorbed in the forms of carboxylate, carbonate and bicarbonate on the ceria sites. These adsorbed species reacted with the dissociated H to produce the main intermediate of formate species. The adsorbed CO was only a side product, rather than intermediate species. Furthermore, DRIFTS experiments on hydrogenation of methanol and formic acid demonstrated that these two species could be converted into methane with the presence of the catalysts. In both situations, methoxy species bonded to surface Lewis acid sites were found to be intermediates in this reaction.

Cam T.S., Anh N.P., Duc B.N., Thuy N.T., Lei J., Thanh N.T., Huy N.

AbstractBy using a simple co‐precipitation method, new Fe2O3‐based nanocatalysts (samples) were synthesized. The samples were composites of two or three transition metal oxides, MOx (M=Fe, Mn, Co, Ni, and Cu). The average size of CuO crystallites in the composites composed of two oxide components (CuO−Fe2O3) was about 14.3 nm, while in those composed of three (CuO−MnOx−Fe2O3), the composite's phase compositions were almost in the amorphous form when annealing the sample at 300 °C. The latter sample had a specific surface area higher than that of the former, 207.9 and 142.1 g/m2, respectively, explaining its higher catalytic CO oxidation. The CO conversion over the CuO−MnOx−Fe2O3‐300 catalyst (1 g of catalyst, 2600 ppm of CO concentration in air, and 1.0 L/min of gas flow rate) begins at about 40 °C; the temperature for 50 % CO conversion (t50) is near 82 °C; and CO removal is almost complete at t99 ≈110 °C. The activity of the optimal sample was tested in different catalytic conditions, thereby observing a high durability of 99–100 % CO conversion at 130 °C. The obtained results were derived from XRD, FTIR, BET, SEM, elemental analysis and mapping, as well as catalytic experiments.

Chen L., Filot I.A., Hensen E.J.

Kondrashkova I.S., Martinson K.D., Popkov V.I.

The successful production of nanopowders consisting of Ho-doped zinc ferrite (ZnFe2-xHoxO4, with x values ranging from 0 to 0.08) has been accomplished using the glycine-nitrate combustion (GNC) method, followed by calcination in air. Various analytical techniques, such as EDXS, DTA-TG, SEM, PXRD, Raman spectroscopy, and vibrating sample magnetometry (VSM), were employed to examine the resulting samples. The outcomes of our investigation indicated that an excess of fuel during the GNC process yields X-ray amorphous foamy products, which subsequently crystallize after being held at a temperature of 550 °C for a duration of 4 h. PXRD data analysis showed that the obtained samples consist of single-phase Ho-doped zinc ferrite with a spinel structure. The incorporation of holmium into the ferrite spinel structure was established to occur when the calcination temperature is elevated to 700 °C. Rietveld refinement revealed that the degree of inversion varies from 0.078 to 0.309 as the level of Ho-doping increases from x = 0 to x = 0.08. Furthermore, the incorporation of Ho leads to a more than twofold reduction in the crystallite size of ZnFe2-xHoxO4, decreasing from 61.7 to 27.3 nm. The magnetic properties of the nanopowders are shown to be systematically altered by changes in the degree of inversion and the crystallite size of zinc ferrite, which are interrelated with the holmium content. For instance, the saturation magnetization (Ms) increases by 20% and attains a value of 54.9 kOe at x = 0.08. This finding suggests that the magnetic behavior of ZnFe2–xHoxO4 nanoparticles can be deliberately adjusted, making them a promising candidate for functional materials in the field of magnetic hyperthermia. In summary, this research provides valuable insights into the synthesis, structure, and magnetic properties of Ho-doped zinc ferrite nanopowders, underscoring their potential applications in the realm of magnetic hyperthermia.

Kushchenko A.N., Syrkov A.G., Ngo Q.K.

Saviano L., Brouziotis A.A., Suarez E.G., Siciliano A., Spampinato M., Guida M., Trifuoggi M., Del Bianco D., Carotenuto M., Spica V.R., Lofrano G., Libralato G.

In recent years, sewage treatment plants did not effectively remove emerging water pollutants, leaving potential threats to human health and the environment. Advanced oxidation processes (AOPs) have emerged as a promising technology for the treatment of contaminated wastewater, and the addition of catalysts such as heavy metals has been shown to enhance their effectiveness. This review focuses on the use of rare earth elements (REEs) as catalysts in the AOP process for the degradation of organic pollutants. Cerium and La are the most studied REEs, and their mechanism of action is based on the oxygen vacancies and REE ion concentration in the catalysts. Metal oxide surfaces improve the decomposition of hydrogen peroxide to form hydroxide species, which degrade the organics. The review discusses the targets of AOPs, including pharmaceuticals, dyes, and other molecules such as alkaloids, herbicides, and phenols. The current state-of-the-art advances of REEs-based AOPs, including Fenton-like oxidation and photocatalytic oxidation, are also discussed, with an emphasis on their catalytic performance and mechanism. Additionally, factors affecting water chemistry, such as pH, temperature, dissolved oxygen, inorganic species, and natural organic matter, are analyzed. REEs have great potential for enhancing the removal of dangerous organics from aqueous solutions, and further research is needed to explore the photoFenton-like activity of REEs and their ideal implementation for wastewater treatment.

Matveyeva A., Omarov S., Gavrilova M., Trofimuk A., Wärnå J., Murzin D.

The impact of the fuel/oxidizer ratio, the fuel type and the oxygen excess in the synthesis of ceria supported Ni and Co catalysts on the physicochemical properties and activity in steam and aqueous-phase reforming of glycerol was studied.