Next Article in Journal
Oxygen Evolution Reaction of Co-Mn-O Electrocatalyst Prepared by Solution Combustion Synthesis
Next Article in Special Issue
A High-Throughput Screening Approach to Identify New Active and Long-Term Stable Catalysts for Total Oxidation of Methane from Gas-Fueled Lean–Burn Engines
Previous Article in Journal
1,4-NADH Biomimetic Co-Factors with Horse Liver Alcohol Dehydrogenase (HLADH), Utilizing [Cp*Rh(bpy)H](OTf) for Co-factor Regeneration, Do in Fact, Produce Chiral Alcohols from Reactions with Achiral Ketones
Previous Article in Special Issue
The Impact of CeO2 Loading on the Activity and Stability of PdO/γ-AlOOH/γ-Al2O3 Monolith Catalysts for CH4 Oxidation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 9
Issue 6
10.3390/catal9060563
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Microstructural Changes in La0.5Ca0.5Mn0.5Fe0.5O3 Solid Solutions under the Influence of Catalytic Reaction of Methane Combustion

by
Evgeny Yu. Gerasimov
1,2,*,
Vladimir A. Rogov
1,2,
Igor P. Prosvirin
1,
Lyubov A. Isupova
1 and
Sergey V. Tsybulya
1,2
1
Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia
2
Novosibirsk National Research University, 630090 Novosibirsk, Russia
*
Author to whom correspondence should be addressed.
Catalysts 2019, 9(6), 563; https://doi.org/10.3390/catal9060563
Submission received: 29 April 2019 / Revised: 16 June 2019 / Accepted: 20 June 2019 / Published: 24 June 2019
(This article belongs to the Special Issue Catalytic Concepts for Methane Combustion)
Browse Figures
Review Reports Versions Notes

Abstract

:
This article attempts to study changes in the microstructure of solid solutions with the perovskite structure La0.5Ca0.5Mn0.5Fe0.5O3 under the action of the methane oxidation reaction medium. By the methods of XRD, XPS and HRTEM the initial condition of the structure and the surface of the perovskite were both investigated. A feature of the structure of this solid solution is the presence of planar defects in the direction of the planes (101). After the methane oxidation reaction, a similar study of perovskite structure was conducted to obtain the changes. It was shown that under the action of the reaction medium, Ca1−xMnxO particles form on the surface of the perovskite phase, while planar defects in La0.5Ca0.5Mn0.5Fe0.5O3 structure remain. In situ XRD experiments on perovskite calcination in helium current up to 750 °C showed the formation of a similar Ca1−xMnxO phase on the perovskite surface.

Graphical Abstract

1. Introduction

Solid solutions with perovskite structure have been intensively studied in recent decades due to a wide and unique set of their physical and chemical properties [1,2,3,4,5]. Certain properties, such as the effect of colossal magnetic resistance, charge ordering, magnetic calorimetric effect [6,7,8,9] are not a complete list found in the perovskite structure. The effects are caused by quite labile structure of the parent compound with the general formula ABO3. In real crystals, positions A and B can be occupied by different ions, including dissimilar ones, which can lead to the formation of cation-deficient structures [10,11]. For example, materials based on La1−xMxMeO3 (M = Ca, Sr, Ba, Me = Mn, Fe, Co) at high temperatures have mixed ionic and electronic conductivity and can be used in high-temperature electrochemical devices such as gas sensors, oxygen permeable membranes and electrodes of solid-state fuel cells and catalysts of high-temperature oxidizing processes [12,13,14].
Catalytic oxidation of methane has been the subject of numerous publications in recent decades [15]. Perovskites are used as catalysts in the reaction of partial oxidation of methane [16,17,18] and as a deep methane oxidation catalysts [19,20,21]. The main task of which was to obtain chemical compositions with the highest possible activity at the lowest possible temperatures. From the literature data [22,23,24,25] it is known that the most active were supported palladium catalysts, which provided a high degree of CH4 oxidation already at 300–450 °C. However, metal oxide-supported PdO catalysts tend to deactivate below 450 °C, which seriously hinders their long-term application in catalytic combustion. Later it was shown that at higher temperatures (up to 550–650 °C) compounds with perovskite structure (ABO3) including oxides of rare-earth metals and 3D elements can compete with Pd-supported catalysts [26,27]. Such compounds are more preferable due to their higher thermal stability and the high cost of noble metals.
A significant aspect in the creation of functional materials is the choice of the method of synthesis and subsequent modification treatments that can lead to the formation of an optimal structure, from the point of view of catalytic properties [28,29]. An important aspect in solving the problems of creating materials based on the perovskite structure used at high temperatures is the reversible nature of oxygen loss and addition during heating/cooling of these oxides [20,30]. One of the ways to solve this problem is the introduction of doping elements to improve the transport properties of solid solutions with perovskite structure. The introduction of bivalent cations to the perovskite A-sublattice containing, as a rule, trivalent cations contributes to the formation of cation vacancies positively affecting the transport of oxygen in the perovskite structure. Simultaneous introduction of variable valency cations such as Mn, Fe, Co to the B-sublattice of the perovskite phase also improves the transport properties of oxygen from the catalyst volume to the surface [31].
Solid solutions (LaMn1−xFexO3) can also be used as active and stable catalysts for complete oxidation in gas purification processes [32,33], The introduction of Ca2+ cations into the La sublattice increases the mobility of O2− anions in the system [34], which positively affects the catalytic activity of samples in deep oxidation reactions, but reduces their thermal and structural stability in media with a low oxygen content. The introduction of Mn cations into the iron sublattice, on the contrary, can contribute to the stabilization of the perovskite structure at high temperatures, preventing the formation of vacancy-ordered phases.
In this study, we investigated the preparation and characterization of La0.5Ca0.5Mn0.5Fe0.5O3 perovskite catalyst by Pechini method and its application to methane combustion. Additional studies of the effect of the reaction medium on the microstructure of perovskite were carried out using the TEM, XPS and XRD methods.

2. Results and Discussion

2.1. Catalyst Characterization

According to ICP MS data obtained on the device Agilent 7700 (USA), the initial compound has a total composition of La0.52Ca0.48Mn0.50Fe0.50O3−δ, which was close to the given chemical formula. The values obtained are presented in Table 1. Measurement of the specific surface area by thermal desorption of argon showed a surface value of 9.3 m2/g, which is the average value for perovskites synthesized by Pechini method (from polymer–salt compositions) at temperatures of 900 °C [35].
According to XRD pattern (Figure 1) La0.5Ca0.5Mn0.5Fe0.5O3 is a well-crystallized solid solution with a perovskite structure (PDF Number: 70-2665) having orthorhombic modification (space group Pnma), which corresponds to the data obtained in Reference [36] for CaLaMnFeO6 and for La0.6Ca0.4Mn1−xFexO3 [37] structures. Reflexes characteristic to the presence of other phases on the XRD pattern were not found. The unit cell parameters were calculated using Rietveld refinement procedure and gave values: a = 5.429 (6) Å, b = 7.671 (6) Å, c = 5.472 (4) Å. The volume of the unit cell of La0.5Ca0.5Mn0.5Fe0.5O3 was V = 227.9 Å3. The coherent scattering region calculated by the Selyakov–Scherrer formula was 260 Å.
According to HRTEM images, La0.5Ca0.5Mn0.5Fe0.5O3 consists of rounded lamellar particles with an average diameter of about 30 nm (consistent with the coherent scattering region calculated from the XRD data). Particles form agglomerates with sizes from 20 nm to several microns (Figure 2a). A distinctive feature of these particles is the presence of planar defects observed in the form of contrast lines (marked with white arrows), randomly located on the surface of the particles. At higher magnifications, it can be seen that the defects are located in the planes (101). This type of defects in the structure of the perovskite La1−xCaxFeO3 was observed in [38], where the composition of the perovskite included Fe cations in the initial state and in the perovskites La1−xCaxMnO3 after the oxidation reaction of CH4 in the sublattice of manganese cations [34]. It is also worth noting the presence of a layer of amorphized carbon on the surface of perovskite particles, the thickness of such a layer is about 0.5 nm.
Analysis of the review photoelectron spectra of the samples showed that only lanthanum, calcium, manganese, iron, carbon and oxygen are present in the samples (Figure 3). No other additional impurities were found within the sensitivity of the XPS method. Analysis of the photoelectron spectra of the Fe2p level of the measured samples allows us to conclude that in the initial samples iron is mainly in the state of Fe3+; this is evidenced by both the value of the binding energy (E = 710.8 ± 0.1 eV) and the shape of the spectrum line. It is known that in the spectra of Fe2+ there are pronounced shake-up satellites located approximately 6 eV higher in the binding energy from the main lines. In the spectra of Fe3+, shake-up satellites are also observed, which are much weaker in intensity, but shifted to a greater value of the binding energy from the main peak of iron (~8 eV). This situation is observed in the Fe2p spectra of the studied samples. From the analysis of Mn 2p level photoelectron spectra, it can be concluded that there is a superposition of peaks from the two states of manganese. In the initial sample, manganese is mainly in the Mn3+ state, in addition, the small shoulder is observed from the large values of the binding energy 642.3 ± 0.1 eV. This value is typical for Mn4+. The ratio of Mn4+ to Mn3+ is 0.94, which practically corresponds to the degree of doping with calcium cations.

2.2. La0.5Ca0.5Mn0.5Fe0.5O3 Catalytic Activity and Microstructure Modifications in the Methane Combustion Reaction

The data of catalytic activity of the sample are given in Table 2. In the temperature range up to 400 °C, the catalytic activity is not significant. At 400 °C activity is about 25%, with an increase in temperature up to 450 °C and 500 °C, significant increase in conversion up to 93.7% occurs. With an increase in temperature to 600 °C, methane conversion is 100% while only products of complete oxidation (CO2 and H2O) are formed. After reducing the temperature to 500 °C, the conversion slightly reduces, but remains almost at the same level with the previous value.
The study of the solid solution after catalytic tests by XRD (Figure 4) revealed no significant changes in the structure of the sample. There was a slight increase in the volume of the unit cell. It can be seen by slightly shift of spent catalyst XRD pattern to small angle region.
However, the study sample by the method of HRTEM showed the presence of CaO particles on the surface of the perovskite phase. In this case, planar defects in the direction of the planes (101) were preserved (Figure 5a). The number of these defects is small, since no superstructural peaks were found in the initial sample and in the sample after catalytic tests according to XRD data. XRD method has also not recorded the allocation of CaO phase. Measurement of the interplanar spacings of the Ca-containing particles on the surface of the perovskite phases showed smaller values of interplanar spacings (2.68 Å) than in CaO structure (2.77 Å for (111) spacing). It can be concluded that the particles also include the cations of Mn (Figure 5b), i.e., it is a solid solution Ca1−xMnxO having a crystal structure similar to CaO. In [39] the authors conducted similar studies on the calcination of solid solutions La1−xCaxMnO3, the separation of CaO and Mn3O4 phases on the surface of perovskite particles was observed. Apparently, the formation of a solid solution occurs due to the simultaneous presence of Mn, Ca and Fe cations in the perovskite structure. Examples of the formation of such solid solutions are given in Reference [40], however, its formation on the surface of perovskite, according to available literature data, the authors observe for the first time.
It is possible that the appearance of Ca-Mn-O particles on the surface of the perovskite phase is due to the lower oxygen content in the gas phase. Moreover, the reduction of the sample is the cause of the observed slight decrease in catalytic activity during the catalytic tests.
Indeed, according to TPR-H2 (Figure 6) in the sample after catalytic tests, the total hydrogen absorption is significantly reduced (in 5.6 times), mainly due to a decrease in the absorption at low (400 °C and 600 °C) temperatures, which indicates a sufficiently strong reduction of the sample during the test. The amount of hydrogen absorbed by the sample decreases after catalytic tests—from 2.73 × 10−3 to 0.49 × 10−3 mol H2/g. In addition, the profile of the recovery curve also varies significantly, which indicates a change in the structure of the near-surface layers of the catalyst as a result of the reaction. According to the data given in Reference [41], the main peak observed in the temperature range of 400–500 °C refers to the recovery of high-charged Mn4+ and Mn3+ cations to the Mn2+ state, the peaks in the region of 600 °C can be attributed to the recovery of iron +3 to +2 cations. The high-temperature region of 800 °C refers to the recovery of iron cations almost to the metal state [42].

2.3. Formation Process of the Ca-Mn-O Phase on the Surface of the Perovskite in He Atmosphere

For a more detailed study of the catalyst reduction processes, in situ XRD experiments were carried out on heating of the catalyst in the helium current to a temperature of 750 °C, which was slightly higher than the temperature of the methane oxidation reaction. XRD patterns obtained during the study are shown in Figure 7. In the range of 300–600 °C the perovskite structure has not undergone significant changes. XRD patterns demonstrated only peak displacements associated with thermal expansion. However, at a temperature of 750 °С peaks characteristic for the Ca1−xMnxO were observed on XRD pattern. The unit cell volume increased with temperature rising. Cooled to room temperature, the unit cell parameters did not return to the original state (Table 3). This fact can be associated with the formation of vacancies in the structure of perovskite occurred as a result of the allocation of Mn and Ca cations at the La0.5Ca0.5Mn0.5Fe0.5O3 surface.
According to photoelectron spectra of the Ca2p region (Figure 8) of the studied samples after testing in helium flow up to 750 °С, it can be concluded that in the spectra two main peaks with binding energies of 346.2 ± 0.1 and 347.1 ± 0.2 eV are observed. The first value is characteristic of calcium in the composition of perovskite, and the peak with a large binding energy can be attributed to Ca1−xMnxO.
The XPS data confirm the formation of Ca1−xMnxO on the surface of the perovskite phase, the proportion of Ca cations on the surface increases significantly both as a result of the participation of the catalyst in the reaction and after calcination of the sample in the He current (Table 4). At the same time, the amount of Mn cations in the calcined in He flow sample is higher than after reaction, which can indicate the formation of a larger number of the Ca1−xMnxO phase on the surface of La0.5Ca0.5Mn0.5Fe0.5O3.
According to TGA (Figure 9) sample lost about 3.8% of the mass when heated in He up to 1000 °C. In the temperature range from 30° to 300 °C the sample lost 2.1% of the mass, which can be associated with the removal of water, CO, –OH groups and adsorbed oxygen from the surface of the sample. Further heating of the sample up to 300 °C–600 °C led to removing of the weakly bound lattice oxygen, which was 0.9%. At the next stage (600°–800 °C), the sample lost about 0.7% of its mass. A wide exothermic peak accompanied this change in mass on the DTA curve at 700 °C. It corresponds to the data obtained from the experiment in situ XRD and is evidence of the formation of a massive phase Ca1−xMnxO. At higher temperatures, the TGA curve showed a slight decrease in the mass about 0.1%.

3. Materials and Methods

La0.5Ca0.5Mn0.5Fe0.5O3 sample was synthesized by the polymerizable precursor (Pechini) method. For this purpose, appropriate amounts of aqueous solutions of lanthanum, calcium, manganese and iron nitrates were combined, citric acid and ethylene glycol were added, and the mixture was evaporated at 70–80 °С until the formation of a resinous polymer (polymer–salt stock). The polymer was subjected to oxidative destruction. The precursor was calcined at 900 °C for four hours with a rise in temperature of 100 °C/h.
The catalytic activity of the samples in a reaction of methane oxidation was determined in a flow system at temperatures of 350–600 °C. A 1-g portion of a catalyst fraction of 0.25–0.5 mm was mixed with 1 cm3 of quartz and placed in a U-shaped quartz reactor with an inside diameter of 4.5 mm. The feed rate of a reaction mixture of 0.9% CH4 + 9% O2 (and the balance N2) was 2.4 L/h. Before the measurements, the sample was kept in the reaction mixture for ~30 min at a specified temperature. After testing at 600 °C, the sample was cooled in the reaction mixture to 500 °C and its activity was determined once again. Only carbon dioxide and water were the oxidation products of methane. The reaction products were determined by chromatography.
Electron microscopy investigation (HRTEM) was performed using a JEM-2200FS (JEOL Ltd., Tokyo, Japan) electron microscope operated at 200 kV with a lattice resolution 0.1 nm for obtaining HRTEM images.
XRD patterns were obtained on the Bruker AXS D8 Advance diffractometer (Karlsruhe, Germany) equipped with a high-temperature and supplying of various gas mixtures and the use of CuKα radiation on scanning with a step of 2θ = 0.05° point by point and an accumulation time of 3 s at each point in a range of the angles 2θ = 15°–80°. Each temperature measurement was performed according to the following conditions: temperature rate of 5 °C/min with He flow of 40 mL/min. Before the measurements, the sample was kept for ~30–50 min at a specified temperature. XRD patterns were processed using X’Pert High Plus software (PANanalytical B.V. Almelo, Netherlands).
XPS (X-Ray Photoelectron Spectroscopy) data were obtained on the SPECS photoelectron spectrometer (Berlin, Germany) using non-monochromatized MgK* radiation (h* = 1253.6 eV, 150 W). The binding energy scale was pre-calibrated to the position of the core level peaks Au 4f7/2 (84.0 eV) and Cu2p3/2 (932.67 eV). The sample was applied to a double-sided conductive adhesive tape. The effect of recharging, arising in the process of electron photoemission, was taken into account by the method of internal standard, as used C1s carbon line (284.8 eV), which is part of hydrocarbon inclusions [43]. Determination of the relative content of elements on the surface of catalysts and the ratio of atomic concentrations was carried out by the integrated intensities of photoelectron lines corrected for the corresponding atomic sensitivity coefficients: C1s—1.0, Ca2p—5.13, O1s—2.85, Mn2p3/2—8.99, Fe2p—16.0, La3d5/2—26.5.
The TPR study of samples with hydrogen were performed in a flow system with a thermal-conductivity detector (LHM-8, LHM, Yoshkar-Ola, USSR) using a fraction of samples with a particle size of 0.25–0.5 mm. Before the reduction, the samples were pretreated in argon at 150 °C for 0.5 h and cooled to room temperature. The samples weight were 75 mg; the flow rate of the reducing mixture (10% H2 in Ar) was 40 mL/min. The samples were heated at a rate of 10 °C/min to 900 °C. The hydrogen uptake (in mol·g−1·s−1) was calculated from calibration obtained for the reduction of standardized sample of copper oxide (CuO). The peak areas of the TPR of samples corresponding to hydrogen consumption (mmoL/(g sample)) were calculated with the use of an asymmetric Gaussian function profile.
Thermal analysis of the sample was performed using a synchronous thermal analysis device STA 449C Jupiter company NETZSCH (Germany). This device combines the methods of differential thermal analysis (DTA) and thermogravimetry analysis (TGA) in one dimension. The weight of the sample was approximately 100 mg. The furnace temperature was increased from 40 °C to 980 °C at a rate of 10 °C/min with He flux of 30 mL/min. The sample weight was monitored continuously as a function of temperature.

4. Conclusions

The solid solution La0.5Ca0.5Mn0.5Fe0.5O3 with orthorhombic perovskite structure was synthesized by the method of polymer–salt compositions. A distinctive feature of this solid solution is the presence of planar defects in the particles in the direction of the crystallographic planes (101).
The catalytic activity study of perovskite in the methane oxidation reaction in the temperature range of 300–600 °C showed that already at 400 °C 25% of methane conversion was achieved, and at a temperature of 550 °C was almost 100%, while only products of complete oxidation (CO2 and H2O) were formed. The study by HRTEM showed the formation of Ca1−xMnxO particles with sizes of about 10 nm on the surface of perovskite after reaction. According to XRD data, the formation of these particles after methane oxidation reaction was not detected, which indicated a small amount of oxide.
According to the XRD and TG data, Ca1−xMnxO phase formation on the perovskite surface occurs at a temperature of 700 °C in helium flow. The impact of the environment with low oxygen content leads to an increase in the proportion of calcium cations on the surface of the solid solution. The formation of Ca1−xMnxO is not typical for perovskites La1−xCaxMnO3, and occurs due to the simultaneous presence of Fe and Mn cations in one perovskite sublattice.

Author Contributions

E.Y.G., L.A.I. and S.V.T. planned and designed the experiments. I.P.P. performed the catalyst characterization by X.P.S. E.Y.G. performed the characterization by T.E.M. and X.R.D. V.A.R. performed TPR-H2 tests. L.A.I. performed the catalytic activity tests. E.Y.G. wrote the manuscript. L.A.I. and S.V.T. revised the manuscript. All authors discussed the results and approved the final version of the manuscript.

Funding

This work was supported by the Russian Science Foundation, grant № 18-73-00139.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Zhu, J.; Li, H.; Zhong, L.; Xiao, P.; Xu, X.; Yang, X.; Zhao, Z.; Li, J. Perovskite oxides: Preparation, characterizations, and applications in heterogeneous catalysis. ACS Catal. 2014, 4, 2917–2940. [Google Scholar] [CrossRef]
  2. Najjar, H.; Batis, H. Development of Mn-based perovskite materials: Chemical structure and applications. Catal. Rev. 2016, 58, 371–438. [Google Scholar] [CrossRef]
  3. Keav, S.; Matam, S.; Ferri, D.; Weidenkaff, A.; Keav, S.; Matam, S.K.; Ferri, D.; Weidenkaff, A. Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review. Catalysts 2014, 4, 226–255. [Google Scholar] [CrossRef]
  4. Niu, G.; Guo, X.; Wang, L. Review of recent progress in chemical stability of perovskite solar cells. J. Mater. Chem. A 2015, 3, 8970–8980. [Google Scholar] [CrossRef]
  5. Wu, H.; Li, L.; Liang, L.-Z.; Liang, S.; Zhu, Y.-Y.; Zhu, X.-H. Recent progress on the structural characterizations of domain structures in ferroic and multiferroic perovskite oxides: A review. J. Eur. Ceram. Soc. 2015, 35, 411–441. [Google Scholar] [CrossRef]
  6. Dong, Q.Y.; Zhang, H.W.; Sun, J.R.; Shen, B.G.; Franco, V. A phenomenological fitting curve for the magnetocaloric effect of materials with a second-order phase transition. J. Appl. Phys. 2008, 103, 116101. [Google Scholar] [CrossRef]
  7. Izyumov, Y.A.; Skryabin, Y.N. Double exchange model and the unique properties of the manganites. Uspekhi Fiz. Nauk 2001, 171, 121. [Google Scholar]
  8. Haghiri-Gosnet, A.-M.; Renard, J.-P. CMR manganites: Physics, thin films and devices. J. Phys. D Appl. Phys. 2003, 36, R127–R150. [Google Scholar] [CrossRef]
  9. Granger, P.; Parvulescu, V.I.; Kaliaguine, S.; Prellier, W. Perovskites and Related Mixed Oxides: Concepts and Applications; John Wiley & Sons: Hoboken, NJ, USA, 2015; ISBN 9783527686605. [Google Scholar]
  10. Takacs, M.; Hoes, M.; Caduff, M.; Cooper, T.; Scheffe, J.R.; Steinfeld, A. Oxygen nonstoichiometry, defect equilibria, and thermodynamic characterization of LaMnO3 perovskites with Ca/Sr A-site and Al B-site doping. Acta Mater. 2016, 103, 700–710. [Google Scholar]
  11. Elsiddig, Z.A.; Xu, H.; Wang, D.; Zhang, W.; Guo, X.; Zhang, Y.; Sun, Z.; Chen, J. Modulating Mn 4+ Ions and Oxygen Vacancies in Nonstoichiometric LaMnO 3 Perovskite by a Facile Sol-Gel Method as High-Performance Supercapacitor Electrodes. Electrochim. Acta 2017, 253, 422–429. [Google Scholar]
  12. Malkhandi, S.; Yang, B.; Manohar, A.K.; Manivannan, A.; Prakash, G.K.S.; Narayanan, S.R. Electrocatalytic Properties of Nanocrystalline Calcium-Doped Lanthanum Cobalt Oxide for Bifunctional Oxygen Electrodes. J. Phys. Chem. Lett. 2012, 3, 967–972. [Google Scholar] [CrossRef] [PubMed]
  13. Kucharczyk, B.; Okal, J.; Tylus, W.; Winiarski, J.; Szczygieł, B. The effect of the calcination temperature of LaFeO3 precursors on the properties and catalytic activity of perovskite in methane oxidation. Ceram. Int. 2019, 45, 2779–2788. [Google Scholar] [CrossRef]
  14. Mueller, D.N.; Machala, M.L.; Bluhm, H.; Chueh, W.C. Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions. Nat. Commun. 2015, 6, 6097. [Google Scholar] [CrossRef] [PubMed]
  15. Wang, W.; Yuan, F.; Niu, X.; Zhu, Y. Preparation of Pd supported on La(Sr)-Mn-O Perovskite by microwave Irradiation Method and Its Catalytic Performances for the Methane Combustion. Sci. Rep. 2016, 6, 19511. [Google Scholar] [CrossRef] [PubMed]
  16. De Santana Santos, M.; Neto, R.C.R.; Noronha, F.B.; Bargiela, P.; da Rocha, M.D.G.C.; Resini, C.; Brandão, S.T. Perovskite as catalyst precursors in the partial oxidation of methane: The effect of cobalt, nickel and pretreatment. Catal. Today 2018, 299, 229–241. [Google Scholar]
  17. Roseno, K.T.C.; Brackmann, R.; da Silva, M.A.; Schmal, M. Investigation of LaCoO3, LaFeO3 and LaCo0.5Fe0.5O3 perovskites as catalyst precursors for syngas production by partial oxidation of methane. Int. J. Hydrogen Energy 2016, 41, 18178–18192. [Google Scholar] [CrossRef]
  18. De, K.T.; Schmal, M.; Brackmann, R.; Alves, R.M.B.; Giudici, R. Partial oxidation of methane on neodymium and lanthanium chromate based perovskites for hydrogen production. Int. J. Hydrogen Energy 2019, 44, 8166–8177. [Google Scholar]
  19. Alifanti, M.; Auer, R.; Kirchnerova, J.; Thyrion, F.; Grange, P.; Delmon, B. Activity in methane combustion and sensitivity to sulfur poisoning of La1−xCexMn1−yCoyO3 perovskite oxides. Appl. Catal. B Environ. 2003, 41, 71–81. [Google Scholar] [CrossRef]
  20. Marchetti, L.; Forni, L. Catalytic combustion of methane over perovskites. Appl. Catal. B Environ. 1998, 15, 179–187. [Google Scholar] [CrossRef]
  21. Szabo, V.; Bassir, M.; Van Neste, A.; Kaliaguine, S. Perovskite-type oxides synthesized by reactive grinding: Part IV. Catalytic properties of LaCo1−xFexO3 in methane oxidation. Appl. Catal. B Environ. 2003, 43, 81–92. [Google Scholar]
  22. Banerjee, A.; McGuire, J.; Lawnick, O.; Bozack, M. Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst. Catalysts 2018, 8, 266. [Google Scholar] [CrossRef]
  23. Schwartz, W.R.; Pfefferle, L.D. Combustion of Methane over Palladium-Based Catalysts: Support Interactions. J. Phys. Chem. C 2012, 116, 8571–8578. [Google Scholar] [CrossRef]
  24. Bassil, J.; AlBarazi, A.; Boutros, M. Catalytic combustion of methane over mesoporous silica supported palladium. Catal. Today 2011, 176, 36–40. [Google Scholar] [CrossRef]
  25. Choudhary, T.; Banerjee, S.; Choudhary, V. Catalysts for combustion of methane and lower alkanes. Appl. Catal. A Gen. 2002, 234, 1–23. [Google Scholar] [CrossRef]
  26. Yang, J.; Guo, Y. Nanostructured perovskite oxides as promising substitutes of noble metals catalysts for catalytic combustion of methane. Chin. Chem. Lett. 2018, 29, 252–260. [Google Scholar] [CrossRef]
  27. Royer, S.; Duprez, D.; Can, F.; Courtois, X.; Batiot-Dupeyrat, C.; Laassiri, S.; Alamdari, H. Perovskites as Substitutes of Noble Metals for Heterogeneous Catalysis: Dream or Reality. Chem. Rev. 2014, 114, 10292–10368. [Google Scholar] [CrossRef] [PubMed]
  28. Melo Jorge, M.; Correia dos Santos, A.; Nunes, M. Effects of synthesis method on stoichiometry, structure and electrical conductivity of CaMnO3−δ. Int. J. Inorg. Mater. 2001, 3, 915–921. [Google Scholar] [CrossRef]
  29. Tan, L.; Gu, X.; Yang, L.; Jin, W.; Zhang, L.; Xu, N. Influence of powder synthesis methods on microstructure and oxygen permeation performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ perovskite-type membranes. J. Membr. Sci. 2003, 212, 157–165. [Google Scholar] [CrossRef]
  30. Leontiou, A.; Ladavos, A.; Bakas, T.; Vaimakis, T.; Pomonis, P. Reverse uptake of oxygen from La1−xSrx (Fe3+/Fe4+)O3±δ perovskite-type mixed oxides (x = 0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, 0.90). Appl. Catal. A Gen. 2003, 241, 143–154. [Google Scholar] [CrossRef]
  31. Ponce, S.; Peña, M.; Fierro, J.L. Surface properties and catalytic performance in methane combustion of Sr-substituted lanthanum manganites. Appl. Catal. B Environ. 2000, 24, 193–205. [Google Scholar] [CrossRef]
  32. Zhao, K.; He, F.; Huang, Z.; Wei, G.; Zheng, A.; Li, H.; Zhao, Z. Perovskite-type LaFe1−x MnxO3 (x=0, 0.3, 0.5, 0.7, 1.0) oxygen carriers for chemical-looping steam methane reforming: Oxidation activity and resistance to carbon formation. Korean J. Chem. Eng. 2017, 34, 1651–1660. [Google Scholar] [CrossRef]
  33. Zheng, S.; Hua, Q.; Gu, W.; Liu, B. Catalytic oxidation of CO on LaMn1−xFexO3 perovskites solid solution. J. Mol. Catal. A Chem. 2014, 391, 7–11. [Google Scholar] [CrossRef]
  34. Isupova, L.A.; Gerasimov, E.Y.; Zaikovskii, V.I.; Tsybulya, S.V.; Kulikovskaya, N.A.; Saputina, N.F. Synthesis of homogeneous La1–xCaxMnO3 solid solutions by the Pechini method and their activity in methane oxidation. Kinet. Catal. 2009, 50, 886–891. [Google Scholar] [CrossRef]
  35. Isupova, L.A.; Kulikovskaya, N.A.; Saputina, N.F.; Gerasimov, E.Y.; Tsybulya, S.V. La1-xCaxFeO3-δ (x = 0-1) perovskites prepared by the Pechini method: Catalytic activity in deep methane and CO oxidation. Kinet. Catal. 2015, 56, 781–787. [Google Scholar] [CrossRef]
  36. Shaheen, R.; Bashir, J.; Rundlöf, H.; Rennie, A.R. The crystal structure of CaLaMnFeO6 double perovskite. Mater. Lett. 2005, 59, 2296–2299. [Google Scholar] [CrossRef]
  37. Othmani, S.; Balli, M.; Cheikhrouhou, A. Structural, magnetic and magnetocaloric properties of La0.6Ca0.4Mn1−xFexO3 (x=0, 0.05, 0.1, 0.15 and 0.2) manganites. Solid State Commun. 2014, 192, 51–55. [Google Scholar] [CrossRef]
  38. Gerasimov, E.Y.; Isupova, L.A.; Tsybulya, S.V. Microstructural features of the La1−xCaxFeO3−δ solid solutions prepared via Pechini route. Mater. Res. Bull. 2015, 70, 291–295. [Google Scholar] [CrossRef]
  39. Isupova, L.A.; Gerasimov, E.Y.; Zaikovskii, V.I.; Tsybulya, S.V. Effect of the reaction medium on the structure of the La1−xCaxMnO3 (x = 0–1) solid solutions prepared by the pechini method. Kinet. Catal. 2011, 52, 104–110. [Google Scholar] [CrossRef]
  40. Jay, A.H.; Andrews, K.W. Note on oxide systems pertaining to steel - making furnace slags: FeO-MnO, FeO-MgO, CaO-MnO, MgO-MnO. J. Iron Steel Inst. 1946, 152, 15–18. [Google Scholar]
  41. Yakovleva, I.S.; Isupova, L.A.; Rogov, V.A.; Sadykov, V.A. Forms of oxygen in La1−xCaxMnO3 + δ (x = 0–1) perovskites and their reactivities in oxidation reactions. Kinet. Catal. 2008, 49, 261–270. [Google Scholar] [CrossRef]
  42. Isupova, L.A.; Yakovleva, I.S.; Rogov, V.A.; Alikina, G.M.; Sadykov, V.A. Oxygen States in Oxides with a Perovskite Structure and Their Catalytic Activity in Complete Oxidation Reactions: System La1 – xCaxFeO3 – y (x = 0–1). Kinet. Catal. 2004, 45, 446–453. [Google Scholar] [CrossRef]
  43. Moulder, J.F.; Stickle, W.F.; Sobol, P.E.; Bomben, K.D. Handbook of X-ray Photoelectron Spectroscopy; Chastain, J., Ed.; Perkin-Elmer: Eden Prairie, MN, USA, 1992. [Google Scholar]
Catalysts 09 00563 g001 550
Figure 1. XRD pattern of the fresh La0.5Ca0.5Mn0.5Fe0.5O3 with orthorhombic indexes.
Figure 1. XRD pattern of the fresh La0.5Ca0.5Mn0.5Fe0.5O3 with orthorhombic indexes.
Catalysts 09 00563 g001
Catalysts 09 00563 g002 550
Figure 2. HRTEM images of perovskite particles with planar defects (a) and crystal lattice of perovskite containing defects in the direction of the planes (101) (b).
Figure 2. HRTEM images of perovskite particles with planar defects (a) and crystal lattice of perovskite containing defects in the direction of the planes (101) (b).
Catalysts 09 00563 g002
Catalysts 09 00563 g003 550
Figure 3. XPS spectra of the fresh sample La0.5Ca0.5Mn0.5Fe0.5O3 with line deconvolution.
Figure 3. XPS spectra of the fresh sample La0.5Ca0.5Mn0.5Fe0.5O3 with line deconvolution.
Catalysts 09 00563 g003
Catalysts 09 00563 g004 550
Figure 4. XRD patterns of the fresh (black line) and spent (red line) La0.5Ca0.5Mn0.5Fe0.5O3.
Figure 4. XRD patterns of the fresh (black line) and spent (red line) La0.5Ca0.5Mn0.5Fe0.5O3.
Catalysts 09 00563 g004
Catalysts 09 00563 g005 550
Figure 5. HRTEM images of perovskite particle after participation in methane oxidation reaction with planar defects (a) and Ca1−xMnxO aggregates on the perovskite surface (b).
Figure 5. HRTEM images of perovskite particle after participation in methane oxidation reaction with planar defects (a) and Ca1−xMnxO aggregates on the perovskite surface (b).
Catalysts 09 00563 g005
Catalysts 09 00563 g006 550
Figure 6. TPR-H2 profiles of the La0.5Ca0.5Mn0.5Fe0.5O3 before (green line) and after (blue line) methane combustion reaction.
Figure 6. TPR-H2 profiles of the La0.5Ca0.5Mn0.5Fe0.5O3 before (green line) and after (blue line) methane combustion reaction.
Catalysts 09 00563 g006
Catalysts 09 00563 g007 550
Figure 7. In situ XRD patterns of La0.5Ca0.5Mn0.5Fe0.5O3 in He flow heating. Magenta line is cooling to room temperature.
Figure 7. In situ XRD patterns of La0.5Ca0.5Mn0.5Fe0.5O3 in He flow heating. Magenta line is cooling to room temperature.
Catalysts 09 00563 g007
Catalysts 09 00563 g008 550
Figure 8. Ca2p level spectra of the studied samples.
Figure 8. Ca2p level spectra of the studied samples.
Catalysts 09 00563 g008
Catalysts 09 00563 g009 550
Figure 9. Thermoanalytical data obtained in the heating of La0.5Ca0.5Mn0.5Fe0.5O3 in He flow.
Figure 9. Thermoanalytical data obtained in the heating of La0.5Ca0.5Mn0.5Fe0.5O3 in He flow.
Catalysts 09 00563 g009
Table
Table 1. ICP MS data La0.5Ca0.5Mn0.5Fe0.5O3.
Table 1. ICP MS data La0.5Ca0.5Mn0.5Fe0.5O3.
Sample Name/Mass %LaCaMnFe
La0.5Ca0.5Mn0.5Fe0.5O332.88.713.814.2
Table
Table 2. La0.5Ca0.5Mn0.5Fe0.5O3 dependence of methane conversion on temperature of reaction medium.
Table 2. La0.5Ca0.5Mn0.5Fe0.5O3 dependence of methane conversion on temperature of reaction medium.
Temperature, °CСН4 Conversion, %
40025.46
45060.71
50093.72
55099.52
600100
50090.02
Table
Table 3. Unit cell parameters for the La0.5Ca0.5Mn0.5Fe0.5O3 in He flow heating.
Table 3. Unit cell parameters for the La0.5Ca0.5Mn0.5Fe0.5O3 in He flow heating.
Temperature, °Ca, Åb, Åc, ÅV, Å3
305.437.675.47227.92
3005.467.715.47230.51
6005.537.835.54239.66
7505.577.875.57244.18
cooling5.537.815.54238.72
Table
Table 4. The ratio of atomic concentrations of the elements presented in the studied samples.
Table 4. The ratio of atomic concentrations of the elements presented in the studied samples.
SamplesMn/FeFe/LaMn/LaMn/CaFe/CaLa/Ca
Initial1.150.690.800.360.310.45
He treatment1.160.610.700.210.180.30
After reaction0.970.760.730.260.270.35

Share and Cite

MDPI and ACS Style

Gerasimov, E.Y.; Rogov, V.A.; Prosvirin, I.P.; Isupova, L.A.; Tsybulya, S.V. Microstructural Changes in La0.5Ca0.5Mn0.5Fe0.5O3 Solid Solutions under the Influence of Catalytic Reaction of Methane Combustion. Catalysts 2019, 9, 563. https://doi.org/10.3390/catal9060563

AMA Style

Gerasimov EY, Rogov VA, Prosvirin IP, Isupova LA, Tsybulya SV. Microstructural Changes in La0.5Ca0.5Mn0.5Fe0.5O3 Solid Solutions under the Influence of Catalytic Reaction of Methane Combustion. Catalysts. 2019; 9(6):563. https://doi.org/10.3390/catal9060563

Chicago/Turabian Style

Gerasimov, Evgeny Yu., Vladimir A. Rogov, Igor P. Prosvirin, Lyubov A. Isupova, and Sergey V. Tsybulya. 2019. "Microstructural Changes in La0.5Ca0.5Mn0.5Fe0.5O3 Solid Solutions under the Influence of Catalytic Reaction of Methane Combustion" Catalysts 9, no. 6: 563. https://doi.org/10.3390/catal9060563

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop