Facile One-Step Flame Synthesis of La1−xSrxMnO3 Nanoparticles for CO Catalytic Oxidation

Zhou, Hao; Wu, Qiwei; Qi, Boyang

doi:https://doi.org/10.1155/2021/9472008

Journal of Chemistry

On this page

Abstract Introduction Results and Discussion Conclusion Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2021 | Article ID 9472008 | https://doi.org/10.1155/2021/9472008

Facile One-Step Flame Synthesis of La_1−xSr_xMnO₃ Nanoparticles for CO Catalytic Oxidation

Hao Zhou,¹Qiwei Wu,¹and Boyang Qi¹

Academic Editor: Gang Feng

Received24 Jul 2021

Accepted03 Sept 2021

Published24 Sept 2021

Abstract

A large amount of CO as hazardous emission in the iron ore sintering process has caused severe harm to the environment and human health. To control the emission of CO more effectively, the preparation of highly efficient catalysts has attracted much attention. In this study, the La_1-xSr_xMnO₃ (0 ≤ x < 1) perovskite catalysts with different Sr²⁺ contents were prepared by the one-step flame synthesis method to treat CO pollutants in the iron and steel industry. The influence of Sr²⁺ doping on the structure and activity of catalytic were characterized and analyzed. La_1-xSr_xMnO₃ perovskite catalysts exhibit good perovskite phases and loose spherical structures. The specific surface areas are between 4.1 and 12.0 m² g⁻¹. Combined with the results of H₂-TPR and O₂-TPD, the improvement of catalytic activity of La_1-xSr_xMnO₃ perovskite can be attributed to the high concentration of active centers and oxygen vacancies. Significantly, the La_0.4Sr_0.6MnO₃ catalyst presented the best reducibility and high content of absorbed active oxygen species, leading to a superior CO oxidation catalytic activity and reaches 50% CO conversion at 134.9°C and 90% at 163.2°C, respectively. The effects of water vapor and CO₂ on the oxidation activity of La_1-xSr_xMnO₃ perovskite was investigated. The flame-produced catalysts exhibit favorable catalytic stability and antisintering ability, achieving 100% CO conversion after fifth consecutive oxidation cycles.

1. Introduction

Carbon monoxide is a typical air pollutant, which is usually produced by the incomplete combustion of carbon-containing materials and hydrocarbons, such as coal, oil, and natural gas [1]. For example, a large amount of CO will also be produced in the start-up of motor vehicles, waste incineration, and industrial production [2]. Generally, in the iron ore sintering process, the CO concentration in the sintering flue gas is between 0.5% and 2% [3]. Meanwhile, the off-gas of industrial production usually contains relatively harmless compounds such as water vapor and carbon dioxide, which will cause some difficulties in removing CO [4]. Thus, it is necessary to explore a suitable method to control the emission of CO.

Among various CO removal methods, catalytic oxidation is considered to be the most effective way to eliminate this poisonous compound from the off-gas [5]. Noble metal catalysts (Ru, Pt, and Au) exhibit high catalytic activity and have been widely researched in CO oxidation. However, they are susceptible to sintering, expensive, and the activity decreases with the increased reaction time [6, 7]. Compared with noble metal catalysts, the perovskite-type catalysts with ABO₃ structure have excellent catalytic activity, high thermal stability, and good structural stability, regarded as a promising candidate catalyst [8]. In addition, the partial substitution of A/B sites can change the cation valence of perovskite to affect the catalytic activity. According to previous research reports, lanthanum-based perovskite, such as La_1−xSr_xMnO₃, has good catalytic activity and is suitable for CO oxidation. Frozandeh-Mehr et al. [9] studied the CO oxidation activity of La_1-xSr_xMnO₃ (0 ≤ x < 0.4). Sr-doping does not affect the single-phase perovskite-type formation and can decrease the CO catalytic oxidation temperature. Teng et al. [10] synthesized the perovskite of La_0.5Sr_0.5MnO₃ by hydrothermal and citrate routes for CO oxidation, in which the complete oxidation temperature of CO was below 220°C. Peng et al. [11] prepared La_1-xSr_xMnO₃ (0 ≤ x ≤ 0.3) with metal foam (MF) as composite catalysts for CO oxidation. They found Sr²⁺ doped could significantly improve the catalyst activity. Hence, Sr-doped perovskite was used for CO oxidation in this work.

Flame synthesis is a fast, economical, and one-step thermal spraying technology. It has attracted much attention due to its rapid preparation with a simplified collection process. The synthesis rate of nanoparticles can reach 30–100 g/h [12]. In the flame synthesis process, the combustible precursor solution with a certain concentration of metal ions compounds was ignited by a high-temperature flame and the products formed in a short time. Then, the nanoparticles are filtered and collected [13, 14]. Nanoparticles prepared by the flame synthesis method have been widely used as functional ceramic powders. Abe and Laine [15] prepared perovskite-type nanoparticles La₂TiO₇ by the flame spray pyrolysis method, and the catalysis had superior photocatalytic activity. And it is very conducive to the preparation of nanoparticle perovskite catalysts with specific morphology and precise chemical composition. Kim et al. [16] synthesized La_0.2Sr_0.8Co_1-xFe_xO_3-δ and Ba_0.5Sr_0.5Co_1-xFe_xO_3-δ nanoparticles perovskites by the flame synthesis, and the results showed that oxygen evolution activity was improved. However, most of the currently reported high-efficiency perovskite catalysts for CO oxidation are synthesized in traditional ways, such as coprecipitation [17], hydrothermal [18], and sol-gel synthesis [19]. And the obtained perovskite catalysts need to be calcined at high temperatures, leading to complex operations and low productivity. Therefore, it is necessary to develop an alternative method for the one-step synthesis of perovskite catalysts for CO oxidation with desired physical and chemical properties.

This study synthesized a series of La_1-xSr_xMnO₃ (0 ≤ x < 1) perovskites catalysts with different Sr²⁺ contents by a one-step flame synthesis method for CO oxidation. The performance evaluation and physicochemical properties of flame-produced nanoparticles were comprehensively analyzed. The effects of Sr-doping on the properties of catalysts were revealed.

2. Experimental Section

2.1. Perovskite Catalysts Preparation

La_1-xSr_xMnO₃ (0 ≤ x < 1) perovskite catalysts were prepared by the flame synthesis method, as shown in Figure 1. For starting, an appropriate proportion of La (NO₃)₃·6H₂O (Macklin, >99.9%), Mn (NO₃)₃·4H₂O (Macklin, >99.9%), and Sr (NO₃)₂ (Macklin, >99.5%) were dissolved in the anhydrous ethanol to obtain a total metal ion concentration of 0.2 mol/L. Meanwhile, the Sr²⁺/La³⁺ molar ratio was controlled as 0, 1/4, 2/3, 3/2, and 4, respectively. Then, the corresponding solution was controlled by a Microflow syringe pump at a constant flow rate of 1.2 mL/min via a central nozzle of the McKenna flame burner. Simultaneously, 0.75 L/min of atomized air was injected as dispersion gas to form a stable precursor spray. The atomized precursor was ignited by the supporting flat flame of the burner (2 L/min, CH₄+20 L/min, air). The precursor spray was heated, oxidized, and sintered due to the energy released during the reaction. Finally, the nanoparticles were collected on the glass fiber filters with the help of negative pressure formed by the vacuum pump.

2.2. Catalyst Characterization

The crystallinity and phase purity of perovskite catalysts are measured by the X-ray diffractometer (XRD). The diffraction patterns were analyzed in a continuous scan mode with a range of 20°–80° and 0.02°per second sampling interval. The morphology of the synthesized powder was studied by field-emission scanning electron microscopy (FE-SEM). And the bulk composition of perovskite samples was determined by the energy-dispersive spectroscopy (EDS) plane scanning method. And the semiquantitative chemical composition characterization was measured with an atomic and mass percentage at three zones for each sample. Nitrogen physisorption isotherms determined the textural properties of the catalysts at −196°C on the Quantachrome AUTOSORB-1C analyzer. The specific surface area (SSA) of the catalyst was calculated by the Brunauer–Emmett–Teller (BET) method. And H₂ temperature-programmed reduction (H₂-TPR) was applied to the samples on an automatic chemisorption machine (BelCata II, Japan). A thermal conductivity detector (TCD) was used to record the signal and calculate the total H₂ consumption. The desorption temperature and intensity of different oxygen species were studied by O₂ temperature-programmed desorption (O₂-TPD). And the desorption amount of O₂ during the TPD process was calculated.

2.3. Catalytic Activity

The catalytic activity of perovskite samples for CO oxidation was conducted in a quartz tube-fixed bed reactor, and the reaction temperature was controlled by a programmed electrical pipe furnace. Figure 2 shows a schematic diagram of the CO catalytic oxidation experiment, and the test conditions are given in Table 1. Prior to the reaction, 1 g of the sample was packed in the quartz tube reactor. The reaction gas (1.0 vol% CO, 10.0 vol% O₂, and balanced with Ar) was introduced with regulation by the mass flow controllers, and the total flow rate was 1.5 L/min. In the mixed gas test, 10.0 vol% CO₂ and 5.0 vol% water vapor were injected into the reactor with the same stream of CO/O₂ balance Ar. The heating stage was performed from room temperature up to 300°C at a rate of 6°C/min. The CO concentration was continuously measured by a flue gas analyzer (Testo 350). Five consecutive catalytic oxidation experiments were carried out to explore the long-term stability of the perovskite catalysts. And the CO conversion was calculated after steady-state by the following equation.where CO_Conv is the CO conversion efficiency, and CO_in and CO_out represent the CO concentration of inlet and outlet.

3. Results and Discussion

3.1. Structural Characterization

Figure 3 shows the XRD patterns of La_1-xSr_xMnO₃ (0 ≤ x < 1) perovskite catalyst. As shown in Figure 3(a), when x = 0, the characteristic peaks at 2θ angles are 19.3°, 32.3°, 40.1°, 47.1°, 53.4°, 57.6°, 67.6°, and 77.5°, and all diffraction peaks are well indexed to that of LaMnO₃ perovskite (PDF-ICDD 75–0440). However, excessive Sr²⁺ doping leads to the appearance of Mn₂O₃ and La₂O₃ phases, which should be attributed to the lattice distortion with Sr²⁺ doping during the synthesis process, and the solubility of cations is limited [20]. The intensity and position of the main diffraction peak of five catalysts do not change significantly and keep in the perovskite phase structure, which is essential for the catalytic reaction [5]. As shown in Figure 3(b), the patterns of the La_0.8Sr_0.2MnO₃ sample have small splitting of the main peak at 32.5°, which indicates the second crystal form of perovskites. And it may be related to the synthesis method and preparation conditions of perovskite [9]. Furthermore, it is observed that the diffraction peaks for x = 0.2–0.8 are shifted toward a higher angle orientation over those substituted catalysts in comparison with LaMnO₃. The partial substitution of La³⁺ by Sr²⁺ will lead to Mn³⁺ (r = 0.58 Å) transfer into smaller Mn⁴⁺ (r = 0.53 Å), resulting in lattice shrinkage [21, 22]. And the gradual shifts toward high-angle orientation could be induced by the decrease in interplanar distance after strontium substitution [23]. A similar phenomenon regarding the diffraction angle shift was previously reported by Li et al. [21]. And the specific surface area (SSA) of La_1−xSr_xMnO₃ is given in Table 2. It is obvious that Sr²⁺ substitution improved the surface area to some extent, and the SSA of La_1−xSr_xMnO₃ is 4.1, 6.2, 8.4, 10.2, and 12.0 m² g⁻¹, corresponding to x = 0, 0.2, 0.4, 0.6, and 0.8, respectively. The maximum specific surface area is found on La_0.2Sr_0.8MnO₃ (12.0 m² g⁻¹). Moreover, the larger specific surface area is considered an effective way to improve the catalytic activity.

(a)

(b)

Figure 4 shows the FE-SEM images of La_1−xSr_xMnO₃ (0 ≤ x < 1). The flame-produced perovskite nanoparticles show loose and porous spherical structures with a diameter of 300–500 nm. As seen from the images, the particle size tends to decrease, and the porosity increases gradually, consistent with the results of the specific surface area. However, some small particles begin to appear on the surface of the catalysts with the addition of Sr²⁺. Combined with XRD results, it could be ascribed to the phase segregation caused by excessive Sr²⁺ during the flame preparation process [9]. The EDS analysis is also performed, and the distribution of different elements in the catalyst is further studied. In the case of La_0.4Sr_0.6MnO₃, as shown in Figure 5, the La, Sr, Mn, and O atoms are homogeneously and finely dispersed in the sample. And the atomic ratios of catalysts are presented in Table 3. The atomic ratio of La and Mn were similar for LaMnO₃, 50.44% and 49.56%, respectively. The theoretical deviation (La + Sr)/Mn in the perovskite samples prepared by the flame synthesis method is in good accordance with the nominal ones.

H₂ temperature-programmed reduction (H₂-TPR) experiments were used to characterize the reduction properties and determine the reaction temperature of the samples. Figure 6 shows that all the samples have similar reduction peaks with two main reduction regions between 150°C and 850°C, which can be divided into a low-temperature region (below 500°C) and a high-temperature region (above 500°C) [22]. With regard to low-temperature regions, the TPR signal begins to appear at 150–200°C, which is related to the reduction of adsorbed oxygen species on the surface [24]. Based on the previous reports, even stoichiometric LaMnO₃ perovskite would exhibit an Mn³⁺/Mn⁴⁺ mixed oxidation state, balanced by excess oxygen in the lattice [5]. Hence, the peak around 300°C can be attributed to removing the nonstoichiometric excess oxygen contained in the perovskite lattice. For Sr-substituted LaMnO₃ catalysts, the reduction peak at 450°C can be attributable to the reduction of Mn⁴⁺ to Mn³⁺. The reaction of the process can be written as equations (2) and (3). Compared with pure LaMnO₃ in Figure 6, the peak signal of Sr²⁺-doped samples increase and move to low temperature. It indicates that the substitution of Sr²⁺ facilitated the oxidation capacity of catalysts in the low-temperature region, which is significant to improving the catalyst’s activity in CO catalytic oxidation.

Another intense reduction peak at the high-temperature region is observed, ascribed to the reduction of Mn³⁺ into Mn²⁺. The reaction of the process is written in the following equation.

The total H₂ consumption of La_1−xSr_xMnO₃ (0 ≤ x < 1) catalysts is calculated by the quantitative analysis and illustrated in Table 4. Noticeably, as the Sr²⁺ substitution increases from 0 to 0.8, the total H₂ consumption of La_1−xSr_xMnO₃ is 1.36 mmol g⁻¹, 1.97 mmol g⁻¹, 2.10 mmol g⁻¹, 2.91 mmol g⁻¹, and 2.85 mmol g⁻¹, respectively. La_0.6Sr_0.4MnO₃ has the highest H₂ consumption among all the catalysts, in which the reduction activity is presumed to be the best.

The profiles of O₂-TPD measurements are shown in Figure 7. Compared with other samples, the O₂ desorption signal of LaMnO₃ is relatively weak. There are three major regions in the TPD profile that begin to appear with the increase of Sr²⁺ doping content and are denoted as O_I, O_II, and O_III.

The O_I region below 350°C is ascribed to the chemisorbed oxygen on the surface of the catalyst [23]. This active oxygen is essential for catalytic activity, which can directly participate in the CO oxidation reaction due to the weak adsorption relationship between chemisorbed oxygen and the perovskite surface. In the O_II region, there is a main peak between 350°C and 550°C. This signal is attributed to the removal of mobile interface oxygen, which can take part in the catalytic oxidation reaction by migrating from the interior of the lattice to the surface. Furthermore, it can be found that the signal intensity of La_0.4Sr_0.6MnO₃ and La_0.2Sr_0.8MnO₃ was strengthened in comparison with LaMnO₃. The TCD signals in the O_III region with a temperature above 550°C are mainly related to the bulk lattice oxygen and could reflect the lattice oxygen mobility [25]. Normally, the desorption capacity is related to the properties of B site metal ions in the perovskite structure [26]. At the low temperature, the oxygen in O_I region was removed, and then, O_II-oxygen was released with the increase of temperature, leading to the reduction of Mn ions and the generation of surface oxygen vacancies. After that, O_III-oxygen diffuses from the bulk to the catalyst surface and desorbs [27]. Moreover, the desorption signal of La_1−xSr_xMnO₃ (0 ≤ x < 1) increases gradually and tends to move to the low-temperature region, suggesting that Sr²⁺ has a positive effect on the surface oxygen capacity and oxygen mobility. According to the quantitative results of O₂-TPD in Table 4, it can be seen that Sr-doped perovskite catalysts exhibited higher desorption amounts of oxygen in three regions than the LaMnO₃ sample, indicating that they have superior oxygen storage capacity and oxygen migration capacity. Furthermore, the La_0.2Sr_0.8MnO₃ sample presents the highest total desorption amount (698 μmol g − 1), beneficially due to the larger specific surface area and the positive role of Sr dopant in oxygen mobility elevation [28].

3.2. Catalytic Activity of Perovskite

The CO catalytic activity of La_1−xSr_xMnO₃ (0 ≤ x < 1) was evaluated, as shown in Figure 8(a). All the catalysts presented good catalytic activity, and the CO conversion presents an obvious S-shape curve during the heating process, which can reach 90% at 170–210°C and then to 100% quickly. And the temperature of full CO conversion is below 250°C. Moreover, La_0.4Sr_0.6MnO₃ exhibits the optimum CO catalytic activity with the lowest T50 and T90 at 134.9°C and 163.2°C, respectively. The results show that the substitution of Sr²⁺ is beneficial to the CO oxidation activity of perovskite catalyst. And the improvement of La_1−xSr_xMnO₃ perovskite catalysts in CO catalytic oxidation can be attributed to the synergistic effect between the larger specific surface area and the high number of active sites of catalysts [11]. Furthermore, combined with the results of H₂-TPR and O₂-TPD, the substitution of Sr²⁺ promoted the decrease of reduction temperature and the improvement of oxygen migration activity. However, the CO catalytic performance of La_0.2Sr_0.8MnO₃ is slightly weaker than that of La_0.4Sr_0.6MnO₃. It may be due to the phase segregation of Mn₂O₃ and La₂O₃ with the excessive Sr²⁺ doping amount, which occupies the effective area of active sites on the catalyst surface. And the destruction of perovskite structure will lead to degradation of CO catalytic performance.

(a)

(b)

In the off-gas of the iron ore sintering industry, water vapor and carbon dioxide usually coexist with CO. They will adsorb on the catalyst surface, resulting in the deactivation of the catalyst. Herein, the effect of water vapor and carbon dioxide on catalytic activity is investigated. Figure 8(b) shows that the performance of five catalysts decreased slightly in the range of 5%–15%, and the pure LaMnO₃ achieves T90 at around 210°C. In comparison, La_0.4Sr_0.6MnO₃ has the highest catalytic activity, and T50 and T90 are 153.1°C and 181.5°C, respectively. Zhang et al. [23] reported Ni partial substitution of LaMnO₃ perovskite under a wet condition and found that the degradation of catalyst performance may be the competitive adsorption of water vapor with O₂. In addition, the O–OH species formed on the surface adsorption competition will limit the access of the reactant molecules to the sample surface, inhibiting the adsorption of CO on the Mn⁴⁺ active site. In order to study the intrinsic activity of La_1-xSr_xMnO₃ catalyst, the ratio of the CO oxidation rate to active oxygen density was measured by isothermal reaction at 120°C. And the TOF value was obtained, as given in Table 5. Compared with pure LaMnO₃ catalyst, Sr-doped materials possessed a higher reaction rate, which suggested that the introduction of Sr ions promotes the adsorption of O₂ and the mass transfer of reactants and products on the perovskite surface [29, 30]. La_0.4Sr_0.6MnO₃ shows the highest TOF value, which is 2.08 × 10⁻³ s⁻¹. However, when x = 0.8, the TOF value of La_0.2Sr_0.8MnO₃ sample decreased, which means that the catalytic activity did not further increase and is consistent with the experimental results of CO catalytic oxidation.

The consecutive oxidation experiments of La_1−xSr_xMnO₃ were carried out to explore the stability of catalytic performance. And the results are given in Tables 6 and 7. After five times consecutive oxidations, all samples can achieve full CO conversion, and the degradation was less than 15%. For comparison, La_0.4Sr_0.6MnO₃ shows superior catalytic activity, which achieved 90% CO conversion at 176.9°C and 194.6°C, respectively. And the decrease of catalytic activity may be due to the consumption of surface chemisorbed oxygen and the reduction of some active sites by CO in the reaction [31]. The XRD patterns of the catalyst after the consecutive oxidation test are shown in Figure 9. Compared with the XRD characterization before and after the reaction, the intensity and position of diffraction peaks do not change significantly after the cyclic test, which demonstrated that the perovskite structure of samples is retained during the consecutive oxidation test. On the other side, the rapid sintering of precursor sprays in high-temperature flame (>1000°C) increased the dispersion and sintering resistance of Mn active components in perovskite catalysts [32]. Ding et al. [28] also reported the preparation of metal oxide-supported single-atom Pt catalysts with high thermal stability by flame spray pyrolysis. Compared with the conventional impregnation method, the flame spray pyrolysis is more conducive to forming the tetragonal-monoclinic phase of ZrO₂, thus improving the sintering resistance at high temperature. Hence, the above results indicate that the flame synthesis method is suitable for preparing perovskite catalysts with superior long-term stability and high CO catalytic activity.

4. Conclusion

In summary, La_1−xSr_xMnO₃ (x = 0, 0.2, 0.4, 0.6, 0.8) perovskite catalyst was successfully prepared by the one-step flame synthesis method for CO catalytic oxidation. The unique synthesis route conducts a fast and efficient production, leading to good perovskite phases and loose spherical structures. The specific surface area increases from 4.1 to 12.0 m² g⁻¹ with Sr²⁺ doping. According to the H₂-TPR and O₂-TPD test results, the Sr²⁺ partial substitution promotes the number of active sites and oxygen vacancies, improving the redox activity. The catalyst has the best catalytic activity when x = 0.6 and achieves 90% CO conversion at 163.2°C. In the continuous catalytic oxidation test, La_0.4Sr_0.6MnO₃ can achieve 90% CO catalytic conversion at 176.9°C in the fifth cycle with adequate catalytic stability. Additionally, the effect of water vapor and carbon dioxide on catalytic activity was investigated. The results illustrated that La_0.4Sr_0.6MnO₃ has the highest catalytic activity in the mixture atmosphere and reaches 50% and 90% CO conversion at 153.1°C and 181.5°C. Moreover, in consecutive oxidation experiments, the rapid sintering of precursor sprays in high-temperature flame enhances the dispersion and sintering resistance of Mn active components, thus exhibiting good antisintering properties and superior CO catalytic oxidation performance. The decrease in catalytic activity may be due to the chemisorbed oxygen consumption and the reduction of active sites on the catalyst surface. In conclusion, the flame synthesis is an efficient and convenient method for preparing perovskite catalysts with high CO oxidation activity.

Data Availability

All data generated or analyzed during this study are included within this article and are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was supported by National Natural Science Foundation of China (52036008).

References

I. Manisalidis, E. Stavropoulou, A. Stavropoulos, and E. Bezirtzoglou, “Environmental and health impacts of air pollution: a review,” Frontiers in Public Health, vol. 8, p. 14, 2020.
View at: Publisher Site | Google Scholar
S. Li, H. Zhu, Z. Qin et al., “Morphologic effects of nano CeO₂-TiO₂ on the performance of Au/CeO₂-TiO₂ catalysts in low-temperature CO oxidation,” Applied Catalysis B: Environmental, vol. 144, pp. 498–506, 2014.
View at: Publisher Site | Google Scholar
Y.-G. Chen, Z.-C. Guo, and G.-S. Feng, “NO x reduction by coupling combustion with recycling flue gas in iron ore sintering process,” International Journal of Minerals, Metallurgy, and Materials, vol. 18, no. 4, pp. 390–396, 2011.
View at: Publisher Site | Google Scholar
R. Hammami, H. Batis, and C. Minot, “Combined experimental and theoretical investigation of the CO₂ adsorption on LaMnO₃ + y perovskite oxide,” Surface Science, vol. 603, no. 20, pp. 3057–3067, 2009.
View at: Publisher Site | Google Scholar
S. Royer and D. Duprez, “Catalytic oxidation of carbon monoxide over transition metal oxides,” ChemCatChem, vol. 3, no. 1, pp. 24–65, 2011.
View at: Publisher Site | Google Scholar
Y. Liu, H. Dai, J. Deng et al., “Mesoporous Co₃O₄-supported gold nanocatalysts: highly active for the oxidation of carbon monoxide, benzene, toluene, and o-xylene,” Journal of Catalysis, vol. 309, pp. 408–418, 2014.
View at: Publisher Site | Google Scholar
K. Ding, A. Gulec, A. M. Johnson et al., “Identification of active sites in CO oxidation and water-gas shift over supported Pt catalysts,” Science, vol. 350, no. 6257, pp. 189–192, 2015.
View at: Publisher Site | Google Scholar
H. Li, K. Yu, C. Wan et al., “Comparison of the nickel addition patterns on the catalytic performances of LaCoO₃ for low-temperature CO oxidation,” Catalysis Today, vol. 281, pp. 534–541, 2017.
View at: Publisher Site | Google Scholar
E. Frozandeh-Mehr, A. Malekzadeh, M. Ghiasi, A. Gholizadeh, Y. Mortazavi, and A. Khodadadi, “Effect of partial substitution of lanthanum by strontium or bismuth on structural features of the lanthanum manganite nanoparticles as a catalyst for carbon monoxide oxidation,” Catalysis Communications, vol. 28, pp. 32–37, 2012.
View at: Publisher Site | Google Scholar
F. Teng, W. Han, S. Liang, B. Gaugeu, R. Zong, and Y. Zhu, “Catalytic behavior of hydrothermally synthesized La_0.5Sr_0.5MnO₃ single-crystal cubes in the oxidation of CO and CH₄,” Journal of Catalysis, vol. 250, no. 1, pp. 1–11, 2007.
View at: Publisher Site | Google Scholar
P.-Y. Peng, Y.-C. Tsai, J.-T. Yeh, Y.-S. Lin, and C.-M. Huang, “Influence of Sr substitution on catalytic performance of LaMnO₃/Ni metal foam composite for CO oxidation,” Aerosol and Air Quality Research, vol. 15, no. 4, pp. 1662–1671, 2015.
View at: Publisher Site | Google Scholar
G. Liu, J. Li, K. Yang et al., “Effects of cerium incorporation on the catalytic oxidation of benzene over flame-made perovskite La_1−xCe_xMnO₃ catalysts,” Particuology, vol. 19, pp. 60–68, 2015.
View at: Publisher Site | Google Scholar
Y. Abe and R. M. Laine, “Photocatalytic La₄Ti₃O₁₂ nanoparticles fabricated by liquid-feed flame spray pyrolysis,” Ceramics International, vol. 46, no. 11, pp. 18656–18660, 2020.
View at: Publisher Site | Google Scholar
H. Zhou and B. Qi, “Investigation of flame spray synthesized La_1-xSr_xCoO₃ perovskites with promotional catalytic performances on CO oxidation,” Journal of the Energy Institute, vol. 93, no. 6, pp. 2381–2387, 2020.
View at: Publisher Site | Google Scholar
Y. Abe and R. M. Laine, “Photocatalytic plate‐like La₂Ti₂O₇ nanoparticles synthesized via liquid‐feed flame spray pyrolysis (LF‐FSP) of metallo‐organic precursors,” Journal of the American Ceramic Society, vol. 103, no. 9, pp. 4832–4839, 2020.
View at: Publisher Site | Google Scholar
B.-J. Kim, E. Fabbri, D. F. Abbott et al., “Functional role of Fe-doping in Co-based perovskite oxide catalysts for oxygen evolution reaction,” Journal of the American Chemical Society, vol. 141, no. 13, pp. 5231–5240, 2019.
View at: Publisher Site | Google Scholar
W. Haron, A. Wisitsoraat, and S. Wongnawa, “Nanostructured perovskite oxides - LaMO₃ (M=Al, Co, Fe) prepared by co-precipitation method and their ethanol-sensing characteristics,” Ceramics International, vol. 43, no. 6, pp. 5032–5040, 2017.
View at: Publisher Site | Google Scholar
G. Xu, H. Bai, X. Huang et al., “Self-assembled 3D flower-like perovskite PbTiO₃ nanostructures and their application in the catalytic oxidation of CO,” Journal of Materials Chemistry, vol. 3, no. 2, pp. 547–554, 2015.
View at: Publisher Site | Google Scholar
S. Wang, X. Xu, J. Zhu, D. Tang, and Z. Zhao, “Effect of preparation method on physicochemical properties and catalytic performances of LaCoO₃ perovskite for CO oxidation,” Journal of Rare Earths, vol. 37, no. 9, pp. 970–977, 2019.
View at: Publisher Site | Google Scholar
J. A. M. Van Roosmalen, P. Van Vlaanderen, E. H. P. Cordfunke, W. L. Ijdo, and D. J. W. Ijdo, “Phases in the perovskite-type LaMnO_3+δ solid solution and the La₂O₃-Mn₂O₃ phase diagram,” Journal of Solid State Chemistry, vol. 114, no. 2, pp. 516–523, 1995.
View at: Publisher Site | Google Scholar
C. Li, T. Li, B. Wang, and H. Yan, “Synthesis of La_1−xSr_xMnO₃ cubic crystals with adjustable doping levels,” Journal of Crystal Growth, vol. 295, no. 2, pp. 137–140, 2006.
View at: Publisher Site | Google Scholar
D. V. Ivanov, L. G. Pinaeva, L. A. Isupova, A. N. Nadeev, I. P. Prosvirin, and L. S. Dovlitova, “Insights into the reactivity of La_1−xSr_xMnO₃ (x = 0 ÷ 0.7) in high temperature N₂O decomposition,” Catalysis Letters, vol. 141, no. 2, pp. 322–331, 2010.
View at: Publisher Site | Google Scholar
C. Zhang, K. Zeng, C. Wang et al., “LaMnO₃ perovskites via a facile nickel substitution strategy for boosting propane combustion performance,” Ceramics International, vol. 46, no. 5, pp. 6652–6662, 2020.
View at: Publisher Site | Google Scholar
X. Wang, K. Huang, J. Qian, Y. Cong, C. Ge, and S. Feng, “Enhanced CO catalytic oxidation by Sr reconstruction on the surface of La x Sr_1−xCoO_3−δ,” Science Bulletin, vol. 62, no. 9, pp. 658–664, 2017.
View at: Publisher Site | Google Scholar
R. Zhang, A. Villanueva, H. Alamdari, and S. Kaliaguine, “Catalytic reduction of NO by propene over LaCo_1-xCu_xO₃ perovskites synthesized by reactive grinding,” Applied Catalysis B: Environmental, vol. 64, no. 3-4, pp. 220–233, 2006.
View at: Publisher Site | Google Scholar
C. Zhang, C. Wang, W. Hua et al., “Relationship between catalytic deactivation and physicochemical properties of LaMnO₃ perovskite catalyst during catalytic oxidation of vinyl chloride,” Applied Catalysis B: Environmental, vol. 186, pp. 173–183, 2016.
View at: Publisher Site | Google Scholar
Q. Gu, L. Wang, Y. Wang, and X. Li, “Effect of praseodymium substitution on La_1-xPr_xMnO₃ (x = 0 − 0.4) perovskites and catalytic activity for NO oxidation,” Journal of Physics and Chemistry of Solids, vol. 133, pp. 52–58, 2019.
View at: Publisher Site | Google Scholar
S. Ding, H.-A. Chen, O. Mekasuwandumrong et al., “High-temperature flame spray pyrolysis induced stabilization of Pt single-atom catalysts,” Applied Catalysis B: Environmental, vol. 281, 2021.
View at: Publisher Site | Google Scholar
F. Fang, N. Feng, P. Zhao et al., “In situ exsolution of Co/CoO_x core-shell nanoparticles on double perovskite porous nanotubular webs: a synergistically active catalyst for soot efficient oxidation,” Chemical Engineering Journal, vol. 372, pp. 752–764, 2019.
View at: Publisher Site | Google Scholar
J. Sun, Z. Zhao, Y. Li et al., “Synthesis and catalytic performance of macroporous La_1-xCe_x CoO₃ perovskite oxide catalysts with high oxygen mobility for catalytic combustion of soot,” Journal of Rare Earths, vol. 38, no. 6, pp. 584–593, 2020.
View at: Publisher Site | Google Scholar
B. Kucharczyk, “Catalytic oxidation of carbon monoxide on Pd-containing LaMnO₃ perovskites,” Catalysis Letters, vol. 145, no. 6, pp. 1237–1245, 2015.
View at: Publisher Site | Google Scholar
X. Yuan, M. Qing, L. Meng, and H. Zhao, “One-step synthesis of nanostructured Cu-Mn/TiO₂ via flame spray pyrolysis: application to catalytic combustion of CO and CH₄,” Energy & Fuels, vol. 34, no. 11, pp. 14447–14457, 2020.
View at: Publisher Site | Google Scholar

Copyright

Copyright © 2021 Hao Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

438

Downloads

683

Citations