Methane combustion over B-site partially substituted perovskite-type LaFeO3 prepared by sol-gel method

Zhong, Ziyi; Chen, Kaidong; Ji, Yong; Yan, Qijie

doi:10.1016/s0926-860x(97)00003-3

Cited by 105 publications

(38 citation statements)

References 16 publications

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“…Thus, the reduction of iron and the formation of Fe o seem to occur only at temperature above 800 °C, which is when the perovskite structure collapses. Such remarkable thermal stability of iron in the perovskite structure has already been documented in the literature [18][19] . The smaller peaks for TPR spectra of D, E and F samples (Figure 4) in the temperature range 300-600 °C are likely related to the reduction of the molybdenum and manganese species present only in small amount.…”

Section: Characterization Of the Perovskitesmentioning

confidence: 53%

LaMn1-xFe xO3 and LaMn0.1-xFe0.90Mo x O3 perovskites: synthesis, characterization and catalytic activity in H2O2 reactions

et al. 2008

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In this work two perovskites were prepared: LaMn 1-x Fe x O 3 , and LaMn 0.1-x Fe 0.90 Mo x O 3 . XRD and Mössbauer spectroscopy suggest the formation of pure phase perovskite with the incorporation of Fe and Mo in the structure. The catalytic activity of these materials was studied in two reactions with H 2 O 2 : the decomposition to O 2 , and the oxidation of the model organic contaminant methylene blue. The perovskite composition strongly affects the catalytic activity, while Fe decreases the H 2 O 2 decomposition Mo strongly improves dye oxidation.

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Section: Characterization Of the Perovskitesmentioning

confidence: 53%

LaMn1-xFe xO3 and LaMn0.1-xFe0.90Mo x O3 perovskites: synthesis, characterization and catalytic activity in H2O2 reactions

et al. 2008

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“…At temperatures higher 650 °C it is observed the beginning of a H 2 consumption that does not end up to 800 °C. It has been reported previously that LaFeO 3 perovskites are remarkably stable towards reduction [18][19][20] . Therefore, this hydrogen consumption is likely related to the second step reduction of the Fe perovskite leading to the collapse of the perovskite structure with the formation of Fe metal, La 2 O 3 and small amounts of MnO and Mo.…”

Section: Controlled Reduction Of the Prepared Perovskitementioning

confidence: 88%

Controlled reduction of LaFe xMn yMo zO3/Al2O3 composites to produce highly dispersed and stable Fe0 catalysts: a Mössbauer investigation

et al. 2008

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were prepared and characterized by XRD, BET, TPR, SEM and Mössbauer spectroscopy. XRD for unsupported perovskite showed the formation of a single phase perovskite structure. The Mössbauer spectra of the perovskites were fitted with hyperfine field distribution model for the perovskite. Supported perovskites on Al 2 O 3 showed a decrease of the hyperfine field in respect to unsupported perovskite, due to decrease of particle size and dispersion of the Fe 3+ specimens on the support. Also showed broaden lines and relaxation effects due to the small particle size. To produce the Fe 0 catalyst, the composite perovskite(25%)/Al 2 O 3 was reduced with H 2 at 900, 1000 and 1100 °C for 1 hour. XRD (Figure 1). This catalyst has been recently investigated for the synthesis of single wall carbon nanotube showing promising results 14. This preparation method shows several potential advantages: i) should allow a good control of the metallic particle size distribution, ii) should improve the thermal stability to the catalyst due to a strong matrix insulation effect (La 2 O 3 and Al 2 O 3 should keep Fe o particles well separated), iii) the precursor elements and stoichiometry can be adjusted to produce catalysts with different metals and different ratios, iv) the metals present in the precursor, e.g. Fe and Mo, should be homogeneously distributed throughout the oxide and produce welldefined metallic particles, and v) the dispersion of the metal particle can be further controlled by the reduction conditions. ) was used. The perovskites were prepared by the reaction of 0.5 mol of citric acid (CA) dissolved in 2 mol of water at 60 °C, followed by the addition of 1 mmol of La(NO 3 ) 3 .6H 2 O and different proportions of the other metals such as Fe(NO 3 ) 3 .9H 2 O, Mn(NO 3 ) 2 .4H 2 O and Mo(acac) 2 O 2 (acac acethylacetonate) in order to produce the desired stoichiometry. The mixture was stirred for about 2 hours, until a clear orange solution of the stable metal-CA complexes is obtained. After the complete dissolution, 400 mmol of ethylene glycol (EG) followed by the addition of the Al 2 O 3 nanopowder in amounts to obtain composites with 25, 33 and 50 wt (%) of perovskite on alumina. The suspension was continuously stirred while the temperature was slowly increased to 90 °C. This step removes the excess of water and allows the polyesterification reaction between CA and EG to be further activated. The prolonged heating at 90 °C occurs for 7 hours and resulted in a viscous orange mass 15 . This resin was then treated at 400-450 °C in air for 2 hours for the charring. The final product, a dark brown powder was ground and then calcined at 800 °C in air for 6 hours. Experimental ProceduresThe powder XRD data were obtained in a Rigaku model Geigerflex equipment using Co Kα radiation scanning from 10 to 80° (2θ) at a scan rate of 4° min -1. Silicon was used as an external standard.

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“…Substitution at the A-site of an element with a different valence (e.g., the replacement of La 3+ by Sr 2+ ) leads to the formation of oxygen vacancies and highvalence cations at the B-site, which results in a significant change in the catalytic activity [57][58][59][60]. When these sensing materials are exposed to reducing gases like CO, CH 4 , and HCHO, their conductivity decreases, and their resistance increases because of the chemical surface reactions between the reducing gas and the surplus oxygen [61][62][63].…”

Section: Hcho Gas Sensormentioning

confidence: 99%

“…Gas mixtures of HCHO/air with the HCHO concentration varying from 10 ppm to 50 ppm were used. As HCHO gas is a reducing gas, free electrons are released due to the reaction between the surplus oxygen in the sensing materials and the gas [62], as shown in the following equation: …”

Section: Hcho Gas Sensormentioning

confidence: 99%

Gas Sensors for Monitoring Air Pollution

Yoo¹

2011

Monitoring, Control and Effects of Air Pollution

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Methane combustion over B-site partially substituted perovskite-type LaFeO3 prepared by sol-gel method

Cited by 105 publications

References 16 publications

LaMn1-xFe xO3 and LaMn0.1-xFe0.90Mo x O3 perovskites: synthesis, characterization and catalytic activity in H2O2 reactions

LaMn1-xFe xO3 and LaMn0.1-xFe0.90Mo x O3 perovskites: synthesis, characterization and catalytic activity in H2O2 reactions

Controlled reduction of LaFe xMn yMo zO3/Al2O3 composites to produce highly dispersed and stable Fe0 catalysts: a Mössbauer investigation

Gas Sensors for Monitoring Air Pollution

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