Activity of perovskite-type mixed oxides for the low-temperature CO oxidation: Evidence of oxygen species participation from the solid (original) (raw)
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2018
ARTICLE INFO ABSTRACT Article history: Received: 2016-08-05 Accepted: 2017-05-30 In this paper, catalytic oxidation of CO over LaFe1-xCuxO3 (x= 0, 0.2, 0.4, 0.6) perovskite-type oxides was investigated. The catalysts were synthesized by sol-gel method and characterized by XRD, BET, FT-IR, H2-TPR, and SEM methods. The catalytic activity of catalysts was tested in catalytic oxidation of CO. XRD patterns confirmed the synthesized perovskites to be single-phase perovskite-type oxides. The synthesized perovskite catalysts show high activity in the range of reaction temperature (50 300 oC). The substitution of Cu in B-site of the perovskite catalysts enhanced their catalytic activity for CO oxidation. Among different synthesized perovskite catalysts, LaFe0.6Cu0.4O3 has the highest activity: nearly complete elimination of CO was achieved at 275 oC with this catalyst. Kinetic studies for CO oxidation were performed based on power law and Mars-van Krevelen mechanisms. According to kinetic ca...
2016
In this paper, catalytic oxidation of CO over the perovskite-type oxides La1-xAxMn0.6Cu0.4O3 (A = Sr and Ce, x = 0, 0.1, 0.2, 0.3 and 0.4) was investigated. The catalysts were synthesized by sol–gel auto-combustion method and were further characterized by XRD, BET, FTIR, H2-TPR and SEM. XRD patterns revealed that the oxides were single-phase perovskite-type oxides. Traces of Cu2O3, Sr2O3 and Ce2O3 were also detected in perovskites with high contents of Sr and Ce. Specific surface areas of perovskites were also determined to be about 16 and 32 m/g. Reducibility of the perovskites, also, is strongly affected by substitution of La in A site by Sr and Ce. Perovskite catalysts show a high activity in catalytic oxidation of CO; substitution of Sr and Ce further enhanced CO oxidation activity. Highest activity was achieved by La0.7Ce0.3Mn0.6Cu0.4O3: Nearly complete elimination of CO was achieved at 145 C with this catalyst. Kinetic studies for CO oxidation were performed based on Langmuir–...
Catalytic oxidation of CO on La1−xSrxCoO3 perovskite oxides
Reaction Kinetics and Catalysis Letters, 1983
Adsorbed oxygen species have been shown to participate in the catalytic oxidation of CO on La l_xSrxCoO3 oxides. Sr substitution appears to alter the strength of binding of these oxygen species and hence also the kinetics of oxidation.
Catalytic Oxidation of CO Over LaMn1−xBxO3 (B = Cu, Fe) Perovskite-type Oxides
Catalysis Letters, 2016
In this paper, catalytic oxidation of CO over perovskite-type oxides LaMn 1-x B x O 3 (B = Cu, Fe and x = 0, 0.1, 0.3, 0.5) were investigated. The perovskite catalysts were synthesized by sol-gel method and characterized by XRD, BET, H 2-TPR, XPS and SEM. XRD patterns showed that the samples are single-phase perovskite. By introduction of Cu and Fe in the structure, Specific surface area of LaMnO 3 was decreased, but the reducibility and oxygen vacancy were increased. The synthesized perovskite catalysts show high activity for the CO oxidation. Substitution of Mn by Cu and Fe enhanced the catalytic activity. The cu-containing perovskites showed a higher activity in CO oxidation compared with Fe-containing perovskites. The LaMn 0.7 Cu 0.3 O 3 perovskite showed the highest activity among the synthesized perovskites (T50 and T90 % of 110 and 142°C). The excellent activity of LaMn 0.7 B 0.3 O 3 was associated to reducibility at low temperature, more oxygen vacancies and synergistic effect between Cu and Mn. The apparent activation energies were obtained and LaMn 0.7 Cu 0.3 O 3 as the most active catalyst, has the least activation energy compared with other synthesized catalysts.
Catalytic Oxidation of CO over Nanocrystalline La 1–x Ce x NiO 3 Perovskite‐Type Oxides
Chemical Engineering & Technology, 2019
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the final Version of Record (VOR). This work is currently citable by using the Digital Object Identifier (DOI) given below. The final VoR will be published online in Early View as soon as possible and may be different to this Accepted Article as a result of editing. Readers should obtain the final VoR from the journal website shown below when it is published to ensure accuracy of information. The authors are responsible for the content of this Accepted Article.
Oxygen storage capability in Co- and Fe-containing perovskite-type oxides
Solid State Ionics, 2014
In this paper we report on oxygen storage-related properties of selected Co-and Fe-containing perovskite-type oxides, and analyze their advantages and disadvantages in relation to the Mn-based, A-site ordered BaYMn 2 O 5 + δ system. In particular, the crystal structure of reduced and oxidized Ln 0.5 A′ 0.5 Co 0.5 Fe 0.5 O 3 − δ (Ln: La, Sm; A′: Sr, Ba) and La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 − δ is given, results of in situ XRD observation of the oxidation process of the reduced materials is presented, as well as oxygen storage capacity and kinetics measured on oxidation/reduction cycles in isothermal and non-isothermal conditions are reported. Rietveld refinement of the crystal structure carried out for reduced compounds revealed the presence of brownmillerite-type phase for La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 2.42 , La 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 2.53 and Sm 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 2.53. Upon oxidation these materials transform to perovskitetype phase. On the contrary, La 0.5 Ba 0.5 Co 0.5 Fe 0.5 O 3 − δ and A-site cation ordered Sm 0.5 Ba 0.5 Co 0.5 Fe 0.5 O 3 − δ possess the same crystal structure in the reduced and oxidized forms. What's more is that the oxidation process causes a significant decrease of the unit cell volume for each studied compound. Rapid in situ XRD studies (1 min scans), performed every 5°C during oxidation of the materials, allowed to observe ongoing structural changes. TG measurements revealed unusually low onset temperatures of oxidation, with reduced La 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 3 − δ oxidizing at about 40°C. Isothermal oxidation/reduction cycles measured with changing of the atmosphere between air and 5 vol.% H 2 in Ar, performed in 400-600°C allowed to establish oxygen storage-related properties of the studied materials, and it was found that La 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 3 − δ shows enhanced kinetics of the reduction process, while for La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 − δ the measured reversible oxygen storage capacity can exceed 4.2 wt.%, well above that of the BaYMn 2 O 5 + δ system. While these results are very promising, the main drawback arises from a low stability of the considered Co-and Fe-containing oxides, especially in terms of their long-time performance.
2016
Catalytic low-temperature abatement of carbon monoxide becomes essential in environmental pollution control. CO Oxidation, CO Preferential Oxidation (PROX) and Water Gas Shift (WGS) reaction are the conventional technologies used to remove carbon monoxide at low temperature. Perovskite-type oxides have been extensively studied in the last years as catalysts for these reactions due to their high activity and catalytic stability. This chapter describes the state-of-the-art of using perovskite-based catalysts of general formula ABO3 in these reactions. Key factors such as the type and nature of A and B ions or the formation of oxygen vacancies or interstitials by doping are discussed in the light of the reaction mechanism in each case.
Copper Catalysts Supported on Barium Deficient Perovskites for CO Oxidation Reaction
Topics in Catalysis
Mixed oxides with perovskite-type structure (ABO3) present interesting physico-chemical properties to be used as catalyst for atmospheric pollution control. In this work, a series of CuX/Ba0.7MnO3 catalysts (being x: 0, 4, 8 and 12 wt%) has been synthesized, characterized and tested for CO oxidation reaction. All the catalysts were active for CO oxidation in the two reactant mixtures tested: low CO mixture (0.1% CO and 1% O2 in He) and near stoichiometric mixture (1% CO and 1% O2 in He). Copper-free perovskite is the most active catalyst in the less demanding conditions (0.1% CO and 1% O2), as it presents the highest amount of oxygen vacancies working as active sites. However, at higher CO concentrations (1% CO in near stoichiometric mixture), copper-containing catalysts were more active than the perovskite support because, due to the saturation of the oxygen vacancies of perovskites, CuO seems to participate as active site for CO and O2 activation. Cu4/Ba0.7MnO3 and Cu12/Ba0.7MnO3 ...
CO oxidation on LnCoO3 perovskite oxides: Effect of initial total pressure and gas composition
1983
The kinetics of oxidation of CO on LnCoO 3 (Ln-La, Nd, Sm, Gd) were studied in the temperature range 150 -360 °C. These systems show an abrupt gradient change in the Arrhenius plots for CO oxidation at about 200 °C. The adsorption isobars constructed for the total amount of gas mixture adsorbed show either a maximum or a minimum at the same temperature, indicating that the change in the mode of adsorption of the reactants is the cause for the break in the Arrhenius plots. The effect of the initial total pressure and an excess of CO or oxygen on the rate of the reaction was studied and the intrinsic rate constants were calculated.