Synthesis and microstructure of La 1− x Ca x CoO 3 nanoparticles and their catalytic activity for CO oxidation (original) (raw)
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International Journal of Hydrogen Energy, 2017
Perovskite oxides of the type of La x Ca 1-x M y Al 1-y O 3-d (M ¼ Co, Cr, Fe, Mn; x ¼ 0.5; y ¼ 0.7e1.0) were prepared using the polymerization methods and evaluated via N 2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX) spectroscopy, temperature-programmed reduction by hydrogen (TPR-H 2) and temperature-programmed oxidation by oxygen (TPO-O 2). Catalytic behaviour of the perovskite oxides during methane oxidation was studied using a tubular fixed-bed reactor. In a partial oxidation, which proceeded in two steps, there was total oxidation in the first step and CO 2 and H 2 O were formed; in the second step, the total oxidation products oxidized methane by (dry and wet) reforming reactions to yield CO and H 2. Total oxidation and the two reforming reactions proceeded on two types of an active centre formed by transition metal ions, oxygen vacancies and oxide ions. The catalytic system La-Ca-CoAl -O which contained aluminium, decomposed in partial oxidation of methane (POM) into a composite that contained firmly bonded cobalt nanoparticles in the surface of a substrate made up of La 2 O 3 , CaO and Al 2 O 3 which catalysed POM with a high methane conversion and hydrogen selectivity.
Catalysis Today, 2008
La1−xCaxFeO3 (x=0.0, 0.1, 0.2, 0.3, 0.4) perovskites prepared by two different methods, via precursor of citrate and via co-precipitation in basic medium, both calcined at 973K have been investigated as catalysts for acetyl acetate and methane combustion. In the case of the citrate method, atomic absorption spectroscopy (AAS), BET specific area measurements, XRD analysis, Raman, SEM, FTIR, TPR and TPD
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–...
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...
International Journal of Electrochemical Science
Perovskite-type series of La 1-x Ca x CoO 3 compounds were synthesized by a modified amorphous citrate precursor method. Their catalytic activities for hydrogen peroxide electroreduction in 3.0 mol dm-3 KOH at 25 °C were evaluated by cyclic voltammetry and galvanostatic measurement. The influence of x in La 1-x Ca x CoO 3 on their catalytic performance was investigated. Among these compounds, La 0.6 Ca 0.4 CoO 3 calcined at 650 °C exhibited the highest catalytic activity. An aluminum-hydrogen peroxide cell containing 0.4 mol dm-3 H 2 O 2 as oxidant and using La 0.6 Ca 0.4 CoO 3 as cathode catalyst achieved a peak power density of 201 mW cm-2 at 150 mA cm-2 .
La0.9Ba0.1CoO3 perovskite type catalysts for the control of CO and PM emissions
Catalysis Communications, 2010
Perovskite type catalysts with LaCoO 3 and La 0.9 Ba 0.1 CoO 3 compositions have been prepared by sol-gel method and their catalytic activity was studied for CO oxidation in presence of CO 2 , water and also for particulate matter (PM)/carbon oxidation. The catalysts were characterized using XRD, BET-SA, SEM, TPD, XPS and their catalytic activity was evaluated using a steady state gas evaluation assembly, as well as thermo gravimetric analysis. La 0.8 Ba 0.1 CoO 3 catalyst shows enhanced catalytic activity as compared to LaCoO 3 for CO and PM oxidation. Barium substitution appears to be responsible for low temperature activity of the catalyst by influencing redox and oxygen desorption properties as also suggested by TPD studies.
Catalytic and physico-chemical properties of La1−xSrxCoO3 perovskites
Reaction Kinetics & Catalysis Letters, 1994
Catalytic properties of strontium-substituted lanthanum cobaltites Lal_xSrxCOO 3 in the reaction of CO oxidation were compared with the data about chemical composition of the surface and bulk defect structure. It was found that (I) the initial catalytic activity correlates with the cobalt concentration on the surface;
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.