Catalytic effects of magnesium chromite spinel on the decomposition of lanthanum oxalate (original) (raw)
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A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds(TMNOCs) viz. CuO, Fe 2 O 3 , TiO 2 and Cr 2 O 3 of 5 mole% ratio has been carried out employing Thermogravimetry, Differential Thermal Analysis and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe 2 O 3 and TiO 2 mixture up to 696K after which the trend is reversed and Fe 2 O 3 becomes relatively more catalytic than TiO 2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr 2 O 3 may be attributed to an irreversible change in oxidation state of Cr 3+ during which it is oxidised to Cr 6 + prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F 3 mechanism in two different regions of α's and the rate follows the order:
Research Paper, 2016
Nanostructured zinc−copper mixed ferrite was synthesized using sol−gel method. Different compositions of ferrite, Zn (1−x) Cu x Fe 2 O 4 (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety .The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu 2+ −Fe + and/or Cu + −Fe 2+ ion pairs besides the one component sites Cu 2+ −Cu + , Fe 3+ −Fe 2+ , as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.
Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc copper ferrite, Zn (1−) Cu Fe 2 O 4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples. With increasing copper concentration, the crystallite size increases from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy showing porous structure of particles throughout the sample. The prepared samples were also analysed by XRD,FTIR,TEM. Catalytic activity of the prepared samples were studied on lanthanum oxalate decomposition by Thermogravimetric methods(TGA).The rate constant 'k' has got the highest value with x=0.75 and 5 mol% concentration and highest value is attributed to high copper concentration and also due to the fact that, beside the one component sites Cu 2+-Cu + , Fe 3+-Fe 2+ , there will be also the mixed sites Cu 2+-Fe + and/or Cu +-Fe 2+ ion pairs as a result of mutual charge interaction.In other words, the increasing activity of mixed oxides might be attributed to increase in the concentration of active sites via creation of new ion pairs. With increasing Zn content increases particle size thereby providing comparatively less surface area for the catalytic activities due to large ionic radii of Zinc.Variation of catalytic activity of ferrite powders are probably due to the changes of the valence state of catalytically active components of the ferrite powders that oxidises the carbon monoxide released from Lanthanum oxalate
Influence of additives to chromium oxide catalysts for the thermal decomposition of KClO4
Surface Technology, 1984
The effect of doping on the catalytic behaviour of Cr203 was studied using the thermal decomposition of KCIO4 as a test reaction. The doping of the catalysts was effected using 5 mol.% Li ÷, Zr 4÷ or U 6÷ ions and calcination at 600 °C for 5 h. Studies were carried out using thermogravimetric analysis and electrical conductivity measurements. The results showed that Cr203 was more effective in enhancing the decomposition process when it was doped with U 6÷ ions than when it was doped with Li ÷ or Zr 4÷ ions. Mechanisms of doping were discussed and the role of defects in the catalytic reaction was interpreted.
Thermal decomposition of iron(II) oxalate–magnesium oxalate mixtures
Journal of Analytical and Applied Pyrolysis, 2002
The thermal decomposition of iron(II) oxalate-magnesium oxalate mixture (2:1 mole ratio) was investigated using DTA-TG, XRD and Mö ssbauer effect measurements. The decomposition of the anhydrous oxalate mixture proceeds in two steps and kinetic analysis of the two steps were performed under non-isothermal conditions using different integral methods of analysis. Integral composite analysis of data showed that the decomposition reactions are best described by the three-phase boundary, R 3 model. Kinetic analysis of data were also carried out in accordance with the methods of Ozawa and Coats-Redfern and the results are discussed in comparison with the composite analysis of data. Mö ssbauer spectra of samples calcined at different temperatures are discussed and show that in the early stages of the decomposition at about 300°C, part of the Fe(III) oxide is formed in superamagnetic doublet state. As the temperature is increased, supermagnetism disappears. The results of XRD analyses are in accordance with the results of the Mö ssbauer effect and show that magnesium ferrite forms in samples heated at higher temperatures.
Investigation of Metal Oxides as Catalysts for the Thermal Decomposition of Potassium Chlorate(VII)
Central European Journal of Energetic Materials, 2018
The results of studies on the thermal decomposition of potassium chlorate(VII) (PP) and the catalytic effects of copper, iron, nickel, titanium, magnesium, chromium and manganese oxides on the process are presented in this paper. The investigated oxides are ranked according to the magnitude of their catalytic effect; of these, CuO and МnО2 show the best catalytic performance. These oxides reduce the PP decomposition temperature from 919.3 K down to even 825.2 K. The share of the catalytic additive in the composition, required to achieve a desirable thermal decomposition profile, was found to be no more than 0.5 wt.%. The activation energy of the decomposition process was determined, using the modified Freeman and Carroll method for both neat PP and PP supplemented with MnO2; the addition of the catalyst produced a 48.8% decrease in the activation energy of thermal decomposition.
Thermochimica Acta, 2000
The effect of temperature on the oxychlorination of Cr 2 O 3 and MgO using Cl 2 +O 2 was evaluated using non-isothermal conditions. A mathematical treatment of the experimental data was performed. Results were compared with those obtained using isothermal conditions. The oxychlorination of Cr 2 O 3 up to 650 °C was characterized by an apparent activation energy 'E a ' of about 83 kJ/mol. Beyond 650 °C, the reaction proceeded with an E a of about 51 kJ/mol. Between 850 °C and 1025 °C, the reaction of MgO with Cl 2 +O 2 was strongly dependent on temperature and its E a was equal to about 215 kJ/mol. The values of the apparent activation energies, found for the oxychlorination of both oxides using non-isothermal conditions, were comparable to those obtained during isothermal treatment.
Thermal decomposition of hafnyl oxalate and ammonium/magnesium hafnyl oxalate
Thermochimica Acta, 1985
Conditions for the preparation of stoichiometric hafnyl oxalate, HfOC,O,.3.5H,O, ammonium hafnyl oxalate, (NH,),HfO(C,O,), .3H,O and magnesium hafnyl oxalate, MgHfO(C,04),.7H,0 have been standardised. The thermal decomposition of these oxalates has been investigated employing thermogravimetric (TG), differential thermal analysis (DTA), infrared spectral and chemical analysis techniques. The decomposition proceeds through three major steps, viz. the dehydration of the hydrated oxalate, the decomposition of the anhydrous oxalate to the carbonate and, finally, the decomposition of the carbonate to the oxide. Pure hafnium oxide, HfO,, is the end product in the thermal decomposition of simple hafnyl oxalate and ammonium hafnyl oxalate, while for magnesium hafnyl oxalate, MgHfO, is isolated as the final decomposition product.
International Journal of Engineering Research and Technology (IJERT), 2012
https://www.ijert.org/kinetics-and-mechanism-of-oxidation-of-l-histidine-by-permanganate-in-aqueous-alkaline-aquo-organic-and-micellar-media https://www.ijert.org/research/kinetics-and-mechanism-of-oxidation-of-l-histidine-by-permanganate-in-aqueous-alkaline-aquo-organic-and-micellar-media-IJERTV1IS10445.pdf The non-isothermal decomposition study of individual FeC 2 O 4 .2H 2 O shows two steps decomposition with Fe 2 O 3 as final product when heated to 300 °C with two dimensional diffusion and Ginling Braunshtein equation. The CuC 2 O 4 shows two steps decomposition with CuO as end product when heated to 320 °C by Avrami equation. The non-isothermal study of the binary mechanical mixture of FeC 2 O 4 .2H 2 O and CuC 2 O 4 in mole ratio (1:2) by TGA when heated up to 260 °C shows mixture of Fe 2 O 3 and CuO. The α Vs time plots of isothermal study of mixture shows Ginling Braunshtein equation and Mampel unimolecular law. The applicability of Mampel unimolecular law to the kinetic data is up to 0.28 < α < 1.00. The end products were characterized using X-ray diffraction and SEM technique. The kinetic parameters like energy of activation (Ea), pre-exponential factor (A) and Correlation factor (r) were obtained from isothermal TGA and EGA.
Thermal decomposition of cerium oxalate and mixed cerium-gadolinium oxalates
Journal of Thermal Analysis, 1991
Cerium oxalate and mixed cerium-gadolinium oxalates containing 20 and 50 tool% gadolinium were subjected to thermal decomposition. Thermal analysis showed that cerous oxalate is transformed to cerium oxide in two steps. The first step involves the endothermie removal of 10 tool of water, with a calculated activation energy of 78.2 kJ/mol. The second step involves the exothermie decomposition of the anhydrous oxalate, with an activation energy of 112.6 kJ/mol. The water content in the mixed cerium-gadolinium oxalates decreases with increasing gadolinium content, while the temperature of exothermie decomposition of the anhydrous oxalate increases with it.