Kinetic and Thermodynamic Studies on the Non-Isothermal Decomposition of Lanthanum Oxalate Hydrate, Catalysed By Transition Metal Nano Oxides (original) (raw)
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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
Catalytic effects of magnesium chromite spinel on the decomposition of lanthanum oxalate
A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr 2 O 4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr 2 O 3 towards the decomposition below 440 8C, above which it increases signi®cantly with increasing percentage of MgCr 2 O 4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D 3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I > stage II < stage III and LO1 > LO2 > LO3 (653±713 K), LO1 < LO2 < LO3 (713±753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr 2 O 4 with lanthanum oxalate.
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.
2009
Nanocrystalline transition metal oxides (NTMOs) have been successfully prepared by three different methods: novel quick precipitation method (Cr 2 O 3 and Fe 2 O 3 ); surfactant mediated method (CuO), and reduction of metal complexes with hydrazine as reducing agent (Mn 2 O 3 ). The nano particles have been characterized by X-ray diffraction (XRD) which shows an average particle diameter of 35 -54 nm. Their catalytic activity was measured in the thermal decomposition of ammonium perchlorate (AP). AP decomposition undergoes a two step process where the addition of metal oxide nanocrystals led to a shifting of the high temperature decomposition peak toward lower temperature. The kinetics of the thermal decomposition of AP and catalyzed AP has also been evaluated using model fitting and isoconversional method.
THERMAL DECOMPOSITION OF CURIUM(III) OXALATE 10HYDRATE
Journal of Inorganic and Nuclear Chemistry, 1968
Previous studies on the thermal decomposition of the lanthanide oxalates have used relatively large samples. For a study of the thermal decomposition of curium oxalate we have sought to evolve a method utilizing less than one mg of material. By continuously analyzing the gaseous reaction products with a mass spectrometer, a study of the thermal decomposition of curium oxalate has been made with -100/zg of sample.
Preparation, Characterization and Catalytic Activity of Transition Metal Oxide Nanocrystals
Journal of Scientific …, 2009
Nanocrystals of four transition metal oxides (TMOs) were prepared by a novel quick precipitation method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). From the XRD patterns, average particle sizes for CuO, NiO, Co 2 O 3 , MnO 2 are calculated to be 15 nm, 4 nm, 13 nm, 40 nm, respectively. The TEM study revealed that the majority of CuO particles are of 6-8 nm in size. Catalytic activities of the TMO nanocrystals for thermal decomposition of ammonium perchlorate (AP) were investigated using differential thermal analysis (DTA), thermogravimetric analysis (TGA) and ignition delay measurements. The order of catalytic activity of these oxide nanocrystals on thermal decomposition of AP was found to be: Co 2 O 3 > CuO > NiO > MnO 2 .
Journal of Thermal Analysis and Calorimetry, 2015
The kinetic and activation energies of thermal decomposition of KNO 3 as an oxidizer in pyrotechnic compositions were studied in the presence of Fe 2 O 3 , Mn 2 O 3 , and TiO 2 nanoparticles as catalysts, using thermogravimetric analysis under argon atmosphere at different heating rates (10, 15, and 20 K min-1). The prepared nanoparticles were characterized by XRD patterns, SEM images, and BET surface area analysis. For verification of data, the activation energies for thermal decomposition of KNO 3 were calculated using non-isothermal isoconversional methods of KAS, OFW, and Friedman for different conversion fraction (a) values in the range 0.1-0.9. The activation energies were 201.6-208.2, 170.0-177.9, 173.9-181.6, and 213.0-223.8 kJ mol-1 , respectively, in the absence and presence of 5 mol% of Fe 2 O 3 , Mn 2 O 3 , and TiO 2. The results indicated that while Fe 2 O 3 and Mn 2 O 3 nanoparticles have catalytic effects, TiO 2 nanoparticles show inhibitory effect on the thermal decomposition of KNO 3 .