Carbochlorination of yttrium oxide (original) (raw)
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Kinetics of yttrium oxide carbochlorination
Thermochimica Acta, 2011
The chlorination kinetics of the Y 2 O 3-sucrose carbon system was studied by thermogravimetry. This work is a continuation of a previous one in which the reaction stages and the stoichiometry of each reaction have been determined. The influence of carbon content, total flow rate, sample initial mass and chlorine partial pressure was evaluated. The effect of carbon content on the reactive mixture was studied between 6.7 and 70% (carbon mass/total mass). The results showed that the reaction rate of each stage is strongly increased as the carbon content increases and the range of occurrence of the stages depends on the amount of carbon in the solid reactive mixture. The formation reaction of YOCl (STAGE I) is chemically controlled for temperatures lower than 700 • C with average effective activation energies of 165 ± 6 and 152 ± 7 kJ/mol for 8.7 and 16.7%C, respectively. The formation of the YOCl follows a nucleation and growth mechanism, with a combination of continuous nucleation and site saturation, and anisotropic growth controlled by diffusion. The kinetics of STAGE I can be expressed by the following global rate equation that includes the variables analyzed: dd t = k 0 B exp − Ea R g T pCl 2 {n(1 −˛)[− ln(1 −˛)]} (n−1)/n where k 0 B = 1.9 × 10 4 , n = 1.20 for 8.7%C, and k 0 B = 8.4 × 10 3 , n = 1.14 for 16.7%C. STAGES II and III correspond to the YOCl carbochlorination to form YCl 3 , being these stages kinetically different. It was not possible to obtain kinetic parameters for these stages. The reaction rate of STAGE II is affected by diffusion of Cl 2 through the gas film surrounding the sample and mass changes in STAGE III have two opposite components: formation and evaporation of liquid YCl 3 .
The Kinetics of the Chlorination of Yttrium Oxide
Metallurgical and Materials Transactions B, 2009
The chlorination kinetics of Y 2 O 3 with chlorine to produce YOCl was studied by thermogravimetry over a temperature range from 575°C to 975°C. The influence of convective mass transfer into the boundary layer surrounding the sample, gaseous diffusion into the sample pores, partial pressure of chlorine, and temperature on the reaction rate were analyzed in order to determine the rate-controlling step. The thermogravimetric and scanning electron microscopy (SEM) results showed that the process follows a model of nucleation and growth, and the process is chemically controlled for temperatures lower than 800°C, with an activation energy (Ea) of 187 ± 3 kJ/mol. In the 850°C to 975°C range the reaction rate was affected by diffusion of Cl 2 through the gas film surrounding the sample, with apparent Ea of 105 ± 11 kJ/mol. A global rate equation that includes these parameters has been developed R ¼ da=dt ¼ 10 5 kPa À1 Á exp À 187 kJÁmol À1 RÁT ÁpCl 2 Á1:51Á 1 À a ð ÞÁÀln 1 À a ð Þ ½ 0:34
Study of the Reaction Stages and Kinetics of the Europium Oxide Carbochlorination
Metallurgical and Materials Transactions B, 2014
The europium oxide (Eu 2 O 3 (s)) chlorination reaction with sucrose carbon was studied by thermogravimetry between room temperature and 1223 K (950°C). The nonisothermal thermogravimetry showed that the reaction consists of three stages, and their stoichiometries were studied. The product of the first stage was europium oxychloride, and it showed independence of the reaction kinetics with the carbon content. Subsequently, in the second stage, the Eu-OCl(s) was carbochlorinated with formation of EuCl 3 (l) and its evaporation is observed in the third stage. The analysis by Fourier transform infrared spectroscopy of gaseous species showed that the reaction at second stage occurs with the formation of CO 2 (g) and CO(g). Both reactants and products were analyzed by X-ray diffraction, scanning electron microscopy and wavelengthdispersive X-ray fluorescence spectroscopy. The influence of carbon content, total flow rate, sample initial mass, chlorine partial pressure, and temperature were evaluated. The second stage kinetics was analyzed, which showed an anomalous behavior caused by generation of chlorine radicals during interaction of Cl 2 (g) and carbon. It was found that the reaction rate at 933 K (660°C) was proportional to a potential function of the chlorine partial pressure whose exponent is 0.56. The conversion curves were analyzed with the Avrami-Erofeev model and it was obtained an activation energy of 154 ± 5 kJ mol-1 .
MethodsX, 2020
A method of synthesis crystalline yttrium citrate dihydrate was proposed as a result of the transformation of the freshly precipitated basic yttrium carbonate phase in a citric acid solution. The synthesis time was determined on the basis of composition analysis, structure and thermogravimetric studies of samples taken during the synthesis. The research methods used have shown that in the initial stage of the synthesis, the processes of citric acid sorption on basic yttrium carbonate and transformation of amorphous yttrium carbonate hydroxide into crystalline yttrium hydroxide occurs. It is only after 72 h of synthesis that the crystalline yttrium citrate dihydrate is formed. • Synthesis crystalline yttrium citrate dehydrate. • The synthesis time 72 h. • Synthesis components: the freshly precipitated basic yttrium carbonate phase in a citric acid solution.
Ceramics
A study of the morphology and evolution of the microstructure during thermal decomposition of Y2(C2O4)3·10H2O was conducted, and the stages and factors having the greatest impact on particle size and specific surface area were identified. The effect of the yttrium oxalate hexahydrate phases on the course of decomposition was also investigated. The evolution of the morphology and microstructure of decomposition products was explained from the analysis of volume shrinkage at various stages of the reaction. The formation of oxycarbonate is accompanied by the largest shrinkage during the reaction. At this stage, there is a significant increase in the specific surface area to 60–90 m2/g. Conversely, the morphology and microstructure of the particles during the transformation of oxycarbonate into yttrium oxide change insignificantly. Yttrium oxide powders obtained from the monoclinic and triclinic hexahydrate phases have the same specific surface area, but different morphology and bulk de...
Thermal decomposition of yttrium(III) hexanoate in argon
Journal of Analytical and Applied Pyrolysis, 2015
The thermal decomposition of yttrium(III) hexanoate (Y(C 5 H 11 CO 2) 3)•xH 2 O in argon was 12 studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray 13 diffraction at a laboratory Cu-tube source and in-situ experiments at a synchrotron radiation 14 source as well as hot-stage optical microscopy. Dehydration occurs between 40°C and 110°C and 15 is accompanied by a transition from solid to liquid crystalline state. At the onset of the main 16 decomposition stage of the anhydrous Y(C 5 H 11 CO 2) 3 , solidification takes place in the 315°C-17 335°C range. Y(C 5 H 11 CO 2) 3 decomposes in a single step into Y 2 O 2 CO 3 with release of CO 2 and 18 6-undecanone between 280°C and 490°C. A side reaction appears to yield elemental carbon and 19 volatile decane (C 10 H 22). Y 2 O 2 CO 3 is converted to Y 2 O 3 with release of CO 2 between 500°C and 20 975°C.
Synthesis and properties of Y2O3 powder obtained by different methods
Journal of the European Ceramic Society, 1992
Three different wet chemical methods for the preparation of fine yttrium oxide powders from chloride solutions were compared: (a) precipitation with ammonia, (b) precipitation with urea, and (c) precipitation from an Y-organometallic complex. Powders with widely different morphological characteristics resulted. Ammonia precipitated powder was strongly agglomerated. Urea precipitated powder consisted of spherical particles with narrow size distribution (mean size ~ 0"4 I~m), whereas powder obtained from the Y-organometallic complex had a foamy structure' and consisted of soft agglomerates very sensitive to mechanical treatment. Powders were characterized by SEM and TEM techniques, and it was observed that agglomerates consist of randomly oriented crystallites with nearly spherical shape. On compare trois diffkrentes mkthodes de prkparation de poudres .fines d'oxyde d'yttrium, ~ partir de solutions de chlorures, par voie chimique humide: (a) prbcipitation avec de l'ammoniaque, (b) prbcipitation avec de l'urke et (c) prbcipitation ~ partir d'un complexe organo-mktallique d'yttrium. II en rbsulte des poudres posskdant des caractOristiques morphologiques trks diffbrentes. La voie (a) donne une poudre trOs agglomkrke, la voie (b) une poudre formOe de particules sphkriques prksentant une granulombtrie resserrbe (taille moyenne d'environ 0"41tm), tandis que la voie (c) produit une poudre ?~ la structure 'en mousse', formke d'agglombrats mous, trks sensibles h un traitement mkcanique. Les poudres ont ktb caractkriskes par une ktude MEB et MET, montrant que les agglomkrats consistent en des cristallites, de forme pratiquemment sphkrique, orientbes de fa¢on alkatoire. Drei verschiedene naflchemische Verfahren zur Herstellung feinkOrniger Y203-Pulver aus chloridischen Ausgangsl6sungen wurden miteinander verglichen: (a) Fiillung mit Ammoniak, (b) Fiillung mit Harnstoff und (c) Fiillung aus einer Y-organometallischen Verbindung. Die erhaltenen Pulver wiesen iiuJ3erst unterschiedliche Morphologien auf Das mit Ammoniak gefiillte Pulver zeigte einen hohen Agglomerationsgrad. Die mit Harnstoff gejgillten Pulver bestanden aus kugelf6rmigen Teilchen mit einer engen Korngrb'flenverteilung (mittlerer Durch-messer~ 0"41~m). Das Pulver aus der Y-organometallischen Verbindung hatte eine 'schwammige Struktur' und wies weiche, durch mechanische Behandlung leicht zerst6rbare, Agglomerate auf Die Pulver wurden mittels REM und TEM charakterisiert. Dabei zeigte sich, daft die Agglomerate aus nahezu kugelf6rmigen Kristalliten mit statistischer Orientierung bestehen.
Some kinetics aspects of chlorine-solids reactions
Revista de Metalurgia, 2010
The present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl 2 +N 2 (chlorination), Cl 2 +O 2 (oxychlorination), and Cl 2 +CO (carbochlorination). Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III) oxide was possible only above 500°C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc.
Activation Energy of Decomposition of Y2bacuo5 Compound in Wet Co2 at Elevated Temperatures
MRS Proceedings, 1989
Decomposition of the Y2BaCuO5 in C02 was studied using simultaneous thermal analysis (STA) and X-ray diffraction (XRD). The time derivative to the thermo-gravimetric analysis data (DTG) was used to calculate the activation energy. The activation energy of decomposition by CO2 into barium carbonate, copper oxide and yttrium oxide was found to be <