Study of the Reaction Stages and Kinetics of the Europium Oxide Carbochlorination
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THE rare earths play an important role in many fields of advanced materials for high technology. In this context, it is very important to study methods of extraction for these elements.[1–3] The chlorination and carbochlorination of metallic oxides are very important processes in the industrial production of pure metals. This method is economic and efficient compared with wet extraction processes. It is well known that chlorine possesses a high reactivity toward many compounds at a relatively low temperature.[4–7] Many metallic oxides can be transformed to metals through a process that consists of three stages. In
FEDERICO J. POMIRO, Researcher, is with the Departamento de Fisicoquı´ mica y Control de Calidad, Complejo Tecnolo´gico Pilcaniyeu, Centro Ato´mico Bariloche, Comisio´n Nacional de Energı´ a Ato´mica, Av. Bustillo 9500, 8400 S.C. de Bariloche, Rı´ o Negro, Argentina. Contact e-mail: [email protected] GASTO´N G. FOUGA and JUAN P. GAVIRI´A, Assistant Professors, are with the Departamento de Fisicoquı´ mica y Control de Calidad, Complejo Tecnolo´gico Pilcaniyeu, Centro Ato´mico Bariloche, Comisio´n Nacional de Energı´ a Ato´mica, and also with the Consejo Nacional de Investigaciones Cientı´ ficas y Te´cnicas (CONICET), Argentina, Av. Rivadavia 1917, 1033 Ciudad Auto´noma de Buenos Aires, Buenos Aires, Argentina. ANA E. BOHE´, Professor, is with the Departamento de Fisicoquı´ mica y Control de Calidad, Complejo Tecnolo´gico Pilcaniyeu, Centro Ato´mico Bariloche, Comisio´n Nacional de Energı´ a Ato´mica, also with the Consejo Nacional de Investigaciones Cientı´ ficas y Te´cnicas (CONICET), Argentina, and also with the Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 S.C. de Bariloche, Rı´ o Negro, Argentina. Manuscript submitted April 11, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
the first, the carbochlorination stage, the oxide reacts with chlorine in presence of carbon to produce the metallic chloride. Subsequently, the metal is obtained from the reduction of the chloride. Finally, the metallic sponge is purified by high-temperature vacuum distillation.[8–11] The carbochlorination at 1273 K and 1473 K (1000 C and 1200 C) with Cl2(g) and carbon has been applied industrially for bastnaesite concentrate ((Ce,La,Nd)(CO3)F).[12] Gimenes and Oliveira studied the reaction among xenotime (YPO4), chlorine, and carbon, and a global rate equation was developed.[13] The rare earth chlorides mixtures obtained by carbochlorination of rare earth minerals with Cl2(g) can be separated using chemical-vapor transport (CVT) mediated by the formation of volatile complexes with KCl and AlCl3.[14,15] The carbochlorination of the Y2O3(s),[10,11] Sm2O3(s),[16] and CeO2(s)[17] with carbon as a reductant and chlorine gas as a chlorination agent has been reported by other authors, but the carbochlorination of Eu2O3(s) has not been studied. In a work recently published we have studied the chlorination reaction of europium oxide. The formation of EuOCl(s) like reaction product at t
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