Kinetics of chlorination and carbochlorination of vanadium pentoxide
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I.
INTRODUCTION
VANADIUM is widely used in the steel, special alloy, magnet, etc., industries. V205is used in ceramics. It is also used as a catalyst, especially for the oxidation of SO2 to SO3 in sulfuric acid production. Various petroleum deposits contain significant amounts of vanadium compounds that are eliminated during the petroleum refining and are concentrated in spent hydrorefining catalysts.tl] Because of increasingly strict environmental regulations, cheap, efficient, and flexible techniques must be investigated for the recovery of metals from industrial wastes as spent catalysts. Chlorination could be one of these techniques.t1] This article summarizes a study of the kinetics of chlorination of V205 with Clz-air, C12-N2, and C12-CO-Nz gas mixtures. It was realized in the framework of a research program focused on the recovery of Co, Ni, Mo, and V compounds from spent hydrorefining catalysts.t2.3.41 Few articles that deal with the chlorination of V205 are published. Timonova et aL t51 have explored the chlorination of g205 by C12. They found that the reaction begins at 590 ~ and leads to the formation of VOC13. Other authors[6,7,s,9] have studied the carbochlorination of V205 using carbon as reducing agent. Saeki et aL t61 found that the presence of carbon reduces the chlorination temperature of V205 with CI2 from 525 ~ to 205 ~ According to them, the chlorination product in the presence of carbon was either VOC13, a mixture of VOCI3 and VCI4, or VC14 alone, depending on the temperature and V205/C molar ratio. VCI 4 was formed upon heating 1.5 mole ratio V205/C to 1000 ~
I. GABALLAH, Senior Researcher, Laboratoire Envirormement et Minefalurgie, and M. DJONA, formerly Graduate Student, Mineral Processing and Environmental Engineering Team, currently Postdoctoral Associate, are with the Institut National Polytechnique de Lorraine, Vandoeuvre, France. E. ALLAIN, formerly Graduate Student, Mineral Processing and Engineering Team, Institut National Polytechnique de Lorraine, Vandoeuvre, France, is currently a Postdoctoral Associate at INASMET, San Sebastian, Spain. Manuscript submitted February 17, 1994. METALLURGICALAND MATERIALSTRANSACTIONSB
According to Terunuma and Rokukawa,t71 the chlorination of V205 with C12 in the presence of carbon starts at 220 ~ In the range of 400 ~ to 800 ~ the reaction product is a mixture of VC14 and VOC13. The VC14 content increases with the increase of the amount of carbon and of the reaction temperature. According to these authors, the chlorination process is divided into two stages. The first stage is the chlorination of V205 to VOCI3, as follows: 1/3 V205 + C12 + [x + (v/2)]C --~ 2/3 VOC13 +xCO+y/2C02 (x+y=
1)
[1]
In the second stage, VOC13 is converted to WC14 according to the following reaction: 2 WOE13 d- C12 q- [x d- (y/2)]C ---) 2 VCI 4 +xCO +y/2CO2 (x+y=
2)
[2]
This second reaction depends on the amount of C added and the reaction temperature. Moreover, the authors state that Reaction [3] is probably included in the second stage: 2 V O C l 3 + C12 + 2 CO ~
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