Kinetics of chlorination and carbochlorination of vanadium pentoxide
- Inst. National Polytechnique de Lorraine, Vandoeuvre (France)
Vanadium is widely used in the steel, special alloy, magnet, etc., industries. V{sub 2}O{sub 5} is used in ceramics. It is also used as a catalyst, especially for the oxidation of SO{sub 2} to SO{sub 3} 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. 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. Kinetics of chlorination of V{sub 2}O{sub 5} with Cl{sub 2}-air, Cl{sub 2}-N{sub 2}, and Cl{sub 2}-CO-N{sub 2} gas mixtures have been studied by nonisothermal and isothermal thermogravimetric measurements. In the temperature range of 500 C to 570 C, the chlorination of V{sub 2}O{sub 5} with Cl{sub 2}-N{sub 2} gas mixture is characterized by an apparent activation energy of about 235 kJ/mole. This could be attributed to chemical reaction. Between 570 C and 650 C, the apparent activation energy is equal to 77 kJ/mole, indicating that the overall reaction rate is controlled by chemical reaction and pore diffusion. The reaction order with respect to chlorine is 0.78. The apparent activation energy of the carbochlorination of V{sub 2}O{sub 5} by Cl{sub 2}-CO-N{sub 2} gas mixture is about 100 kJ/mole in the temperature range of 400 C to 620 C. In this case, the chemical reaction is the limiting step. At temperatures higher than 620 C, an anomaly is observed in the Arrhenius plot, probably due to thermal decomposition of COCl{sub 2} formed in situ and/or transformation of the vanadium oxide physical state. The maximum reaction rate is obtained by using a Cl{sub 2}-CO-N{sub 2} gas mixture having a Cl{sub 2}/CO volume ratio equal to about 1.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 94381
- Journal Information:
- Metallurgical Transactions, B, Journal Name: Metallurgical Transactions, B Journal Issue: 4 Vol. 26; ISSN MTTBCR; ISSN 0360-2141
- Country of Publication:
- United States
- Language:
- English
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