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Author Petrushina, I. M. ♦ Bjerrum, N. J. ♦ Cappeln, F.
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ENVIRONMENTAL SCIENCES ♦ CHEMISTRY ♦ SULFUR DIOXIDE ♦ OXIDATION ♦ VANADIUM OXIDES ♦ POTASSIUM SULFATES ♦ CESIUM SULFATES ♦ SODIUM SULFATES ♦ MOLTEN SALTS ♦ PROMOTERS ♦ REDOX REACTIONS ♦ WASTE PRODUCT UTILIZATION ♦ SULFURIC ACID ♦ AIR POLLUTION CONTROL
Abstract The electrochemical behavior of the molten V{sub 2}O{sub 5}-M{sub 2}S{sub 2}O{sub 7} (M = K, Cs, or Na) system was studied using a gold working electrode at 440 C in argon and air atmosphere. The aim of the present investigation was to find a possible correlation between the promoting effect of Cs{sup +} and Na{sup +} ions on the catalytic oxidation of SO{sub 2} in the V{sub 2}O{sub 5}-M{sub 2}S{sub 2}O{sub 7} system and the effect of these alkali cations on the electrochemical behavior of V{sub 2}O{sub 5} in the alkali pyrosulfate melts. It has been shown that Na{sup +} ions had a promoting effect on the V(V) {r_reversible} V(IV) electrochemical reaction. Sodium ions accelerate both the V(V) reduction and the V(IV) oxidation, the effect being more pronounced in the case of the V(IV) oxidation. Sodium ions also had a significant (almost 0.2 V) depolarization effect on the V(IV) {r_arrow} V(V) oxidation. The peak current of the V(IV) {r_arrow} V(V) oxidation waves vs. Na{sub 2}S{sub 2}O{sub 7} concentration plots had maximums at ca. 8.5 mol % of Na{sub 2}S{sub 2}O{sub 7} in air atmosphere for all the studied potential scan rates. In the Cs{sub 2}S{sub 2}O{sub 7}-K{sub 2}S{sub 2}O{sub 7} (1:1) melt the V(IV) {r_arrow} V(V) oxidation was affected by Cs{sup +} ions with a depolarization effect of 0.2 V and an even more significant acceleration than the molten V{sub 2}OO{sub 5}-Na{sub 2}S{sub 2}O{sub 7}-K{sub 2}S{sub 2}O{sub 7} system. The V(IV) {r_arrow} V(V) oxidation peak currents were approximately 1.5 times higher than in the V{sub 2}O{sub 5}-K{sub 2}S{sub 2}O{sub 7} system at all studied potential scan rates. No correlation has been found between the described effects and the electric conductivity of the systems. The rate-determining stage in the catalytic SO{sub 2} oxidation most likely is the oxidation of V(IV) to V(V) and the Na{sup +} and Cs{sup +} promoting effect is based on the acceleration of this stage. It has also been proposed that voltammetric measurements can be used for fast optimization of the composition of the vanadium catalyst (which is approximately V{sub 2}O{sub 5}-M{sub 2}S{sub 2}O{sub 7}) for sulfuric acid production.
ISSN 00134651
Educational Use Research
Learning Resource Type Article
Publisher Date 1998-11-01
Publisher Place United States
Journal Journal of the Electrochemical Society
Volume Number 145
Issue Number 11


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