Catalytic Oxidation of Sulfur Dioxide on Carbon Suspended in Sulfuric Acid

Abstract

In the activated-carbon processes for flue gas desulfurization, SO₂ is catalytically oxidized to 1-12SO₄ on activated carbon. In the previous paper, it was proposed that this reaction consists of an anodic oxidation of SO₂ and -a cathodic reduction of 02. Such electrochemical mechanism was confirmed in the case of the reaction on Pt in H₂SO₄ solution. In this paper, it was intended to make clear this reaction on carbon from the electrochemical point of view. Carbon powder was suspended in the electrolyte (1 N H₂SO₄) in which SO₂ and/or 02 were dissolved and the current-potential curves were determined by using Pt gauze as a collector electrode, while the rate of catalytic oxidation of SO₂ was measured by an analytical method. Anodic and cathodic polarization curves were obtained reproducibly, which corresponded to electroche- mical oxidation of SO₂ and reduction of 02 on suspended carbon particles, respectively (Fig.2). Reciprocal slope (di/dE), of micropolarization curve around rest potential in the presence of dissolved SO₂ and 02 was proportional to the amount of suspended carbon and the stirring rate. The rate of catalytic reaction of SO₂ and 02 dissolved in FI2SO₄ solution was proportional to (di/dE), for various carbons (Fig.11). This fact was interpreted by the quantitative consideration of charge which transfered between the carbon particles and collector electrode on collision. It was found that carbon which exhibited high- activity to cathodic reduction of 02 was also active to catalytic oxidation of SO₂.