Chemical Engineering Use of Catalyzed Sulfite Oxidation Kinetics for the Determination of Mass Transfer Characteristics of Gas-Liquid Contactors

[1] We use observations of the oxygen-17 excess (Δ 17 O) of sulfate in the Arctic to quantify the sulfate source from aqueous SO 2 (S(IV)) oxidation by O 2 catalyzed by transition metals. Due to the lack of photochemically produced OH and H 2 O 2 in high latitudes during winter, combined with high anthropogenic SO 2 emissions in the Northern Hemisphere, oxidation by O 3 is predicted to dominate sulfate formation during winter in this region. However, Δ 17 O measurements of sulfate aerosol collected in Alert, Canada, are not consistent with O 3 as the dominant oxidant and indicate that a S(IV) oxidant with near-zero Δ 17 O values (O 2 ) is important during winter. We use a global chemical transport model to interpret quantitatively the Alert observations and assess the global importance of sulfate production by Fe(III)- and Mn(II)-catalyzed oxidation of S(IV) by O 2 . We scale anthropogenic and natural atmospheric metal concentrations to primary anthropogenic sulfate and dust concentrations, respectively. The solubility and oxidation state of these metals is determined by cloud liquid water content, source, and sunlight. By including metal-catalyzed S(IV) oxidation, the model is consistent with the Δ 17 O magnitudes in the Alert data during winter. Globally, we find that this mechanism contributes 9-17% to sulfate production. The inclusion of metal-catalyzed oxidation does not resolve model discrepancies with surface SO 2 and sulfate observations in Europe. Oxygen isotope measurements of sulfate aerosols collected near anthropogenic and dust sources of metals would help to verify the importance of this sulfur oxidation pathway.

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Transition Metal-Catalyzed Oxidation of Atmospheric Sulfur: Global Implications for the Sulfur Budget

This study examines the effect of a number of additives on the oxidative degradation of monoethanolamine (MEA) in the presence of dissolved Cu. Additives were selected from three categories:  O2 scavengers and reaction inhibitors, chelating agents, and stable salts. Three proprietary inhibitors have been identified that significantly inhibit the rate of degradation at concentrations below 100 mM. Inhibitor A is a stable compound, while Scavengers B and C are stoichiometrically degraded to products that must be removed in an industrial application. Hydroquinone, ascorbic acid, manganese sulfate, and potassium permanganate all increased the rate of oxidative degradation. EDTA (ethylene-diamine-tetraacetic acid) was an effective chelating agent but lost inhibiting capacity over time. Phosphate was a weak chelating agent. Heat stable salts, including potassium chloride, potassium bromide, and potassium formate, were also ineffective oxidation inhibitors. Potassium formate was the strongest of the stable salts...

S. Bengtsson

Papers

Catalytic oxidation of sulphite in diluted aqueous solutions