ctivated carbon has been known as an effective catalyst for SO, oxidation for many years (Hartman and Coughlin, 1972). Haure A et al. (1989) found that the productivity of some activated carbons at room temperature was comparable with commercial catalysts such as V,O, or platinum for the oxidation of SO, . Since the Hartman and Coughlin work, there have been several laboratory studies of scrubbing SO, from stack gas and converting this waste t o sulfuric acid.Indeed, several commercial processes have been proposed. Early work was done using activated carbon in the form of pellets in trickle-bed reactors washed with water as a flushing agent. Two problems arise: pressure drops in packed beds are too large for the process to be attractive industrially, and washing with water results in a dilute acid that is impossible to market. Our research team at University of Waterloo has explored using periodic flushing of the TBR to increase SO, removal and productivity per unit weight of carbon (Metzinger et al., 1994; Haure et al., 1989; Lee et al., 1995). A concentrated acid could not be made, however. Vladea et al. (1 997) found that using activated carbon coated onto a structured packing employing a hydrophobic binder provides high SO, removal and high carbon productivity with just a small pressure drop. This work continues these studies.Our principal objective was thus to examine the use of moderately polar organic solvents such as the ketones as the scrubbing or flushing agent in a carbon packed TBR in place of water. Most solvents exhibit much lower hydrogen bonding in the liquid phase than water and so may be evaporated from a solution at a relatively low energy input. If sufficient water is present along with SO, and 0 , in the gas phase to form sulfuric acid on the activated carbon surface, evaporation of the solvent would release a concentrated acid product. A key consideration is the solubility of sulfuric acid in polar organic solvents. In recent work, we have discovered that sulfuric acid as well as SO, and 0 , are soluble in the ketone solvents (Won et al., 2000).Ketones were chosen as the polar organic solvents for our study. The lowest molecular weight ketone, acetone, exhibits relatively high solubility for oxygen and SO, at room temperature. The solubility of oxygen in acetone at 20°C is almost tenfold greater than in water. SO, is sixfold more soluble in acetone than in water. Since the trickle bed in this study is operated near room 'Author to whom correspondence may be addressed: E-mail address: rhudgins@ cape Experiments were carried out on the performance of several ketone solvents for the scrubbing of dilute SO, from a gas stream and its conversion to sulfuric acid in a trickle-bed reactor packed with activated carbon. Using a bench-scale trickle bed packed with a structured packing based on Sulzer static mixers coated with CentaurTM activated carbon and a Teflon binder, measurements of SO, removal, conversion to acid and catalyst productivity showed that all were considerably greater than levels a...

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