Contrasting effects of sulfur dioxide on cupric oxide and chloride during thermochemical formation of chlorinated aromatics.
Sulfur dioxide (SO2) gas has been reported to be an inhibitor of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) formation in fly ash. However, other research has suggested little or no inhibitory effect of SO2 gas. Although these studies focused on reactions between SO2 gas and gas-phase chlorine (Cl) species, no attention was paid to thermochemical gas-solid reactions. In this study, we found contrasting effects of SO2 gas depending on the chemical form of copper (CuO vs CuCl2) with a solid-phase inorganic Cl source (KCl). Chlorinated aromatics (PCDD/Fs, polychlorinated biphenyls, and chlorobenzenes) increased and decreased in model fly ash containing CuO + KCl and CuCl2 + KCl, respectively, with increased SO2 injection. According to in situ Cu K-edge and S K-edge X-ray absorption spectroscopy, Cl gas and CuCl2 were generated and then promoted the formation of highly chlorinated aromatics after thermochemical reactions of SO2 gas with the solid-phase CuO + KCl system. In contrast, the decrease in aromatic-Cls in a CuCl2 + KCl system with SO2 gas was caused mainly by the partial sulfation of the Cu. The chemical form of Cu (especially the oxide/chloride ratio) may be a critical factor in controlling the formation of chlorinated aromatics using SO2 gas.
Department of Global Ecology, Graduate School of Global Environmental Studies and ‡Department of Environmental Engineering, Graduate School of Engineering, Kyoto University , Katsura, Nisikyo-ku, Kyoto 615-8540, Japan.
Takashi
T
Fujimori
Yoshihiro
Y
Nishimoto
Kenji
K
Shiota
Masaki
M
Takaoka
D001572:Benzofurans / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D002722:Chlorobenzenes / Q000737:chemistry; D060729:Coal Ash / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins / Q000737:chemistry; D006843:Hydrocarbons, Chlorinated / Q000032:analysis / Q000737:chemistry*; D017745:Incineration; D008956:Models, Chemical; D011078:Polychlorinated Biphenyls / Q000737:chemistry; D011189:Potassium Chloride / Q000737:chemistry; D013458:Sulfur Dioxide / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
D001572:Benzofurans; D002712:Chlorides; D002722:Chlorobenzenes; D060729:Coal Ash; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins; D006843:Hydrocarbons, Chlorinated; D013458:Sulfur Dioxide; D011189:Potassium Chloride; D003300:Copper; D011078:Polychlorinated Biphenyls; C020887:dibenzo(1,4)dioxin; C029892:cupric chloride; C030973:cupric oxide