Catalytic effects by metal oxides on the formation and degradation of
chlorinated aromatic compounds in fly ash
Öberg, T., Bergbäck, B., Filipsson, M.
Chemosphere 71, 1135-1143 (2008).
Abstract
Polychlorinated benzenes, dibenzo-p-dioxins (PCDD), and dibenzofurans (PCDF) may
be formed below the combustion temperature in fly ash from municipal solid waste
incinerators (MSWI). Copper catalyzes this formation, possibly by the Deacon
reaction. Many other elements are also Deacon catalysts or promoters, and here
we report results from a statistically designed experiment with 15 metal oxides
added to fly ash and heated at 300 ºC for 2 h in an air atmosphere. A
resolution IV fractional factorial design with four replicates was completed in
36 runs with the oxides of magnesium, yttrium, titanium, vanadium, niobium,
chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc,
and tin. All samples were analyzed for chlorinated benzenes and the results were
evaluated by analysis of variance. The addition of copper significantly
increased the amounts of the chlorinated benzenes, while cobalt, chromium and
vanadium decreased the net formation. The oxides of zinc and iron seemed to have
a slightly positive and negative effect respectively. The findings in this study
seem to corroborate our previously reported results regarding the different
catalytic effects of copper and chromium, and lack of a significant effect by
nickel. Besides chromium, it also identifies cobalt and vanadium as potent
catalysts for oxidative degradation of the chlorinated aromatic compounds found
in MSWI fly ash.
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