Decomposition of Chlorinated Hydrocarbons
on Iron-Group Metals

I. V. Mishakov*, V. V. Chesnokov**, R. A. Buyanov**, and N. A. Pakhomov**

* Novosibirsk State University, Novosibirsk, 630090 Russia

** Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090 Russia

Received January 21, 2000

Abstract—The decomposition of 1,2-dichloroethane and chlorobenzene on nickel–alumina, cobalt–alumina,
and iron–alumina catalysts at 400–600°C was studied. Thermodynamic calculations demonstrated that the sus-
ceptibility of metals to chlorination under exposure to HCl increases in the order Ni < Co < Fe. The addition of
hydrogen to the reaction mixture was found to dramatically decrease the rate of carbon deposition in the decom-
position of 1,2-dichloroethane because of the intense hydrogenation of intermediates that are graphite precur-
sors. Two fundamentally different reaction paths were found in the degradation of 1,2-dichloroethane: decom-
position via a carbide-cycle mechanism with the formation of carbon as the main product (under conditions of
a deficiency of hydrogen) and 1,2-dichloroethane hydrodechlorination accompanied by methanation of the
formed carbon (under conditions of an excess of hydrogen). The degradation of chlorobenzene diluted with
hydrogen in a molar ratio of 1 : 50 was not accompanied by carbon formation on the catalyst. A comparison
between the selectivity for reaction products on nickel–alumina and cobalt–alumina catalysts indicated that the
former catalyst is more active in the rupture of C–C bonds and in the methanation reaction of deposited carbon,
whereas the latter is more favorable for hydrodechlorination. The optimum conditions and thermal regime for
efficient and stable operation of the catalysts were found.

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