The sodium hydride based reducing agents were prepared the method of Caubere (Angew. Chem. Int. Ed. Engl., 1983, 22, 599-613). Reagents were prepared containing nickel, iron and zinc metals. All were effective in dechlorinating 1,3-dichlorobenzene, 4-methoxy-chlorobenzene, and arochlor 1254. Most work focused on nickel based reagents, the most active. The nickel-based reducing agent used in THF at 65°C reduced to 200 ppm 1,3-dichlorobenzene (to benzene) and arochlor 1254 (to biphenyl) to below 0.2 ppm in less than 15 minutes. A two stage reduction reduced arochlor 1254 to below a detectable level as determined by gas chromatography using f.i.d. detector. Using 1,3-dichlorobenzene as a model showed that the first halogen is reduced more rapidly. Accordingly, 4-methoxy-chlorobenzne was reduced to methoxybenzene less efficiently--but polychlorinated ethers are expected to react rapidly. The presence of water reduced the activity of the Ni catalyst--i.e.--reduced the rate of dechlorination. Two staged reductions of 1,3-dichlorobenzene using iron and zinc based catalysts at 65°, 1 hr per stage, gave more than 99% reduction. Use of the Ni based reagent as catalyst with hydrogen at 2 atm as reducing agent converted 1,3-dichlorobenzene to benzene; rate data have yet to be taken. The overall results provide a base for some additional pilot studies using the iron and zinc based reagents with the aim of increasing the reagent activity. The results are expected to give clearer directions for a planned comprehensive study.
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The work upon which this report is based was supported in part by funds provided by the United States Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1984. Public Law 98-146.
Taylor, K. Grant, "Reductive Dechlorination of Toxic Chlorocarbons" (1985). KWRRI Research Reports. 43.