Dechlorination of polychlorobiphenyls using NaBH4 and NaBH4/LiCl at 120-310°C in glyme solvents

High temperature PCB dechlorination (Aroclor 1016) occurred using NaBH4 alone in tetraglyme at 290-310 degreesC within 2 h in a sealed tube. Aroclor 1016 dechlorination was also quantitatively achieved using NaBH4/LiCl/glyme solvents (di-, tri-, or tetraglyme) at 125-135 degreesC. The best results were obtained by prestirring NaBH4, LiCl and the glyme solvent at room temperature before heating at 125-135 degreesC. At equivalent conditions, PCB dechlorination rates were found to depend on solvent in the order: tetraglyme, triglyme > diglyme. At 130 degreesC, Aroclor 1016 can be dechlorinated in NaBH4/LiCl/tetraglyme in 4 h. 2-Chlorobiphenyl and 2,2'-dichlorobiphenyl were the least reactive congeners in dechlorinations with NaBH4/LiCl in diglyme. Competitive dechlorinations with NaBH4/LiCl in diglyme showed 3-chloro- and 4-chlorobiphenyl reacted faster than 2-chlorobiphenyl at 130 degreesC. The reactions were clean with no solvent decomposition in the range of 120- 162 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.