Catalytic hydrodechlorination of chlorohydrocarbons in a medium of sodium hydroxide solutions, Part 2: Transformations of hexachloroethane and other polychloroethanes

In part one of this work, it was shown that in addition to sodium formate, hexachloroethane (HCE) and perchloroethylene are the main products of the catalytic hydrodechlorination of CCl₄ in a medium of sodium hydroxide solutions. These products undergo mutual transformations under the conditions of the process. Since the industrial requirements for perchloroethylene considerably exceed those for HCE, the regularities of the catalytic hydrodechlorination of HCE, pentachloroethane, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, and 1,2-dichloroethane are studied in part two, using 1.5 wt % Pd on sibunit as the catalyst. It is found the fraction of hydrogen substited for chlorine grows and the reactivity of the products diminishes with a reduction in the number of chlorine atoms in a polychloroethane molecule. Ethane and ethylene are the final reaction products after a rather long contact time. The kinetics of HCE catalytic hydrodechlorination is studied n the temperature range of 353–393 K and at hydrogen partial pressures of 50–810 kPa. It is shown that the only reaction product is perchloroethylene; i.e., the transformation of HCE proceeds via the elimination of two chlorine atoms, while the limiting stage of the process is product dissolution in the aqueous-alkaline reaction mass. The form of the kinetic equation is found to be w = 2.1 × 10^?6 × exp?(16200 ± 400)/RT]C _HCE C _cat $P_{H_2 }^{0.5} $ mol/(L s). The possibility of using the catalytic hydrodechlorination of chlorohydrocarbons in a medium of sodium hydroxide solutions for the recycling of chloroorganic wastes containing CCl₄ and polychloroethanes is demonstrated.