Hydrolytic removal of the chlorinated products from the oxidative free-radical-induced degradation of chloroethylenes: acid chlorides and chlorinatedacetic acids

Progressive hydrolytic decomposition of acyl chlorides, among them the chlo rinated acetyl chlorides, which are produced in the gas-phase oxidation of chlorinated ethylenes, permits the complete mineralization of organically b ound chlorine to chloride anion. Hydrolysis rate constants (100% water) hav e been determined for the following acyl chlorides: acetyl (350 s(-1)); chl oroacetyl (5.5 s(-1)), dichloroacetyl (300 s(-1)), trichloroacetyl (>350 s( -1)), and oxalyl dichloride (>350 s(-1)). The chlorinated acetyl chlorides thereby give rise to the chloroacetates whose decomposition has also been s tudied and the kinetic parameters determined. Mono- and dichloroacetate ani on undergo hydrolytic dechlorination (k(obs) = k(o) + k(OH-) x [OH-]; ClCH2 C(O)O-: A(o) 6.4 x 10(15) s(-1), E-o 148 kJ mol(-1), A(OH-) 1.6 x 10(9) dm( 3) mol(-1) s(-1), EOH- 86 kJ mol(-1). Cl2CHC(O)O-: A(o) 3.2 x 10(16) s(-1), E-o 156 kJ mol(-1), A(OH-) 3.2 x 10(10) dm(3) mol(-1) s(-1), EOH- kJ mol(- 1)). Trichloroacetate anion decomposes by another mechanism, undergoing dec arboxylation which is base-uncatalyzed: A(o) 2.1 x 10(17) s(-1), E-o 146 kJ mol(-1). Procedures on a pilot-plant scale are pointed out that allow the elimination of these compounds upon oxidation of the strip-gas produced whe n contaminated water is freed from chlorinated ethylenes by air-stripping.