Hydrolytic removal of the chlorinated products from the oxidative free-radical-induced degradation of chloroethylenes: acid chlorides and chlorinated acetic acids
作者:Lutz Prager、Peter Dowideit、Helmut Langguth、Heinz-Peter Schuchmann、Clemens von Sonntag
DOI:10.1039/b101687n
日期:——
Progressive hydrolytic decomposition of acyl chlorides, among them the chlorinated acetyl chlorides, which are produced in the gas-phase oxidation of chlorinated ethylenes, permits the complete mineralization of organically bound chlorine to chloride anion. Hydrolysis rate constants (100% water) have been determined for the following acyl chlorides: acetyl (350 s−1), chloroacetyl (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 studied and the kinetic parameters determined. Mono- and dichloroacetate anion undergo hydrolytic dechlorination (kobs = ko + kOH− × [OH−]; ClCH2C(O)O−: Ao
6.4 × 1015 s−1, Eo 148 kJ mol−1, AOH− 1.6 × 109 dm3 mol−1 s−1, EOH− 86 kJ mol−1. Cl2CHC(O)O−: Ao 3.2 × 1016 s−1, Eo 156 kJ mol−1, AOH− 3.2 × 1010 dm3 mol−1 s−1, EOH− 104 kJ mol−1). Trichloroacetate anion decomposes by another mechanism, undergoing decarboxylation which is base-uncatalyzed: Ao 2.1 × 1017 s−1, Eo 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 when contaminated water is freed from chlorinated ethylenes by air-stripping.
酰氯,包括氯化乙酰氯,在氯乙烯气相氧化反应中生成,其渐进水解分解过程可以将有机结合的氯完全矿化为氯离子。已经确定了以下酰氯在100%水中的水解速率常数:乙酰氯(350 s−1)、氯乙酰氯(5.5 s−1)、二氯乙酰氯(300 s−1)、三氯乙酰氯(>350 s−1)和草酰二氯(>350 s−1)。氯乙酰氯因此生成氯乙酸酯,其分解过程也被研究并确定了动力学参数。单氯乙酸根和二氯乙酸根经历水解脱氯(kobs = ko + kOH− × [OH−]; ClCH2C(O)O−: Ao 6.4 × 1015 s−1, Eo 148 kJ mol−1, AOH− 1.6 × 109 dm3 mol−1 s−1, EOH− 86 kJ mol−1. Cl2CHC(O)O−: Ao 3.2 × 1016 s−1, Eo 156 kJ mol−1, AOH− 3.2 × 1010 dm3 mol−1 s−1, EOH− 104 kJ mol−1)。三氯乙酸根通过另一种机制分解,经历脱羧反应,这是一个非碱催化的过程:Ao 2.1 × 1017 s−1, Eo 146 kJ mol−1。指出在中试规模上的程序,允许在通过空气剥离从污染水中去除氯乙烯时产生的脱气通过氧化来消除这些化合物。