KINETICS OF THE CHLORINATION OF PROPANOIC ACID IN THE PRESENCE OF CHLOROSULFONIC ACID

The chlorination kinetics of propanoic acid was investigated in a semi batch reactor at 70-130 degrees C using chlorosulphonic acid as a cata lytic agent and oxygen as a radical trapper. 2-Monochloropropanoic aci d was obtained as the main product and 2,2- and 2,3-dichloropropanoic acids appeared as by-products. The formation kinetics of 2-monochlorop ropanoic and 2,2-dichloropropanoic acids were autocatalytic, whereas t he kinetics of 2,3-dichloropropanoic acid was noncatalytic. The kineti c data were described with a rate model based on a reaction mechanism, where propanoyl chloride is the key intermediate. The rate determinin g steps in the mechanism are the acid catalyzed enolization of propano yl chloride and the chlorination of the enol. The parameters of the ra te model were estimated with nonlinear regression analysis. Simulation s showed that the kinetic model is able to describe the autocatalytic formation kinetics of 2-monochloropropanoic and 2,2-dichloropropanoic acids.