Kinetic and mass transfer studies in the catalytic oxidation of thiophenol in a gas—liquid reactor

Abstract

A study has been made of the absorption of gaseous oxygen in a thiophenol solution. The chemical reaction which occurred in solution was promoted by a copper chloride—pyridine catalyst. There were two reaction products, diphenyldisulphide and diphenylthiolsulphinate. In some experiments the liquid was unstirred, in other experiments the liquid was either stirred with a rotating bar or vigorously agitated with a vibrating disc. The reaction process was apparently zero order with respect to the thiophenol. The concentration of the catalyst affected both the reaction rate and the product ratio. The relationship between the absorption rate and catalyst concentration depended markedly on the mixing conditions within the reactor. The course of the absorption cannot be described simply in terms of the “classical” regimes of mass transfer with chemical reaction. However, it is probable that the absorption is in the transition region between the “diffusion” and “fast” regimes at low catalyst concentration and approaches the “instantaneous” regime at high catalyst concentrations. The relative yield of disulphide increases as the catalyst concentration increases and as the temperature increases. Improvements in the agitation of the liquid can lower the proportion of disulphide in the reaction product. These results have important implications for the processes which use this catalyst in the “selective” manufacture of disulphides and polydisulphides.