Kinetics and feasibility studies of thiol oxidation using magnetically separable Mg-Al layered double hydroxide supported cobalt phthalocyanine catalyst

Abstract

This work describes kinetic studies of the catalytic oxidation of thiols (RSHs) found in kerosene to disulphides using a magnetically separable iron oxide coated Mg-Al layered double hydroxide supported tetra-sulphonated cobalt phthalocyanine (CoPcS/LDH@Fe3O4) catalyst in an alkali-free environment. Using 1-octanethiol as a representative RSH, we investigated the effects of different experimental parameters on RSH oxidation kinetics, including catalyst concentration, temperature (30–60°C), and initial thiol concentration ([RSH]0, 100–300ppm). The catalyst concentration was varied so that the [RSH]0/[Co]tot molar ratio ranged from 45 to 180. Based on the results, we propose a mechanistic rate expression to explain the observed oxidation of RSH in the presence of the CoPcS/LDH@Fe3O4 catalyst. The proposed rate law resembles double substrate Michaelis-Menten kinetics, however, for commonly encountered industrial conditions, we were able to simplify it to a linear form. This rate law for RSH oxidation can be used to design industrial reactors for an alkali-free sweetening process.