Mechanistic kinetics of catalytic oxidation of 1-butanethiol in light oil sweetening

In the present study the kinetics of liquid phase oxidation of light thiols using novel cobalt phthalocyanine sulphonamide catalyst developed indigenously was investigated in a semi batch reactor. 1-Butanethiol was chosen to represent thiols in lighter range of petroleum fractions like liquefied petroleum gas and light straight run naphtha. Rate data was collected under experimental conditions representing industrial conditions. Effects of process parameters like catalyst concentration and initial feed mercaptan concentration on reaction rates were investigated. A mechanism based rate expression was deduced to explain the observed behavior. Its parameters estimated using Line weaver plots and further fine tuned by using optimization technique. The effective rate law represented a first order kinetics which explained the observed experimental phenomenon reasonably well for commonly encountered industrial conditions.

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► Cobalt phthalocyanine sulphonamide catalyst (CoPSc) has been found more active and stable than commercial catalyst.
► Kinetics of catalytic oxidation of light thiols using a novel CoPSc catalyst was investigated.
► A mechanism based rate expression was used to explain the observed rate behavior at higher RSH feed concentration and its parameters estimated.
► Optimum catalyst CoPSc dosage was established as 200 ppm.
► A linear rate expression was proposed for industrial scale oxidizer design.