Kinetic and thermodynamic study of a traditional dye as catalyst for thiol oxidation in sour kerosene

Abstract

The oxidation process of thiols is industrially used to treat light petroleum products in the presence of a supported catalyst. A low-cost, traditional dye, cobaltous phthalocyanine salt, was used as the active component for catalyst preparation. The supported catalyst was experimentally prepared by impregnation the activated carbon (dp = 1.971mm) with the uric dye solution in a batch unit. The prepared catalyst was tested for the oxidation of thiols present in row kerosene. All kinetic experiments were carried out at constant pressure concurrent fixed-bed unit. The effect of temperature and LHSV on conversion percent was investigated. Attempts were made to correlate the data with first and second-order reactions, and it was found that the first-order kinetics correlates the data well with an activation energy of 24.48 kJ/mol. This indicates that the synthesized catalyst is effective and necessary for the reaction to proceed at moderate temperatures with a sufficient rate. Also, the change of enthalpy and entropy were found to be equal to 21.94 kJ/mol and 0.153 kJ/molK, respectively, with an average Gibbs free energy change of −24.802 kJ/mol. These values indicate that the reaction is weakly spontaneous and thermodynamically favorable, and could proceed at a suitable rate in the presence of the prepared catalyst. Furthermore, the Thiele modulus and internal effectiveness factor were examined, and it was found that the internal diffusion is the major resistance for the oxidation reaction proceeding, and the oxidation reaction takes place only on the outer layer of the surface of the pellets.