The oxidative desulfurization (ODS) of light gas oil (LGO) is investigated with an in-house-designed catalyst consisting of cobalt oxide loaded on alumina (gamma-Al2O3), in the presence of air as an oxidizing agent, under moderate operating conditions (temperatures of 403-473 K, liquid hourly space velocity (LHSV) = 1-3 h(-1), initial concentration = 500-1000 ppm). The Incipient Wetness Impregnation (IWI) method of cobalt oxide over gamma-alumina (2% Co3O4/gamma-Al2O3) is used for the preparation of the catalyst. The optimal design of experiments is studied to evaluate the effects of several process variables (namely, temperature, LHSV, and concentration of dibenzothiophene) and their optimal values were found to be 473 K, 1 h(-1), and 1000 ppm, respectively. For the conversion of dibenzothiophene to sulfone and sulfoxide, the results indicates that the IWI method is suitable to prepare this type of the catalyst. Based on the experiments, mathematical models that represent a three-phase reactor for describing the behavior of the ODS process are developed. In order to develop a useful model for simulation, control, design, and scaleup of the oxidation process, accurate evaluation of important process parameters, such as reaction rate parameters, is absolutely essential. For this purpose, the parameter estimation technique available in the general Process Modeling System (gPROMS) software is employed in this work. With the estimated process parameters, further simulations of the process is carried out and the concentration profiles of dibenzothiophene within the reactor are generated.