Oxidative desulfurization of model and real fuel samples with natural zeolite-based catalysts: experimental design and optimization by Box-Behnken method

In this study, oxidative desulfurization was performed on simulated oil fraction consist of 1000 ppm dibenzothiophene. Cobalt supported on natural zeolite of Kaolin has been used as heterogeneous catalysts. 10% Co/metaKaolin with hydrogen peroxide as oxidant and acetonitrile as extraction solvent have shown excellent performance on desulfurization. Response surface methodology in experimental design and its subset Box-Benken was used to evaluate the performance of the selected catalyst in different operating conditions such as temperature, oxidant to sulfur molar ratio, time and catalyst amount. Also, optimum conditions was obtained are equal to 60 degrees C, O/S molar ratio (10.8 mol/mol), time (46 min) and catalyst amount 0.04 g with 97.1% sulfur removal. Oxidative desulfurization of model oil containing 1000 ppm of each sulfur component benzothiophene and thiophene was also tested at the optimum conditions, Oxidative desulfurization yield was ordered as DBT > BT > Th. In addition, after four steps consecutive recycle under optimum conditions oxidative desulfurization capacity of 10% Co/metaKaolin catalyst decreased from 97% to 92%, which is still high desulfurization capability. Finally, the performance of 10% Co/metaKaolin catalyst in oxidative desulfurization was evaluated for real oil fractions, gasoline and gasoil that was provided from regional oil refinery with sulfur content of 286 ppm and 7900 ppm, respectively. At the optimum conditions of operating variables desulfurization yield was 58% and 79% of total sulfur removal for gasoline and gasoil respectively with no significant changes in fuels properties.

Automated summary

This study investigated the oxidative desulfurization of a simulated oil fraction containing 1000 ppm dibenzothiophene using cobalt supported on natural zeolite as the catalyst. The performance of the catalyst under different operating conditions was evaluated using response surface methodology. The optimum conditions for desulfurization were determined and the catalyst exhibited high desulfurization capability even after consecutive recycling. Furthermore, the catalyst was also evaluated for real oil fractions with high sulfur content, achieving significant sulfur removal without affecting the fuel properties.