Development of Novel Nonhydrogenation Desulfurization Process — Oxidative Desulfurization of Distillate

This selective review discusses nonhydrogenation desulfurization processes, particularly oxidative desulfurization, for the manufacture of ultra clean fuels. The environmental regulations for transportation fuels are becoming more and more severe, and the statutory sulfur content in various fuels was reduced to below 10 ppm in 2005, and will be lower in the near future. However, there is considerable doubt whether conventional hydrodesulfurization processes can provide fuels with sulfur content less than 5 ppm. This review describes recent advances in nonhydrogenation desulfurization processes, particularly oxidative desulfurization, as well as our latest research results. The review consists of three sections as follows. (I) The oxidation reactivities of various sulfur- containing compounds present in fuels, oxidation and oxidative mechanisms for various oxidant-catalyst systems are introduced. (II) The oxidation of various practical fuels such as light gas oil, kerosene, and vacuum gas oil, and others are described; and the potential of various oxidative desulfurization processes for the fuels are evaluated. (III) Removal methods of oxidized sulfur compounds in various fuels are described.