Selective Elimination of Alkyldibenzothiophenes from Gas Oil by Formation of Insoluble Charge-Transfer Complexes

Abstract

To protect urban areas, new environmental regulations have been adopted to limit the sulfur level in diesel fuel. It is well established that among all sulfur-containing compounds present in gas oil, alkyldibenzothiophenes are the most refractory to the achievement of deep classical hydrodesulfurization. Considering the electron-rich structure of alkylDBTs, we have studied their ability to form charge-transfer complexes (CTC) with π-acceptors in order to develop a new highly selective method for their specific removal from gas oil. In this article, we describe the selective formation of insoluble CTC between dibenzothiophene derivatives and tetranitrofluorenone in synthetic solutions which model the gas oil matrix. By the same procedure the global sulfur level was lowered in gas oils. Furthermore, we have shown that our method is specific for dibenzothiophenes with regard to benzothiophenes. The complexation activity and selectivity have been correlated to the frontier molecular orbital energies and their shapes.