Desulfurization of Diesel Fuel by Extraction with Lewis-Acidic Ionic Liquid

Abstract

Ionic liquids were found to be highly selective for the extractive removal of aromatic sulfur compounds from fuels at room temperature. The efficiency of ionic liquids for the removal of aromatic sulfur compounds is dependent on the properties and structure of the ionic liquids. In this work, the Lewis-acidic ionic liquid 1-butyl-3-methylimidazolium tetrahalogenoferrate(III) ([BMIM] [FeCl₄]) was synthesized and demonstrated to be more effective for the removal of aromatic sulfur compounds from diesel over ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] [BF₄]) because of its Lewis-acidic property. The ionic liquids favorably extracted organic compounds with a higher density of aromatic π-electrons. [BMIM][FeCl₄] ionic liquid can be regenerated through reextraction by hexane, and could be used in multiple steps for the removal of sulfur compounds from diesel.

Keywords:

• Desulfurization
• diesel
• extraction
• ionic liquid
• lewis-acidic

ACKNOWLEDGMENTS

This work was financially supported by the National High Technology Research and Development Program of China (No. 2006AA02Z209) and State Major Basic Research Development Program of China (No. 2006CB202507).

Notes

^a Model oil: 160 ppm S as sulfur compound in n-octane; mass ratio of ionic liquid to model diesel = 1:3, mixing time 15 min, room temperature.