Deep Desulfurization of Diesel Oil with Extraction Using Pyridinium-Based Ionic Liquids

Abstract

The pyridinium-based ionic liquids (ILs) 1-butyl-3,5-dimethylpyridinium tetrafluoroborate , 1-hexyl-3,5-dimethylpyridinium tetrafluoroborate and, 1-octyl-3,5-dimethylpyridinium tetrafluoroborate were found to be effective for the selective removal of aromatic heterocyclic sulfur compounds from diesel. The results suggested that the structure and size of the cation greatly affect the extractive performance of ILs. For each sulfur compound studied here (4,6-Dimethyldibenzothiophene (4,6-DMDBT), dibenzothiophene (DBT), benzothiophene (BT), and thiophene (TS)), the extractive performance using pyridinium-based ILs followed the order of [C₄Py][BF₄] < [C₆Py][BF₄] < [C₈Py][BF₄] <  <  <  <  <  < . In addition, the pyridinium-based ILs would not contaminate the diesel due to their insolubility. On the other hand, diesel has a certain solubility in pyridinium-based ILs, varying from 0.49 wt% for [C₄Py][BF₄] to 19.6 wt% for . Considering these results, ILs studied in this work are more competitive and feasible for extractive desulfurization applications. Moreover, the extractive desulfurization using pyridinium-based ILs could be used at least as a complementary process to hydrodesulfurization (HDS).

Keywords:

• desulfurization
• diesel
• extraction
• pyridinium-based ionic liquids

ACKNOWLEDGEMENTS

We are grateful to the National Basic Research Program (973 Program) of China (No. 2011CB200905) and the State Major Basic Research Development Program of China (Grant 2006CB202507) for their partial financial support of this research.

Notes

^a 25°C.

^b 60°C.

Model oil: 160 ppm S as sulfur compound in n-dodecane; mass ratio 1:1, mixing time 15 min.

^a Room temperature.

^b 60°C.

^a Model oil: (17) 500 ppm S as DBT in n-dodecane; mass ratio 1:1, mixing time 15 min, room temperature.

^b 60°C.

^c Real gasoline: (14) sulfur as DBT, 298.15 K.

^d Model oil: 160 ppm S as DBT in n-dodecane; mass ratio 1:1, mixing time 15 min, room temperature.

^e 60°C.