Ultrasound-assisted oxidative desulfurization of diesel

Abstract EN

Due to the dramatic environmental impact of sulfur emissions associated with the exhaust of diesel engines, last environmental regulations for ultra-low-sulfur diesel require a very deep desulfurization (up to 15 ppm), which cannot be met by the conventional hydrodesulfurization units alone.

The proposed method involves a batch ultrasound-assisted oxidative desulfurization (UAODS) of a previously hydrotreated diesel (containing 480 ppm sulfur) so as to convert the residual sulfur-bearing compounds into their corresponding highly polar oxides, which can be eliminated easily by extraction with a certain highly polar solvent.

The oxidizing system utilized was H2O2 as an oxidant, CH3COOH as a promoter, with FeSO4 as a catalyst; whereas acetonitrile was used as extractant.

The major influential parameters related to UAODS process have been investigated, namely: ratio of oxidant/fuel, ratio of the promoter/oxidant, dose of catalyst, reaction temperature, and intensity of ultrasonic waves.

Kinetics of the reaction has been also studied; it was observed that the UAODS of diesel fuels fitted pseudo-first-order kinetics under the best experimental conditions, whereas values of the apparent rate constant and activation energy were 0.373 min-1 and 24 KJ/mol, respectively.

The oxidation treatment, in combination with ultrasonic irradiation, revealed a synergistic effect for diesel desulfurization.

The experimental results showed that sulfur removal efficiency could amount to 89% at mild operating conditions (70 ○C and 1 bar).

This indicates that the process is efficient and promising for the production of ultra-low-sulfur diesel fuels.