Oxidative Desulfurization of Model Diesel Using Ionic Liquid 1-Octyl-3-methylimidazolium Hydrogen Sulfate: An Investigation of the Ultrasonic Irradiation Effect on Performance

Abstract

A Brønsted acidic ionic liquid (IL), 1-octyl-3-methylimidazolium hydrogen sulfate ([Omim]­[HSO4]), was prepared and utilized as the extractant and catalyst to study the oxidative desulfurization of dibenzothiophene (DBT) in n-decane as the model oil. The effects of the alkyl chain length of the IL cation, temperature, H2O2/DBT molar ratio (O/S), IL/oil mass ratio, initial S-content, and sulfur species on the sulfur removal of the model oil were investigated. Complete removal of DBT was observed by [Omim]­[HSO4], O/S molar ratio of 5, and IL/oil mass ratio of 1:2 after 70 min at 25 °C. The order of observed oxidizing reactivity for different sulfur species was as follows: DBT > benzothiophene (BT) > thiophene (TH) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The IL could be reused six times without a significant decrease in the desulfurization activity. The kinetics of oxidative desulfurization for DBT by [Omim]­[HSO4] was found to be pseudo-first-order with an apparent rate constant of 0.0734 min–1 (at 298 K) and the apparent activation energy of 24.51 kJ/mol. The ultrasound-assisted oxidative desulfurization (UAOD) process was also applied and represented a high desulfurization performance for the model oil in a fast reaction. The effects of various parameters, including irradiation time, settling time, O/S molar ratio, and IL/model oil mass ratio, on the UAOD process were studied. The complete sulfur removal efficiency could be reached after 3 min of ultrasonic irradiation with an ultrasonic power of 30 W, ultrasonic frequency of 20 kHz, O/S molar ratio of 5, and IL/oil mass ratio of 1:2. It was observed that the application of ultrasonic irradiation allows the desulfurization process to be performed in a shorter time. The sulfur removal of real diesel was 77.2% in the ODS process, and 76.3% in the UAOD process under the optimal conditions.

Sono-oxidative desulfurization of fuels using heterogeneous and homogeneous catalysts: A comprehensive review

“…In a study [189] where 1-butyl-3-methyl imidazolium hydrogen sulfate [Bmim][HSO 4 ] and 1-octyl-3-methyl imidazolium hydrogen sulphate [Omim][HSO 4 ] with two different alkyl lengths were synthesized and used instead of aqueous phase, approximately 100% desulfurization yield of the model fuel containing 500 ppmw DBT in n-decane was obtained using [Omim][HSO 4 ] at O/S = 5 molar ratio and mass ratio IL/model fuel = 2 under 30 W power and 25 kHz direct US at 25 °C in 3 min. In the experiments in the absence of ultrasound, it was explained that the desulfurization with [Omim][HSO 4 ] is higher than the desulfurization with [Bmim][HSO 4 ] by applying the same optimum operating conditions as the case of using ultrasound under stirring at 900 rpm.…”

“…Moreover, whether the properties such as density, viscosity, cetane number, boiling range distribution of the desulfurized fuel produced in large quantities (factory scale) have changed is a matter of investigation separately and must be checked one by one. In most research papers [171] , [187] , [188] , [189] , when H 2 O 2 /S mole ratio initially increases, desulfurization generally increases, then reaches a certain value and decreases slowly after this optimum value. It was reported that this decline is due to dilution of the aqueous phase.…”

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

“…In order to boost the reaction rate, ultrasound irradiation was integrated into an ODS system with a Brønsted acidic IL, [Omin][H 2 SO 4 ], as the catalyst and extractant. 108 With ultrasound, the reaction time for [Omin][H 2 SO 4 ] to attain 100% DBT oxidation was shortened from 70 min to 3 min under the same operating conditions. This was ascribed to the intense mixing that enhanced the mass transfer of sulfur compounds into the IL phase and propelled the interactions between catalyst and reactants.…”

Brønsted acidic ionic liquid-promoted direct C3-acylation of N-unsubstituted indoles with acid anhydrides under microwave irradiation

“…40,41 Recently, Brønsted acidic ionic liquids (ionic liquids with acidic properties) have been widely used for various organic transformations due to their unique properties. 19,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Nevertheless, to the best of our knowledge, they have never been used for the direct C3-acylation of N-unsubstituted indoles. Thus, we now report the development of a highyielding and regioselectivity method for the C3-acylation N-unsubstituted indoles using Brønsted acidic ionic liquid as an efficiently homogeneous catalyst under microwave irradiation.…”