Oxidative desulfurization of diesel fuel oil using supported Fenton catalysts and assisted with ultrasonic energy

Abstract

An ultrasound-assisted heterogeneous catalytic oxidation process was applied to eliminate sulfur from commercial diesel fuel oil. The studied variables were catalyst concentration, type of catalyst (homogeneous or heterogeneous), oxidizing agent concentration, and the application of ultrasound energy. Supported catalysts were prepared by impregnation of coal fly ash with an iron(II) sulfate aqueous solution using ultrasound energy. After drying, the catalyst was calcined at 500 °C for 4 h. The oxidizing agent was hydrogen peroxide. Ultrasound energy was applied with a frequency of 47 kHz and an intensity of 147 W. Ethanol was employed for extracting the oxidized compounds from the hydrocarbon mixture. Coal fly ash and ethanol were used with the purpose of applying low-cost raw materials in chemical processes. It was found that under the studied conditions, increasing oxidizing agent concentration and the application of ultrasound energy can enhance the sulfur removal from commercial diesel fuel oil. Catalyst concentration did not play a significant role in the process. Similar results were obtained using homogeneous or heterogeneous catalyst, which is important since the heterogeneous catalyst could be recovered, reactivated, and used in many cycles.

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

“…Nanoparticles improve the adsorption of sulfur compounds due to their large surface area [53] . Photocatalyst under UV [54] or visible light [55] , nano-sized silica particles including mesoporous silica [56] , aluminum oxide particles [57] , transition metal oxides [58] , activated carbons [59] , modified metal–organic frameworks [60] , Ni catalyst also called sponge metal [61] , nanocomposite [62] , graphene oxide [63] , activated carbon (AC)-supported phosphotungstic acid [64] and fly ash-modified fenton catalysts [65] are used. In the case of using heterogeneous catalysts, the catalytic ODS mechanism [66] , [67] , [68] , [69] , [70] is illustrated in Scheme 1 .…”

“…Since homogeneous Fenton catalysts (FeSO 4 ) dissolve in the aqueous phase and consequently, making their recovery difficult [140] after ODS reactions, water-insoluble Fenton-like catalysts supported on coal fly ash (which is a very cheap waste from coal-fired power plants) were synthesized [141] . Approximately 30% desulfurization was carried out as a result of simultaneous oxidation and extraction of sulfur compounds from commercial diesel fuel containing 595 ppm S using 10 wt% H 2 O 2 and ethanol solvent in the presence of the Fenton-like catalyst in an ultrasonic bath at 47 kHz frequency and 147 W power [65] . It has been suggested that the oxidation stems from the hydroxyl radicals formed from the reaction between Fe 2+ and H 2 O 2 .…”

“…Above an optimum reaction volume, sulfur removal decreases due to the lower ultrasonic power density [78] , [196] . With increasing HP concentration (i.e., a more concentrated HP solution) up to a certain value in aqueous phase, UAODS usually increases due the formation of more HO· radicals than HP [65] , [126] . Above an optimum concentration, HP can have a scavenging effect on hydroxyl radicals [157] .…”

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Fig. 4 DPEs in the presence of heterogeneous catalysts (where 1–3, 4, 5–7, 8, 9, [10,14], 11, 12, 13, [15,19], 16, 17, 18, 20, 21 and 22 represent the references [98] , [133] , [134] , [84] , [151] , [145] , [97] , [119] , [118] , [126] , [124] , [123] , [150] , [65] , [78] , [121] , respectively). *49, 43.50 and 35.50 are DPE values calculated for DBT, 4,6-DMDBT and BT, respectively, pertaining to reference [98] .

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Catalytic oxidative desulphurization of pyrolytic oils to fuels over different waste derived carbon-based catalysts

“…This procedure achieved remarkably performances in the degradation of benzothiophene [34] and desulphurization of diesel-like fuels [35] by using nanostructured catalysts. Nonetheless, these systems were produced by using unfriendly procedures and lead to the merely deposition of the iron nanoparticles onto the support surface.…”