Ultrasound-assisted Oxidative Desulfurization Research Articles

Experimental study of high-pressure ultrasound-assisted oxidative desulfurization (UAOD) and sulfone adsorption/desorption using zeolite-13X

The sulfurous compounds in natural gas liquids should be reduced to the extent of satisfying the standard recipes due to corrosion, poisoning of catalysts in downstream processes, reduction in the quality of hydrocarbon products and environmental issues. Ultrasound-assisted oxidative desulfurization is an emerging method for sulfur removal from natural gas liquids. Since natural gas liquids exist in the liquid form of hydrocarbons at high pressures and ambient temperature (25 °C), this work aims to investigate the optimal conditions governing ultrasound-assisted oxidative desulfurization for various sulfurous compounds including mercaptan, sulfide and thiophene at high pressure and finally to appraise the adsorption of oxidized sulfurs and the regeneration of the adsorbent using elution with hot water. So, the effects of sulfur content and ultrasonication time were evaluated at 30 bar. Results showed that as the initial sulfur concentration in normal heptane was increased from 0.00 to 3000 ppmS, the sulfur removal efficiency was enhanced by less than 2 % of 95.9 % and of course, the increased ultrasonication time improved the sulfur removal efficiency. Next, results of the sulfone adsorption using zeolite-13X at 30 bar in continuous mode confirmed that the breakthrough time was reduced from 63 to 12 min as the weight hourly space velocity was increased from 5 to 20 h−1 and pursuantly, the mass transfer zone diminished. Besides, the breakthrough time decreased by 45 - 10 min for increasing the initial sulfur content from 200 to 1000 ppmS. Changing the pressure of the adsorption process from 1 to 30 bar caused the improvement of sulfone adsorption capacity by approximately 3.75 times. In continued, the regeneration of zeolite-13X contaminated with sulfone by flowing hot water was evaluated and the zeolite-13X bed was completely regenerated.

Characterization and optimization of ultrasound assisted oxidative desulfurization of a model fuel using a novel magnetic deep eutectic solvent

ABSTRACT In various studies, researchers have utilised different solvents to extract sulfur compounds from the fuels. This paper introduces a novel magnetic deep eutectic solvent employed in the ultrasound-assisted oxidative desulfurisation of dibenzothiophene within a model fuel. The solvent, synthesised at 85°C by combining choline chloride, p-toluene sulfonic acid, and FeCl₃, underwent characterisation through Fourier transform-infrared, Vibrating-sample magnetometer, and Raman spectrometry. Exploration of the key parameters, including oxidant to model fuel volumetric fraction percentage (0.2–0.3), Iron (III) chloride to choline chloride mole fraction (0.1–0.3), and Magnetic deep eutectic solvent to model fuel volumetric fraction (0.2–0.3), was conducted to assess their impact on dibenzothiophene conversion rates. Employing response surface methodology based on central composite experimental design, optimal operational parameters for the ultrasound-assisted oxidative desulfurisation process were identified, resulting in a sulfur removal rate of 98.7%. The findings highlight the solvent sustained efficiency even at higher dibenzothiophene concentrations. Additionally, the solvent paramagnetic properties facilitated an expedited separation from the fuel, leading to the significantly reduced process times.

Modeling and Experimental Investigation of Sulfurous Compounds Removal from Gas Condensate through Ultrasound-Assisted Oxidative Desulfurization Method.

This study employed an ultrasound-assisted oxidative desulfurization process (UAOD) to investigate the degradation of three sulfurous compounds in the synthetic gas condensate. Various parameters, including oxidizers (hydrogen peroxide, sodium peroxide, potassium superoxide), promoters (formic acid, acetic acid), catalysts (phosphotungstic acid, ferrous(II) sulfate, zirconium dioxide, vanadium pentoxide, aluminum oxide γ, copper(II) oxide), and phase transfer agents (isobutanol, tetraoctylammonium bromide, and tetra-n-butylammonium fluoride), were examined to identify the optimal combination for reducing sulfurous compounds in the UAOD process. The influence of the extraction stage and reactor vessel material on the desulfurization efficiency was also investigated. Results revealed that hydrogen peroxide, formic acid, phosphotungstic acid, and isobutyl alcohol were the most effective oxidizers, promoters, catalysts, and phase transfer agents, respectively. Response surface methodology was used to determine the optimal conditions by evaluating different concentrations of these reagents within specific ranges. The study considered ranges such as 10-70 vol % of hydrogen peroxide, 5-70 vol % of formic acid, 1-30 wt % of phosphotungstic acid, 1-30 vol % of isobutanol, and 5-40 min of ultrasonic ripple time. Empirical models were developed for each sulfurous compound type, providing optimal conditions for sulfur removal with an error margin of less than 0.1%. The validity of the suggested models was confirmed through an industrial data analysis. Additionally, it was observed that increasing the number of extraction stages improved desulfurization efficiency, and using a stainless-steel reactor vessel was more suitable than using a glass vessel.

Synergetic ultrasound assisted catalytic oxidative extractive desulfurization of tire pyrolysis oil employing sustainable protic deep eutectic solvents

One-pot ultrasound-assisted selective oxidative extractive desulfurization (UA-SOEDS) of tire pyrolysis oil (TPO) was carried out with sustainable protic deep eutectic solvent (pDES) synthesized with quaternary ammonium salts as HBA and organic acids as HBD. The Tetrabutyl ammonium chloride and malic acid-based pDES with moderate viscosity resulted in a maximum Sulphur removal of (92.6 % (w/v)). A central composite design-based optimization of essential variables (US time (12 min), US temperature (333.15 K), US power (1.2 kW) and pDES/TPO ratio (22.5 % v/v)) was carried out resulting in an effective sulfur removal rate of (93.6% w/w). The pDES post extraction was recovered with the addition of isooctane and reused for consecutive cycles of UA-SOEDS process, loosing its characteristic oxidative extraction property after 3rd cycle (68.53%). The chromatographic analysis confirmed the presence of long-chain hydrocarbons in the oxidized TPO which confirms its property as a good fuel. The physicochemical properties and the calorific value of the resulting base oil were determined making it a suitable candidate as an alternative green fuel meeting the international standards of soluble Sulphur.

Sono-catalytic oxidative desulfurization of fuels using Fe6W18O70@ZrFe2O5

Due to the most recent environmental requirements, wide desulfurization has become an increasingly important way to obtain ultra-clean fuels for transportation of less than 15 ppm of sulfur, such as diesel, gasoline, and jet fuel. As a result of the strict requirements for transportation fuels. Therefore, we report a novel sandwich-type [(FeW9O34)2 Fe4(H2O)2]−10 Fe6W18O70 cluster incorporated zirconium ferrite (ZrFe2O5) catalyst composite to successfully remove sulfur. The structural properties of these samples were systematically investigated by X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermal techniques. A series of Ultrasound assisted oxidative desulfurization UAODS processes were carried out to evaluate the optimization of the desulfurization performance catalysts prepared in this work. As well as the reactivity of various sulfur compounds. Fe6W18O70@ZrFe2O5 removed sulfur (98.2%) in 40 min and could be regenerated five times with no loss of sulfur removal. In addition, the catalyst's reaction mechanism for the UAODS process was investigated.

LaMnxCo1‐xO3 (x=0, 0.25) Perovskites: Novel Nano Catalysts for Removal of Thiophene compounds in Fuels by Catalytic and Ultrasound‐assisted Oxidative Desulfurization

AbstractLaMnxCo1‐xO3 (x=0, 0.25) perovskites were developed as novel nanocatalysts for the desulfurization of thiophenes compounds by catalytic oxidative desulfurization (CODS) and ultrasound‐assisted oxidative desulfurization (UAOD). The perovskites were synthesized by the sol‐gel auto‐combustion method and characterized by X‐ray diffraction (XRD), temperature programmed reduction (TPR), Scanning electron microscopy (SEM) and BET surface area. The experiments were designed by the Box‐Behnken method of response surface methodology. The catalytic experiments were designed by response surface methodology (RSM). LaMn0.25Co0.75O3 despite having a lower surface area rather than LaCoO3 exhibited superior activity due to easy reducibility and high surface electron density approved by TPR. Pareto analysis indicated that the DBT concentration had the most effect on the CODS process. Ultrasound waves enhanced the activity of the catalysts via the formation of hot spots as an accelerating and de‐agglomerating agent in the UAOD process, leading the LaMn0.25Co0.75O3 to be reusable at least for 5 cycles. A mechanism for DBT oxidation was proposed by the formation of DBT sulfone. Due to steric hindrance and the electron density of the sulfur atoms in thiophene derivatives, the following order resulted in their desulfurization rate: DBT>4‐MDBT>BT. The study indicated that perovskites could be novel and promising nanocatalysts for the desulfurization of fuels.

Ultrasound-assisted oxidative desulfurization of bitumen and analysis of sulfur forms in a treated bitumen

Bitumen contains approximately 5 wt% sulfur so it must be removed before being used as fuel. Herein, we performed oxidative desulfurization of bitumen at room temperature using n-pentane and ultrasound to reduce bitumen viscosity and mix the bitumen-dissolved n-pentane and aqueous reaction solution physically. The oxidative states of sulfur in bitumen and desulfurization ratio were investigated to confirm the oxidative desulfurization process. Additionally, we developed a novel method for separating bitumen into maltene and asphaltene. Thus, 81.0% of sulfur in maltene was successfully removed by removing asphaltene, which is difficult to remove sulfur using n-pentane in oxidative desulfurization.

Application of response surface methodology (RSM) for optimizing and statistical analysis of ultrasound-assisted oxidative desulfurization (UAOD) of an Iranian heavy crude oil

In this study, optimization and statistical analysis of oxidative desulfurization (ODS) of an Iranian heavy crude oil (HCO) by applying ultrasonic waves were performed. The investigated HCO was from the West Paydar Field of Iran (sulfur: 38638 ppm, viscosity: 78.76 cSt (20 °C), API: 18.53). The process was performed in the presence of acetic acid (catalyst), hydrogen peroxide (oxidant), and copper sulfate (PTA, phase transfer agent). The studied parameters included power (10–15 W/ml), temperature (60–80 °C), PTA (0–1 wt%), and catalyst (4.8–19.2 wt%). The processing time was 10 min. Acetonitrile was an extraction solvent. The experimental design was performed based on Box Behnken design (BBD) and consisted of 27 experiments. RSM was applied to model the response and to investigate the effects of one factor, parameter interactions, and optimization. A quadratic polynomial equation was presented for the model of HCO sulfur reduction. Based on the results, power, PTA, and catalyst had significant effects on the response. The regression coefficient of 0.9273 indicated a good agreement between the experimental results and the model results. Optimization results showed that under optimal conditions including power: 14.63 w/ml, temperature: 72.47 °C, PTA: 0.79 wt%, and catalyst: 4.84 wt%, desulfurization was 45.10 wt%.

Sonocatalytic oxidative desulfurization of diesel oil using a novel BiVO4/FeMn LDH nanocomposite.

A novel BiVO4/FeMn layered double hydroxide (LDH) nanocomposite was fabricated and applied for green and efficient ultrasound-assisted oxidative desulfurization (UAODS) of real fuel (hydrotreated oil). The physicochemical properties of the prepared BiVO4/FeMn LDH nanocomposites are elucidated using techniques such as XRD, FT-IR, BET, SEM, XPS, Raman, and TGA. The desulfurization results revealed that both BiVO4 and FeMn LDH were crucial in the UAODS process in the presence of H2O2 as a green oxidant and acetonitrile as an extracting solvent. The desulfurization activity was optimized by varying the process conditions (time, catalyst weight, type of oxidant, O/S molar ratio, ratio of solvent to oil, and type of sonicator). The prepared nanocomposite exhibited remarkable desulfurization performance, reaching up to 99.8% under the optimized reaction conditions. Moreover, the catalyst exhibited high stability and could be reused four times without a notable decline in the performance. Significantly, this research reveals the robustness of the newly synthesized nanocomposite for efficient UAODS in a short time and low catalyst dosage. The proposed desulfurization mechanism was investigated.

Recent Advances and Challenges in Developing Technological Methods Assisting Oxidative Desulfurization of Liquid Fuels: A Review

To meet the requirements of sulfur standards, the desulfurization of liquid fuels is crucial. Oxidative desulfurization (ODS) has been widely employed to desulfurize liquid fuels. Various techniques can be combined with ODS to increase its efficiency. The present study surveys recent advances in the techniques of ultrasound-assisted oxidative desulfurization, plasma oxidative desulfurization, microwave-assisted oxidative desulfurization, hydrodynamic cavitation-assisted oxidative desulfurization, photocatalytic oxidative desulfurization, electrochemical oxidative desulfurization, magnetic field-assisted oxidative desulfurization, and bio-oxidative desulfurization. The advantages, drawbacks, and prospects of each method to desulfurize liquid fuels have been reviewed. All of these methods are in the research and development phases and often are at the laboratory stage. However, ultrasound-assisted ODS has been extensively investigated and its usage in industrial plants has been reported. The industrial applications of ODS and techniques assisted with ODS require more investigation.

Ultrasound assisted oxidative desulfurization: A comprehensive optimization analysis using untreated diesel oil

In this research, a process system optimization in the ultrasound assisted oxidative desulfurization (UAOD) with the NaPW/H2O2 system was investigated to determine its sustainability to produce clean diesel. The UAOD process was used to identify the effect of sulfur conversion with ultrasound time (6 to 30 min), amplitude (20 to 60%), catalyst dosage (10 to 500 mg), and temperature (30 to 70 °C). Results showed that the variables of amplitude, catalyst dosage, and temperature were extremely significant (p-value < 0.0001). Strong statistical significance (p-value < 0.0001 and F-value = 24.8) has been displayed for the generated model. The optimum sulfur conversion of 99.6% (theoretical) and 95.0% (verified) in diesel was attained at 27.1 min, 39.9% amplitude, 320.9 mg catalyst, and 69.7 °C. Thus, the results of this study indicated the novel applicability of the UAOD as a desulfurization technology in industrial practice.

Choline chloride-based deep eutectic solvents for ultrasonic-assisted oxidative desulfurization of actual heavy crude oil

Deep eutectic solvents (DESs) are acquiring increasing interest as ionic liquid analogues because of their wide application, low-cost characteristics and environmentally friendly. In this study, choline chloride-based (ChCl) as a type of DESs were synthesized using polyethylene glycol (PEG), and applied to reduce sulfur content of actual heavy crude oil with sulfur content 37900 ppm (3.79 wt%). The synthesized DESs were characterized using Fourier-transform infrared spectroscopy (FTIR), as well as viscosity and density measurements. The DESs were evaluated for extractive ultrasound-assisted oxidative desulfurization (EUAODS), with 30 wt% H2O2 as the oxidant and formic acid as the catalyst. This study looked at the effects of oxidative desulfurization (ODS) and single ODS under ultrasonic treatment. Different systems for DESs were tested to find the desulfurization selectivity of the better reaction system; and it was found that extractive desulfurization (EDS) removed 24.57% of the sulfur, followed by extractive and ultrasonic-assisted desulfurization (EUADS) at 26.78%, then ODS at 37.28%, with ultrasonic-assisted oxidative desulfurization (EUAODS) providing the best result of 62%. According to the comparison trials, combining DESs with ultrasonic treatment improved processing. This study contributes to the body of information on the use of ultrasonic treatment in heavy crude oil desulfurization.

Ultrasound-assisted oxidative desulfurization of fuel using butyl triphenyl phosphonium chloride as a promising catalyst

The traditional hydrodesulfurization process has severe disadvantages, such as operating at a higher temperature and pressure and the inability to remove refractive sulfur compounds (S-compounds). To overcome these difficulties, the present study reports the synthesis and characterization of ionic liquid (IL), butyl triphenyl phosphonium chloride ([BTPP]Cl) and its application to the S-removal of model fuel (MF) using ultrasound-assisted oxidative desulfurization (UAODS). Ultrasound irradiation enhances the desulfurization efficiency by eliminating resistance to mass transfer between the organic and aqueous phases. The application of ultrasound generates more active free radicals which help in the conversion of S-compounds to their respective sulfones. MF contains dibenzothiophene (DBT) in n-octane (500 ppm), where 78.45% removal of DBT was achieved under optimized conditions of mass ratio of IL to MF:1/1, mole ratio of oxidant to sulfur:20/1, 50 °C, and 30 min under the application of sonication. Moreover, [BTPP]Cl could be regenerated and recycled for six consecutive cycles. The driving force behind the higher desulfurization performance using [BTPP]Cl was supposed to be the interactions between the IL and DBT. Various S-compounds such as thiophene (T), benzothiophene (BT), and 3-methyl thiophene (3-MT) were also studied for their UAODS reactivity. Thus, [BTPP]Cl proved to be a potential catalyst for application in the UAODS of a fuel, and the process can be employed for industrial application.

Ultrasound assisted oxidative desulfurization of a model fuel using a deep eutectic solvent: Optimization and experimental design

The ultrasound assisted oxidative desulfurization (UAOD) of dibenzothiophene (DBT) in model diesel fuel was investigated using deep eutectic solvent (DES). The choline chloride/p-toluenesulfonic acid DES was synthesized by simple mixing of raw materials at 85 °C. DES was used as both extractant and catalyst in the UAOD process. To find the optimal values of the parameters influencing the removal of DBT, response surface methodology (RSM) based on Box-Behnken experimental design (BBD) was applied. Independent parameters including time, DES and oxidant volumes were optimized and the percentage of sulfur removal reached as high as 97.53% under optimal conditions of 121.168 s, 0.203 of VDES/VFuel and 6.42 of n(H2O2)/n(DBT). The model was successfully validated under these conditions. The time of the UAOD process was also compared with the time of the conventional oxidative desulfurization. The results indicated that UAOD process was completed in a significantly shorter time.

Parametric Screening Analysis for the Oxidative Desulfurization of Diesel Oil

This research utilized a real raw diesel oil to be subjected in an innovative desulfurization technique. The novelty of this study is in the use of screening analysis in the ultrasonication enhancement of sulfur oxidation in actual fuel. This addresses the research gap in literature that have yet to compare and completely analyze all factors in the ultrasound-assisted oxidative desulfurization (UAOD) method. Specifically, the effects of ultrasonication via amplification and irradiation time, material usage of tetraoctylammonium bromide, hydrogen peroxide, polyoxometalate catalyst and the process parameters of fuel to oxidant molar ratio and temperature were examined. A definitive screening design (DSD) using the JMP 11.0 was utilized for a statistical screening analysis to determine the essential and non-essential parameters in the UAOD. Upon the oxidation of sulfur compounds in diesel oil, results suggested that the enhancement technique via ultrasonication, polyoxometalate catalyst and temperature were the only significant factors based on the p-value < 0.05. The aforementioned factors are essential due to being able to instigate an oxidation reaction of sulfurs into its sulfone forms. Based on the generated DSD experimental runs, sulfur conversion can range from 36.41 % to 92.69 %.

Ultrasound-assisted oxidative desulfurization of Arabian extra light oil (AXL) with molecular characterization of the sulfur compounds

The oxidative desulfurization (ODS) of model oil (BT, DBT, and 4,6-DMDBT) was studied with Mo/Ti-TUD-1 catalyst under mechanical stirring and ultrasonic-assisted conditions. ODS of DBT followed the pseudo-first-order kinetic model under both conditions and achieved a maximum conversion of 99%. The use of ultrasound instead of mechanical stirring significantly shortens the reaction time from 80 to 15 min. The oxidative reactivity of sulfur compounds in the model oil followed the same order under the mechanical stirring and ultrasound: 4,6-DMDBT > DBT > BT. Then ultrasound-assisted oxidative desulfurization of Arabia extra light oil was performed at 60 °C. It removed 55.1% of sulfur from the Arabian extra light oil feedstock. APPI FT-ICR characterized the sulfur compounds distribution. The S1, S2, O2S1, and O4S2 class species were identified in Arabian extra light oil feedstock, raffinate, and methanol extraction phase samples. The abundant O2S1 class species which had 9–15 Double Bond Equivalent (DBE) values and 15–30 carbon numbers, O4S2 class species with 11–20 DBE and 20 < carbon number < 40 were detected in the extraction phase. 1H NMR and 13C NMR results revealed that the molecular structure in Arabian extra light oil is aromatic-base with a high alkylation degree. Combined with the FT-ICR and NMR results, those sulfur-containing compounds with lower alkylation degrees were converted to sulfone over Mo/Ti-TUD-1 catalyst and extracted by methanol.

A Review of the Desulfurization Processes Used for Waste Tire Pyrolysis Oil

The increasing global population and the rapid industrial development associated therewith have increased the demand for fossil-derived fuel oils. The sources of fossil fuels are limited, and many studies have been being conducted to find alternative fuel sources. Waste tire pyrolysis oil (WTPO) attracts considerable attention as an alternative fuel because its properties are similar to those of diesel oil. However, WTPO has a high sulfur content of &gt;1.0 wt%, which is above the environmental standard limit of 0.1 wt%; therefore, it cannot be used in engines directly. It is thus highly necessary to remove sulfur compounds from tire-derived oils. However, finding an appropriate and environmentally friendly process is proving difficult. This review article presents the various desulfurization methods used to removal sulfur from WTPO, such as hydrodesulfurization (HDS), oxidative desulfurization (ODS), ultrasound-assisted oxidative desulfurization (UAOD), and acid treatment. Of these, HDS is the most expensive as it involves high consumption of hydrogen, high temperature (~450 °C), and high pressure (~200 bar), whereas UAOD is an efficient and economic method of reducing the sulfur content of WTPO.

Ultrasound-assisted oxidative desulfurization (UAOD) of Iranian heavy crude oil: Investigation of process variables

The ultrasonic-assisted oxidative desulfurization (UAOD) process of an Iranian heavy crude oil was performed for the first time. The applied heavy crude oil was from the West Paydar Field, Iran. Its main properties included API gravity, 18.53 and sulfur content, 38638 ppm. Hydrogen peroxide, acetic acid, CuSO 4 , and acetonitrile were applied as oxidant, catalyst, phase transfer agent (PTA), and extraction solvent, respectively. The effects of different parameters, including ultrasound power at five levels, PTA amount at seven levels, catalyst amount at five levels, preheating temperature at three levels, reaction time at five levels, were investigated. Two scenarios of experiments were conducted in each section. The results indicated that increasing ultrasonic power, reaction time, and catalyst amount had positive influences on sulfur reduction. There was an optimal point in increasing PTA and preheating temperature. At the best conditions, including preheating temperature, 70 °C; acetic acid as catalyst, 4.8 wt%; hydrogen peroxide as oxidant, 2.92 wt%; reaction time, 10 min; CuSO 4 as PTA, 1 wt%; ultrasonic power, 7 W/ml, the sulfur reduction was 48.68 wt%. In addition, the influences of PTA type (CuSO 4 , FeSO 4 , FeCl 2 , FeCl 3 ), PTA size, the number of extraction stages at three levels, and multistage UAOD at three levels were evaluated. According to the results of this part, CuSO 4 showed the best performance. With increasing the number of stages of extraction and UAOD, sulfur removal increased from 48.68 wt% to 52.15 wt% and 53.55 wt%, respectively. Also, the comparison between UAOD and oxidative desulfurization (ODS) processes was performed. The results indicated that the sulfur reduction of UAOD process during 10 min was three times more than that of ODS process during 90 min. The results of this research revealed that UAOD process is effective for sulfur removal of heavy crude oil. • UAOD process is performed for Iranian heavy crude oil for the first time. • The effects of various parameters on UAOD process are systematically investigated. • The investigated parameters include power, PTA (type, amount, size), catalyst, time. • Also, the number stages (extraction, UAOD), UAOD and ODS comparison are evaluated. • At the best conditions, the sulfur removal of heavy crude oil was 53.35 wt%.

Triphenyl methyl phosphonium tosylate as an efficient phase transfer catalyst for ultrasound-assisted oxidative desulfurization of liquid fuel.

The novel phosphonium-based ionic liquid (IL), triphenyl methyl phosphonium tosylate ([TPMP][Tos]), has been synthesized and applied as a phase transfer catalyst (PTC) in the ultrasound-assisted oxidative desulfurization (UAODS). Oxidation of model fuel (MF) containing dibenzothiophene (DBT) was carried out using an equimolar mixture of H2O2-CH3COOH as an oxidant at 40-70 °C in the presence of IL. The sulfur compound is converted into polar sulfone, and the maximum desulfurization efficiency was examined. The effect of process parameters such as reaction temperature, reaction time, molar ratio of oxidant to sulfur (n(O/S)), and the mass ratio of ionic liquid to model fuel (m(IL/MF)) was studied, and the conditions for maximizing the DBT conversion rate were found. Maximum conversion (> 99%) was obtained at a temperature of 70 °C with m(IL/MF) of 0.8. The oxidation reactivity of various sulfur compounds was studied at different time intervals. To verify the effect of ionic liquid and ultrasound irradiation, extractive desulfurization (EDS), oxidative desulfurization (ODS), and UAODS in the presence of IL were carried out. The experimental results show that the UAODS process gives the highest desulfurization efficiency. A kinetic study was performed to estimate the rate constant and the order of oxidation reaction.

Ultrasound assisted oxidative desulfurization of marine fuels on MoO3/Al2O3 catalyst

Oxidative desulfurization (ODS) was applied to three marine fuels with viscosities between 380 and 700 cSt (centistokes) and sulfur contents between 0.79 and 3.27 wt.%, using a MoO3/Al2O3 catalyst. H2O2 was chosen as oxidizing agent with a low oxidant to sulfur ratio of 3, for economic and environmental reasons. Global sulfur removal was obtained after extraction of sulfones by dimethylformamide. Oxidation efficiency was evaluated by monitoring the conversion of alkyl-benzothiophenes and dibenzothiophene molecule by gas chromatography (GC) with a sulfur specific detector. Applying ultrasounds prior to oxidation was found to significantly enhance conversions and sulfur removal, the effect being more pronounced when initial efficiency was low, that is for more refractory molecules and heavier fuels. Ultrasound assisted ODS (UAOD) was effective on raw fuels with initial viscosity below 700 cSt. Indeed, dilution decreased the viscosity of the fuels, allowing reaction to be effective even on initially very heavy fuels. The presence of asphaltenes dissolved or precipitated in the feed did not affect the conversion of Cx-BTs and DBT significantly, with only slight variations of global sulfur removal rates. Global desulfurization rates between 60 and 80 % were obtained, clearly showing the efficiency of UAOD applied to complex matrices such as marine fuels.