Assisted Oxidative Desulfurization Research Articles

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.

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.

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.

Mixing assisted oxidative desulfurization using a synthesized catalyst of the activated carbon supported phosphotungstic acid: A process optimization study

Desulfurization technology is vital in the removal of sulfur compounds in diesel to attain clean fuels. In this research, the mixing assisted oxidative desulfurization (MAOD) in conjunction with a high shear mixer was used with the catalyst of the activated carbon supported phosphotungstic acid. This study discusses the desulfurization of a simulated diesel, containing 2.3 wt% S of dibenzothiophene and benzothiophene in real fuel oil. The influences of mixing speed (8,000 rpm to 16,800 rpm), mixing time (30 min to 90 min), and mixing temperature (25°C to 65°C) were examined for the sulfur oxidation. A 2k full factorial design and a face-centered cube design were utilized for the screening and optimization studies, respectively, in the experimental runs. The analysis of variance was able to determine and generate a simplified quadratic model to predict the response in the MAOD process. The optimum variables for sulfur conversion were achieved at 88.5 min (mixing time), 16,800 rpm (mixing speed), and 63.28°C (mixing temperature). The confirmatory run resulted in percent oxidation of 62.37 % and validated the generated model. Moreover, the fundamental properties of diesel oil were analyzed for comparison prior to and after the MAOD method. The results revealed the retention of essential properties of the simulated diesel oil even after the MAOD treatment step. Thus, the MAOD process has successfully preserved the properties of diesel oil even after its treatment process. This indicates a promising result of the MAOD process favorable for its future applications.

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.

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.

Ultrasound assisted oxidative desulfurization of simulated diesel using flow cell and longitudinal bath in combination with different oxidants

Ultrasound assisted oxidative desulfurization (UAOD) of simulated diesel containing dibenzothiophene (DBT) as a model sulfur compound has been investigated using ultrasonic flow cell (FC) and ultrasonic longitudinal bath operated individually and in combination with different oxidants. The influence of process parameters such as H2O2 loading (10 mL/L–40 mL/L), acetic acid (AA) loading (30 mL/L–90 mL/L), time (15 min–180 min), temperature (40 °C–70 °C), recirculation flow rate (45 mL/min– 85 mL/min) and potassium persulfate (KPS) loading (6 g/L to 14 g/L) on the progress of desulfurization has been studied using ultrasonic flow cell. Significant enhancement in the extent of desulfurization was observed with the use of optimum conditions and best approach for desulfurization of DBT was found to be FC + KPS + AA+H2O2 resulting in 100% desulfurization. A marginally better effect was demonstrated in a longitudinal bath at a working capacity of 4 L. The kinetic data revealed that the desulfurization process followed pseudo-first-order reaction kinetics. The thermodynamic parameters were also established for the desulfurization. Overall it was demonstrated that desulfurization was intensified using oxidants in combination with ultrasound and best results were shown at capacity of 4 L for the first time using a longitudinal bath.

Butyl triphenyl phosphonium bromide as an effective catalyst for ultrasound assisted oxidative desulfurization process

Oxidation of dibenzothiophene (DBT) from the stock solution using hydrogen peroxide-acetic acid mixture was carried out at a temperature range of 40–70 °C in the presence of phase transfer catalyst (PTC) namely butyl triphenyl phosphonium bromide [BTPP]Br by one pot method. [BTPP]Br was characterized by FTIR, NMR, UV–VIS analysis. Desulfurization process was analyzed for alternation in a variety of parameters i.e. ultrasound oxidation time, temperature, amount of hydrogen peroxide-acetic acid consumed, amount of catalyst under ultrasound irradiation. The result indicates that [BTPP]Br acts as a phase transfer catalyst as well as extractant in ultrasound assisted oxidative desulfurization (UAODS) and 75.23% conversion was achieved within 30 min irradiation time and 50 °C temperature. Recycling and regeneration of [BTPP]Br were also carried out under optimum conditions. Multistage extraction using [BTPP]Br lead to 86.13% desulfurization efficiency.

Optimization of a continuous ultrasound assisted oxidative desulfurization (UAOD) process of diesel using response surface methodology (RSM) considering operating cost

A continuous-flow ultrasound-assisted oxidative desulfurization (UAOD) of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system. The effects of different operating parameters of oxidation stage including residence time (2–24 min), formic acid to sulfur molar ratio (10–150), and oxidant to sulfur molar ratio (5–35) on the sulfur removal have been studied using response surface methodology (RSM) based on Box–Behnken design. Considering the operating costs of the continuous-flow oxidation stage including chemical and electrical energy consumption, the appropriate values of operating parameters were selected as follows: residence time of 16 min, the formic acid to sulfur molar ratio of 54.47, and the oxidant to sulfur molar ratio of 8.24. In these conditions, the sulfur removal and the volume ratio of the hydrocarbon phase to the aqueous phase were 86.90% and 4.34, respectively. By drastic reduction in the chemical consumption in the oxidation stage, the volume ratio of the hydrocarbon phase to the aqueous phase was increased up to 10. Therefore, the formic acid to sulfur molar ratio and the oxidant to sulfur molar ratio were obtained 23.64 and 3.58, respectively, which lead to sulfur removal of 84.38% with considerable improvements on the operating cost of oxidation stage in comparison with the previous works.

Ultrasound assisted oxidative deep-desulfurization of dimethyl disulphide from turpentine.

A promising approach of ultrasound assisted oxidative desulfurization (UAOD) was studied for deep desulfurization of simulated sulphated turpentine containing dimethyl disulphide (DMDS) as model pollutant. The effect of ultrasound parameters such as power (80-120W) and duty cycle (50-80%) as well as operating conditions as initial concentration (50-100ppm), volume (100-300ml) and temperature (28°C as ambient condition, 50-70°C) on the extent of desulfurization have been studied. The effect of addition of various oxidizing agents such as hydrogen peroxide over the range of 3-18g/L, Fenton reagent by varying FeSO4 loading from 0.75g/L to 1.75g/L at constant H2O2 loading and titanium dioxide (loading over the range 1-4g/L) in the presence of ultrasonic horn have also been investigated at laboratory scale. The addition of oxidizing agents in presence of ultrasound enhanced the extent of DMDS removal. The extent of desulfurization was found to be remarkably low for individual approaches as compared to combination approaches of US/oxidizing agents. The kinetic analysis revealed that oxidation follows first order kinetics. A significant increase in cavitational yield was observed for combination approach of US/H2O2/TiO2 (5.78×10-9g/L) compared to individual ultrasound approach (2.04×10-9g/L). Under best conditions of 120W power, 70% duty cycle, 50ppm initial concentration, 15g/L H2O2 loading and 4g/L TiO2 loading, 100% desulfurization was obtained at 23.19 Rs/L as the treatment cost. Based on the obtained results it can be concluded that US/H2O2/TiO2 approach is highly efficient desulfurization technique for deep desulfurization of simulated sulphated turpentine.

Optimization of oxidative polymerization-desulfurization of a model fuel using polyoxometalate: Effect of ultrasound irradiation

The possibility of using ultrasound irradiation to enhance a model fuel desulfurization process has been investigated in this work. For this reason, oxidative desulfurization (ODS) and ultrasound assisted oxidative desulfurization (UAOD) processes were applied, using oxygen, as the only oxidative agent, and polyoxometalate (POM) catalysts. The catalysts were analyzed using FT-IR, XRD, EDX, SEM and N2 adsorption–desorption isotherms along with BET. The response surface method was employed to optimize the ODS and UAOD processes. The ODS results revealed the process could not convert more that 70% of the DBT due to polymer deposition on the surface of the particles and lack of oxygen. Applying ultrasound irradiation in UAOD process solved these issues and increased the DBT conversion rate by 120%.

A novel multi-probe continuous flow ultrasound assisted oxidative desulfurization reactor; experimental investigation and simulation

In this work, a cylindrical multi-probe continuous flow system with different injection strategies was exploited to study ultrasound assisted oxidative desulfurization process. The effects of nozzle number, nozzle diameter, ultrasonic power and volumetric flow rate (residence time) on the desulfurization efficiency of the diesel fuel were investigated. It was found that the sulfur removal increases by increasing the nozzle diameter when the flow rate is fixed. Sulfur removal was increased by increasing the residence time, for all types of the nozzles. Injection of the aqueous phase below the horn tip in the active zone provides the conditions by which the higher interfacial area between the phases and thus greater conversion rate can be obtained. The results indicated that over 97% sulfur removal was achieved using the double-nozzle injection with nozzle diameter of 1.5 mm, residence time of 15 min, electrical power of 277.2 W and volumetric flow rates of the aqueous and oil phases 48.89 and 244.44 mL/min, respectively. The simulation results showed that choosing a proper injection strategy has an impact on the hydrodynamic and flow pattern induced by ultrasonic field and in turn could effectively influence the mixing of the two-immiscible phases. A more uniform distribution of the aqueous-phase volume fraction was observed in the system with double-nozzle injection in comparison with the single nozzle injection.

Hydrodynamic and mass transfer investigation of oxidative desulfurization of a model fuel using an ultrasound horn reactor

Ultrasound assisted oxidative desulfurization (UAOD) is a promising technology, which can result in ultra-low sulfur fuels in order to reduce the environmental crisis. Most of the researches have been conducted with the experimental approaches. In the present study, a computational fluid dynamic (CFD) model has been developed to investigate the hydrodynamics as well as the reactions involved in a sonoreactor. The results indicate that the physical and chemical effects associated with the ultrasonic field can contribute to the enhancement of the reaction and sulfur removal rates. However, the physical effects are predominant as compared to the chemical effects. Indeed, homogenous mixing and fine micro-emulsification caused by the physical effects lead to increase the interfacial area and mass transfer rate between the immiscible aqueous and oil phases. The dibenzothiophene concentration predicted by the simulation was in a reasonably good agreement with the corresponding experimental data. Another key hydrodynamic parameter induced by ultrasonic field was turbulent kinetic energy, which can play an important role in the sulfur removal rate. The results indicate the higher desulfurization efficiency has been attained at the regions with the higher velocity fluctuations.

Mechanistic investigation of Sono–Phosphotungstic acid/phase transfer agent assisted oxidative desulfurization of liquid fuel

AbstractThe aim of this paper is to identify the physical and chemical mechanism of ultrasound in presence of phase transfer agent (PTA) and phosphotungstic acid on desulfurization process. With different experimental procedures, we made an effort to identify the individual effect of phase transfer agent and ultrasound on oxidative desulfurization. Ultrasound‐assisted process is the modern technique to enhance the kinetic of the liquid–liquid heterogeneous system. Physical and intrinsic properties of liquid fuels such as diffusivity of PTA‐cation complex and also through effect on cavitation have a strong influence on Desulfurization of liquid fuels. Due to low vapor pressure of solvents, the beneficial effect of higher static pressure (that eliminates cavitation effect) is not seen in present reaction system. Phase transfer agent or phosphotungustic acid‐assisted ultrasound desulfurization has radical and ionic reaction mechanism, which is revealed in terms of lower activation energy (energetic nature of radicals) as well as collision factor (due to instability of radicals) than magnetically stirred system. This study has revealed crucial mechanistic aspects of ultrasound assisted oxidative desulfurization in presence of phase transfer agent and phosphotungustic acid, which will give more insight for further research.

Ultrasound assisted catalytic oxidative desulfurization of diesel oil using CdO nanoparticles

ABSTRACTIn this paper, sol-gel auto-combustion method is used to synthesize CdO nanoparticles. The synthesised sample is characterized for its size and structure using X-Ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. And some molecular groups containing in the nanoparticle are detected by Fourier transformer Infra Red (FT-IR). Then, the sample is used to remove the organic sulfur from hydrogenation desulfurated diesel under ultrasonic condition. The influence parameters including catalyst dosage, oxidant dosage, oxidation temperature, oxidation time and extracting times are been researched. The obtained result indicates that under the optimal condition, the desulfurization degree can be reached 72.7%.

Sonoreactor optimization for ultrasound assisted oxidative desulfurization of liquid hydrocarbon

ABSTRACTIn this study, the geometrical parameters of sonoreactor like the probe, reactor diameters, probe immersion depth and amplitude are assessed. The reaction time and H2O2 concentration effect on the sulfur removal efficiency are studied. The results indicate that, first, an increase in probe diameter decreases the efficiency of the process and further increase up to 40 mm diameter increases desulfurization efficiency up to 98.25%. An increase in probe immersion depth, increases desulfurization efficiency. Reactor diameter of 7.4 cm among other diameters (6.1, 6.5, 8 cm and 8.6 cm) achieved higher desulfurization efficiency.

Optimized Ultrasound-Assisted Oxidative Desulfurization Process of Simulated Fuels over Activated Carbon-Supported Phosphotungstic Acid

Recent technological advancements respond to the call to minimize/eliminate emissions to the atmosphere. However, on the average, fuel oils which is one of the major raw materials, is found to increase in sulfur concentration due to a phenomenon called thermal maturation. As such, a deeper desulfurization process is needed to obtain low/ultra-low sulfur fuel oils. In the present study, the ultrasound assisted oxidative desulfurization (UAOD) processes using the H2O2 and HPW-AC oxidizing system applied to simulated fuel (~2800 ppm sulfur in the form of dibenzothiophene, benzothiophene, and thiophene dissolved in toluene), were optimized. After the pre-saturation of the HPW-AC with the simulated fuel, H2O2 was added just before the reaction was commenced under ultrasonic irradiation. After the application of both 2k-factorial design of experiment for screening and Face-Centered Design of Experiment for optimization, it was found that 25.52 wt% of H2O2 concentration, 983.9 mg of catalyst dose, 9.52 mL aqueous phase per 10 mL of the organic phase and 76.36 minutes of ultrasonication time would render 94.74% oxidation of the sulfur compounds in the simulated fuel. After the application of the optimized parameters to kerosene and employing a 4-cycle extraction using acetonitrile, 99% of the original sulfur content were removed from the kerosene using the UAOD optimized parameters. The desulfurization process resulted in a low-sulfur kerosene which retained its basic fuel properties such as density, viscosity and calorific value.

Ultrasound assisted photocatalytic oxidative desulfurization of model diesel fuel

ABSTRACTUltrasound assisted photocatalytic oxidation technology is an efficient and gentle technology to remove the organic sulfur from diesel. The influence parameters of catalytic oxidation phase include catalyst dosage, reaction temperature, oxidation time, hydrogen peroxide to diesel fuel ratio and time of the extraction process. Furthermore, the comparison of the results under two conditions of ultrasound irradiation and mechanical agitation are also specially examined. The obtained results indicate that under the optimal condition, ultrasound assisted oxidative desulfurization (UAOD) is more efficient for sulfur removal which the desulfurization degree can be reached 99.47%.

Continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process: An efficient diesel treatment by injection of the aqueous phase

A new continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process was developed in order to decrease energy and aqueous phase consumption. In this process the aqueous phase is injected below the horn tip leading to enhanced mixing of the phases. Diesel fuel as the oil phase with sulfur content of 1550ppmw and an appropriate mixture of hydrogen peroxide and formic acid as the aqueous phase were used. At the first step, the optimized condition for the sulfur removal has been obtained in the batch mode operation. Hence, the effect of more important oxidation parameters; oxidant-to-sulfur molar ratio, acid-to-sulfur molar ratio and sonication time were investigated. Then the optimized conditions were obtained using Response Surface Methodology (RSM) technique. Afterwards, some experiments corresponding to the best batch condition and also with objective of minimizing the residence time and aqueous phase to fuel volume ratio have been conducted in a newly designed double-compartment reactor with injection of the aqueous phase to evaluate the process in a continuous flow operation. In addition, the effect of nozzle diameter has been examined. Significant improvement on the sulfur removal was observed specially in lower sonication time in the case of dispersion method in comparison with the conventional contact between two phases. Ultimately, the flow pattern induced by ultrasonic device, and also injection of the aqueous phase were analyzed quantitatively and qualitatively by capturing the sequential images.

Prediction of dibenzothiophene conversion in the ultrasound assisted oxidative desulfurization process

ABSTRACTIn order to produce ultra-low sulfur diesel, ultrasound-assisted oxidation desulfurization of dibenzothiophene (DBT) was carried out with acetic acid and hydrogen peroxide. Due to its complexity, ultrasound-assisted oxidation process lacks a precise analytical solution. This paper explores the application of linear multiple regression and neural network for the prediction of dibenzothiophene conversion. Models were employed with respect to hydrogen peroxide dosage, temperature, reaction time, initial DBT concentration, and rate constant. The most accurate results were achieved by neural network model. Developed models facilitate future research in terms of better understanding the influence of process conditions of DBT conversion.