Oxidative Desulfurization Of Model Diesel Research Articles

Catalytic Oxidative Desulfurization of Model Diesel Using TBHP-DMF System

Hydrodesulfurization (HDS) technique is no longer applicable in achieving ultra-low sulfur diesel because of high operational cost, high operating temperature and low efficiency. Due to these disadvantage, catalytic oxidative desulfurization (Cat-ODS) has been introduced as a new technique in achieving ultra-low sulfur diesel. The performance of the Fe catalyst was investigated in Cat-ODS of model diesel using terbutyl hydroperoxide (TBHP) as oxidant and dimethylformamide (DMF) as an extracting solvent. The physicochemical analysis of this catalyst was accomplished using several characterization techniques such as BET, EDX and HRTEM. It posseses high surface area of 226 m2g-1 with small particle sizes in the range of 6-7 nm and less metal leaching. Under optimize condition, about 90% of sulfur was removed from model diesel. In the absence of catalyst, only about less than 80% of organosulfur compounds were removed. The Cat-ODS system showed the promising technology to be compliment with hydrodesulfurization (HDS) to produce low sulfur diesel.

Oxidative desulfurization of model diesel fuel catalyzed by carbon-supported heteropoly acids: Effect of carbon support

Keggin-type heteropoly acids (HPAs) H3PMo12O40 and H3PW12O40 supported on activated carbon were shown to be highly active catalysts for oxidative desulfurization (ODS) of model diesel fuel containing dibenzothiophene (DBT) and heptane by 30% H2O2. A number of commercial activated carbons differing in their acid-base properties were tested as the HPA support to reveal a strong effect of basicity of carbon support on the integrity of HPA structure on the carbon surface and catalyst activity. The most active catalysts, comprising decomposed H3PW12O40, outperformed best reported heterogeneous catalysts for ODS in similar systems, exhibiting 100% DBT removal from the model diesel fuel at 40–60 °C and H2O2/DBT = 3 mol/mol in 20–30 min with 85–88% H2O2 efficiency and could be recovered and reused without loss of activity. DRIFTS studies provided an insight into the mechanism of ODS reaction on carbon-supported HPAs.

A new catalytic system for oxidative desulfurization of model diesel by hierarchical TiO2 nanotube arrays on titanium foil

A new catalytic system for oxidative desulfurization of model diesel by hierarchical TiO2 nanotube arrays on titanium foil

Lacunary phosphomolybdate PMo11 supported on mesoporous KIT-6 as catalyst for oxidative desulfurization of model diesel

In this study, an efficient simultaneous extraction-oxidation catalytic system for deep desulfurization of a model fuel was investigated. For this purpose, mono lacunary phosphomolybdate (PMo11) was synthesized. Then a series of PMo11 catalysts were supported on mesoporous silica material (KIT-6). Structural characterization of the catalysts was performed by various techniques such as SEM, TEM, FT-IR, FT-Raman, ICP, BET and XRD. The results of the XRD and SEM analysis showed that the synthesized PMo11 has a semi-crystalline structure. It was observed that the catalyst with 30% PMo11 loading had the most catalytic activity on dibenzothiophene and benzothiophene removal in the oxidative desulfurization process. In this catalytic system, various conditions such as temperature, oxidizing agent value, catalyst amount, and extractant solvent type were varied and their effect on the reaction was evaluated. Under optimal conditions, dibenzothiophene was eliminated up to over 92.5%. The catalyst could be recycled and reused four times without significant reduction in its catalytic activity.

Novel acidic eutectic mixture as peroxidase mimetics for oxidative desulfurization of model diesel

A new generation of green solvent, deep eutectic solvents (DESs), are being received increased interest in the fields of organic synthesis, electrochemistry, catalysis and oxidative desulfurization (ODS) process. Despite possessing high ODS activity, little is known for the mechanism of the excellent desulfurization performance of DES. In this study, a class of acidic eutectic mixture was prepared with different molar ratios of acetamide and glutaric acid. It was found that desulfurization process was significantly affected by the composition of prepared DES. Under optimal conditions, the desulfurization efficiencies of acetamide/glutaric acid (molar ratio 1 : 2) DES was capable to reach up to 99% within only 3 h.Density functional theory (DFT) calculation revealed that acetamide/glutaric acid DES possessed intrinsic peroxidase-like property and reduced greatly TS barriers in oxidation process. The synergy cooperation of acetamide and carboxylate likes the active site of enzyme, achieving the catalytic oxidation of dibenzothiophene (DBT). In addition, this DES system was successfully applied for the deep oxidation desulfurization of real fuels, which demonstrated extraordinary catalytic performances.

Extraction Coupled with Aerobic Oxidative Desulfurization of Model Diesel Using a B-type Anderson Polyoxometalate Catalyst in Ionic Liquids

An efficient aerobic oxidative desulfurization system was explored with polyoxometalate (DODMAC)3Co(OH)6Mo6O18·3H2O (DODMAC: Dimethyldioctadecylammonium Chloride) combined ionic liquids (ILs) as extraction solvent as well as reaction media for aerobic oxidative desulfurization of model diesel. N-octylpyridinium tetrafluoroborate ([Opy]BF4) was employed in the desulfurization system and the amazing recoverability showed without noticeable decrease in activity after seven cycles has aroused the great interest of us. Systematically investigations were carried out on the factors influencing the removal of DBT. The possible mechanism was also investigated hoping to provide new insights into diesel deep desulfurization processes.

Oxidative desulfurization of model diesel fuel catalyzed by carbon-supported heteropoly acids

Keggin-type heteropoly acids supported on activated carbon (HPA/C) are active catalysts for oxidative desulfurization (ODS) of diesel fuel under mild conditions in a biphasic system composed of a benzothiophene-containing model diesel fuel (heptane) and aqueous 30% H2O2. The catalytic activity of HPA/C was found to decrease in the order of HPA: H3PMo12O40 > H3PW12O40 > H4SiW12O40. The most active catalyst, H3PMo12O40/C, exhibited 100% removal of benzothiophenes from model diesel fuel at 60 °C, and could be recovered and reused without loss of activity. This catalyst outperforms other recently reported heterogeneous catalysts for ODS in similar systems. Kinetic and DRIFTS studies provide new insights into the mechanism of ODS reaction on carbon-supported HPAs.

Oxidative Desulfurization of Model Diesel Fuel by Vanadium Granular-Shape Mesoporous (V/GMS) Silica System as Nanocatalyst

The performance of V-containing granular-shape mesoporous (V/GSM) silica systems in oxidative desulfurization of model diesel fuel was studied. FTIR, XRD, SEM, TEM, N2 adsorption-desorption, UV-Vis, and NH3-TPD techniques were used to analyze the surface properties of the functionalized catalyst. The mesostructure of silica remains intact after vanadium modifications as shown by XRD and adsorption-desorption analysis, while spectroscopy indicates the successful impregnation of neat vanadium oxide inside the porous silica support. The oxidation desulfurization of model diesel fuel was effectively catalyzed by this catalyst and the highest activity was shown by 4.8% V/GSM catalyst. Compared with their conventional V/MCF and V/MCM-41 counterparts, SSM-supported vanadium catalysts showed much higher activity. This may be associated with the higher reducibility and better diffusion of reactants and products in V/MCF and V/MCM-41catalysts.

Ultrasound-assisted synthesis and catalytic activity of mesostructured FeOx/SBA-15 and FeOx/Zr-SBA-15 catalysts for the oxidative desulfurization of model diesel

Abstract Two series of FeOx/SBA-15 and FeOx/Zr-SBA-15 mesoporous catalysts were synthesized with ultrasound-assisted method by varying Fe content from 10 wt% to 20 and 30 wt%. The crystalline structure, textural properties, surface morphologies, surface acidity, and phase composition of the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in situ Fourier transform infrared spectroscopy (FTIR). The XRD, Raman and Mossbauer spectroscopic characterizations showed that both γ-Fe2O3 and α-Fe2O3 nanoparticles were present in all the catalysts and Fe3+ ions were dispersed on the surface of SBA-15 with different coordination. In the oxidation desulfurization (ODS) of a model diesel, the reaction parameters (temperature, time, and catalyst mass), Fe content, zirconium doping, and surface acidity of the catalysts were all critical for the ODS in a biphasic reaction system. All catalysts chiefly contained Lewis acidity which was related to iron content and zirconium modification and could correlate well with catalytic activity. Zirconium incooperating into the SBA-15 solid increased surface acidity and promoted γ-Fe2O3 formation by inhibiting the amorphous iron oxide in the Fe/Zr-SBA-15 catalysts, thus improved the ODS efficiency. The reaction temperature 60 °C was the optimal for ODS reaction, temperature greater than 80 °C led to oxidant partial decomposition. Under the optimal reaction condition, 0.1 g of the best catalysts (30%Fe/SBA-15 and 30%Fe/Zr-SBA-15) could remove all dibenzothiophene (DBT) (300 ppm DBT in 100 ml n-hexadecane) at 60 °C within 30 min. Thus, the combination of catalysis, oxidation and extraction in our polar-nonpolar-solid reaction system was simultaneously realized in one unit, which will be promising for effectively removal of organosulfur compounds for production of ultralow sulfur fuels.

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%.

Optimization of oxidative desulfurization of Malaysian Euro II diesel fuel utilizing tert-butyl hydroperoxide–dimethylformamide system

Deep oxidative desulfurization of model diesel consisting of thiophene, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated with various oxidants followed by extraction step using dimethylformamide (DMF). Response surface methodology based on Box–Behnken design was used to evaluate the effects of the main operating parameters, including the oxidant to sulfur molar ratio (2.0–4.0), oxidation temperature (40–60°C) and oxidation time (10–60min), on the 4,6-dimethyldibenzothiophene conversion. Among the oxidants used; tert-butyl hydroperoxide (TBHP) was led to the highest oxidation of model sulfur compounds. Meanwhile, the statistical results revealed that TBHP/sulfur ratio was the most important parameter followed by oxidation time and oxidation temperature. The optimum oxidative desulfurization conditions for 4,6-DMDBT conversion had been attained at TBHP/sulfur ratio of 3.0, temperature of 48°C and period time of 31min, respectively with the highest conversion of 4,6-DMDBT of 84.5%. The experimental optimum yield fitted-well with the predicted value with less than 5% error. The mechanistic study showed that the reaction between TBHP and 4,6-DMDBT was efficient to produce corresponding sulfoxide, instead of sulfone compound.

Ultrasound assisted oxidative desulfurization of model diesel fuel

Very stringent environmental regulations have limited the level of sulfur in diesel, therefore deep desulfurization of fuels is required. For that purpose, the frequently used industrial process is hydrodesulfurization (HDS) which enables effective elimination of sulfur compounds such as mercaptanes, thiols, sulfides, disulfides from diesel oil, but removal of thiophene sulfur compounds (benzothiophene, dibenzothiophene, 4,6 dimethyldibenzothiophene) is insufficient. Ultrasound assisted oxidative desulfurization (UAOD) as one of several new technologies enables performance under mild conditions without use of explosive hydrogen. A higher reactivity of thiophene sulfur compounds during UAOD also provides conversion into highly polar sulfoxides and sulfones that are easily removed by adsorption or extraction. Nowadays, different catalyst/oxidants systems are being studied to improve oxidation reaction efficiency and enhance the mass transfer in the interfacial region. In this paper, the effect of reaction temperature (40–70°C) and oxidation time (5–150min) for UAOD of model diesel fuel with a catalyst/oxidants system (acetic acid/hydrogen peroxide) was investigated in a 70ml batch reactor. Furthermore, the effects of different initial concentrations of dibenzothiophene (DBT) and of ultrasound amplitude were additionally examined to achieve efficient sulfur removal. The obtained results indicated that temperature and US amplitude of 70°C and 80% respectively were efficient for conversion of DBT (sulfur concentration up to 3976.86ppm). The results indicate a rise in the yield of sulfones at higher temperatures and subsequent extraction with N,N-dimethylformamide conducted after the process of oxidation at different solvent/oil ratio revealed sulfur removal efficiency of 98.35%.

Catalytic oxidative desulfurization of diesel oil by Co/Mn/Al2O3 catalysts—tert-butyl hydroperoxide (TBHP) system: preparation, characterization, reaction, and mechanism

The hydrodesulfurization (HDS) technique available is no longer suitable for the purpose of achieving ultra-low sulfur diesel. Therefore, in this study, the catalytic oxidative desulfurization of model diesel was carried out using tert-butyl hydroperoxide along with inexpensive alumina-supported manganese-based oxide catalysts, and later, the oxidized sulfur compounds were extracted by dimethylformamide, a polar solvent. The effect of dopant ratio, calcination temperature, reaction time, and reaction temperature were investigated in detail. The oxidation reactivity of different substrates was in the following order: DBT > Th > 4,6-DMDBT. The best desulfurization efficiency of model diesel, under mild reaction conditions, was 85.3 % thiophene, 85.0 % dibenzothiophene, and 74.5 % 4,6-dimethyldibenzothiophene using the 2.14 %Co/13.17 %Mn/Al2O3 catalyst calcined at 400 °C. Besides, this catalyst retained a high conversion of sulfur after three rounds of reaction cycles and can be used as a reusable active catalyst in ODS treatment. Under the optimal conditions, the S-content in the commercial diesel could be decreased from 415 to less than 10 ppmw. The oxidation mechanism was studied in detail, and TBHP-Co/Mn catalyst was the main active oxidizing species on the oxidation of DBT.

Oxidative desulfurization of model diesel via dual activation by a protic ionic liquid

A novel and green carboxylate-anion-based protic ionic liquid (PIL), [Hnmp]HCOO, was prepared through a simple and atom economic neutralization reaction between N-methyl-2-pyrrolidonium (NMP) and formic acids. Both FT-IR spectra and 1H NMR confirmed its simple salt structure. [Hnmp]HCOO exhibited so high catalytic activity that the dibenzothiophene (DBT) removal reached 99% at 50°C in 3h under conditions of VPIL/Vmodel oil=1:10 and H2O2/DBT (O/S, molar ratio)=5. The catalytic oxidation reactivity of S-compounds was found to be in the order of DBT>4,6-dimethyldibenzothiophene (4,6-DMDBT)>benzothiophene (BT). The investigation on mechanism showed that oxidative desulfurization was realized through dual activation of PIL. Moreover, [Hnmp]HCOO can be recycled for five times with an unnoticeable decrease in desulfurization activity.

Hydrogen peroxide oxidative desulfurization of model diesel mixtures using azacrown ethers

Hydrogen peroxide oxidative desulfurization of model diesel fuel mixtures in the presence of azacrown ethers and their complexes with niobium pentachloride at 40–80°C has been studied. It has been found that the use of complexes of azacrown ethers with NbCl5 leads to a decrease in the total sulfur content in the model mixtures to 13% of the initial amount. The structure of the azacrown ether used has little effect on the extent of desulfurization of the model mixture.

Oxidative desulfurization of model diesel using [(C4H9)4N]6Mo7O24 as a catalyst in ionic liquids

An extraction and catalytic oxidation desulfurization (ECODS) system, composed of an Anderson-type catalyst [(C4H9)4N]6Mo7O24, model diesel, 30% H2O2 and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), was conducted under mild conditions. The sulfur-containing compounds, such as benzothiophene (BT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), were extracted into ionic liquid (IL) from the model oil and oxidized to corresponding sulfones using H2O2 as oxidant in the presence of the [(C4H9)4N]6Mo7O24. In the case of ECODS, the sulfur removal of DBT can reach 99.0%, which was superior to that of the simple extraction with IL or the chemical oxidation. The amounts of ILs and oxidant dosage play vital roles in ECODS. The reactivity of sulfur-containing compounds in the ECODS was followed: DBT>4-MDBT>4,6-DMDBT>BT. This ECODS system could be recycled six times without a significant decrease in activity.

Investigation of process variables and intensification effects of ultrasound applied in oxidative desulfurization of model diesel over MoO3/Al2O3 catalyst

A new heterogeneous sonocatalytic system consisting of a MoO3/Al2O3 catalyst and H2O2 combined with ultrasonication was studied to improve and accelerate the oxidation of model sulfur compounds of diesel, resulting in a significant enhancement in the process efficiency. The influence of ultrasound on properties, activity and stability of the catalyst was studied in detail by means of GC-FID, PSD, SEM and BET techniques. Above 98% conversion of DBT in model diesel containing 1000μg/g sulfur was obtained by new ultrasound-assisted desulfurization at H2O2/sulfur molar ratio of 3, temperature of 318K and catalyst dosage of 30g/L after 30min reaction, contrary to the 55% conversion obtained during the silent process. This improvement was considerably affected by operation parameters and catalyst properties. The effects of main process variables were investigated using response surface methodology in silent process compared to ultrasonication. Ultrasound provided a good dispersion of catalyst and oxidant by breakage of hydrogen bonding and deagglomeration of them in the oil phase. Deposition of impurities on the catalyst surface caused a quick deactivation in silent experiments resulting only 5% of DBT oxidation after 6 cycles of silent reaction by recycled catalyst. Above 95% of DBT was oxidized after 6 ultrasound-assisted cycles showing a great improvement in stability by cleaning the surface during ultrasonication. A considerable particle size reduction was also observed after 3h sonication that could provide more dispersion of catalyst in model fuel.

Aerobic oxidative desulfurization of model diesel using a B-type Anderson catalyst [(C18H37)2N(CH3)2]3Co(OH)6Mo6O18·3H2O

A B-type Anderson polyoxomolybdates with mixed-valence molybdenum ions, [(C18H37)2N(CH3)2]3Co(OH)6Mo(V,VI)6O18, was prepared and characterized by Fourier transform infrared spectroscopy(FT-IR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), differential thermal analysis (DTA) and X-ray photoelectron spectrum (XPS). The polyoxometalate shows high catalytic activity in aerobic oxidative desulfurization of model diesel and the turnover number (TON) can reach about 4200 in absence of any sacrificial agent under mild conditions. The quaternary ammonium cations in the catalysts play a vital role in the aerobic oxidative desulfurization system. The catalytic activity for the oxidation of sulfur-containing compounds decreases in the order of 4,6-DMDBT>DBT>BT.

Effect of transition metal oxides catalysts on oxidative desulfurization of model diesel

In this paper, model diesel is used to study the performance of oxidative desulfurization (ODS) system compared to hydrodesulfurization (HDS) process. A detailed parametric experimental study was performed to select the best technique for sulfur removal. The effects of solvent, oxidant, bimetallic oxide catalyst, dopant, dopant ratio and calcination temperature were investigated. Dimethylformamide (DMF) and tert-butyl hydroperoxide (TBHP) were found to be the best solvent and oxidizing agent for the removal of sulfur compounds in model diesel. Both solvent and oxidant were then applied to explore the applicability of various catalysts, such as iron, manganese, molybdenum, tin, zinc and cobalt in model diesel. The results showed that the catalytic activity was decreased in the order: Mo>Mn>Sn>Fe≈Co>Zn. Further investigation of doped molybdenum revealed that 4.35% WO3/16.52% MoO3/Al2O3 in the ratio of 10:90 with calcination temperature at 500°C was assigned as the best catalyst in this research. Under mild reaction condition, this catalyst showed high conversion with appreciable stability until 150hours and can be used as a reusable active catalyst in ODS treatment. Additionally, on the basis results obtained, a mechanistic proposal for this reaction was postulated, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of WO3/MoO3/Al2O3.

Hydrogen peroxide oxidative desulfurization of model diesel fuel mixtures in the presence of crown ethers and transition metal peroxo complexes

The catalytic ability of crown ethers and their complexes with transition metal cations in the desulfurization reaction of mixtures that simulate diesel fuel has been investigated. It has been found that the use of monoaza-15-crown-5-ethers with an admixture of NbCl5 resulted in a fourfold decrease of the total sulfur content, thereby indicating partial oxidation of benzothiophenes and dibenzothiophenes. The complexation of azacrown ethers with NbCl5 has been studied by 1H NMR spectroscopy. A moderate efficiency of adsorption purification procedure using silica and alumina for both initial and oxidized model mixtures has been revealed.