Oxidative Desulfurization Of Diesel Fuel Research Articles

Multi-walled carbon nanotubes coated on defective tungsten oxide for deep oxidative desulfurization of diesel fuels

The interface properties of metal oxides considerably affect the catalyst activity during the removal process of persistent organic sulfur pollutant in diesel fuels. Herein, we report that the hydrophilicity of defective metal oxides can be well shielded by refining the interface. As a proof of point, multi-walled carbon nanotubes (CNTs) were employed as a solid modifier to be wound on the Mo-doped W18O49 nanowire clusters (MoWO-x@CNTs) for enhanced catalytic performance. The results show that the full conversion of dibenzothiophene is achieved within 12.5 min. The turnover frequency value is up to 79.7 h−1, much higher than other catalysts. Compared with the bare W18O49, the MoWO-x@CNTs exploits a rough hierarchical structure, which overcomes the limitation of the hydrophilic W18O49 interface. Furthermore, the persistent organic sulfur in diesel fuels is <6.2 ppm, achieving the goal of ultra-deep desulfurization. Besides, no more secondary extraction is required, which also alleviating environmental pollution caused by the abuse of organic waste.

Ultrafast Oxidative Desulfurization of Diesel Fuel Catalyzed by Polyoxometalate-Based Catalyst Immobilized on Functionalized Y-Sba-15

Ultrafast Oxidative Desulfurization of Diesel Fuel Catalyzed by Polyoxometalate-Based Catalyst Immobilized on Functionalized Y-Sba-15

In situ fabrication of hollow silica confined defective molybdenum oxide for enhanced catalytic oxidative desulfurization of diesel fuels

Hollow nanomaterials are considered to be excellent carriers due to the nanoreactor confinement effect, which can improve the performance of the supported catalysts. In this work, a hollow silica confined defective molybdenum oxide catalyst (MoOx/HS) was obtained by using phosphomolybdic acid grafted polystyrenes as the templates. Compared with solid silica-supported catalyst (MoO3/SS), MoOx/HS could make better use of active components to achieve complete desulfurization. The calculated turnover value (TON) of MoOx/HS was 1.37 mol/mol, which is three times more than that of MoO3/SS. The presence of oxygen defects also facilitated the oxidation reaction. In addition, the catalyst MoOx/HS had good stability and selectivity, and the desulfurization rate of dibenzothiophene (DBT) remained 95.3% after being recycled for 5 times.

Life cycle assessment of environmental impacts associated with oxidative desulfurization of diesel fuels catalyzed by metal-free reduced graphene oxide

This study aimed to analyze the environmental impacts of the oxidative desulfurization (ODS) process catalyzed by metal-free reduced graphene oxide (rGO) through life cycle assessment (LCA). The environmental impacts study containing the rGO production process, the ODS process, the comparison of different oxidants and solvents was developed. This study was performed by using ReCiPe 2016 V1.03 Hierarchist midpoint as well as endpoint approach and SimaPro software. For the production of 1 kg rGO, the results showed that hydrochloric acid (washing), sulfuric acid (mixing), hydrazine (reduction) and electricity were four main contributors in this process, and this process showed a significant impact on human health 14.21 Pt followed by ecosystem 0.845 Pt and resources 0.164 Pt. For the production of 1 kg desulfurized oil (400 ppm), main environmental impacts were terrestrial ecotoxicity (43.256 kg 1,4-DCB), global warming (41.058 kg CO2), human non-carcinogenic toxicity (19.570 kg 1,4-DCB) and fossil resource scarcity (13.178 kg oil), and the main contributors were electricity, diesel oil and acetonitrile. The whole ODS process also showed a greatest effect on human health. For two common oxidants hydrogen peroxide and oxygen used in ODS, hydrogen peroxide showed a greater impact than oxygen. On the other hand, for three common solvents employed in ODS, N-methyl-2-pyrrolidone had a more serious impact on human health followed by acetonitrile and N,N-dimethylformamide. As such, LCA results demonstrated the detailed environmental impacts originated from the catalytic ODS, hence elucidating systematic guidance for its future development toward practicality.

Oxidative Desulfurization of Diesel Fuel Using Three Kinds of Carboxylic Acids Supported by Iron(III) Chloride

Aqueous carboxylic acids (CA) are generally used as attractive catalytic extractants in the field of desulfurization of petroleum products. In the present study, a triple system consisting of CA-ferric chloride-hydrogen peroxide has been used for the removal of aromatic S-compounds from partially hydrotreated diesel by liquid−liquid oxidative-extraction. The influence of various operating parameters affecting the oxidative desulfurization was experimentally investigated. Formic acid (HCOOH), acetic acid (CH3COOH), and propanoic acid (CH3CH2COOH) as aqueous solutions with hydrogen peroxide and iron(III) chloride (FeCl3) as oxidant and catalytic agent, respectively, were used. All experiments were carried out at 55°C with different oxidant to sulfur mole ratios (nH2O2/nS) (15–36), CA to sulfur mole ratios (nCA/nS) (2–26), and oxidation reaction times (5–25 min). Within 25 min of the treatment, a maximum elimination of aromatic S-compounds of 65.1% was obtained when molar ratio of oxidant to sulfur (nH2O2/nS) was 36 and molar ratio of CA to sulfur (nCA/nS) was 26. Surface tension calculations for the CAs demonstrated that the average void radius of the acids has a pronounced effect on the fitting of S-compounds from diesel fuel into acids and is important to sulfur removal. Further, increasing the desulfurization efficiency was also energetically affected in the presence of ferric halide. The obtention of the sulfur removal ability value was noticeably higher than was achieved by employing similar reaction conditions in the absence of FeCl3.

Ultrafast Oxidative Desulfurization of Diesel Fuels by Mass Transfer Enhancement of Polyoxometalate Modified Alumina Catalysts

Deep desulfurization of fuels has long been and remains to be a highly challenging issue. In this work, a trilacunary polyoxometalate of Na12[α-P2W15O56]·24H2O (P2W15) was covalently tethered onto ...

Deep oxidative desulfurization of diesel fuels using homogeneous and SBA-15-supported peroxophosphotungstate catalysts

A combination of catalytic oxidation and extraction was used for the desulfurization of a model diesel containing benzothiophene, dibenzothiophene and 4,6-dimethyldibenzothiophene, or a real diesel sample with a sulfur content of 2300 ppm. The catalysts used were the soluble peroxo compound (nBu4N)3{PO4[WO(O2)2]4} (PW4) and a supported material denoted as PW4@TMA-SBA-15 that was prepared by immobilization of PW4 in an ordered mesoporous silica (SBA-15) derivatized with propyltrimethylammonium groups (TMA). The supported catalyst was characterized by FT-IR, FT-Raman, 31P and 13C MAS NMR spectroscopies, powder X-ray diffraction and scanning electron microscopy. Under optimized conditions (H2O2/S molar ratio = 7, 70 °C, acetonitrile as extraction solvent), both catalysts led to complete desulfurization of the model diesel within a reaction time of 2 h. The desulfurization systems could be recycled 10 times with only a slight decrease in performance being observed between the 9th and 10th oxidative desulfurization cycles. Application of the PW4 system to the real diesel led to an outstanding desulfurization efficiency of 89% after a reaction time of 2 h.

High efficient and selective oxidative desulfurization of diesel fuel using dual-function [Omim]FeCl4 as catalyst/extractant

Lewis acidic ionic liquid (IL) of 1-octyl-3-methylimidazolium tetrachloroferrates ([Omim]FeCl4) with an interesting structure, was synthesized and introduced as a highly effective catalyst and also as extractive solvent in oxidative desulfurization (ODS) of model and real diesel fuels with H2O2 oxidant. FT-IR, H-NMR and TG-DSC analysis were used for characterization of the prepared ILs. GC-FID, GC-PFPD and GC–MS measurements were also employed to investigate the ODS yields and mechanism. The adequate structure and acidic properties of [Omim]FeCl4 allowed removal of thiophenic compounds with high efficiency in an extraction and then oxidation process. The effects of the major processing variables on ODS performance of [Omim]FeCl4 were studied in detail. At the optimal conditions of VIL/Voil of 1/10, O/S molar ratio of 5, reaction time of 15 min and room temperature, BT and DBT were totally eliminated, and 4,6-DMDBT was removed by 99% from the model diesel. Moreover, [Omim]FeCl4 was able to desulfurize two real diesel fuels containing 590 and 2573 ppmw of sulfur with the efficiency of 85% and 61.2%, respectively, at a short time of 15 min. The experimental results also showed a remarkable selectivity of 0.919 for elimination of thiophenic compounds in competition with non-sulfur aromatic model of 2-methyl naphthalene. [Omim]FeCl4 exhibited an excellent recyclability with no significant decline in activity after use in 7 reaction cycles. An overall mechanism was also suggested for desulfurization by the proposed system.

Oxidative Desulfurization of Diesel Fuel Using a Brønsted Acidic Ionic Liquid Supported on Silica Gel

A novel heterogeneous catalyst was prepared by supporting the ionic liquid (IL) 1-octyl-3-methylimidazolium hydrogen sulfate ([Omim][HSO4]) in the silica-gel matrix using a sol–gel method and employed in oxidative desulfurization of a model oil containing dibenzothiophene (DBT) and real diesel fuel. The properties of the supported ionic liquid (SIL) were characterized by FT-IR, TGA, BET-BJH, SEM-EDS, and PSA. The results showed that the ionic liquid was successfully incorporated in the silica-gel matrix, and a catalyst having high surface area was prepared. The effects of H2O2/DBT molar ratio (O/S), temperature, SIL/oil mass ratio, initial S content, and sulfur species on the sulfur removal of the model oil were studied. The highest DBT removal efficiency of 99.1% was obtained with the prepared catalyst having 17 wt % supported IL loading in the conditions of SIL/oil (w/w) of 1:3 and O/S molar ratio of 5 in 50 min at 50 °C. The prepared catalyst can be efficiently applied in oxidative desulfurization with...

Brønsted–Lewis Acidic Ionic Liquids and Application in Oxidative Desulfurization of Diesel Fuel

Study on alternative methods to hydrodesulfurization is always an interesting area, because of the ineffectiveness for hydrodesulfurization to remove some cyclic sulfur compounds (S-compounds) and the high cost from harsh operation conditions and expensive catalyst, among which oxidative desulfurization (ODS) using ionic liquids (ILs) as solvent is intensively studied recently. Here, we synthesize a series of Brønsted–Lewis acidic ILs of N-methylpyrrolidonium zinc chloride ([Hnmp]Clx/(ZnCl2)y, x:y from 2:1 to 1:2) and investigate the ODS of both model diesel fuel composed of n-octane and dibenzothiophene and real FCC feedstock where such ILs are used as extractant and catalyst and 30 wt % H2O2 is used as oxidant, involving the factors such as IL composition (or x:y), temperature, dose of oxidant (or molar ratio of O/S), dose of IL (or mass ratio of IL/oil), recycling of IL and multistage desulfurization. IL composition has an important effect on sulfur removal (S-removal) efficiency, and [Hnmp]Cl/ZnCl2 (x:y = 1, the structure nature was characterized with ESI-MS and FT-IR) shows the highest desulfurization capability with good recyclability. With [Hnmp]Cl/ZnCl2, the S-content in model diesel fuel can be reduced to <1 ppm from 500 ppm with 99.9% S-removal at 75 °C, IL/oil = 1/3 and O/S = 8 after only one stage, while the sulfur removal for real FCC diesel fuel is less than 38% in one stage and can reach 83% after five stages, which might be ascribed to more-complex S-species in real fluidized catalytic cracking (FCC) diesel fuel as indicated by gas chromatography–sulfur chemiluminescence detection (GC-SCD) chromatogram analyses. The sulfur content (S-content) in FCC diesel fuel, however, can be reduced to 5.3 ppm with a total S-removal of 97.6% after five-stage ODS with one more extractive desulfurization with furfural as the extractant. This work shows that such Brønsted–Lewis acidic ILs are potential solvents used in ODS to produce clean fuel oils.

The Role of Molybdenum Oxide Based Catalysts on Oxidative Desulfurization of Diesel Fuel

The industrial technology, hydrodesulfurization (HDS) is incapable to meet ultra-low sulfur standard due to the limited treatment on organosulfur compound in diesel fuel. In this paper, catalytic oxidative desulfurization of thiophene, dibenzothiophene and 4,6-dimethyldibenzothiophene using molybdenum oxide based catalyst was investigated. A detailed parametric experimental study; number of coating, calcination temperature, addition of dopant was performed on sulfur removal. It was shown that 4.35% WO3/16.52% MoO3/γ-Al2O3 , calcined at 500°C was successfully removed 92.5% of thiophene, 100% of DBT and 100% of 4,6-DMDBT in model diesel at short reaction time and lower temperature.

Catalytic Oxidative Desulfurization of Diesel Fuels Using Air in a Two-Step Approach

This study presents a novel approach to fuel desulfurization in two steps where air is used as oxidant for the in situ generation of hydroperoxides from aromatics in diesel fuel and then the sulfur compounds are oxidized by the hydroperoxides to sulfones. Bulk and supported CuO based catalysts were examined for oxidation of surrogate and real diesel fuels for generation of hydroperoxides in situ using air. Among bulk CuO, CuO/Al2O3, CuO/SiO2, CuO/TiO2, and CuO-ZnO/Al2O3 tested, CuO/Al2O3 gave the highest conversion, but the highest yield and selectivity for hydroperoxide was obtained on bulk CuO catalyst for liquid phase air oxidation of isopropylbenzene. H2-Temperature programmed reduction (H2-TPR) revealed the presence of dispersed CuO phase on supported catalysts with bulk CuO as the dominant phase on the unsupported catalyst. Three real diesel fuels were tested for liquid phase air oxidation at 120 °C in the presence of bulk CuO catalyst which revealed different levels of hydroperoxides generation. Th...

The Ultra-deep Oxidative Desulfurization of Diesel Fuel by an MnO2/Al2O3/Hydrogen Peroxide/Aldehyde System

Oxidative desulfurization of hydrogenation diesel was studied using MnO2/Al2O3 as catalyst in the presence of H2O2, formic acid and isobutyl aldehyde at 60°C and atmospheric pressure. The sulfur impurities in diesel were oxidized to sulfate and dissolved into the water phase. The sulfur content could be reduced from 500 to 1 ppm in 30 min in appropriate reaction conditions. The combination of two oxidative processes by adding isobutyl aldehyde could remove the sulfur impurities in diesel easily without solvent extraction.

Oxidative desulfurization of diesel fuels in the presence of crown ethers and transition metal peroxo complexes

The catalytic activity of crown ethers and their complexes with transition metal cations in diesel fuel desulfurization has been investigated. With dibenzo-18-crown-6 in combination with NbCl5, the total sulfur content of the fuel can be reduced by a factor of 2 or larger. The effects of the reaction temperature, nature of metal and crown ether, and sorbent acidity on the residual sulfur content are reported. Methods of separation of oxidized compounds, namely adsorption chromatography and extraction are compared in terms of desulfurization efficiency. The latter method is demonstrated to be preferable.

Deep oxidative desulfurization of diesel fuels by Lewis acidic ionic liquids based on 1-n-butyl-3-methylimidazolium metal chloride

A series of Lewis acidic ionic liquids (ILs) based on 1-n-butyl-3-methylimidazolium metal chloride, i.e., [C4mim]Cl/MCl2 (M=Zn, Fe, Cu, Mg, Sn, Co), are synthesized and used to investigate the oxidative removal of sulfur compounds (S-compounds) from diesel fuels, with ILs serving as both extractant and catalyst and 30wt% H2O2 solution as oxidant. It is observed that metal chloride species affect S-removal, as S-removal efficiency follows the order: [C4mim]Cl/ZnCl2>[C4mim]Cl/FeCl2>[C4mim]Cl/CoCl2>[C4mim]Cl/MgCl2>[C4mim]Cl/CuCl2>[C4mim]Cl/SnCl2. The highly efficient [C4mim]Cl/ZnCl2 is selected to investigate the effects of ZnCl2 content on desulfurization. It is interesting to find out that ZnCl2 content has a significant influence on desulfurization; specifically, 99.9% S-removal is observed for [C4mim]Cl/3ZnCl2 after 3h at 45°C, O/S molar ratio of 8, IL/oil mass ratio of 1/2. [C4mim]Cl/3ZnCl2 then undergoes series of parallel experiments to systematically investigate the influence of factors such as temperature, molar ratio of O/S, mass ratio of IL/oil, and ILs recycling. The incorporation of real diesel fuel into this study demonstrates the efficacy of this IL in desulfurization. This work shows that oxidative desulfurization using Lewis acidic ILs may be a new option for producing cleaner diesel fuels.

Deep Oxidative Desulfurization of Diesel Fuels by Acidic Ionic Liquids

Ionic liquids (ILs), a new class of green solvents, have recently been undergoing intensive research on the removal of thiophenic sulfur species (e.g., dibenzothiophene) from fuels because of the limitation of the traditional hydrodesulfurization method in removing these species. In this work, deep oxidative desulfurization of diesel fuels by six functional acidic ILs are studied, in which ILs are used as both extractant and catalyst, and 30 wt % H2O2 solution as oxidant. These ILs include both Lewis acidic species such as 1-butyl-3-methylimidazolium chloride/2ZnCl2 ([C4mim]Cl/2ZnCl2 and [C4mim]Cl/ZnCl2) and Brønsted acidic species such as 1-methyl-3-ethylcarboxylic acid imidazolium hydrogen sulfate ([CH2COOHmim]HSO4), 1-methyl-3-(butyl-4-sulfinate) imidazolium hydrogen sulfate ([SO3H–C4mim]HSO4), [Hmim]HSO4, and [C4mim]HSO4 where different acidic groups such as −H, −COOH, and −SO3H are appended to the cations. Except for [CH2COOHmim]HSO4, both Brønsted and Lewis acidic ILs are capable of effectively removing dibenzothiophene from model diesel fuels, where 100% sulfur removal is obtained for [C4mim]Cl/2ZnCl2 and [SO3H–C4mim]HSO4. The effects of temperature, molar ratio of O/S, mass ratio of IL/oil, and IL regeneration on desulfurization are investigated systematically for [C4mim]Cl/2ZnCl2 and [SO3H–C4mim]HSO4. The desulfurization ability is not sensitive to the mass ratio of IL/oil, which is desired for reducing IL dosage in industrial application; the ILs can be recycled six times with merely a negligible loss in activity. [C4mim]Cl/2ZnCl2 can reduce the sulfur content in real commercial diesel fuel from 64 to 7.9 ppm with a sulfur removal of 87.7%; however, it is not too effective for coke diesel fuel with high initial sulfur content of 5380 ppm. This work tends to show that diesel fuels can be purified to sulfur-free or ultralow sulfur fuels by further deep oxidative desulfurization by using ILs after hydrodesulfurization.

Oxidative Desulfurization of Diesel Fuel Using Ultrasound

Catalytic oxizdation is a non-HDS technology to remove sulfur compounds from diesel fuel, and ultrasound irradiation was introduced to provide energy for this reaction. The effects of reaction temperature, time, and the ratio of oxidant and oil were investigated. The results show that under certain conditions, the optimal conditions were as follows: volume ratio of oxidant to oil was 1:10, reaction temperature was 50°C, and oxidation time was 10 min.

Phosphotungstic Acid/Semi-Coke Catalysts for Oxidative Desulfurization of Diesel Fuel

This work presents the results obtained in the development of phosphotungstic acid/semi-coke catalysts in the oxidative desulfurization (ODS) process of diesel oil using hydrogen peroxide as the oxidizing agent. Phosphotungstic acid /semi-coke (60wt%) prepared by impregnation. These catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), The effect of the amount of catalyst used , on the efficiency of desulfurization was investigated. In addtion. the diesel after oxidation and extraction was analyzed by GC-FPD for sulfur content. The chromatograph shows that virtually all the sulfur containing compounds in diesel were removed.

Oxidative Desulfurization of Diesel Fuels with Hydrogen Peroxide in the Presence of Activated Carbon and Formic Acid

Oxidative desulfurization (ODS) of diesel fuels with hydrogen peroxide was studied, using activated carbon as the catalyst. The adsorption and catalytic properties of activated carbons for dibenzothiophene (DBT), and the correlation between them, were investigated. The higher the adsorption capacity of the activated carbons, the higher the catalytic performance in the oxidation of DBT. DBT is oxidized by active oxygen species on the carbon surfaces when DBT is adsorbed on the carbon surfaces. The effect of the aqueous pH on the catalytic activities of the activated carbons was also investigated. It is observed that the oxidation rate of DBT on the carbons is enhanced when the aqueous pH is <2. The addition of formic acid can promote the oxidation of DBT in the presence of the wood carbons. The ODS of a commercial diesel fuel (with a sulfur content of 800 ppm) with hydrogen peroxide was investigated in the presence of activated carbon and formic acid. A much lower residual sulfur content (142 ppm) in the oxidized oil is observed after the oxidation, using the hydrogen peroxide−activated carbon−formic acid system, compared to that for a hydrogen peroxide−formic acid system, and the resulting oil, which contained 16 ppm of sulfur, is obtained after activated carbon adsorption; 98% of the sulfur could be removed from the diesel oil, with 96.5% oil recovery. Activated carbon has a high catalytic activity for the oxidative treatment of diesel fuels and can be used repeatedly. The reaction and adsorption in the desulfurization process are coupled, which causes low residual sulfur content in the oxidized oil. These results may indicate that activated carbon has a potential application in ODS to meet future regulations of sulfur in diesel fuels.

A Novel Oxidative Desulfurization System for Diesel Fuels with Molecular Oxygen in the Presence of Cobalt Catalysts and Aldehydes

Oxidative desulfurization of diesel fuels with molecular oxygen was examined by using cobalt salts and aldehydes as catalysts and sacrificial materials, respectively. At first, the authors conducted desulfurization of model oils consisting of benzene and dibenzothiophene. A mixture of benzene, dibenzothiophene, n-octanal, and an appropriate cobalt salt (acetate or chloride) was stirred at 40 °C under atmospheric pressure of oxygen to afford dibenzothiophene sulfone in almost quantitative yield within 15 min. Dibenzothiophene sulfone produced could be easily removed from the model oils by silica or alumina adsorption. Several organic sulfides including thioanisole, diphenyl sulfide, benzothiophene, and 4,6-dimethyldibenzothiophene also could be converted to the corresponding sulfones in almost quantitative yields. Then, the authors examined ultra deep desulfurization of a commercial diesel fuel, which contains 193 wt ppm of sulfur. By using the system consisting of cobalt acetate, aldehyde, and molecular o...