Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

Ordered mesoporous phosphotungstic acid/SiO₂ (HPW/SiO₂) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO₂ framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H₂O₂ as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.     

Investigation of the HDS kinetics of dibenzotiophene and its derivatives in real gas oil ??

Summary The hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4-methyl-dibenzothiophene (4 M-DBT), 4,6-dimethyldibenzothiophene (4,6 DM-DBT) and 4,6-diethyldibenzothiophene (4,6 DE-DBT) as real gas oil components on NiMo/Al₂O₃ catalyst was investigated. On the basis of the first order rate constants of HDS of the individual sulfur compounds calculated by both integral and differential evaluations the reactivities of the investigated compounds decreased in the order DBT >> 4 M-DBT > 4,6 DE-DBT ? 4,6 DM-DBT. Additionally, results showed that product inhibition during HDS does not take place.     

Effect of the nature of sulfur compounds on their reactivity in the oxidative desulfurization of hydrocarbon fuels with oxygen over a modified CuZnAlO catalyst

The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al₂O₃ catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene < DBT < 4,6-DMDBT. The degree of sulfur removal in the form of SO₂ from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.     

Mesoporous zirconium–silica nanocomposite modified with heteropoly tungstophosphoric acid catalyst for ultra-deep oxidative desulfurization

An adsorbent catalyst was proposed to reduce the leaching of active species of the catalyst and enhance the kinetics of the oxidative desulfurization (ODS) reaction of dibenzothiophene (DBT) from model diesel fuel. By loading phosphotungstic acid (HPW) species onto a zirconium-modified hexagonal mesoporous silica (Zr-HMS), a novel catalyst was synthesized and utilized for the ODS process. An ultrafast ODS kinetics was specifically identified using 20%HPW/Zr-HMS as catalyst. Within 30 min, more than 95% of the 350 ppm DBT content of the model fuel was oxidized by H₂O₂. The synthesized catalyst retained its sulfur removal ability even after five subsequent ODS reactions and the leaching of HPW species was found to be suppressed successfully. Overall, this new reusable catalyst provided an alternative for highly efficient ultra-deep desulfurization process.     

银离子修饰的介孔磷钨酸/二氧化硅催化剂氧化脱硫性能研究

采用银修饰介孔磷钨酸/二氧化硅（mesoporous HPW/SiO₂）催化剂,并研究了其在模拟柴油和真实柴油氧化脱硫反应中的催化性能。通过银修饰介孔HPW/SiO₂,结合银离子对有机硫化物的选择吸附性和HPW对有机硫化物的催化氧化活性,以达到选择氧化脱硫的目的。模拟柴油分别采用石油醚、苯、1-辛烯和二苯并噻吩配制,当银离子与HPW的摩尔比为2时,催化剂具有最高的选择催化氧化活性。采用N₂ 吸附-脱附、XRD、UV-vis和EDS表征了银修饰的介孔HPW/SiO₂催化剂,结果表明,银物种分散均匀且以Ag⁺形式存在。真实柴油的脱硫研究表明,相比介孔HPW/SiO₂催化剂,修饰的催化剂介孔Ag₂-HPW/SiO₂脱硫率提高了4.6%,初始硫含量为1800×10^-6的直馏柴油能被脱除至228×10^-6,脱硫率为87.3%。介孔Ag₂-HPW/SiO₂催化剂具有良好的再生性能,经再生处理后,Ag的损失量极少,其三次脱硫率达到84.8%。     

Macroporous 3D carbon-nitrogen (CN) confined MoOx catalyst for enhanced oxidative desulfurization of dibenzothiophene

Macroporous 3D carbon doped with nitrogen confined Mo catalyst (MoO_x@CN) had been prepared by a facile one-step pyrolysis technique using silica as a template and was employed for oxidative desulfurization (ODS) of dibenzothiophene (DBT) in model fuel with H₂O₂ as oxidant. The effect of different operating conditions (i.e., reaction temperature and time, catalyst dosage, H₂O₂/DBT (O/S) molar ratio) were also systematic investigated. Under the optimal reaction condition, MoO_x@CN catalyst exhibited highly excellent ODS performance toward DBT, the highest sulfur removal efficiency can be up to 99.9% and sulfur content was wiped out from 800 ppm to 10 ppm. Due to the robust 3D structure promoting rapid transfer, in addition to the increased number of active sites induced by the Mo vacancies, the catalyst, prepared using chitosan and ammonium heptamolybdate in a mass ratio of 1:0.5, displayed rapid kinetics and low activation energy in the oxidation of dibenzothiophene. Moreover, it exhibited excellent recyclability after five cycles without any obvious decrease in catalytic activity for the oxidative desulfurization reaction.     

Ultrasonic Auxiliary Ozone Oxidation-Extraction Desulfurization: A Highly Efficient and Stable Process for Ultra-Deep Desulfurization

For ultra-deep desulfurization of diesel fuel, this study applied the ultrasound-assisted catalytic ozonation process to the dibenzothiophene (DBT) removal process with four Keggin-type heteropolyacids (HPA) as catalysts and acetonitrile as extractant. Through experimental evaluations, H₃PMo₁₂O₄₀ was found to be the most effective catalyst for the oxidative removal of DBT. Under favorable operating conditions with a temperature of 0 °C, H₃PMo₁₂O₄₀ dosage of 2.5 wt.% of n-octane, and ultrasonic irradiation, DBT can be effectively removed from simulated diesel. Moreover, the reused catalyst exhibited good catalytic activity in recovery experiments. This desulfurization process has high potential for ultra-deep desulfurization of diesel.     

Deep oxidative desulfurization of dibenzothiophene with molybdovanadophosphoric heteropolyacid-based catalysts

Three hydrophobic Keggin-type heteropolyacid catalysts, [C₃H₃N₂(CH₃)(C₂H₄)]₅PMo₁₀V₂O₄₀ ([C₂mim]PMoV), [C₃H₃N₂(CH₃)(C₄H₈)]₅PMo₁₀V₂O₄₀ ([C₄mim]PMoV) and [C₃H₃N₂(CH₃)(C₆H₁₂)]₅PMo₁₀V₂O₄₀ ([C₆mim]PMoV), were synthesized by reacting molybdovanadophosphoric acid with imidazolium bromides, and characterized by spectroscopic methods. Their use as catalysts in the extractive catalytic oxidative desulfurization process using hydrogen peroxide as the oxidant and acetonitrile as phase transfer agent was studied. The catalytic properties decreased in the order: [C₆mim]PMoV > [C₄mim]PMoV > [C₂mim]PMoV. The main factors influencing the rate of removal of dibenzothiophene (DBT) were investigated, including reaction temperature, the amounts of catalyst, H₂O₂ and acetonitrile. Nearly 100 % sulfur removal rate was achieved under optimal conditions. The catalyst could be recycled six times with only a slight decrease in activity. A reaction mechanism for DBT oxidation is proposed, in which the Keggin anions first obtain active oxygen from H₂O₂, then the DBT is oxidized to dibenzothiophene sulfones.     

Enhanced Dibenzothiophene Biodesulfurization by Immobilized Cells of Brevibacterium lutescens in n-Octane–Water Biphasic System

In this study, it was the first report that the Brevibacterium lutescens CCZU12-1 was employed as a sulfur removing bacteria. Using dibenzothiophene (DBT) as the sole sulfur source, B. lutescens could selectively degrade DBT into 2-hydroxybiphenyl (2-HBP) via the “4S” pathway. In the basal salt medium (BSM) supplemented with 0.25 mM DBT and 0.5 g/L Tween-80, high desulfurization rate (100 %) was obtained by growth cells after 60 h. Furthermore, the n-octane–water (10:90, v/v) biphasic system was built for the biodesulfurization by resting cells. Moreover, a combination of magnetic nano Fe₃O₄ particles with calcium alginate immobilization was used for enhancing biodesulfurization. In this n-octane–water biphasic system, immobilized B. lutescens cells could be reused for not less than four times. Therefore, B. lutescens CCZU12-1 shows high potential in the biodesulfurization.     

Photooxidation of dibenzothiophene on TiO(2)/hectorite thin films layered catalyst

A new titanium(IV) oxide-hectorite nanofilm photocatalyst was prepared on quartz slides. It was evaluated in the photooxidation of dibenzothiophene (DBT) in nonpolar organic solution (tetradecane), as a model for diesel fuel. A removal regimen was developed consisting of catalytic photooxidation followed by adsorption of products on silica gel. Photooxidation of DBT was performed with and without catalyst, at 254 and 300 nm. Comparison was made with a commercially available TiO(2) catalyst, Degussa P25. The catalyst was analyzed by nitrogen adsorption, XRD, SEM, and TGA-DTA. DBT concentrations were measured by HPLC and UV spectrophotometry. Preliminary qualititative analysis of products was performed by UV and HPLC. Results indicated that the outlined process was effective in reducing sulfur levels to below 10 ppm sulfur.     

An organic‐inorganic heterogeneous catalyst based on Keplerate polyoxometalates for oxidation of dibenzothiophene derivatives with Hydrogen peroxide

An organic‐inorganic material (NH₄)₂(MimAM)₄₀[Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] have been synthesized by reacting [(NH₄)₄₂[Mo^VI₇₂ Mo^V₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] with the ionic liquid 3‐Aminoethyl‐1‐methylimidazolium bromide. The catalyst showed remarkably a high catalytic performance in the oxidation of dibenzothiophene (DBT) derivatives with H₂O₂ 35% as a safe and green oxidant. The main parameters affecting the process including catalyst, acid additive, hydrogen peroxide amounts and temperature have been investigated in detail. Sulfur removal of DBT in n‐heptane reached to 98.3% yield at 40 °C using 2.5 mmol H₂O₂ and 100 mg of (NH₄)₂(MimAM)₄₀[Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂] after 90 min. Under the optimal conditions, BT (benzothiophene), DBT (dibenzothiophene) and 4,6‐DMDBT (4,6‐dimethyl‐dibenzothiophene) achieved high desulfurization efficiency. Our results showed that the reactivity order of different model sulfur compounds are thiophene <4,6‐dimethyl dibenzothiophene< dibenzothiophene. The catalysts could be easily separated from the reaction solution by simple filtration and recycled for several times without loss of activity.     

Deep oxidative desulfurization of benzothiophene and dibenzothiophene with a peroxophosphotungstate–ionic liquid brush assembly

A novel, efficient and reusable heterogeneous catalytic assembly of peroxophosphotungstate held in an ionic liquid brush was synthesized and an extraction and catalytic oxidative desulfurization (ECODS) procedure was developed for a model oil of benzothiophene (BT) and dibenzothiophene (DBT) using 30 wt% hydrogen peroxide as terminal oxidant and methanol as solvent under mild conditions. Several factors that affect sulfur removal were investigated in detail. The highest sulfur removal can reach 100% for BT in 7 h at 70 °C when the molar ratio of H₂O₂, S and catalyst is 10:1:0.025. The sulfur removal for DBT can also reach 100% in 4 h at 50 °C with the same molar ratio of H₂O₂, S and catalyst. The experimental results demonstrate that this ECODS process has no apparent scale‐up effect. The catalyst can be easily recovered (via simple filtration) and recycled five times without a significant decrease in activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Electronic and topological properties of interactions between imidazolium-based ionic liquids and thiophenic compounds: a theoretical investigation

To deepen the understanding the interactions of thiophenic compounds in ionic liquids, we have performed a systemic study on the electronic structures, and topological properties of interactions between N-ethyl-N-ethylimidazolium diethyl phosphate ([EEIM][DEP]) ionic liquid and 3-methylthiophene (3-MT), benzothiophene (BT), or dibenzothiophene (DBT) using density functional theory. From NBO atomic charges and electrostatic potential analyses, most of the positive charge is located on C2–H2 in the [EEIM] cation, and the negative charge is focused on oxygen atoms in [DEP] anion, implying oxygen atoms in [DEP] should easily attack C2–H2 in [EEIM]. The electrostatic interaction between anion and cation may be dominant for the formation of the [EEIM]–[DEP] ion pair. The large stabilizing effect is due to the strong orbital interactions between the antibonding orbital of proton donor σ*(C2–H2) in [EEIM] cation and the lone pairs of proton acceptor LP(O) in [DEP] anion. A common feature of [EEIM][DEP], [EEIM][DEP]-3-MT/BT/DBT complexes is the presence of hydrogen bonds between [EEIM] cation and [DEP] anion. This work has also given the interacting mechanism of 3-MT, BT, and DBT adsorption on [EEIM][DEP] ionic liquid. Both [EEIM] cation and [DEP] anion are shown to play important roles in interactions between 3-MT, BT, DBT and [EEIM][DEP], which has been corroborated by NBO and AIM analyses. The π···π, π···C–H and hydrogen bonding interactions occur between [EEIM][DEP] and 3-MT, BT, DBT. The strength of sulfur involved interactions between 3-MT, BT, DBT and [EEIM][DEP] follows the order of 3-MT > BT > DBT. The order of interaction energies between [EEIM][DEP] and 3-MT, BT, DBT is 3-MT < BT < DBT, in agreement with the order of extractive selectivity from fuel oils (DBT > BT > 3-MT) in terms of sulfur partition coefficients.     

Sulfur-Selective Desulfurization of Dibenzothiophene and Diesel Oil by Newly Isolated Rhodococcus erythropolis NCC-1

A dibenzothiophene （DBT）-desulfurizing bacteria strain was isolated from oil-contaminated soils and identified as Rhodococcus erythropolis NCC-1. Strain NCC-1 was found to convert DBT to hydroxybiphenyl （2-HBP） via the 4S pathway and also be able to use organic sulfur compounds other than DBT as a sole sulfur source. The strain could desulfurize 4,6-dimethyldibenzothiophene （4,6-DMDBT）, which is one of the most recalcitrant dibenzothiophene derivatives to hydrodesulfurization. When two type of oils, a model oil [n-hexadecane （n-C16） containing DBT] and a hydrodesulfurized diesel oil with various organic sulfur compounds, were treated with Rhodococcus erythropolis NCC-1 cells, the total sulfur content significantly decreased, from 150 to 20 mg/L for n-C16 and from 554 to 274 mg/L for diesel oil. The newly isolated strain NCC-1 is considered to have good potential for application in the biodesulfurization of fossil fuels.     

二苯并噻吩和吲哚在NiMoS/γ-Al2O3上加氢脱硫和加氢脱氮反应的相互影响

在固定床高压微反装置上考察了预硫化型NiMoS/γ-Al2O3催化剂上二苯并噻吩（DBT）加氢脱硫（HDS）反应和吲哚加氢脱氮（HDN）反应之间的相互影响。结果表明,吲哚对DBT的加氢脱硫反应具有抑制作用,其中对加氢路径（HYD）比对氢解路径（DDS）的抑制作用强,温度升高后,吲哚的抑制作用减弱。吲哚对DBT加氢脱硫反应的抑制作用源于吲哚及其HDN反应的中间产物在活性位上的竞争吸附。DBT和原位生成的H2S促进了催化剂表面硫阴离子空穴（CUS）向B酸位的转化,从而提高1,2-二氢吲哚（HIN）分子中C(sp3)—N键的断裂能力,使得吲哚的转化率和产物中邻乙基苯胺（OEA）的相对含量增大。HDN活性相的形成虽然需要硫原子的参与,但是活性相的保持并不需要大量的硫原子,较高含量硫化物存在时加氢活性位减少,不利于脱氮反应。     

Desulfurization of model and real fuels by extraction and oxidation processes using an indenylmolybdenum tricarbonyl pre-catalyst

Regulations on the permissible levels of sulfur in transportation fuels are becoming ever more strict, with a global shift towards “zero sulfur” fuels, and the revamp of existing hydrodesulfurization (HDS) facilities to meet these lower caps is cost-prohibitive. Metal-catalyzed sulfoxidation chemistry is viewed as an economically viable desulfurization strategy that could complement conventional HDS technology. In the present work, the complex [η⁵-IndMo(CO)₃Me] ( 1 ) (Ind = indenyl) was employed in the catalytic oxidative desulfurization (CODS) of model and real liquid fuels, using aqueous hydrogen peroxide (H₂O₂) as oxidant. After optimization of the CODS reaction parameters (diesel/H₂O₂ ratio, catalyst amount, temperature), a high-sulfur (2000 ppm) model diesel containing benzothiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene could be completely desulfurized within 2 hr under solvent-free conditions or in the presence of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) as extraction solvent. The catalyst formed under solvent-free conditions could be recycled without a significant decrease in desulfurization activity. The high performance of the CODS system was verified in the sulfur removal from a commercial untreated diesel fuel with a sulfur content of 2300 ppm, and a jet fuel with a sulfur content of 1100 ppm. Solvent-free CODS in combination with initial/final extraction gave desulfurization efficiencies of 70% for the diesel fuel and 55% for the jet fuel. CODS with [BMIM]PF₆ in combination with initial/final extraction led to a sulfur removal of 95.9% for the diesel fuel, which is one of the best results yet reported for ODS of commercial diesels.     

Biodesulfurization of Model Compounds and De-asphalted Bunker Oil by Mixed Culture

In this study, complicated model sulfur compounds in bunker oil and de-asphalted bunker oil were biodesulfurized in a batch process by microbial consortium enriched from oil sludge. Dibenzothiophene (DBT) and benzo[b]naphtho[1,2-d]thiophene (BNT1) were selected as model sulfur compounds. The results show that the mixed culture was able to grow by utilizing DBT and BNT1 as the sole sulfur source, while the cell density was higher using DBT than BNT1 as the sulfur source. GC-MS analysis of their desulfurized metabolites indicates that both DBT and BNT1 could be desulfurized through the sulfur-specific degradation pathway with the selective cleavage of carbon–sulfur bonds. When DBT and BNT1 coexisted, the biodesulfurization efficiency of BNT1 decreased significantly as the DBT concentrations increased (>0.1 mmol/L). BNT1 desulfurization efficiency also decreased along with the increase of 2-hydroxybiphenyl as the end product of DBT desulfurization. For real bunker oil, only 2.8 % of sulfur was removed without de-asphalting after 7 days of biotreatment. After de-asphalting, the biodesulfurization efficiency was significantly improved (26.2–36.5 %), which is mainly attributed to fully mixing of the oil and water due to the decreased viscosity of bunker oil.     

四氟硼酸改性活性炭的制备及其吸附脱除二苯并噻吩性能

采用浸渍法制备了四氟硼酸(HBF₄)改性活性炭,并研究了其对模拟油中二苯并噻吩(DBT)的吸附脱除性能。利用傅里叶红外光谱(FT-IR)、差示热分析仪(TG-DTA)、X射线光电子能谱(XPS)以及N₂吸附技术对吸附剂的表面态和孔结构进行了表征,考察了四氟硼酸浓度、热处理温度以及模拟油中DBT浓度对吸附脱硫效果的影响。结果表明,经质量分数0.5%的HBF₄溶液浸渍、140 ℃热处理后,在剂油比1:100条件下,活性炭的吸附容量为352 mg/g,较未改性活性炭提高了72.5%。     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Removal of dibenzothiophene in diesel oil by oxidation over a promoted activated carbon catalyst

Oxidative removal of dibenzothiophene (DBT) in n-octane solution by H₂O₂ on a promoted activated carbon (AC) catalyst was studied. DBT adsorption and catalytic behaviors on AC were examined. Effects of pH in aqueous phase, amounts of AC and formic acid (HCOOH) for promotion as well as initial molar H₂O₂/S ratio were investigated. Experimental results led to conclusion that DBT was readily oxidized by H₂O₂ over an AC catalyst promoted by HCOOH. Suitable amount of AC can improve the activity of H₂O₂ resulting in a deeper extent of sulfur removal. A 100% conversion of DBT in an octane solution by H₂O₂ oxidation was attained on the HCOOH-H₂O₂/AC catalyst at 80°C for a reaction time of 30 min.