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.     

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.     

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.     

Iron promotion of V‐HMS mesoporous catalysts for ultra‐deep oxidative desulfurization

Bimetallic Fe‐V‐HMS (HMS, hexagonal mesoporous silica) catalysts with various molar ratios of iron to vanadium were synthesized using a co‐synthesis method, and investigated for oxidative desulfurization of dibenzothiophene (DBT) using tert‐butyl hydroperoxide as an oxidant. The catalysts were characterized using X‐ray diffraction, temperature‐programmed desorption of ammonia, Fourier transform infrared spectroscopy and N₂ physical adsorption–desorption techniques. The Fe‐V‐HMS catalyst with a 2:1 molar ratio of iron to vanadium exhibited the highest total acidity and the highest catalytic activity. DBT was almost completely oxidized to dibenzothiophenesulfone, a species with a higher polarity that could be subsequently adsorbed on the Fe‐V‐HMS, and therefore the Fe‐V‐HMS acts as both a catalyst and an adsorbent simultaneously. The desulfurization rate was 98.1%. A pseudo‐first‐order model was fitted to the experimental data, and the activation energy was found to be 38.79 kJ mol^?1. The encouraging performance of Fe‐V‐HMS offers the prospect of the design of a one‐pot oxidative desulfurization process without needing extraction of sulfones from fuel oil with a chemical solvent.     

Facile synthesis of inorganic–organic Fe2W18Fe4@NiO@CTS hybrid nanocatalyst induced efficient performance in oxidative desulfurization of real fuel

In this work, a new nanocatalyst, Fe₂W₁₈Fe₄@NiO@CTS, was synthesized by the reaction of sandwich‐type polyoxometalate (Fe₂W₁₈Fe₄), nickel oxide (NiO), and chitosan (CTS) via sol–gel method. The assembled nanocatalyst was systematically characterized by FT‐IR, UV–vis, XRD, SEM, and EDX analysis. The catalytic activity of Fe₂W₁₈Fe₄@NiO@CTS was tested on oxidative desulfurization (ODS) of real gasoline and model fuels. The experimental results revealed that the levels of sulfur content and mercaptan compounds of gasoline were lowered with 97% efficiency. Also, the Fe₂W₁₈Fe₄@NiO@CTS nanocatalyst demonstrated an outstanding catalytic performance for the oxidation of dibenzothiophene (DBT) in the model fuel. The major factors that influence the desulfurization efficiency and the kinetic study of the ODS reactions were fully detailed and discussed. The probable ODS pathway was proposed via the electrophilic mechanism on the basis of the electrophilic characteristic of the metal‐oxo‐peroxo intermediates. The prepared nanocatalyst could be reused for 5 successive runs without any appreciable loss in its catalytic activity. As a result, the current study suggested the potential application of the Fe₂W₁₈Fe₄@NiO@CTS hybrid nanocatalyst as an ideal candidate for removal of sulfur compounds from fuel.     

Evaluation of adsorption and kinetics of neem leaf powder (Azadirachta indica) as a bio-sorbent for desulfurization of dibenzothiophene (DBT) from synthetic diesel

The need for a sustainable environment has necessitated the development of a green adsorbent that is efficient, cheap, and readily available to serve as an alternative adsorbent for the removal of the refractory sulfur-containing compound from diesel. In this current study, neem-leaf powder (NLP) was activated using H₂SO₄ and tested in desulfurization adsorption experiments of synthetic diesel containing Dibenzothiopene (DBT) during a batch operation. The synthetic diesel contained 0.1 g of DBT in 100 mL of hexane. Before testing, physio-chemical characteristics of the adsorbent were checked via Fourier transmission infrared (FTIR) spectroscopy for surface chemistry; via N₂ physisorption at 77 K for textural properties; SEM quipped with EDX for morphology and elemental composition; and XRD for purity and crystallinity. The results showed that the physico-chemical nature of the adsorbent played a significant role in enhancing the adsorption capacity of the material for DBT. Activated NLP displayed DBT removal of 65.78% at 30 °C using 0.8 g of the adsorbent. Furthermore, the behaviour of the adsorbent during the adsorption could be adequately described using the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetics model describe well the adsorption kinetics of DBT onto the activated NLP.     

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%。     

Regulating sulfur removal efficiency of fuels by Lewis acidity of ionic liquids

It is urgent to develop a new deep desulfurization process of fuels as the environmental pollution increases seriously. In this work, a series of Lewis acidic ionic liquids (ILs) [C₄³MPy]Cl/nZnCl₂ (n=1, 1.5, 2, 3) were synthesized and used in extraction and catalytic oxidative desulfurization (ECOD) of the fuels. The effects of the Lewis acidity of ILs, the molar ratio of H₂O₂/sulfur, temperatures, and different substrates including dibenzothiophene (DBT), benzothiophene (BT) and thiophene (TS), on sulfur removal were investigated. The results indicated that [C₄³MPy]Cl/₃ZnCl₂ presented near 100% DBT removal of model oil under conditions of 323 K, H₂O₂/DBT molar ratio 6:1. Kinetics for the removal of DBT, BT and TS by the [C₄³MPy]Cl/₃ZnCl₂-H₂O₂ system at 323 K is first-order with the apparent rate constants of 1.1348, 0.2226 and 0.0609 h^-1, and the calculated apparent activation energies for DBT, BT and TS were 61.13, 60.66, and 68.14 kJ/mol from 298 to 308 K, respectively. After six cycles of the regenerated [CC₄³MPy]Cl/₃ZnCl₂, the sulfur removal had a slight decrease. [CC₄³MPy]Cl/₃ZnCl₂ showed a good desulfurization performance under optimal conditions.     

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.     

Evaluation of vacuum microwave-assisted extraction technique for the extraction of antioxidants from plant samples

In the present work, vacuum microwave-assisted extraction (VMAE) was to perform microwave-assisted extraction in vacuum. Two well-known antioxidants, vitamin C from guava and green pepper, and vitamin E (α-tocopherol and γ-tocopherol) from soybean and tea leaves, which were easy to be oxidized, were chosen as representative target compounds for the evaluation of VMAE. The extraction yields of vitamin C, α-tocopherol and γ-tocopherol in VMAE and those in MAE performed in atmosphere (air-MAE) were compared and the effects of extraction time, extraction temperature and sample matrix were studied. Moreover, the effects of the oxygen and subpressure invacuo were also discussed via performed MAE in N₂ atmosphere (N₂-MAE). The extraction yields of vitamin C, α-tocopherol and γ-tocopherol in VMAE were higher than that in air-MAE, 35% increments of vitamin C from green pepper, 22% increments of α-tocopherol and 47% increments of γ-tocopherol from tea leaves were obtained, respectively. The comparable increased extraction yields of vitamin C, α-tocopherol and γ-tocopherol in N₂-MAE to that in air-MAE confirmed that oxygen in system was the crucial factor for the oxidation of vitamin C and vitamin E, VMAE was beneficial for the extraction of these oxygen-sensitive compounds. In addition, the subpressure invacuo in the VMAE system also showed positive affect on the extraction yields. On the basis of preventing oxidation and improving extraction efficiency of target compounds because of less oxygen and subpressure invacuo in the extraction system, VMAE has good potential for the extraction of oxygen-sensitive and thermosensitive compounds from plant samples.     

Enhancement of Dibenzothiophene Desulfurization by Gordonia alkanivorans Strain 1B Using Sugar Beet Molasses as Alternative Carbon Source

There are several problems limiting an industrial application of fossil fuel biodesulfurization, and one of them is the cost of culture media used to grow the microorganisms involved in the process. In this context, the utilization of alternative carbon sources resulting from agro-industrial by-products could be a strategy to reduce the investment in the operating expenses of a future industrial application. Recently, Gordonia alkanivorans 1B was described as a fructophilic desulfurizing bacterium, and this characteristic opens a new interest in alternative carbon sources rich in fructose. Thus, the goal of this study was to evaluate the utilization of sugar beet molasses (SBM) in the dibenzothiophene (DBT) desulfurization process using strain 1B. SBM firstly treated with 0.25 % BaCl₂ (w/v) was used after sucrose acidic hydrolysis or in a simultaneous saccharification and fermentation process with a Zygosaccharomyces bailii Talf1 invertase (1 %), showing promising results. In optimal conditions, strain 1B presented a μ _max of 0.0795 h^?1, and all DBT was converted to 2-hydroxybiphenyl (250 μM) within 48 h with a maximum production rate of 7.78 μM h^?1. Our results showed the high potential of SBM to be used in a future industrial fossil fuel biodesulfurization process using strain 1B.     

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%。     

Highly Efficient Extraction and Oxidative Desulfurization System Using Na7H2LaW10O36⋅32 H2O in [bmim]BF4 at Room Temperature

Highly efficient, deep desulfurization of model oil containing dibenzothiophene (DBT), benzothiophene (BT), or 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) has been achieved under mild conditions by using an extraction and catalytic oxidative desulfurization system (ECODS) in which a lanthanide‐containing polyoxometalate Na₇H₂LnW₁₀O₃₆ ? 32 H₂O (LnW₁₀; Ln=Eu, La) acts as catalyst, [bmim]BF₄ (bmim=1‐butyl‐3‐methylimidazolium) as extractant, and H₂O₂ as oxidant. Sulfur removal follows the order DBT>4,6‐DMDBT>BT at 30 ° C. DBT can be completely oxidized to the corresponding sulfone in 25 min under mild conditions, and the LaW₁₀/[bmim]BF₄ system could be recycled for ten times with only slight decrease in activity. Thus, LaW₁₀ in [bmim]BF₄ is one of the most efficient systems for desulfurization using ionic liquids as extractant reported so far.     

MoO3/介孔Al2O3催化氧化脱除模拟油中的硫

以环己烷为溶剂,二苯并噻吩（DBT）、苯并噻吩（BT）、4,6-二甲基二苯并噻吩（4,6-DMDBT）、噻吩（Th）作为模型含硫化合物配制成模拟油,在MoO3/介孔Al2O3-H2O2体系中对模拟油催化氧化脱硫进行了研究. 考察了MoO3负载量、氧化剂用量、催化剂用量、氧化反应温度及反应时间对DBT脱除效果的影响. 实验结果表明：在MoO3负载量为20%,催化剂用量为1.5%,氧化剂H2O2与模拟油中硫的摩尔比为4,反应温度为60℃,反应时间为40分钟时DBT脱除率最高,达99.4%,几乎可以被完全脱除;在此条件下模型化合物的氧化反应活性顺序为：DBT > 4,6-DMDBT >BT>Th.     

胺类吸收剂模拟烟气脱硫

以醇胺和乙二胺为原料,配制0.3 mol/L的水溶液,用于实验室模拟烟气脱硫的研究。通过碘量法测定脱硫率,采用离子色谱测定SO₂吸收容量、吸收液中SO₂的氧化率和解吸率,同时探讨了循环次数对脱硫率和富液中SO₂含量的影响。结果表明,吸收进行30 min时,吸收液的脱硫率均保持在99 %以上,60 min时,乙二胺类溶液的脱硫率仍达99 %,醇胺吸收液脱硫效果明显下降。乙二胺溶液对SO₂ 的吸收容量为455 mg/L,远远高于醇胺类吸收液。若乙二胺溶液中加入硼酸,则其对SO₂的吸收容量略低(450 mg/L),但提高了溶液的抗氧化性,吸收液中SO₂的氧化率由1.14 %减至0.29 %,同时解吸率由38.0 %增至59.0 %。10次吸收-解吸循环实验数据显示,乙二胺/硼酸溶液的平均脱硫率均在99 %以上,富胺液中SO₂含量由0.44 mol/L减至0.40 mol/L,表明吸收液的脱硫性能良好,可以作为烟气脱硫剂。     

An experimental and theoretical method for determination of standard electrode potential for the redox couple diphenyl sulfone/diphenyl sulfide

DFT calculations were performed for diphenyl sulfide and diphenyl sulfone. The electrochemistry of diphenyl sulfide on the gold electrode was investigated by cyclic voltammety and the results show that standard electrode potential for redox couple diphenyl sulfone/diphenyl sulfide is 1.058 V, which is consistent with that of 1.057 calculated at B3LYP/6-31++G(d,p)-IEFPCM level. The front orbit theory and Mulliken charges of molecular explain well on the oxidation of diphenyl sulfide in oxidative desulfurization. According to equilibrium theory the experimental equilibrium constant in the oxidative desulfurization of H₂O₂, is 1.17 × 10⁴⁸, which is consistent with the theoretical equilibrium constant is 2.18 × 10⁴⁸ at B3LYP/6-31++G(d,p)-IEFPCM level.     

Vanadium(IV) catalysed oxidation of organosulfur compounds in heavy fuel oil

The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organo-sulfur compounds are such that they emit SO_x to the environment when combusted, thereby reducing air quality. Herein, oxidative desulfurization (ODS) which is a complementary step to hydrodesulfurization (HDS) was carried out in an attempt to eliminate sulfur compounds in fuels. Refractory organosulfur compounds were oxidized using tert-butyl hydroperoxide as an oxidant and a poly[VO(allylSB-co-EGDMA)], (vanadium(IV) functionalized polymer of 6,6′-(1E,1′E)-(1,2-phenylenebis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-allylphenol) crosslinked with ethyleneglycol dimethacrylate) as a catalyst to convert sulfur compounds to polar sulfones. Some of the organosulfones were adsorbed via the use of molecularly imprinted polybenzimidazole nanofibers. The sulfur in heavy fuel oil after the oxidation/adsorption method fell below 8900 ± 200 ppmw S from the initial value of 17 920 ± 100 ppmw S.     

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.     

TiO2-CeO2光催化吸附协同脱除柴油中的有机硫

采用共沉淀法制备TiO₂-CeO₂光催化吸附脱硫材料,通过低温N₂吸附脱附和X射线衍射等技术对TiO₂-CeO₂的物理化学性质进行了表征。结果表明,紫外光辐射显著提高了TiO₂-CeO₂的吸附脱硫性能;柴油中有机硫在TiO₂-CeO₂表面发生了光催化氧化转化为极性较强的砜类,可选择性地吸附在材料表面而被脱除。当TiO₂-CeO₂材料中钛铈物质的量比为9：1、煅烧温度为500℃时,其光催化吸附协同脱硫效果最好;在紫外光辐射下反应5 h,油品中DBT的脱除率高达99.6%。TiO₂-CeO₂光催化吸附协同脱硫工艺可有效解决吸附脱硫工艺中芳烃竞争吸附导致吸附脱硫选择性低的问题;在模拟油品中添加质量分数为25%的甲苯,反应7 h后油品脱硫率仍高达96.6%。TiO₂-CeO₂对不同硫化物的光催化吸附协同脱硫效果顺序为：4,6-DMDBT> DBT> BT。TiO₂-CeO₂经四次再生循环使用后,脱硫率没有明显降低。