Catalytic oxidative desulfurization of diesel utilizing hydrogen peroxide and functionalized-activated carbon in a biphasic diesel-acetonitrile system

This paper presents the development of granular functionalized-activated carbon as catalysts in the catalytic oxidative desulfurization (Cat-ODS) of commercial Malaysian diesel using hydrogen peroxide as oxidant. Granular functionalized-activated carbon was prepared from oil palm shell using phosphoric acid activation method and carbonized at 500 °C and 700 °C for 1 h. The activated carbons were characterized using various analytical techniques to study the chemistry underlying the preparation and calcination treatment. Nitrogen adsorption/desorption isotherms exhibited the characteristic of microporous structure with some contribution of mesopore property. The Fourier Transform Infrared Spectroscopy results showed that higher activation temperature leads to fewer surface functional groups due to thermal decomposition. Micrograph from Field Emission Scanning Electron Microscope showed that activation at 700 °C creates orderly and well developed pores. Furthermore, X-ray Diffraction patterns revealed that pyrolysis has converted crystalline cellulose structure of oil palm shell to amorphous carbon structure. The influence of the reaction temperature, the oxidation duration, the solvent, and the oxidant/sulfur molar ratio were examined. The rates of the catalytic oxidative desulfurization reaction were found to increase with the temperature, and H₂O₂/S molar ratio. Under the best operating condition for the catalytic oxidative desulfurization: temperature 50 °C, atmospheric pressure, 0.5 g activated carbon, 3 mol ratio of hydrogen peroxide to sulfur, 2 mol ratio of acetic acid to sulfur, 3 oxidation cycles with 1 h for each cycle using acetonitrile as extraction solvent, the sulfur content in diesel was reduced from 2189 ppm to 190 ppm with 91.3% of total sulfur removed.     

用过氧化氢和乙酸对未经氢化处理的煤油进行直接氧化脱硫

The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS 8 and 23 for the reaction temperatures of 25 and 60C, respectively. The maximum observed sulfur removal in the present oxidative desulfurization system was 83.3%.     

Energy-efficient ultra-deep desulfurization of kerosene based on selective photooxidation and adsorption

Selective photooxidation and adsorptive desulfurization of kerosene was investigated for fuel cell applications. Photooxidation was conducted using a 5 W low-pressure mercury lamp at 25 °C in the presence of O₂. It was found for the first time that the rates of photooxidation of dominant sulfur compounds remaining in commercial kerosene after hydrogenation were at least 100 times higher than those of benzothiophenes (BTs) and dibenzothiophenes (DBTs), although their molecular forms were not clarified. The photooxidation of these highly reactive sulfur compounds was completed within 30 min and made them removable by adsorbents such as molecular sieves. On the other hand, non-reactive sulfur compounds such as DBTs were removed by adsorbents such as activated carbon. Using this proposed method, which combines selective photooxidation of highly reactive sulfur compounds and adsorptive desulfurization of reactive and non-reactive sulfur compounds, the total sulfur content in kerosene can be efficiently reduced to less than 0.1 μg g⁻¹ (ppm) under mild conditions.     

Sulfur removal from hydrotreated petroleum fractions using ultrasound-assisted oxidative desulfurization process

Ultrasound-assisted oxidative desulfurization (UAOD) process was applied to diesel oil and petroleum product feedstock containing model sulfur compounds (benzothiophene, dibenzothiophene and dimethyldibenzothiophene). The influence of oxidant amount, volume of solvent for the extraction step and time and temperature of ultrasound treatment (20 kHz, 750 W, operating at 40%) was investigated. Using the optimized conditions for UAOD, sulfur removal up to 99% was achieved for model compounds in petroleum product feedstock using a molar proportion for H₂O₂:acetic acid:sulfur of 64:300:1, after 9 min of ultrasound treatment at 90 °C, followed by extraction with methanol (optimized solvent and oil ratio of 0.36). Using the same reagent amount and 9 min of ultrasound the removal of sulfur was higher than 75% for diesel oil samples. Sulfur removal without ultrasound using the same conditions was lower than 82% for model compounds and 55% for diesel oil samples showing that ultrasound improved the efficiency of oxidative desulfurization. In comparison to conventional hydrodesulfurization, the proposed UAOD process can be performed under relatively mild conditions (atmospheric pressure and 90 °C, without using metallic catalysts).     

Deep desulfurization of diesel via peroxide oxidation using phosphotungstic acid as phase transfer catalyst

High sulfur level in diesel fuel has been identified as a major contributor to air pollutant in term of sulfur dioxide (SO_x) through diesel fueled vehicles. The main aim of the present work is to develop a promising methodology for ultra deep desulfurization of diesel fuel using oxidation followed by phase transfer of oxidized sulfur. Experiments were carried out in a batch reactor using n-decane as the model diesel compound and also using commercial diesel feedstock. To remove sulfur tetraoctylammonium bromide, phosphotungstic acid, and hydrogen peroxide were used as phase transfer agent, catalyst and oxidant respectively. The percent sulfur removal increases with increasing the initial concentration of sulfur in fuel and with increasing the reaction temperature. Similar trends were observed when commercial diesel was used to carry out desulfurization studies. The amphiphilic catalyst serves as a catalyst and also as an emulsifying agent to stabilize the emulsion droplets. The effects of temperature, agitation speed, quantity of catalyst and the phase transfer agent were studied to estimate the optimal conditions for the reactions. The sulfur removal from a commercial diesel by phase transfer catalysis has been found effective and removal efficiency was more than 98%. Kinetic experiments carried out for the desulfurization revealed that the sulfur removal results are best fitted to a pseudo first order kinetics and the apparent activation energy of desulfurization was 30.6 kJ/mol.     

Application of artificial neural networks to predict chemical desulfurization of Tabas coal

This paper presents a neural network model to predict the effects of operational parameters on the organic and inorganic sulfur removal from coal by sodium butoxide. The coal particle size, leaching temperature and time, sodium butoxide concentration and pre oxidation time by peroxyacetic acid (PAA) were used as inputs to the network. The outputs of the models were organic and inorganic sulfur reduction. Feed-forward artificial neural network with 5-7-10-1 arrangement, were capable to estimate organic and inorganic sulfur reduction, respectively. Simulated values obtained with neural network correspond closely to the experimental results. It was achieved quite satisfactory correlations of R² = 1 and 0.96 in training and testing stages for pyritic sulfur and R² = 1 and 0.97 in training and testing stages, respectively, for organic sulfur reduction prediction. The proposed neural network model accurately reproduces all the effects of operational variables and can be used in the simulation of Tabas coal desulfurization plant.     

Deep desulfurization of diesel oil oxidized by Fe (VI) systems

Fe (VI) compound, such as K₂FeO₄, is a powerful oxidizing agent. Its oxidative potential is higher than KMnO₄, O₃ and Cl₂. Oxidation activity of Fe (VI) compounds can be adjusted by modifying their structure and pH value of media. The reduction of Fe (VI), differing from Cr and Mn, results in a relatively non-toxic by-product Fe (III) compounds, which suggests that Fe (VI) compound is an environmentally friendly oxidant. Oxidation of model sulfur compound and diesel oil by K₂FeO₄ in water-phase, in organic acid and in the presence of phase-transfer catalysts is investigated, respectively. The results show that the activity of oxidation of benzothiophene (BT) and dibenzothiophene (DBT) is low in water-phase, even adding phase-transfer catalyst to the system, because K₂FeO₄ reacts rapidly with water to form brown Fe(OH)₃ to lose ability of oxidation of organic sulfur compounds. The activity of oxidation of the BT and DBT increases markedly in acetic acid. Moreover, the addition of the solid catalyst to the acetic acid medium promotes very remarkably oxidation of organic sulfur compounds. Conversions of the DBT and BT are 98.4% and 70.1%, respectively, under the condition of room temperature, atmospheric pressure, acetic acid/oil (v/v) = 1.0, K₂FeO₄/S (mol/mol) = 1.0 and catalyst/K₂FeO₄ (mol/mol) = 1.0. Under the same condition, diesel oil is oxidized, followed by furfural extraction, the results display sulfur removal rate is 96.7% and sulfur content in diesel oil reduces from 457 ppm to 15.1 ppm.     

Liquid-liquid extraction of oxidized sulfur-containing compounds of non-hydrotreated kerosene

An experimental study was conducted on the desulfurization of non-hydrotreated kerosene with oxidation followed by liquid-liquid extraction. Various types of solvents including acetonitrile, methanol, and ethanol have been examined in the extraction of oxidized sulfur-containing compounds of kerosene. The performance of these solvents has been carefully examined and compared. It was found that their performance follows the order: acetonitrile > methanol > ethanol. The effects of number of extraction stages and solvent to kerosene ratio on the desulfurization and recovery of kerosene have been investigated. The experimental results show that for all three solvents, solvent/kerosene ratio and number of extraction stages greater than 2 are not practically acceptable because of high kerosene loss in the extraction step and no significant increase in the desulfurization. Over 99% desulfurization of kerosene has been achieved after extraction of oxidized sulfur-containing compounds. Furthermore, the desulfurization of kerosene by single extraction was compared to oxidation followed by liquid-liquid extraction (ODS). These experimental results clearly indicate that the desufurization achieved by single extraction is much lower than that of oxidation followed by liquid-liquid extraction.     

On-site low-pressure diesel HDS for fuel cell applications: Deepening the sulfur content to ?1 ppm

This work investigates the feasibility of ultra-deep hydrodesulfurization (i.e. ?1 ppm of sulfur content) of several diesel feedstocks, viz., regular (R), premium (P) and hydrotreated straight-run (HSR) at low pressures, i.e. 10 bar, to lower significantly the operation costs. The premium and regular diesel contain additive packages with several components such as cetane boosters, antioxidants that show to negatively affect the sulfur conversion at low pressures. In the hydrotreated straight-run diesel fuel, which does not contain an additive package, total desulfurization can be obtained at 10 bar, T = 340 °C and LHSV = 1 h⁻¹. As a model for the additive package, FAME (fatty acid methyl ester), an ingredient that encounters the demands of a sustainable future, was added to the hydrotreated straight-run diesel (HSR + FAME) in order to check its influence on the total sulfur conversion. Results show that this biofuel component hindered tremendously the sulfur removal process by lowering the sulfur removal from 98% to zero at 10 bar, probably by competitive adsorption. At higher pressures, e.g. 30 bar, when FAME was present, new sulfur compounds were formed during the HDS process and the effective sulfur removal was very low.     

Oxidation desulfurization of fuel using pyridinium-based ionic liquids as phase-transfer catalysts

In this work, several ionic liquids based on pyridinium cations are prepared. The ionic liquids are employed as phase-transfer catalysts (PTCs) for phase-transfer catalytic oxidation of dibenzothiophene (DBT) dissolved in n-octane. The partition coefficients of DBT between ionic liquids and n-octane are investigated. Then H₂O₂-formic acid is used as an oxidant and ionic liquids are used as PTCs. The reaction turns to be heterogeneous and desulfurization rate of DBT increased apparently. When IL ([BPy]HSO₄) is used as PTC, and the condition are: temperature is 60 °C, time is 60 min, H₂O₂/sulfur molar ratio (O/S) is 4, the desulfurization rate reaches the maximum (93.3%), and the desulfurization of the real gasoline is also investigated, 87.7% of sulfur contents are removed under optima reaction conditions. The PTC [BPy]HSO₄ can be recycled for five times without significant decrease in activity.     

Oxidative desulfurization of Gas oil by polyoxometalates catalysts

Several polyoxometalates: Na₂HPM₁₂O₄₀, H₃PM₁₂O₄₀, Na₂HPM₁₂O₄₀, (VO)H[PM₁₂O₄₀] and (n-Bu₄N)₃[PM₁₂O₄₀] (M = Mo and W) as well as (n-Bu₄N)_3 + x[PW_12−xV_xO₄₀] (x = 0–3) were synthesized and characterized. Benzothiophene, dibenzothiophene and 4,6-dimethyl-dibenzothiophene were used as model sulfur compounds in gas oil. The oxidation reaction was performed using different polyoxometalates as catalyst and H₂O₂/acetic acid. The experimental results show that the W-based polyoxometalate catalysts are more active than the Mo catalysts. The oxidation reactivity of the catalysts depends on the type of countercation: Na⁺ > H⁺ > (VO)⁺ > (n-Bu₄N)⁺. In a series of (n-Bu₄N)_3 + x [PW_12−xV_xO₄₀] (x = 0–3) the order of catalytic activity is V₃ > V₂ > V₁ > V₀. The reactivity order of the sulfur compounds is: dibenzothiophene > 4,6-dimethyldibenzo-thiophene > benzothiophene. The catalytic system in this work was used for the oxidation of gas oil combined with solvent extraction to remove sulfur content in gas oil. Under mild reaction condition, high sulfur removal up to 98% can be achieved with high oil recovery (90%).     

Highly Efficient Oxidative Desulfurization of Fuels by Lewis Acidic Ionic Liquids Based on Iron Chloride

Acidic ionic liquids (ILs) have been employed as extractant and catalyst in the oxidative desulfurization (ODS) process of fuels in recent years. Several Lewis acidic ionic liquids [C₆³MPy]Cl/nFeCl₃ (molar fraction n = 0.5, 1, 2, 3) and [C₆MIM]Cl/FeCl₃ were prepared and used to remove the aromatic sulfur compounds dibenzothiophene and benzothiophene from fuels. In the ODS process, the used ILs acted as both extractant and catalyst with 30 wt % hydrogen peroxide aqueous solution as oxidant. The effects of Lewis acidity of ILs, IL's cation structure, molar ratio of O/S, reaction temperature, and different sulfur compounds on the sulfur removal of model oil were investigated. The results indicated that the sulfur removal for dibenzothiophene was affected by Lewis acidity of ILs and nearly reached 100 % by [C₆³MPy]Cl/FeCl₃ at conditions of 298 K, IL/oil mass ratio of 1/3, O/S molar ratio of 4/1, in 20 min. The sulfur removal of real gasoline reached 99.7 % after seven ODS runs in the [C₆³MPy]Cl/FeCl₃‐H₂O₂ system.     

Using response surface methodology to optimize ultrasound-assisted oxidative desulfurization

Latest strict environmental regulations have restricted the sulfur content of diesel fuels; therefore, deep desulfurization of fuels is required. Ultrasound-assisted oxidative desulfurization (UAOD) is an alternative for conventional desulfurization methods which can remove sulfur compounds from fuels under mild process conditions. In this study, UAOD of gasoil using tungstophosphoric acid catalyst and tetraoctylammonium bromide as a phase transfer agent in the presence of hydrogen peroxide as an oxidant was optimized. The optimal design of experiments was generated based on central composite face-centered design of Response surface methodology (RSM) to study effects of four process variables such as oxidant volume, mass of catalyst, mass of phase transfer agent and the ultrasonic wave amplitude on the sulfur conversion of gasoil. In addition, a predictive model of sulfur conversion was obtained based on RSM. The optimal values of process variables were evaluated to be 21.96 mL of oxidant, 1 gr of catalyst and 0.1 gr of phase transfer agent to achieve the maximum sulfur conversion of 95.92%.     

Desulfurization matching with coal poly-generation system based on dual gas resources

The coal poly-generation system for the production of alcohol and ether fuels as well as power is one of advanced coal utilization techniques. The team leaded by Professor Xie Kechang is carrying out the research on the poly-generation system to produce the syngas from the combination of gasified and pyrolyzed coal gas (dual gas resources) for the alcohol ether synthesis. Gas desulfurization is one of the key technologies for this system. The desulfurization matching with dual gas resources based poly-generation system for the production of alcohol and ether fuels as well as power is presented according to gas components, sulfur content, sulfur species and desulfurization accuracy in this technology. This matching desulfurization is classified into hot gas desulfurization, normal gas desulfurization, warm gas desulfurization and organic sulfur catalytic conversion. The preparation of H₂S removal sorbents, organic sulfur hydrolysis catalyst and the evaluation of their activities involved in the system were investigated. The H₂S removal efficiencies of the crude and fine desulfurization sorbents prepared for hot gas desulfurization are 90% and 99% at 500 °C in simulating coal gas, and their sulfur capacities are 21.85 wt.% and 24.91 wt.%, respectively. The organic sulfur catalyst shows the high hydrolysis activity, and the hydrolysis conversion of COS is more than that of CS₂ on the same catalyst. The research will provide necessary information for the matching desulfurization technology in the demonstration project on dual gas resources coal poly-generation system.     

Deep desulfurization by selective adsorption on a heteroatoms zeolite prepared by secondary synthesis

Gallium atoms have been introduced into the framework of Y zeolite by treating the zeolite with an aqueous solution of ammonium hexafluoro gallate. Desulfurization of various model fuels containing about 500 μg/g sulfur were studied over the synthesized Y zeolite ([Ga]AlY) with a liquid hourly space velocity of 7.2 h^− 1 at ambient conditions. The sulfur adsorption capacity was 7.0, 14.5, and 17.4 mg(S)/g adsorbent for thiophene, 4,6-dimethyldibenzothiophene (4,6-DMDBT), and tetrahydrothiophene (THT), respectively. The charges on S atom in thiophene, 4,6-DMDBT and THT, calculated by using density functional theory (DFT), are − 0.159, − 0.214 and − 0.298, respectively, implying that the S–M bond between the adsorption sites and thiophene is much weaker than that between the adsorption sites and THT or 4,6-DMDBT.     

成品柴油氧化萃取法脱硫脱氮工艺研究

以双氧水-有机酸体系作氧化剂,采用氧化反应与溶剂萃取相结合的方法对焦化柴油进行了氧化脱氮研究。通过单因素实验确定了最适宜的氧化工艺参数为：双氧水-甲酸作氧化体系,氧化温度为70℃,氧化时间为1 min,剂油体积比为0.24,V（双氧水）/V（有机酸）为0.5。萃取实验条件为：在室温条件下,萃取剂油比为0.8,搅拌5 min。以低硫、低氮成品柴油为例,考察了氧化萃取法在最佳工艺条件下对硫、氮的深度脱除,以及对硫类型和氮类型的选择性研究。结果表明：柴油回收率为94.20%,总氮脱出率为76.39%,总硫脱出率为87.38%,这种工艺对柴油中较难脱出的咔唑、噻吩类化合物具有较好的脱出效果。     

磷钨酸烷基甜菜碱催化氧化燃料油脱硫的性能

以磷钨酸烷基甜菜碱为相转移催化剂,双氧水为氧化剂,在乳液体系下,催化氧化脱除燃料油中的硫化物,研究了磷钨酸十四烷基二甲基甜菜碱、磷钨酸十六烷基二甲基甜菜碱以及磷钨酸十八烷基二甲基甜菜碱的催化性能,考察了催化剂用量、制乳时间、制乳转速以及氧硫比对脱硫效果的影响。结果表明,烷基甜菜碱的烷基链越长,催化效果越好;在催化剂的用量为0.003（剂油比）、制乳时间8min、制乳转速2500r/min、氧硫比为11的条件下,脱硫率可达到91.23%。     

焦化柴油过氧化环己酮氧化脱硫工艺研究

为了满足日趋严格的环保标准及市场对低硫柴油的巨大需求,柴油氧化脱硫技术显得日益重要。实验采用氧化萃取相结合的方法对焦化柴油进行了氧化脱硫实验。以自制过氧化环己酮为脱硫氧化剂,分别考察了氧化剂用量、氧化温度、氧化时间、萃取剂用量和二次萃取对焦化柴油硫含量的影响。结果表明,反应温度为100℃,反应时间3h,氧化剂与柴油的体积比0．04,萃取剂氮一甲基吡咯烷酮与柴油的剂油比为0．5,一级萃取可以脱除焦化柴油中93％的硫化物,柴油回收率达99％。二级萃取,可以脱除焦化柴油中95％的硫化物,柴油回收率为94．5％,硫含量可达到43．6μg·g^-1,小于50μg·g^-1,满足欧Ⅳ标准。     

离子液体脱除汽油中含硫化合物的研究

Brφnsted酸性吡咯烷酮离子液体N-甲基-2-吡咯烷酮氟硼酸盐([Hnmp]BF4)为萃取剂和催化剂,质量分数30%双氧水为氧化剂,将萃取脱硫和氧化脱硫相结合,对含有噻吩的模型油和FCC汽油进行萃取氧化脱硫研究。考察了氧与硫摩尔比、温度等对脱硫率的影响。结果表明:[Hnmp]BF4既是萃取剂又是催化剂,与H2O2作用产生的羟基自由基能将模型油中的噻吩和FCC汽油中的含硫化合物氧化,离子液体再生4次后脱硫性能开始下降,汽油的脱硫率达到82.7%。     

甲基咪唑盐酸盐/草酸型低共熔溶剂的制备及其在模拟油中氧化脱硫中的应用

通过简单加热并搅拌甲基咪唑盐酸盐和草酸的混合物合成了甲基咪唑盐酸盐/草酸（[HMIM]Cl/H₂C₂O₄）型酸性低共熔溶剂,以[HMIM]Cl/H₂C₂O₄为萃取剂和催化剂、H₂O₂为氧化剂催化氧化法脱除模拟油中的二苯并噻吩,考察不同的脱硫体系、反应温度、催化剂加入量、氧硫比、模拟油中含硫化合物类型对脱硫率的影响。实验表明,在反应温度为40℃、模拟油量为5 ml、[HMIM]Cl/H₂C₂O₄加入量为1.25 ml、O/S 12、反应时间为140 min的最佳反应条件下二苯并噻吩的脱除率可以达到92.2%。动力学分析表明,该氧化脱硫体系符合一级反应动力学方程。循环使用7次后催化剂的活性没有明显降低。