Study of diesel fuel desulfurization by adsorption

Removal of sulfur from diesel fuel by adsorption on a commercial activated carbon and 13X type zeolite was studied in a batch adsorber. Kinetic characterization of the adsorption process was performed applying Lagergren's pseudo-first order, pseudo-second order and intraparticle diffusion models using data collected during experiments carried out to determine the sulfur adsorption dependency on time. The experiments investigating adsorption efficiency regarding initial sulfur concentration were also performed and the results were fitted to Langmuir and Freundlich isotherms, respectively. Activated carbon Norit SXRO PLUS was found to have much better adsorption characteristics. The process of sulfur adsorption on the fore mentioned activated carbon was further studied by statistically analyzing data collected during experiments which were carried out according to three-factor two-level factorial design. Statistical analysis involved the calculation of effects of individual parameters and their interactions on sulfur adsorption and the development of statistical models of the process.     

Liquid phase desulfurization of jet fuel by a combined pervaporation and adsorption process

Since the conventional hydrodesulfurization process employed in the refinery industry is not suitable for mobile fuel cell applications (e.g. auxiliary power units, APUs), the present study aims at developing an alternative process and determining its technical feasibility. A large number of processes were assessed with respect to their application in fuel cell APUs. The results revealed that a two-step process combining pervaporation and adsorption is a suitable process for the on-board desulfurization of jet fuel. Therefore, a pervaporation process with subsequent adsorption was selected for detailed investigation. Six different membrane materials and ten sorbent materials were screened to choose the most suitable candidates. Further laboratory experiments were conducted to optimize the operating conditions and to collect data for a pilot plant design. Different jet fuel qualities with up to 1675 ppmw of sulfur can be desulfurized to a level of 10 ppmw. The aim of developing a suitable process for the desulfurization of jet fuel in fuel cell APUs was thus achieved.     

柴油氧化吸附脱硫工艺的研究

以过氧化氢为氧化剂,甲酸为催化剂,Al2O3为吸附剂,研究柴油氧化吸附脱硫工艺条件。实验结果表明,在n（氧）∶n（硫）=10.0,氧化时间为40min,氧化温度为70℃,V（吸附剂）∶V（油）=1∶5.5,吸附时间为30min,吸附温度为40℃时,吸附柴油的脱硫率为97.32%,柴油w（硫）=20.5μg/g,达到欧洲Ⅳ柴油标准：w（总硫）〈50μg/g。     

A new approach to deep desulfurization of gasoline by electrochemically catalytic oxidation and extraction

In order to further reduce the sulfur content in gasoline, a new desulfurization process for gasoline was obtained by means of electrochemically catalytic oxidation and extraction with an electrochemical fluidized-bed reactor. The particle group anode was activated carbon-supported lead dioxide (β-PbO₂/C). The electrolyte was aqueous NaOH solution, and copper pillar was cathode in the electrochemical reactions. The β-PbO₂/C particle group anodes can remarkably accelerate the electrochemical reaction rate and promote the electrochemical catalysis performance for the electrochemical desulfurization reaction. Also, gasoline desulfurization rule was investigated in an alkali solution. The experimental results indicated that the optimal desulfurization conditions were as follows: the cell voltage, the pH value of the electrolyte, feed volume flow rate and the β-PbO₂ percentage by weight were 3.2 V, pH value 13.1, 300 ml min^{− 1} and 5.0 wt.%, respectively. Under these conditions the concentration of sulfur in gasoline was reduced from 310 to 40 μg g^{− 1}, and the main properties of the product were not significantly affected. Based on these experimental results, a mechanism of indirect electrochemical oxidation was proposed.     

Hydrodesulfurization of jet fuel by pre-saturated one-liquid-flow technology for mobile fuel cell applications

To prevent the catalysts in fuel cell systems from poisoning by sulfur containing substances the fuel to be used must be desulfurized to a maximum of 10 ppm of sulfur. Thereby, damage to the catalysts in the fuel cell and the reformer can be avoided. Diesel fuel for road vehicles within the EU is already desulfurized at the refinery. However, jet fuel is permitted to have up to 3000 ppm of sulfur. Since the hydrodesulfurization process used in refineries is not suitable for mobile applications, the aim of the present work was to develop an alternative desulfurization process for jet fuel and to determine its technical feasibility.To this end, many processes were assessed with respect to their application in fuel cell based auxiliary power units (APUs). Among them, hydrodesulfurization with pre-saturation was selected for detailed investigations. Laboratory tests revealed that also syngas operation is possible without any performance loss in comparison to operation with hydrogen. Pure hydrogen is not available in a fuel cell system based on reforming of jet fuel. The effects of reaction temperature, operating pressure and liquid hourly space velocity (LHSV) were investigated. Different jet fuel qualities with up to 3000 ppm of sulfur were desulfurized to a level of 15-22 ppm.Finally, the technical applicability of hydrodesulfurization with pre-saturation was demonstrated in a pilot plant with an electrical power of 5 kW, going beyond the laboratory scale. In a 200-h experiment, a commercial jet fuel with 712 ppm of sulfur was desulfurized to a maximum sulfur content of 10 ppm. Besides this, H₂S separation by stripping with air turned out to be a suitable method for APU applications. The aim of developing a suitable process for the desulfurization of jet fuel in fuel cell APUs has thus been achieved.     

Deep desulfurization of gasoline using ion-exchange zeolites: Cu(I)- and Ag(I)-beta

Solid adsorbents Cu(I) and Ag(I) metal exchanged beta zeolites were prepared by solid-state ion-exchange (SSIE) method. Crystallographic structure of the prepared adsorbents has been characterized by XRD analysis. The texture of the prepared adsorbents was investigated using N₂ sorption. Pyridine IR measurements have been carried out to investigate the nature of the acid sites of the adsorbents. The deep-desulfurization performance of such adsorbents has been evaluated through fixed-bed adsorption technique with model gasoline containing thiophene and benzothiophene at ambient temperature and pressure. The obtained results revealed that the breakthrough capacities of Cu(I)- and Ag(I)-beta zeolite with the optimized Cu⁺ or Ag⁺ content are 0.239 mmol S/g and 0.237 mmol S/g, respectively. The remaining sulfur in the desulfurized gasoline is less than 1 ppmw. Their desulfurization capacity for actual FCC gasoline blend is reduced about 30% due to the competitive adsorption from olefins and aromatics. However, The capacity regeneration of Cu(I)- and Ag(I)-beta zeolite sorbents was carried out for 9 times. It is more than 95% recovery of desulfurization after the first regeneration, and it keeps little reduction after subsequent 8 times of regeneration. Such studies included the effect factors on desulfurization performance, such as metal exchange content, SiO₂/Al₂O₃ ratio, acidity, and other texture properties of the zeolite etc.     

轻质油品脱硫技术研究进展

介绍目前国际上正在应用或开发的轻质油品脱硫新技术，阐述这些技术工艺的原理、特点及脱硫性能，并综合进行比较得出吸附法脱除油品中的含硫化合物具有操作简单、投资少、适合于深度脱硫、无污染等优点，是一项具有工业应用前景的汽油脱硫新技术。     

柴油脱硫技术的研究进展

对目前清洁燃料油的生产技术进行了概述.随着世界清洁柴油中含硫标准的提高,降低柴油中硫含量已成为全球性关注的问题.近几年,出现了许多新的脱硫技术,其中柴油非加氢脱硫技术的研究进展较快.介绍了氧化脱硫和非氧化脱硫技术的理论基础,重点概述了这方面取得的最新成果,并从清洁生产的角度出发,对柴油脱琉技术的发展进行了辰望.     

A novel method for oxidative desulfurization of liquid hydrocarbon fuels based on catalytic oxidation using molecular oxygen coupled with selective adsorption

The present study explored a novel oxidative desulfurization (ODS) method of liquid hydrocarbon fuels, which combines a catalytic oxidation step of the sulfur compounds directly in the presence of molecular oxygen and an adsorption step of the oxidation-treated fuel over activated carbon. The ODS of a model jet fuel and a real jet fuel (JP-8) was conducted in a batch system at ambient conditions. It was found that the oxidation in the presence of molecular oxygen with Fe(III) salts was able to convert the thiophenic compounds in the fuel to the corresponding sulfone and/or sulfoxide compounds at 25 °C. The oxidation reactivity of the sulfur compounds decreases in the order of 2-methylbenzothiophene > 5-methylbenzothiophene > benzothiophene  dibenzothiophene. The alkyl benzothiophenes with more alkyl substituents have higher oxidation reactivity. In real JP-8 fuel, 2,3-dimethylbenzothiophene was found to be the most refractory sulfur compound to be oxidized. The catalytic oxidation of the sulfur compounds to form the corresponding sulfones and/or sulfoxides improved significantly the adsorptivity of the sulfur compounds on activated carbon, because the activated carbon has higher adsorptive affinity for the sulfones and sulfoxides than thiophenic compounds due to the higher polarity of the former. The remarkable advantages of the developed ODS method are that the ODS can be run in the presence of O₂ at ambient condition without using peroxides and aqueous solvent and thus without involving the biphasic oil–aqueous-solution system.     

Imidazolium-based alkylphosphate ionic liquids - A potential solvent for extractive desulfurization of fuel

N-ethyl-imidazolium-based alkylphosphate ionic liquid (IL), viz. N-ethyl-N-methyl-imidazolium dimethylphosphate ([EMIM][DMP]), N-ethyl-N-ethyl-imidazolium diethylphosphate ([EEIM][DEP]) and N-butyl-N-ethyl-imidazolium dibutylphosphate ([BEIM][DBP]) were demonstrated to be effective for the removal of aromatic sulfur compounds (S-compound) 3-methylthiophene (3-MT), benzothiophene (BT) and dibenzothiophene (DBT) from fuel oils in terms of sulfur partition coefficients (K_N) at 298.15 K. It was shown that the extractive ability of the alkylphosphate ILs was dominated by the structure of the cation and followed the order [BEIM][DBP] > [EEIM][DEP] > [EMIM][DMP] for each S-compound studied with their K_N-value being 1.72, 1.61 and 1.17, respectively for DBT. For a specified IL the sulfur selectivity followed the order DBT > BT > 3-MT with their K_N-value being 1.61, 1.39 and 0.78, respectively for [EEIM][DEP]. The alkylphosphate ILs are insoluble in fuel while the fuel solubility in ILs varies from 20.6 mg(fuel)/g(IL) for [EMIM][DMP] to 266.9 mg(fuel)/g(IL) for [BEIM][DBP]. The results suggest that [EEIM][DEP] might be used as a promising solvent for the extractive desulfurization of fuel, considering its higher sulfur extractive ability, lower solubility for fuel and thus negligible influence on the constituent of fuel, and the ease of regeneration for the spent IL via water dilution process.     

柴油氧化脱硫技术新进展

柴油低硫化及其含硫标准的日趋严格,是世界各国柴油产品质量与标准的发展趋势。加氢脱硫技术生产低硫柴油,存在投资大、操作费用高和操作条件苛刻的缺点,导致柴油成本大幅攀升,柴油氧化脱硫技术已成为研究热点。综述了国内外柴油氧化脱硫技术的研究进展,认为柴油氧化脱硫技术将成为今后生产超低硫清洁柴油的主要工艺之一。     

微波作用下柴油脱硫新方法的研究

用φ(H2O2)=30%-HCOOH为氧化剂,N,N-二甲基甲酰胺(DMF)为萃取剂,采用微波辐射对柴油进行氧化脱硫,实验结果表明,在微波辐射压力为0.5MPa,微波功率为450W,恒压辐射时间为10min,氧化剂与油的体积比为1∶10,萃取剂与油的体积比为3∶4,萃取时间为15min的条件下,脱硫率可达到95.8%,收率达99.5%。     

Catalytic adsorptive desulfurization of mercaptan,sulfide and disulfide using bifunctional Ti-based adsorbent for ultra-clean oil

Ultra-deep desulfurization of transformer oil is of great demand among power industry. In this work, the effective and deep removal of various types of organosulfurs, including mercaptan, sulfide and disulfide via catalytic adsorptive desulfurization (CADS) using bifunctional Ti-based adsorbent is reported. Compared to adsorptive desulfurization (ADS), dramatically improvement of the organosulfur uptakes were achieved under CADS process. The equilibrium adsorption capacity at 5 μg·g^-1 S reached up to 15.7, 33.4, 11.6 and 11.9 mg·g^-1 for propyl mercaptan(n-PM), dimethyl sulfide(DMS), di-t-butyl disulfide (DTBDS) and dibenzyl disulfide (DBDS), which was 262, 477, 97 and 128 times to that of ADS process, respectively, and was the highest among the reported desulfurization adsorbents. Moreover, it achieved superior breakthrough capacity of 2050, 530 and 210 ml F·(g A)^-1 at the breakthrough S concentration of 1 μg·g^-1 of the commercial transformer oil S containing 10, 50 and 150 μg·g^-1, respectively. The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant, which can be readily captured by silanol groups on SiO₂ through H-bonding interaction. The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment. This work provides an effective and economic approach for the elimination of trace amount of mercaptan, sulfide and disulfide from transformer oil.     

Experimental investigation of surrogates for jet and diesel fuels

The low and intermediate temperature reactivities of 2:1:1 n-decane:n-butylcyclohexane:n-butylbenzene and 1:1:1 n-decane:n-butylcyclohexane:n-butylbenzene were examined as possible surrogates for jet and diesel fuel, respectively. The hydrocarbons and the proportions were chosen as they match the average composition of the real fuels. The candidate surrogates and the real fuels were oxidized in a pressurized flow reactor at temperatures of 600–800 K, pressure of 0.8 MPa, and equivalence ratio of 0.30. The three-component mixtures were significantly more reactive than the real fuels. The difficulties of tuning both properties and behavior of the surrogates to the real fuels are discussed. Surrogate fuels that maintain the molecular weight of the real fuels but with reduced reactivity may require the addition of a heavy iso-paraffin.     

A new method for obtaining ultra-low sulfur diesel fuel via ultrasound assisted oxidative desulfurization☆

Due to the requirement of stringent rules for ultra-low sulfur content of diesel fuels, it is necessary to develop alternative methods for desulfurization of fossil fuel derived oil. Using appropriate oxidants and catalysts with the assistance of ultrasound irradiation, model compounds such as dibenzothiophene can be quantitatively oxidized in minutes. For diesel fuels containing various levels of sulfur content, and through the use of catalytic oxidation and ultrasonication followed by solvent extraction, removal efficiency of sulfur-bearing compounds can reach or exceed 99% in a short contact time at ambient temperature and atmospheric pressure. This simple approach can be the basis for obtaining ultra-low sulfur-containing diesel oil. GC-PFPD, GC-MS, and GC-SIMDIS were used to monitor the change of organic sulfur compounds and hydrocarbons in diesels during the process.     

FCC gasoline desulfurization using a ZSM-5 catalyst: Interactive effects of sulfur containing species and gasoline components

This study evaluates the influence of gasoline hydrocarbon components on thiophene conversion over H-ZSM5 zeolite. Experiments are carried out in a CREC fluidized riser simulator under mild conditions using thiophene/hydrocarbon mixtures as representatives of gasoline. Results show a high and selective thiophene conversion, forming H₂S, aromatics, alkyl-thiophenes, benzothiophene, and coke. It is also found that gasoline octane number is enhanced and olefin content reduced. This is accomplished with minimum gasoline losses. On the basis of the data reported it is hypothesized that thiophene conversion takes place via ring opening and alkylation, with gasoline hydrocarbon components having key roles as hydrogen donors in thiophene ring opening reactions as well as co-reactants in thiophene alkylation. These observations are in good agreement with previous thermodynamic and kinetic analysis developed using sulfur containing compounds by the CREC-UWO research group [4] and [10].     

Development of an advanced,thermally stable,coal-based jet fuel

A candidate coal-based jet fuel that would serve the dual purpose of providing propulsion energy and excellent heat-sink capabilities was produced at pilot-plant scale by hydrotreating a 1:1 mixture of coal-derived refined chemical oil and petroleum-derived light cycle oil. The fuel was characterized using current specification methods for JP-8 fuel. Oxidative and pyrolytic thermal stability tests were conducted. Combustion tests were performed in a model high-pressure gas turbine combustor and in a T-63 turboshaft engine. Low-temperature viscosity properties and O-ring swelling were also evaluated. The candidate coal-based fuel meets most JP-8 specifications, although a few results were outside the current specification limits. The major hydrocarbon class in the coal-based fuel is cycloalkanes (e.g. decalin and its derivatives), which accounts for this fuel being significantly more dense than JP-8. The higher density could be of importance for volume-limited applications in aircraft and missiles. The candidate coal-based fuel showed excellent thermal stability, better than a JP-8 containing the currently qualified JP-8+100 additive package. In the model combustor, soot formation characteristics were essentially identical to JP-8; in the T-63 engine, the overall emissions produced were only slightly greater than from a typical JP-8. The candidate coal-based fuel appears to remain a single-phase liquid down to − 70 °C, desirable behavior for long-duration, high-altitude flights. The coal-based fuel has the same swelling characteristics for nitrile O-rings as does JP-8.     

Modeling of multi-component fuel vaporization and combustion for gasoline and diesel spray

The present study applied a continuous thermodynamics approach to consider the multi-component nature of petroleum fuels during the vaporization process. A gamma distribution was used to describe the molecular weight of the fuel. The model was first used to study the vaporization of single diesel and gasoline drops. Results showed that the mean molecular weight of the fuel drop kept increasing, indicating that the lighter components vaporized earlier in the process. The present vaporization model was also integrated with an engine simulation code for diesel spray combustion study. Results of diesel spray modeling showed that heavy fuel components survived during the early vaporization process such that the drops in the outer regions of the spray were mostly composed of heavier components. In this study, detailed chemistry was used for diesel combustion modeling. Results showed that good levels of agreement between experiments and predictions were obtained in flame structures and soot distributions. Effects of ambient temperature in the sooting tendency of diesel spray were also predicted by the present model. Under the conditions studied , soot emissions were not seen for ambient temperature less than 850 K, which is consistent with the concept of low-temperature engine combustion for low emissions.     

The application of theoretical solutions to the differential mass balance equation for modeling of adsorptive desulfurization in a packed bed adsorber

Adsorptive removal of organosulfur compounds, lumped as total sulfur content, from a real diesel fuel was carried out in a packed bed adsorber. A novel approach was taken in the application of theoretical solutions to the differential mass balance equation using modern software tools, and one classic method as point of reference. Adsorptive desulfurization is a perspective downstream process to hydrodesulfurization for achieving sulfur concentration levels of less then 10 mg kg⁻¹. Compared to the conventional hydrodesulfurization process, the deep desulfurization can be accomplished without changing the physical properties of the product and at relatively low temperature and pressure. The adsorber apparatus comprised computer control, enabling completely automated operation. Adsorbent was activated carbon SOLCARB C from Chemviron Carbon, Belgium. The experimental results regarding the influence of flow rate and bed depth on the outlet sulfur concentration were evaluated as well as the models ability to describe the adsorption kinetics and to estimate the breakthrough curves. Ultra deep desulfurization of diesel fuel was achieved and it was determined that outlet sulfur concentration was being lowered by decreasing flow rate and increasing bed depth. The closest fit to the experimental data was achieved for the Bohart-Adams model.     

Deep hydrodesulfurization of diesel fuel: Design of reaction process and catalysts

Deep hydrodesulfurization (HDS) of diesel fuel oil was designed based on the recognition that alkyl dibenzothiophenes such as 4-methyl-and 4,6-dimethyldibenzothiophenes were the main target for deep HDS. Multi-stage and fractional HDS were very effective to achieve satisfactory HDS in terms of both sulfur level and fluorescent color of desulfurized oil. Catalysts with the selective hydrogenation of refractory sulfur species in major aromatic partners and isomerization-disproportionation of their alkyl groups prior to HDS were also designed to promote the desulfurization of such sulfur species.