Model Diesel Research Articles

Adsorptive removal of refractory sulfur compounds by tantalum oxide modified activated carbons

Adsorptive desulfurization of a model diesel fuel consisting of dibenzothiophene (DBT) or 4,6‐dimethyldibenzothiophene(4,6‐DMDBT) in hexadecane was performed over activated carbons and tantalum oxide modified (Ta‐x/ACC, x= 2, 5 or 10 wt % Ta, Activated Carbon Centaur) activated carbons at 50°C. The adsorption isotherm for ACC followed the Langmuir model while the adsorption on Ta‐5/ACC fitted the Sips equation indicating more than one type of adsorption sites. Characterization studies indicated new types of adsorption site resulting from the incorporation of Ta oxide into the porous structure of the ACC. XPS data suggested interaction of Ta with the S atom in DBT. The heats of adsorption in the liquid phase determined from micro flow calorimetry for DBT in C16 confirmed the interaction of Ta with DBT. Ta‐5/ACC exhibited the highest adsorption capacity for 4,6‐DMDBT compared to literature reports. Competitive adsorption experiments showed the adsorption capacity as follows: quinoline> DBT≫ naphthalene. © 2017 American Institute of Chemical Engineers AIChE J, 2017

Plasma-Catalytic Reforming of Biofuels and Diesel Fuel

The replacement of fossil hydrocarbons with the renewable biomass alternatives is an inevitable requirement in our transition toward a sustainable economy. However, traditional petrochemical technologies are not designed to operate using biomass raw materials. Thus, the development of new hydrocarbon processing methods is essential. This paper deals with the study of the hybrid plasma-catalytic reforming of liquid hydrocarbons. The system for the reforming of liquid hydrocarbons, which used low-power rotating gliding discharge as a plasma generator, was studied. Sunflower oil (C17H33COOH) and ethanol (C2H5OH) have been used as model oxygen-containing hydrocarbons and diesel fuel (C16H34) has been used as a model hydrocarbon without oxygen. Reforming products have been analyzed using mass spectrometry and gas chromatography, and the combustion of produced syngas was studied. The values of the reforming efficiency, the ratio between the chemical energy of the produced syngas and the electric energy spent on the plasma generation, and the efficiency of the produced syngas combustion in the standard water heaters were obtained.

Desulfurization process conciliating heterogeneous oxidation and liquid extraction: Organic solvent or centrifugation/water?

The present work presents a strategic oxidative desulfurization system able to efficiently operate under sustainable conditions, i.e. using an eco-friendly oxidant and without the need of extractive organic solvents. The catalytic performance of Eu(PW11O39)2@aptesSBA-15 was evaluated for the oxidative desulfurization of a multicomponent model diesel using a solvent-free or biphasic systems. The results reveal its remarkable desulfurization performance achieving complete desulfurization after just 2h of reaction. Moreover, the composite has shown a high recycling ability without loss of catalytic activity for ten consecutive ODS cycles. Interestingly, under solvent-free conditions it was possible to maintain the desulfurization efficiency of the biphasic system while being able to avoid the use of harmful organic solvents. In this case, a successful extraction of oxidized sulfur compounds was found conciliating centrifugation and water as extraction solvent. Therefore, this work reports an important step towards the development of novel eco-sustainable desulfurization systems with high industrial interest.

Ultra-deep desulfurization of diesel fuel via selective adsorption over modified activated carbon assisted by pre-oxidation

Commercial adsorbents were tested for removing the dibenzothiophene sulfone (DBTO) from a model diesel fuel and organosulfur oxidized products (sulfones) from a real diesel fuel under ambient conditions. Activated carbons treated by concentrated H2SO4 at high temperature showed increasing adsorption capacity and affinity towards DBTO. On the basis of adsorption tests and the characterization by BET, base titration, SEM, XPS, Visible-Raman and FTIR, the acidic-oxygenated groups incorporated to the surface act as adsorption sites for selective adsorption of sulfone. The specific interaction may be formed through the acid-base interaction involving the SO group. Activated carbon treated by steam at 900 °C and followed by concentrated H2SO4 at 250 °C displayed significantly enhanced DBTO adsorption performance and a sulfur capacity of 5.8 mg S/g adsorbent for removing organosulfur compound from a real diesel to less than 10 ppmw.

Sustainable Desulfurization Processes Catalyzed by Titanium-Polyoxometalate@TM-SBA-15

A titanium-polyoxometalate with a µ-hydroxo dimeric structure [(PW11O39Ti)2OH]7− ((PW11Ti)2OH) was used efficiently for the desulfurization of a model diesel containing a mixture of various refractory sulfur compounds present in real fuels. The catalytic performance of the µ-hydroxo dimeric compound was compared in its homogeneous form and also when immobilized in the trimethylammonium-functionalized SBA-15 ((PW11Ti)2OH@TM-SBA-15). An optimization study was performed using the homogeneous and heterogeneous catalysts to obtain high catalytic efficiency, sustainability and cost-effectiveness of the system. Different optimized conditions were found using the homogeneous and heterogeneous catalysts. Lower amounts of solvent extraction (MeCN, 175 µL), catalyst (0.5 µmol of active center) and oxidant (50 µL) were used to produce sulfur-free model diesel after 2 h at 70 °C, using the heterogeneous (PW11Ti)2OH@TM-SBA-15 catalyst. On the other hand, complete desulfurization was achieved with homogeneous (PW11Ti)2OH catalyst after only 40 min, although higher amounts of MeCN (750 µL), catalyst (1.5 µmol) and oxidant (75 µL) were used. Both systems combined liquid–liquid extraction and catalytic oxidation. Using the heterogeneous catalyst, adsorption of oxidized-sulfur compound was also observed. Both homogeneous and heterogeneous desulfurization systems presented a high capacity to be reused/recycled for consecutive desulfurization cycles.

Denitrogenation and desulfurization of model diesel fuel using functionalized polymer: Charge transfer complex formation and adsorption isotherm study

This study is a perquisite to the fundamental understanding of the adsorption of heterocyclic nitrogen and sulfur compounds present in petroleum feedstock over fluorenone derived π-acceptor functionalized polymers. Quinoline (basic nitrogen compound), 9-ethylcarbazole (non-basic nitrogen compound) and dibenzothiophene (sulfur compound) were scanned to study the adsorptive denitrogenation and desulfurization of model diesel fuel. Batch reactor was used to compare the adsorption capacity and selectivity of these compounds at three sets of temperature (298K, 313K and 328K). Total Nitrogen/Sulfur analyzer measured the change in nitrogen and sulfur content of the model fuels after adsorption over π-acceptor, 2,4,5,7-tetranitro-9-fluorenone (TENF) functionalized polymer. 60% extraction of total nitrogen compounds was obtained in one step, whereas the sulfur reduction was only 23% from a mixed model feed containing 700ppm each of nitrogen and sulfur compounds. Charge transfer complexes were easily detected by the appearance of new bands in the visible region of UV–vis absorption spectrum. Adsorption isotherms facilitated the measurement of equilibrium binding capacities and adsorption affinities for this novel adsorbent. Functionalized polymer contributed towards higher adsorption of quinoline as compared to carbazole derivative and dibenzothiophene. Adsorption of these compounds was found to be reversible and multilayer over the heterogeneous surface of the functionalized polymer. At 298K, maximum adsorption capacity increases as follows: quinoline>dibenzothiophene>9-ethylcarbazole. Calculation of the thermodynamic properties revealed that the adsorption is favorable and spontaneous in nature. Molar enthalpies were calculated between −3.9 and −22kJ/mol; which are characteristic of the electron donor acceptor complexes.

Physicochemical Studies of Adsorptive Denitrogenation by Oxidized Activated Carbons

A commercially available activated carbon was oxidized by concentrated sulfuric acid, saturated ammonium persulfate solution, and mixed sulfuric acid and ammonium persulfate, respectively. The original carbon and the modified carbons were evaluated by batch adsorption using model diesel fuels. The pore structure and surface chemistry of adsorbents were characterized with N2 adsorption/desorption, Fourier transform infrared spectroscopy, and Boehm’s titration. Both physical and chemical aspects of the selectively adsorptive denitrogenation of oxidized activated carbons were investigated. Appropriate oxidation can promote the carbon’s ability to adsorb nitrogen-containing compounds. The effect of the density of acidic oxygen-functional groups on the adsorption of nitrogen-containing compounds was demonstrated by the regression method and quantum chemistry calculations. The capacities due to physisorption were also estimated. The behaviors of N-containing compounds in a competitive adsorption system were dep...

Oxidative Desulfurization of Diesel Using Vanadium-Substituted Dawson-Type Emulsion Catalysts

In this study, we aimed at investigating the catalytic oxidative desulfurization (CODS) of the model diesel oil and real diesel oil using the vanadium-substituted Dawson-type emulsion catalyst ([cetrimonium]6+xP2W18–xVxO62 (x = 1, 3, 5)). Among all prepared samples, [cetrimonium]11P2W13V5O64 showed the best results in CODS of model diesel oil under determined conditions (10 g/L catalyst and O/S mole ratio = 4). The Taguchi method was then applied to optimize the catalyst dosage, hydrogen peroxide dosage, and the reaction temperature in CODS using the best emulsion catalyst. Then formic acid and acetic acid were used as a co-oxidant to improve the oxidation ability. Under optimum conditions, a mixture of H2O2/formic acid (1:1), in the presence of [cetrimonium]11P2W13V5O62 could remove 98% of dibenzothiophene and 82% of benzothiophene. Finally, under optimum conditions of CODS, 90% of total sulfur was removed from a real diesel sample. It is worth mentioning that we could recycle [cetrimonium]11P2W13V5O64, ...

Effect of pore structure and oxygen-containing groups on adsorption of dibenzothiophene over activated carbon

Activated carbons chemically treated by steam and concentrated H2SO4, were used as adsorbents for removing organic sulfur compounds from a model diesel. The modified activated carbon was characterized by N2 sorption, base titration and FTIR spectroscopy. As compared with the untreated activated carbon, the treatment by a steam at 900°C increased the mesoporous volumes from 0.248 to 0.856cm3/g and sulfur adsorption capacity for dibenzothiophene from 10.9 to 20.6mg/g and the treatment by a concentrated H2SO4 at 250°C increased the amount of surface acidic-oxygenated groups from 0.05 to 1.95mmol/g, and total adsorption capacity for dibenzothiophene from 10.9 to 33.3mg/g. The total adsorption capacity for dibenzothiophene is found to be proportional to the mesoporous volume and the amount of surface oxygen-containing groups. It is proposed that direct interaction between the sulfur atom and surface oxygen-containing groups plays an important role in the adsorption of organic sulfur compound.

Efficient eco-sustainable ionic liquid-polyoxometalate desulfurization processes for model and real diesel

This work presents a successful recycling system based in homogeneous polyoxometalate catalysts to desulfurize model and real diesels. Various Keggin-type polyoxometates entrapped in a room temperature ionic liquid (RTIL) phase were investigated. The desulfurization process here proposed conciliates efficiently an extraction and an oxidative catalytic process under sustainable and moderate conditions (H2O2 as oxidant, 50°C). The ionic liquid acts as an extraction solvent and also as an effective immobilization medium for the active homogeneous catalysts. The zinc-polyoxometalates presented high stability and high capacity to be recycled for various consecutive cycles with no loss of desulfurization efficiency. Complete desulfurization of model diesel was achieved at short reaction time (3h). Under the same experimental conditions, 80% of sulfur was removed from real diesel (Sinitial=2300ppm).

Oxidative Desulfurization of Model Diesel Using a Fenton‐Like Catalyst in the Ionic Liquid [Dmim]BF4

AbstractA Fenton‐like catalyst prepared from tetrabutylammonium chloride and ferric trichloride was characterized by Fourier transform infrared, UV‐vis and Raman spectroscopy. The catalyst (C4H9)4NFeCl4 (TBAFeCl4) in an extraction and catalytic oxidative desulfurization (ECODS) system containing H2O2 and the ionic liquid (IL) 1‐decyl‐3‐methylimidazolium tetrafluoroborate ([Dmim]BF4) exhibited high catalytic activity for the removal of dibenzothiophene (DBT) in model diesel. Desulfurization with the Fenton‐like catalyst TBAFeCl4 in ECODS involves the structural distortion of DBT via polarization of the IL and its subsequent oxidation. The catalytic system could be recycled multiple times without significant decrease in desulfurization activity due to the high stability of the system.

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique is presented. The technique entails splitting kaolin to alumina and silica components. These components were further recombined to synthesize zeolite Y. The as-synthesized NaY zeolite was transformed to REY zeolite. Characterizations of the as-synthesized zeolite Y were carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) texture analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared (FTIR) spectroscopy. Catalytic desulfurization of the as-synthesized REY zeolite was studied using microwave assisted desulfurization of model diesel. The Si/Al molar ratio of the as-synthesized NaY zeolite was 4.27. The crystallinity of the as-synthesized NaY and REY zeolites were 79.1 and 56.5% respectively. The as-synthesized NaY and REY zeolites possessed hexagonal morphology with average crystal sizes of 200 and 100 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized NaY zeolite were 732 m2 g−1, 0.2611 cm3 g−1 and 1.426 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized REY zeolite were 456 m2 g−1, 0.1591 cm3 g−1 and 1.395 nm respectively. Zeolite Y synthesized using the split technique possessed physiochemical properties comparable to the commercial zeolite Y, it was also free of quartz and competing phase impurities reported in previous works. The as-synthesized REY zeolite resulted to 79% sulfur reduction when used as a catalyst in a microwave desulfurization of model diesel at 100 °C for 15 min.

Extractive-oxidative removals of dibenzothiophene and quinoline using vanadium substituted Dawson emulsion catalyst and ionic liquid based solvents

Extractive-catalytic oxidative desulfurization (ECODS) of model diesel using vanadium substituted Dawson-type emulsion catalyst has been investigated for the first time. At different operational conditions, ECODS was studied using selected solvents and [cetrimonium]11P2W13V5O62 by means of Taguchi methods Under the optimized conditions (ionic liquids/oil volume ratio 1:8, 7.5 g/L catalyst, O/S mole ratio 8, T = 70 °C after 45 min) 94% of sulfur and 100% of quinoline were removed. It is worth mentioning that in the presence of catalyst, solvent/oil volume decreases by 45% while sulfur removal increases by 54% compared to extraction desulfurization.

Coupled Heterogeneous and Homogeneous Hydrocarbon Oxidation Reactions in Model Diesel Oxidation Catalysts

In testing model diesel oxidation catalysts to treat exhaust from low temperature combustion (LTC) vehicle engines, the simulated exhaust conditions were such that both homogeneous and heterogeneous oxidation of some hydrocarbons took place. When homogeneous oxidation occurred, NO was readily oxidized to NO2 and the larger hydrocarbon species were partially oxidized to aldehyde, alcohol, and alkene intermediates. The homogeneous oxidation potentials of several hydrocarbons were compared in the absence and presence of a model oxidation catalyst. Of the hydrocarbons evaluated, diethyl ether led to the best NO to NO2 oxidation in terms of temperature and extent of conversion, and it did not inhibit the oxidation of other hydrocarbon species. The clear evidence of homogeneous reactions occurring within the monolith catalyst channels, and the formation of associated reaction intermediates, may impact reactions that would normally be considered isolated to the catalyst surface. These findings demonstrate that, in modeling such reactions, the homogeneous reactions need to be considered and may influence future catalyst design, especially considering the importance of NO2 for downstream selective catalytic reduction and particulate filter catalyst systems.

Diffusion behavior study of model diesel components in polymer membranes based on neural network for pattern recognition

A neural network for a pattern recognition model is developed for the first time to predict the diffusion behavior of the model diesel components (dibenzothiophene and quinolone) in three different membranes of polyvinyl alcohol, polyvinyl chloride and polymethyl acrylate. The simulation results show that the excellent performance target parameter optimization area can be obtained and the effective desulfurization and denitrification agent can be found. Compared with the advanced molecular dynamic simulation method and verified by adsorption experiments, the simulation values are in good agreement with the experimental data and molecular dynamic simulation data. The results reveal that the polyvinyl chloride membrane can improve the diffusion selectivity of dibenzothiophene and it is selected as the most effective desulfurization agent, while the polyvinyl alcohol membrane is selected as the most effective denitrification agent to remove the nitrogen compounds. Development time and effort of screening desulfurization agent and denitrification agent tests are also reduced because the neural network for the pattern recognition modelprovides ready-made decisions. Therefore, the neural network for pattern recognition is a prospect and practicable theoretical method to research the diffusion behavior of model diesel components in polymer membranes.

Adsorption diffusion behaviour of 4,6‐DMDBT from diesel fuel

The equilibrium and kinetics of adsorption desulphurization of model diesel fuel under different operating conditions were investigated. The homogeneous surface diffusion model (HSDM) and pore diffusion model (PDM) taking into account external resistance and intraparticle resistance were employed to represent the adsorption kinetics of 4,6‐dimethyldibenzothiophene (4,6‐DMDBT). The equilibrium isotherm analysis revealed that the equilibrium can be represented well by the Freundlich model. The proposed HSDM model and PDM model can successfully describe the adsorption of 4,6‐DMDBT for different operating conditions studied. The adsorbate was absorbed rapidly initially because the adsorption rate at the beginning was dominated only by external diffusion. The Biot numbers proved that the predominant rate‐controlling step was intraparticle diffusion. Simultaneously, the adsorption rate was mainly controlled by surface diffusion at lower initial bulk phase concentration and less adsorbent dosage, while pore diffusion played a significant role at higher initial bulk phase concentration and more adsorbent dosage. The temperature had little effect on the diffusion of 4,6‐DMDBT from diesel fuel. The estimated values of pore diffusion coefficient and surface diffusion coefficient were 1.55 × 10−12 m2/s and 5.855 × 10−14 m2/s, respectively. They were independent of adsorbent dosage, initial 4,6‐DMDBT concentration, and temperature, which can provide guidance for fixed‐bed adsorption columns design and process operation.

Synthesis of a hybrid Anderson-type polyoxometalate in deep eutectic solvents (DESs) for deep desulphurization of model diesel in ionic liquids (ILs)

A novel hybrid Anderson-type polyoxometalate, {[(CH3)3N(CH2)2OH]2}[H0.2K0.2Na2.6(H2O)6][IMo6O24] (Abbreviated as (ChO)2K0.2Na2.6IMo6) was synthesized in a deep eutectic solvent and characterized by XRD, FT-IR, thermal analysis, electrochemical measurements and inductively-coupled plasma, atomic emission spectrometer (ICP-AES). This hybrid polyoxometalate was used as a catalyst in ionic liquids (ILs) for desulfurization of model diesel. The catalyst (ChO)2K0.2Na2.6IMo6 in the extraction and catalytic oxidative desulfurization (ECODS) system, containing H2O2 and 1-octyl-3-methylimidazolium tetrafluoroborate (OmimBF4), displayed so high activity that the removal of DBT can reach 100% at 60°C in 60min. Sulfur removal for S-compounds was in the following order: DBT>4,6-DMDBT>BT. The desulfurization system shows so good stability that it can be recycled 20 times without noticeable decrease in activity.

Zinc‐Substituted Polyoxotungstate@amino‐MIL‐101(Al) – An Efficient Catalyst for the Sustainable Desulfurization of Model and Real Diesels

The zinc‐substituted polyoxotungstate [PW11Zn(H2O)O39]5– (PW11Zn) has been encapsulated within the aluminium(III) 2‐aminoterephthalate NH2‐MIL‐101(Al) metal–organic framework (MOF) either directly through a one‐pot microwave‐assisted synthesis or by an impregnation method. The resultant composite materials were characterized by elemental analysis, powder X‐ray diffraction, FTIR spectroscopy, and 31P magic‐angle spinning (MAS) NMR spectroscopy. The desulfurization of a model diesel containing three refractory organosulfur compounds (1‐benzothiophene, dibenzothiophene, and 4,6‐dimethyldibenzothiophene) was studied with the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate as an extractant, the PW11Zn@MOF composites as sulfoxidation catalysts, and aqueous H2O2 as an oxidant. The composite obtained by direct synthesis was the most efficient catalyst and led to almost complete desulfurization of the model diesel under mild conditions. Moreover, the solid catalyst could be recovered readily and recycled without significant loss of desulfurization performance. The application of this system to the treatment of a real diesel sample provided a very good sulfur removal of 83 % when combined with liquid–liquid extraction.

Fabrication of Aromatic Polyimide Membrane to Study the Pervaporative Separation of Phenanthrene/n-tetradecane Mixtures (Model Diesel) and Process Optimization Using Response Surface Methodology

To meet stringent fuel specifications, separation of aromatics from aliphatics is an everyday challenge for a refiner. In the present investigation, an aromatic polyimide membrane is fabricated and explored for the separation of a polyaromatic hydrocarbon (phenanthrene) from a model diesel composition (n-tetradecane) via pervaporation. The pervaporative membrane is prepared by casting a solution of polyamic acid, N,N-dimethylacetamide (DMAc), and phenanthrene using a simple and low-cost procedure. Scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), and swelling in feed solution of the synthesized membrane have been conducted for its characterization. The membrane allows preferential permeation of phenanthrene. The influence of different physico-chemical parameters, on permeation flux and enrichment factor for n-tetradecane/phenanthrene mixtures, has been studied. Statistical software Design Expert 7.1.4 is used to derive the regression equation, which describes the effect of time, downstream pressure, feed solute concentration, and operating temperature on the Pervaporation Separation Index (PSI). These factors are optimized using response surface methodology (RSM). The highest value of the PSI obtained is 0.623 kg m−2 h−1 and the corresponding optimized condition is: operating time is 11.58 h, the feed solute concentration is 162.96 ppm with a downstream pressure of 0.58 mm of Hg and an operating temperature of 449.03 K.

Separation of phenanthrene/N‐tetradecane mixtures (model diesel) via pervaporation using an aromatic polyimide membrane

The present investigation focuses on the separation of phenanthrene (a polyaromatic hydrocarbon) from n‐tetradecane (model diesel composition) via pervaporation using a fabricated aromatic polyimide membrane. The experiments demonstrate preferential permeation of the polyaromatic for all films within the studied experimental range. The influence of operating temperature, membrane pretreatment time, membrane composition, and membrane thickness on the pervaporative performance were investigated. Statistical software Design Expert 7.1.4 was used to derive the regression equation describing the effect of the above mentioned factors on the pervaporation separation index. These factors are optimized using response surface methodology. The highest value of pervaporation separation index obtained is 1.5277 kg m−2 h−1 and the corresponding optimized condition is: operating temperature 493 K, pretreatment time 16.55 h with a membrane composition of 2.76 wt% of phenanthrene in polyamic acid and thickness 53.22 µm. POLYM. ENG. SCI., 57:392–402, 2017. © 2016 Society of Plastics Engineers