Initial Dibenzothiophene Concentration Research Articles

Enhanced oxidative desulfurization of dibenzothiophene under visible light using carbon quantum dot-decorated novel Z-scheme BiVO4/MOF-808/CN photocatalyst: Mechanism, performance and stability

BackgroundPhotocatalytic oxidative desulfurization technology enabling the facile oxidation of these compounds to sulfones, deep desulfurization, operation at ambient temperature and pressure, and minimal energy consumption. MethodsThis study introduces a novel photocatalyst, BiVO4/MOF-808/CN integrated with carbon quantum dots (BMC-CQD), designed for the oxidative desulfurization of dibenzothiophene (DBT) under visible light irradiation. Significant findingsNovel approach was undertaken by integrating the photocatalyst BiVO4, g-C3N4 with MOF-808 and carbon quantum dots to enhance the interaction between semiconductors. This innovative photocatalyst addresses several limitations associated with MOF-808, including enhanced visible light absorption (2.21–2.60 eV), reduced electron-hole recombination, rapid charge transfer, high surface area (1370 m2/g), large pore volume (0.908 cm3/g). Under optimized conditions of a catalyst dosage of 1.5 g/L, a reaction temperature of 50 °C, an O/S molar ratio of 6, and an initial DBT concentration of 500 mg/L, the 10 %BMC-CQD photocatalyst achieved an impressive 99.5 % DBT removal efficiency in just 25 min. Incorporating CQD into the BMC framework significantly amplifies the removal rate of the DBT by 10.69, 2.13 and 8.7 times compared to the BiVO4, MOF-808 and CN, respectively. The radical trapping experiments have shown that the •OH and •O2− radicals play a key role in the DBT removal process.

In-silico design of Metal oxide-Biochar composites for enhanced dibenzothiophene adsorption: DFT and statistical physics approach

This study proposes an efficient in-silico adsorbent material selection strategy for clean fuel combustion by leveraging Density Functional Theory (DFT) calculated reactivity parameters to optimize material configurations for enhanced dibenzothiophene (DBT) adsorption from model fuel oil (n-octane). A DFT screening identified TiO2 as the optimal material for DBT adsorption from biochar and four metal oxide (MOx) based on calculated adsorption energies (Eads). Further DFT optimization identified a 10 % TiO2 composition with biochar (TBC10) as the optimal material. This composite exhibited the strongest DBT interaction (−370.3 kcal mol−1) and a remarkably short sulfur-titanium bond (2.64 Å), indicative of an ideal adsorption geometry. Notably, TBC10 features a unique composite structure: TiO2 connected to BC via van der Waals forces, while DBT directly interacts with AC through π-π stacking and covalent sulfur-titanium bonds. To validate theoretical predictions, the designed composites were synthesized and experimentally evaluated. The excellent alignment between experimental adsorption performance and DFT-calculated adsorption energies corroborated TBC10′s superior DBT adsorption capacity. Employing a systematic optimization process, the most effective parameters for TBC10′s DBT removal from a 150 mL solution containing an initial DBT concentration of 45 mg L-1 were established as: a 30 min contact time, an adsorbent dosage of 13 mg, and a temperature of 25 °C. Under these conditions, TBC10 achieved a remarkable removal efficiency (RRDBT) of 99.82 % and a maximum DBT uptake capacity (qDBT) of 31.1 mg g−1. Kinetic and statistical physics modeling revealed a multi-molecular adsorption process with distinct binding sites, characterized by spontaneous endothermic interactions and involving both physical and chemical mechanisms. The in-silico methodology for adsorbent design reduces experimentation time, cost and identifies optimal candidates for DBT removal, enhancing fuel desulfurization and promoting sustainable combustion. This novel in-silico design paradigm holds immense potential for the development of next-generation adsorbents for various environmental remediation and industrial separation processes.

Photocatalysis oxidative desulfurization of dibenzothiophene in extremely deep liquid fuels on the Z-scheme catalyst ZnO-CuInS2-ZnS intelligently integrated with carbon quantum dots: performance, mechanism, and stability.

In this study, we improved the electrochemical and photocatalytic properties of the ZnO-CuInS2-ZnS (ZCZ) material by integrating with carbon quantum dots (CQD) with particle sizes from 2 to 5 nm. The integration of ZnO-CuInS2-ZnS with carbon quantum dots (ZnO-CuInS2-ZnS/CQD:ZCZ-CQD) enhanced the visible light absorption, significantly reduced the electron-hole recombination rate, and facilitated the electron transfer and separation processes as confirmed by UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), and electrochemical impedance spectroscopy (EIS). The successful integration of ZCZ with carbon quantum dots was confirmed using X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) methods. The ZCZ/CQD photocatalyst removed up to 98.32% of DBT after 120 minutes of reaction, maintained over 90% durability after 10 cycles, and retained its structure without any changes. The ZCZ photocatalyst integrated with CQD enhances faster dibenzothiophene (DBT) removal by 4.46, 3.24, 2.53, and 1.72 times compared to ZnO, CuInS2, ZnS, and ZnO-CuInS2-ZnS, respectively. Factors influencing the oxidation process of DBT including the mass of the photocatalyst, initial DBT concentration, stability, and reaction kinetics were studied. Through active species trapping experiments, this study demonstrated that the formation of ˙O2 - and ˙OH radicals determines the reaction rate. The mechanism of photocatalysis on ZCZ-CQD materials and the intermediate products formed in the process of photocatalytic oxidative desulfurization of dibenzothiophene is proposed based on electrochemical measurements and GC-MS results.

Robust interaction of ZnO and TiO2 nanoparticles with layered graphitic carbon nitride for enhanced photocatalytic oxidative desulfurization of fuel oil: mechanism, performance and stability.

Sulfur compounds in fuel such as thiophene, benzothiophene and dibenzothiophene are the primary source of SO x emissions, leading to environmental pollution and acid rain. In this study, we synthesized a layered oxygen-doped graphitic carbon nitride (OCN) structure and integrated ZnO and TiO2 nanoparticles onto the OCN surface through a microwave-assisted sol-gel method. The X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) results confirmed a robust interaction between the ZnO and TiO2 nanoparticles and the oxygen-doped g-C3N4 (OCN) surface, as indicated by the formation of C-N-Ti and C-O-Ti bonds. This interaction notably improved the optoelectronic properties of the ZnO-TiO2/OCN composite, yielding increased visible light absorption, reduced charge recombination rate, and enhanced separation and transfer of photogenerated electron-hole pairs. The oxygen doping into the CN network could alter the band structure and expand the absorption range of visible light. The ZnO-TiO2/OCN photocatalyst demonstrated remarkable desulfurization capabilities, converting 99.19% of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBT-O2) at 25 °C, and eliminating 92.13% of DBT from real-world fuel oil samples. We conducted in-depth analysis of the factors impacting the redox process of DBT, including the ZnO ratio, initial DBT concentration, catalyst dosage, stability, and O/S molar ratio. Radical trapping experiments established that ˙O2 -, ˙OH and h+ radicals significantly influence the reaction rate. The obtained results indicated that the ZnO-TiO2/OCN photocatalyst represents a promising tool for future fuel oil desulfurization applications.

Fabrication of Unique Mixed-Valent CoICoII and CuICuII Metal-Organic Frameworks (MOFs) for Desulfurization of Fuels: A Combined Experimental and Theoretical Approach toward Green Fuel.

Herein, metal-organic framework (MOF)-based adsorbents are designed with distinct hard and soft metal building units, namely, [Co2ICoII(PD)2(BP)] (Co_PD-BP) and [Cu2ICuII(PD)2(BP)] (Cu_PD-BP), where H2PD = pyrazine-1,4-diide-2,3-dicarboxylic acid and BP = 4,4'-bipyridine. The designed MOFs were characterized via spectral and SCXRD techniques, which confirm the mixed-valent states (+1 and +2) of the metal ions. Topological analysis revealed the rare ths and gwg topologies for Co MOF, while Cu-MOF exhibits a unique 8T21 topology in the 8-c net (point symbol for net: {424·64}). Moreover, severe environmental issues can be resolved by effectively removing heterocyclic organosulfur compounds from fuels via adsorptive desulfurization. Further, the developed MOFs were investigated for sulfur removal via adsorptive desulfurization from a model fuel consisting of dibenzothiophene (DBT), benzothiophene (BT), and thiophene (T) in the liquid phase using n-octane as a solvent. The findings revealed that Cu_PD-BP effectively removes the DBT with a removal efficiency of 86% at 300 ppm and an operating temperature of 25 °C, with a recyclability of up to four cycles. The adsorption kinetic analysis showed that the pseudo-first-order model could fit better with the experimental data indicating the physisorption process. Further, the studies revealed that adsorption capacity increased with the increasing initial DBT concentration with a remarkable capacity of 70.5 mg/g, and the adsorption process was well described by the Langmuir isotherm. The plausible reason behind the enhanced removal efficiency shown by Cu_PD-BP as compared to Co_PD-BP could be the soft-soft interactions between soft sulfur and soft Cu metal centers. Interestingly, density functional theory (DFT) studies were done in order to predict the mechanism of binding of thiophenic compounds with Cu_PD-BP, which further ascertained that along with other interactions, the S···π and S···Cu interactions predominate, resulting in a high uptake of DBT as compared to others. In essence, Cu_PD-BP turns out to be a promising adsorbent in the field of fuel desulfurization for the benefit of mankind.

Chitosan-based molecularly imprinted sponge for selective recognition and recycling of dibenzothiophene from diesel

Recycling of high value-added dibenzothiophene (DBT) from diesel using adsorption technology is a convenient and economical strategy to realize “Resources Reuse”, but the conventional adsorbents have the disadvantages of low adsorption selectivity and difficult retrieval. Herein, in this study, we elaborately designed and constructed a chitosan-based molecularly imprinted sponge (CS-MIS) with three-dimensional network structure via a bulk polymerization-lyophilization protocol. Batch adsorption experiments were conducted three replications to appraise the potential of CS-MIS for DBT adsorption. The influence of adsorbent dosage, initial DBT concentration, adsorption time and temperature on the adsorption performance were systematically investigated. The adsorption experimental results showed that CS-MIS exhibited a superior maximum adsorption equilibrium capacity of 15.17 mg/g for DBT compared to the chitosan-based non-imprinted sponge (CS-NIS; 6.34 mg/g). The DBT adsorption on CS-MIS coincided well with the pseudo-second-order kinetic and Langmuir isotherm models. The selective tests in the presence of multiple interfering molecules indicated the remarkable selective recognition of CS-MIS toward DBT with the relative selectivity coefficients for benzothiophene, indole, and fluorene of 1.99, 2.28, and 1.41, respectively. The notable selectivity of CS-MIS for DBT adsorption were mainly attributed to the imprinted sites matched well with DBT geometry on the surface of CS-MIS. Additionally, CS-MIS exhibited the excellent regeneration performance.

Insights into the Kinetics of the Microbial Degradation of Dibenzothiophene (DBT) by Acidithiobacillus ferrooxidans

Dibenzothiophene (DBT) is a major form of organo-sulfur compound chiefly found in coal. Acidithiobacillus ferrooxidans cells played the role of catalyst in degrading DBT to 2-hydroxy biphenyl (2HBP) through the formation of dibenzothiophene-sulfone and releasing the sulfur present in it. Experiments on the biodegradation of DBT by A. ferrooxidans bacterium using 9K medium with DBT at 3 g/L in a 500 mL shake flask scale achieved degradation of DBT up to 95% in 12 days. The A. ferrooxidans cells degrade DBT to 2-hydroxy biphenyl and release the sulfur atom in DBT through the formation of the intermediate dibenzothiophene-sulfone. The formation of 2HBP from microbial degradation of DBT followed the chemical control model of shrinking core reactions model in solid-liquid interactions. The kinetics of the DBT degradation by A. ferrooxidans followed first-order for a low initial concentration of DBT (3 g/L), and the kinetics were shifted to second-order with an increase in DBT concentration to 5 g/L.

Bio-catalytic degradation of dibenzothiophene (DBT) in petroleum distillate (diesel) by Pseudomonas spp.

Biodesulfurization (BDS) was employed in this study to degrade dibenzothiophene (DBT) which accounts for 70% of the sulfur compounds in diesel using a synthetic and typical South African diesel in the aqueous and biphasic medium. Two Pseudomonas sp. bacteria namely Pseudomonas aeruginosa and Pseudomonas putida were used as biocatalysts. The desulfurization pathways of DBT by the two bacteria were determined by gas chromatography (GC)/mass spectrometry (MS) and High-Performance Liquid Chromatography (HPLC). Both organisms were found to produce 2-hydroxy biphenyl, the desulfurized product of DBT. Results showed BDS performance of 67.53% and 50.02%, by Pseudomonas aeruginosa and Pseudomonas putida, respectively for 500 ppm initial DBT concentration. In order to study the desulfurization of diesel oils obtained from an oil refinery, resting cells studies by Pseudomonas aeruginosa were carried out which showed a decrease of about 30% and 70.54% DBT removal for 5200 ppm in hydrodesulfurization (HDS) feed diesel and 120 ppm in HDS outlet diesel, respectively. Pseudomonas aeruginosa and Pseudomonas putida selectively degraded DBT to form 2-HBP. Application of these bacteria for the desulfurization of diesel showed promising potential for decreasing the sulfur content of South African diesel oil.

Preparation, characterization, and desulfurization performance of the activated carbon prepared from mixed agro-wastes: an isothermal and kinetic study

ABSTRACT The essential target of this work was to exploit some locally obtainable hard bio-wastes viz. date pits and pistachio shells, in preparing varioufigs activated carbons (ACs) via the optimised ZnCl2 and H3PO4 activation routes. After preparing ACs from an equal blend of the hard bio-waste, the best samples were identified for their BET surface area and pore volume, X-ray diffraction (×RD), Fourier Transform Infra-Red spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray (EDX). The ACZnCl2 exhibited a higher BET surface area (895.53 m2/g) than the ACH3PO4 (419.60 m2/g). The optimal ACs were implemented in the adsorptive elimination of dibenzothiophene (DBT) from model gasoline. The DBT trials were optimized by investigating the impact of the initial concentration of DBT (25–200 mg/L), ACs mass (0.05–0.40 g), temperature (0.0–60 °C), and working period (5.0–80 minutes). The highest elimination of DBT by ACZnCl2 reached 97.78% using 0.30 g of it at 40°C for 60 minutes employing 25 mL of 200 mg/L DBT, while ACH3PO4 revealed the superlative elimination of DBT (88.46%) utilising 0.35 g of it at 40°C for 70 minutes using 25 mL of 200 mg/L DBT. Besides the kinetics investigations, isothermal studies indicated that the Freundlich isotherm and the pseudo-2nd-order kinetic best described the DBT adsorption by the ACs more than the other models. In a batch process, the adsorption capacities of DBT by both ACZnCl2 and ACH3PO4 were 26.31 mg/g and 20.23 mg/g, respectively. The typical adsorption conditions for each adsorbent were employed to eliminate S- compounds from commercial gasoline and DBT in a fixed-bed system. In conclusion, the ACs above could be reutilised for 5 successive runs with an insignificant loss in their desulphurisation ability. They can thus be recommended for the desulfurization of fuels on an industrial scale.

Biodesulfurization of Dibenzothiophene and Its Alkylated Derivatives in a Two-Phase Bubble Column Bioreactor by Resting Cells of Rhodococcus erythropolis IGTS8

Biodesulfurization (BDS) is considered a complementary technology to the traditional hydrodesulfurization treatment for the removal of recalcitrant sulfur compounds from petroleum products. BDS was investigated in a bubble column bioreactor using two-phase media. The effects of various process parameters, such as biocatalyst age and concentration, organic fraction percentage (OFP), and type of sulfur compound—namely, dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and 4,6-diethyldibenzothiophene (4,6-DEDBT)—were evaluated, using resting cells of Rhodococcus erythropolis IGTS8. Cells derived from the beginning of the exponential growth phase of the bacterium exhibited the highest biodesulfurization efficiency and rate. The biocatalyst performed better in an OFP of 50% v/v. The extent of DBT desulfurization was dependent on cell concentration, with the desulfurization rate reaching its maximum at intermediate cell concentrations. A new semi-empirical model for the biphasic BDS was developed, based on the overall Michaelis-Menten kinetics and taking into consideration the deactivation of the biocatalyst over time, as well as the underlying mass transfer phenomena. The model fitted experimental data on DBT consumption and 2-hydroxibyphenyl (2-HBP) accumulation in the organic phase for various initial DBT concentrations and different organosulfur compounds. For constant OFP and biocatalyst concentration, the most important parameter that affects BDS efficiency seems to be biocatalyst deactivation, while the phenomenon is controlled by the affinities of biodesulfurizing enzymes for the different organosulfur compounds. Thus, desulfurization efficiency decreased with increasing initial DBT concentration, and in inverse proportion to increases in the carbon number of alkyl substituent groups.

Magnetic iron nanoparticles (Fe3O4) supported on activated carbon as a hybrid adsorbent for desulphurisation of liquid fuels

ABSTRACT In this work, efficient hybrid adsorbents were developed through surface modification of commercial activated carbon with magnetic iron nanoparticles (Fe3O4). These modified adsorbents were characterised for their texture, morphology, and other surface properties and investigated for sulphur removal from model fuel consisting of thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) in liquid phase using hexane as a solvent. The effect of temperature and contact time was studied to understand the thermodynamics and kinetics of the adsorption process, and experimental adsorption data were interpreted using standard isotherms such as Langmuir, Freundlich, and Temkin model. The findings showed that the iron-loaded activated carbon could effectively remove the DBT (a representative sulphur compound) much better than the precursor nascent carbons in single and multicomponent models fuels under the optimised dosage of 30 g.L−1 and operating temperature of ~ 40°C. The kinetic analysis revealed that the pseudo-second-order model could represent the surface binding mechanism of DBT. The rate-limiting step, as indicated by the Weber-Morris plot, involved several steps. It was observed that the adsorption potential of the prepared materials increased with the increasing initial DBT concentration, exhibiting a maximum capacity of 29 mg.g−1, and the adsorption process was well described by the Freundlich isotherm (R2 = 0.95 to 0.99). Fe@AC-2 also demonstrated their ability to satisfactorily remove T, BT, and DBT from multi-component model fuel systems with higher selectivity for the more refractory DBT. Thermal regeneration of Fe@AC-2 saturated with DBT at 350°C could be recycled till the fourth cycle, and loss in adsorbent mass was observed in each cycle. Analysis of real diesel fuel pre- and post-adsorption with Fe@AC-2 showed a negligible change in the gross calorific value, density, and kinematic viscosity of the treated diesel from the untreated diesel.

N-CNT/ZIF-8 nano-adsorbent for adsorptive desulfurization of the liquid streams: Experimental and

With the aim of providing clean fuels through the desulfurization, the nanocomposite of Nitrogen-doped carbon nanotube/ZiF-8 (NCNT/ZIF-8) was prepared via the hydrothermal method. The nanocomposite sorbents were evaluated in the adsorption of dibenzothiophene (DBT) from the liquid phase. In this regard, the microstructure, morphology, particle size, thermal stability and physicochemical properties of nanoadsorbents were determined by using different characterization techniques. Influences of various parameters on the adsorption capacity of the nanoadsorbents were investigated; such as the adsorbent type, adsorption time, temperature and the initial DBT concentration. The as-prepared nanoadsorbents, ZiF-8 and NCNT/ZIF-8, possessed a high surface area of 1123.9 and 1207.4 m2/g, respectively. The NCNT/ZIF-8 exhibited the DBT adsorption capacity of 81.2 mg/g which is much higher than that of the pure ZIF-8 (69.1 mg/g). This excellent performance can be ascribed to the synergistic effects of both NCNT and ZiF-8, the presence of basic groups in the NCNT structure, and the high surface area and pore volume. Moreover, the DBT equilibrium adsorption was investigated by using Langmuir, Freundlich models. The Langmuir isotherm indicated a good agreement with experimental results. In addition, adsorption kinetics were studied and it was revealed that the pseudo-second-order model exhibited a favorable fitting with the experimental data. Finally, the regenerated NCNT/ZIF-8 provided a good performance even after 3 adsorption-desorption cycles and its adsorption capacity was almost unchanged.

Polyethylene terephthalate waste‐derived activated carbon for adsorptive desulfurization of dibenzothiophene from model gasoline: Kinetics and isotherms evaluation

AbstractThe present study concentrates on the preparation of activated carbon (AC) from a low‐cost precursor, namely, polyethylene terephthalate waste, as a potential alternative adsorbent to commercially activated carbon for desulfurization of model gasoline at ambient temperature. Polyethylene terephthalate was carbonized at 450°C, and the produced char was steam activated at 750°C for 90 min to prepare the AC. The morphology, crystallinity, and surface functional groups of as‐synthesized adsorbent were examined by scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy, respectively. The so‐synthesized AC was employed in the adsorptive desulfurization of dibenzothiophene (DBT) from model gasoline. The effect of the initial concentration of DBT, AC dose, temperature, and contact time on the removal efficiency of DBT was investigated. The maximum desulfurization level (97.10%) was performed at 40°C using 0.30 g of the AC for 60 min. The Langmuir model best demonstrated the adsorption results with an adsorption capacity of 49.56 mg/g. The pseudo‐second‐order model best described the adsorption kinetics of DBT by the so‐synthesized AC. The obtained consequences exhibited that AC with high desulfurization capability could be synthesized from polyethylene terephthalate waste.

The performance of an efficient polymer and Cloisite 30B derivatives in the adsorption desulfurization process

Adsorption desulfurization process is one of the most convenient and cost-effective methods to remove sulfur-containing organic pollutants from fuel liquids. In this paper, the adsorptive desulfurization of n-hexane containing 100 to 1000 ppm dibenzothiophene (DBT) as model gasoline has been evaluated using various industrially available adsorbents including Cloisite 30B, acid-treated Cloisite 30B, Cu-MOF, and Cloisite 30B-Cu-MOF. Poly(diallyldimethylammonium) chloride (PDADMAC) was used as an adsorbent in this field for the first time, and its performance was compared with the other adsorbents. Characterization of the adsorbent structure was carried out using techniques such as Fourier transform infrared, X-ray diffraction (XRD), adsorption–desorption analysis, field-emission scanning electron microscopy, and UV–visible spectrophotometer. Parameters such as adsorption capacity and the adsorbent dosage, and effect of contact time and initial concentration of DBT on the adsorption efficiency and adsorption capacity were examined, and results indicated that Cloisite 30B-Cu-MOF and PDADMAC exhibited the highest sulfur elimination.

Amine modified nano-sized hierarchical hollow system for highly effective and stable oxidative-adsorptive desulfurization

Oxidative-adsorptive desulfurization (OADS) has become a frontier scientific topic. The main factors affecting the oxidation and adsorption performance are the polarity and size of porous catalysts. Herein, highly active and stable phosphotungstic acid immobilized on amino grafted nano-sized hierarchical hollow silica spheres (HPW-NH2-HHSS) was successfully prepared and completely characterized. The hierarchical hollow structure of HHSS support can be maintained after being functionalized with amine groups, and the active species of phosphotungstic acid H3PW12O40 (HPW) were well dispersed on the amine-modified HHSS and retained its Keggin structure of the heteropolyanions. The prepared catalyst was applied to simultaneous oxidation and adsorption of dibenzothiophene (DBT) from model fuel. The effects of contact time, the loading content of HPW, the dosage of catalyst, the [O]/[S] mole ratio, initial DBT concentration, and temperature on the removal efficiency of the OADS system were investigated. 20% HPW-NH2-HHSS demonstrated a high catalytic performance and its desulfurization efficiency could be reached to 99.36% in 30 min at a lower O/S rate (2.5). Meanwhile, the equilibrium adsorption capacity of dibenzothiophene sulfone (DBTO2) of this catalyst is about 374 mg g−1. Beside this there was no significant decline in catalyst performance after seven catalytic cycles, assigned to the chemical force between the positive charges of NH2 and the negative charges of HPW. It is the first time that this work involving the nano-sized hierarchical hollow system has been used for high-efficiency desulfurization and the theory has been advanced that the polar groups of catalysts replace polar solvents to adsorb S-oxidation products.

Boosting oxidative desulfurization of model fuel by POM-grafting ZIF-8 as a novel and efficient catalyst

In this article, a water-soluble Keplerate-type polyoxometalate (POM), known as {Mo132} nanoballs, was supported over the zeolitic imidazolate framework-8 (ZIF-8) to achieve a highly efficient heterogeneous nano-structure catalyst (ZIF-8@{Mo132}) evaluated in oxidative desulfurization (ODS) of dibenzothiophene (DBT) presenting in model fuel. The ZIF-8@{Mo132} nano-structured catalyst was characterized using various methodologies including FT-IR, XRD, SEM, TGA, UV–Vis spectra of solid state and N2 adsorption–desorption confirming the incorporation of the {Mo132} nanoballs over the ZIF-8. The catalytic ODS performances of the as-synthesized catalyst revealed that high DBT removal efficiency around 87% and 92% after 6 and 12 h of reaction, respectively, in the presence of tert-butyl hydroperoxide (TBHP) as an oxidant, while they were only around 40% and 55% for pristine ZIF-8 at the same condition. The reaction mechanism suggested that the presence of Mo atoms enhances the formation of metal-peroxide formed by nucleophilic attack of TBHP and consequently enhancing DBT removal from a model fuel. Thin-layer chromatography (TLC) and gas chromatography (GC) were implemented for DBT concentration determination. In addition, the operating variables, including catalyst dosage, temperature, initial concentration of DBT, and oxidant to sulfur (O/S) ratio affecting the ODS efficiency were investigated to find the optimum condition. Finally, the remarkable heterogeneous catalyst indicated recyclability for various catalytic cycles.

Oxidative desulfurization of dibenzothiophene with molecular oxygen using cobalt and copper salen complexes encapsulated in NaY zeolite

Abstract The objective of the research is to develop a new method for removal of organic sulfur in liquid fuels. Cobalt and copper salen (salen=N, N’-bis(salicylidene)ethylenediamine) complexes were simultaneously encapsulated in zeolite NaY by using the flexible ligand method, and employed as catalysts in the oxidation of dibenzothiophene (DBT) with molecular oxygen as the oxidant. The material was substantiated by UV–Vis spectroscopy, thermo-gravimetric and differential-thermal analyses, X-ray powder diffraction as well as scanning electron microscope. Effect of various parameters including reaction temperature, initial concentration of DBT, molar ratio of Cu to Co and recycle of the material were investigated. The prepared bimetal material showed much higher activity than single metal salen complexes CusalenY and CosalenY due to the synergetic effect of Cu2+ and Co2+. The desulfurization process was mainly governed by the activation of molecular oxygen using (Cu-Co)salenY. The results prove the feasibility of the proposed desulfurization process for industrial application.

Oxidative removal of dibenzothiophene and related sulfur compounds from fuel oils under pressurized oxygen at room temperature with hydrogen peroxide and a phosphorus-free catalyst: sodium decatungstate

We investigated the removal of dibenzothiophene (DBT) and related compounds, 4-methyldibenzothiophene (4-MeDBT), 4,6-dimethyldibenzothiophene (4,6-DMeDBT), 2,8-dimethyldibenzothiophene (2,8-DMeDBT), and 1-benzothiophene (1-BT) from several oil media at room temperature under pressurized O2 (0.6 MPa) by means of a three-phase reaction system consisting of the oil phase, an aqueous phase containing the phosphorus-free polyoxotungstate catalyst Na4W10O32·8H2O, H2O2, and tetraoctylammonium bromide, and the gas phase. Under conditions in which the initial DBT concentration in octane was 10.1 mM, the desulfurization ratio reached 87% after reaction for 6.5 h. The sulfur atoms in the initial DBT were well accounted for by the sulfur atoms in the residual DBT, the dibenzothiophene sulfone and dibenzothiophene 5-oxide in the octane phase, and the dibenzothiophene sulfone that precipitated. Prolonged reaction time to 18 h resulted in 92% desulfurization. The desulfurization of octane decreased in the order 2,8-DMeDBT ~ DBT > 4-MeDBT >1-BT ~ 4,6-DMeDBT. Light oil and kerosene could also be desulfurized efficiently: after reaction for 6.5 h, the desulfurization ratios reached 77 and 78% for light oil and kerosene, respectively.

Synthesis of iron oxide nanoparticles modified mesoporous carbon and investigation of its application for removing dibenzothiophene from fuel model

In this study, magnetic ordered mesoporous carbon (γ-Fe2O3/CMK-3) containing iron oxide nanoparticles embedded in the carbon walls by wet impregnation method was prepared and used as a high effective magnetic adsorbent to adsorb polyaromatic sulfur compound (dibenzothiophene). The structure and morphology of adsorbent were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption (BET), thermal gravimetric (TGA) and alternating gradient force magnetometer techniques (AGFM). These techniques illustrate that the maghemite nanoparticles have an average size of 10 ± 3 nm and are well distributed on the ordered mesoporous carbon host. After embedding maghemite nanoparticles, the uniformity of mesoporous framework of CMK-3 still remaining stable, which has an ordered two-dimensional hexagonal (p6mm) structure, high specific surface area, maxima pore size of 5.5 nm and large pore volume (up to 1.01 cm3 g−1). The γ-Fe2O3/CMK-3 nanocomposite shows superparamagnetic behavior with a saturation magnetization of 0.5 emu g−1, which makes it favorable compound for magnetic separation procedure. The resulting magnetic mesoporous nanocomposite was investigated for adsorption of dibenzothiophene (DBT) as a model sulfur compound in n-hexane as fuel model. Various factors influencing the adsorption of DBT, including adsorption temperature, contact time and initial DBT concentration were studied. The kinetic data was well described by pseudo-second-order kinetic model and the equilibrium adsorption data was fitted to the Langmuir thermodynamic model. In addition, the adsorbent could be regenerated by washing with toluene and over 85% adsorption capacity could be maintained after three regeneration cycles. The results confirmed that γ-Fe2O3/CMK-3 has the potential superiority in removal of DBT from fuel model with a maximum adsorption capacity of 67 mg DBT per gram of adsorbent and an easy magnetically separable process.

Ultrasound-assisted oxidative-adsorptive desulfurization using highly acidic graphene oxide as a catalyst-adsorbent

Modified graphene oxide by acetic acid moiety (GO/COOH) was synthesized and employed in the ultrasound-assisted oxidative-adsorptive desulfurization processes. The modified graphene oxide was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The fabricated material was applied to simultaneous oxidation and adsorption of dibenzothiophene (DBT) from model fuel. Adsorption studies were carried out to evaluate its potential for DBT removal. The effects of contact time, initial DBT concentration, and temperature on the removal efficiency of the catalyst-adsorbent were investigated. The equilibrium adsorption results was well-described by the Freundlich isotherm model (at room temperature) and oxidation-adsorption of DBT were achieved by GO/COOH with an outstanding adsorption capacity of 370mgg−1. The adsorption process followed a pseudo-first-order kinetic model and the adsorption kinetic data suggests that physical interactions are mainly involved on the entire adsorption process (Ea<40kJmol−1). The initial sulfur content of 1000ppm was reduced to <50ppm within 300min, achieving a sulfur removal of about 95%. As a whole, a model fuel with ultra-low sulfur content was obtained by the developed procedure and GO/COOH shows a high potential for effective desulfurization of diesel fuel asa catalyst-adsorbent.