Oxidative Desulfurization Research Articles

Recent Advances in the Synthesis and Application of TS‐1 Zeolite for Green Catalytic Oxidation

AbstractTS‐1 has a unique structure, and TS‐1/H2O2 oxidation system for composition shows excellent catalytic performance in the oxidation of a variety of organic matter. The response conditions of the reaction system are mild, and the ultimate oxidation product is water. It is a typical “green catalytic” system and has received widespread attention from researchers. Here, the synthesis progress of TS‐1 to improve the accessibility and activity of active sites by doping mesoporous and microporous structures into traditional TS‐1 zeolite in recent five years are reviewed, including hydrothermal synthesis, dry gel conversion synthesis, solvent‐free synthesis, microwave assisted synthesis, and isomorphous substitution. Meanwhile, the application of TS‐1/H2O2 system in oxidative desulfurization, ketone ammonia oxidation, olefin epoxidation, and hydroxylation of aromatic hydrocarbons reactions are summarized and discussed. What's more, the reaction mechanism based on TS‐1/H2O2 system is proposed on regarding the isolated skeleton Ti site in titanium‐silicon zeolite as the active central site. Finally, the challenges and future development prospects of TS‐1 zeolite in synthesis and catalytic applications are predicted.

Development of magnetical Wells-Dawson polyoxometalates with defects for the highly effective oxidative desulfurization of fuel oil

Developing high-performance and recyclable catalysts for the oxidation desulfurization of fuel oils remains largely a challenge. Herein, the Wells-Dawson phosphotungstic acid (P2W18) with oxygen vacancy (OV) defects was embedded into the carbon shell of magnetic microspheres (Fe3O4) encapsulated by the carbon matrix, developing the Fe3O4@C@P2W18 catalyst. The as-prepared Fe3O4@C@P2W18 catalyst was applied in the oxidation desulfurization (ODS) reaction of model fuels with H2O2 as oxidant. Under Fe3O4@C@P2W18 catalyst, fuel oil (2000 ppm S) could reach 100 % of sulfur removal in 15 min at 70 ℃ with a theoretical O/S molar ratio of 2, collaborating its extraordinary ODS performance. The eminent catalyst activity is mainly given the credit to the intrinsically high activity of Wells-Dawson P2W18 with OV defects, more accessible active sites induced by the highly even dispersion of P2W18, and the microenvironment effect of the carrier. Moreover, Fe3O4@C@P2W18 shows facile separation through external magnetic field as well as excellent reusability with a negligible reduction of sulfur removal after twelve cycles. Additionally, according to the free radical experiments and electron paramagnetic resonance (EPR) detection, a •OH radical mechanism is disclosed to be responsible for the current catalytic ODS reaction of fuel oils. Therefore, the catalyst developed by this study holds great promise for highly efficient and deep oxidation desulfurization of fuel oils.

Preparation of 30%PMoV2@MOF@mSiO2 (MOF = MIL-101, HKUST-1, UiO-67, ZIF-8) catalysts and their oxidative desulfurization performance

Preparation of 30%PMoV2@MOF@mSiO2 (MOF = MIL-101, HKUST-1, UiO-67, ZIF-8) catalysts and their oxidative desulfurization performance

The ordered mesoporous TS-1 synthesized with geometrically matched surfactant and its application in the deep oxidative desulfurization

The ordered mesoporous TS-1 synthesized with geometrically matched surfactant and its application in the deep oxidative desulfurization

Simulation and optimization of heavy fuel oil (HFO) refining platform to low sulfur marine fuel (LS-FO) by oxidative desulfurization

The International Maritime Organization (IMO) has implemented new sulfur content regulations for marine fuels in response to growing environmental concerns, including global warming. These regulations severely and costly restrict refinery operations. Oxidative desulfurization (ODS) is an attractive desulfurization method that has advantages such as mild operating conditions and a hydrogen-free process over traditional processes such as hydrodesulfurization (HDS). One can employ oxidative desulfurization in addition to or instead of hydrodesulfurization. Organic sulfur molecules undergo oxidative desulfurization, which results in the formation of polar sulfones. The refined fuel oil is then separated from the oxidized sulfones using methods such liquid-liquid extraction, distillation, and absorption. This work examines and simulates the process of separating sulfur-containing oxidized chemicals from fuel oil utilizing oxidative desulfurization technology. Acetic acid served as the catalyst and hydrogen peroxide as the chosen oxidant. This effort involved simulating the oxidative desulfurization of fuel oil and then using absorption methods to separate the oxidized sulfones. Subsequent procedures including absorption and distillation were used to separate and recover the resultant effluent, solvent, and oxidant from the remaining components. According to the simulation results, the procedure was run at 80 °C and a modest pressure of less than 5 bar. Sulfur content in the original hydrocarbon fuel was 3.5% by weight; at the output, it was less than 0.5% by weight. The findings of the sensitivity analysis of a few key factors demonstrated that the conversion percentage increased from 84 to 98% when the reactor’s diameter was changed from 0.5 to 1.2 m and its length was extended to the desired amount. The reaction conversion percentage has increased significantly when the mass flow rate of hydrogen peroxide is increased from 0.5 to 1.5 kg/h, the pressure is increased from 1.5 to 5 bar, and the temperature is raised to 30 °C. According to the process optimization data, the ideal state had an exergy efficiency of 55.57%, a solvent waste rate of 1.75%, and a sulfur content of 0.22% in the fuel.

Unraveling the roles of oxygen vacancies in tungsten‐based ionic liquid materials for enhanced catalytic oxidative desulfurization

AbstractDefect engineering is often used to improve the performance of catalysts. Here, plasma etching was first used as a strategy to introduce defects to modify the phosphotungstic acid‐based ionic liquids (C14PWIL) catalyst for oxidative desulfurization (ODS) in fuel. The valence band/conduction band value of the catalyst indicates that the formation of oxygen vacancies plays an essential role in enhancing the oxidation capacity. In combination with X‐ray photoelectron spectroscopy results, the enriched electrons in the oxygen vacancies can increase the electron density on the catalyst surface, which promotes the electron migration process between the catalyst and H2O2, thus favoring the activation of H2O2 and enabling an efficient ODS process. The desulfurization efficiency of C14PWIL‐P at room temperature is 3 times that of C14PWIL, which exhibits good cycling stability.

A non-catalytic oxidative desulfurization of thiophene and benzothiophene by peroxyacetic acid oxidant

A non-catalytic oxidative desulfurization of thiophene and benzothiophene by peroxyacetic acid oxidant

Simultaneous visualization of lipid droplets and tracking of the endogenous hypochlorous acid in psoriatic mice models with a novel fluorescent probe in a wash-free fashion

Psoriasis is an autoimmune inflammation-related disease accompanied by a variety of complications. Reactive oxygen species (ROS) are modulators of inflammation, and their excessive production caused by oxidative/anti-oxidative imbalance has been observed in psoriatic patients. Hypochlorous acid (HOCl) is a ROS produced by myeloperoxidase (MPO) from chloride ions (Cl-) and hydrogen peroxide (H2O2). Endogenous HOCl has recently been studied as a potential biomarker of psoriasis underlying the necessity for the development of efficient analytical tools for its detection and real time monitoring. Herein, we designed a novel highly sensitive and selective coumarin-based fluorescent probe for HOCl detection, named CN2-CF3-S. The probe itself featured negligible fluorescence because of the heavy atom effect of the thiocarbonyl group. However, upon responding to HOCl a conversion to sulfur-free derivative CN2-CF3-O occurs, resulting in a dramatical fluorescent enhancement setting the detection limit for HOCl of 3.2 nM. The HOCl-recognition mechanism could be ascribed to the HOCl-triggered oxidative desulfurization process that agrees with liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) computations. The probe’s design incorporated a synergistic combination of two structural features for efficient lipid droplets (LDs)-targeting imaging. An efficient push–pull system reinforced by the presence of two strongly electron-donating dimethylamino groups equipped CN2-CF3-O with pronounced solvatochromism realized through the enhanced blue-shifted emission in non-polar media. Meanwhile, the presence of trifluormethylphenyl moiety at the acceptor side led to an increased lipophilicity. The CN2-CF3-S probe has been successfully utilized to track the endogenous HOCl in cells and on skin of the psoriatic mice in a wash-free manner. As a result, we have demonstrated that the concentration of HOCl in skin might correlate positively with the degree of inflammation in psoriasis. Thus, CN2-CF3-S constitutes the first example of LDs-imaging fluorescent probe for detecting the psoriasis-linked HOCl, offering a convenient tool for further in-depth investigation of psoriasis pathophysiology.

Comb-grafted poly(vinyl phosphate)-based molybdovanadate heteropoly acid for efficient deep oxidative desulfurization using ionic liquid extractants under mild conditions

The development of simple and efficient desulfurization catalysts has garnered increasing attention in the field of desulfurization. In this study, comb-grafted polyethylene phosphomolybdenum-vanadium heteropoly acid catalysts (P-VPA-MomVn) were synthesized via the bulk polymerization method. The structure and morphology of the catalysts were investigated by FTIR, GPC, 1H NMR, XRD, XPS and SEM. By incorporating ionic liquid as an extractant, the P-VPA-Mo10V2 demonstrates high activity in oxidative desulfurization, removing all DBT from the model oil with a low O/S molar ratio under mild conditions. It is noteworthy that when the reaction temperature is 30 °C, the O/S molar ratio is 3, and the reaction time is 60 min, the catalyst exhibits excellent recycling lifetime of 10 cycles without a significant decline in activity. The incorporation of the ionic liquid further enhances its extraction efficiency, indicating that the catalyst not only possesses a stable structure but also holds strong prospects for industrial application.

Ultra-thin C/Si Shell Pieces as Amphiphilic Janus Materials for Efficient Oxidation Desulfurization.

Constructing favorable morphology is considered to be an effective strategy to enhance the amphiphilic performance of materials. The directional alignment of ultra-thin lamellar materials significantly facilitates utilization of active sites at the bi-phase interface. Herein, an ultra-thin amphiphilic C/Si shell pieces Janus material (d = 10.4nm) prepared by graphene oxide and SiO2 is reported. The outer SiO2 layer is associated with hydrophilicity, while the inner C layer exhibits hydrophobicity. A Pickering emulsion interface catalyst for fuel oil oxidative desulfurization is constructed by impregnating an amino-modified C/Si Janus material with keggin-type HPW. The results demonstrate that amphiphilic catalyst with an ultra-thin C/Si shell pieces exhibits superior performance in terms of emulsification rate (100%) and desulfurization rate (99.62%) in the O/W emulsion formed by n-octane/acetonitrile. The catalyst demonstrates the advantages of easy recovery and regeneration, maintains a higher activity after oxidative desulfurization (ODS) process, and has higher industrial application value.

Oxidative Desulfurization of Dibenzothiophene Using Catalyst of NiO Impregnated on Magnetic Silica Sand from Parangtritis Beach

Oxidative desulfurization of dibenzothiophene (ODS-DBT) using catalyst of NiO impregnated on magnetic silica sand from Parangtritis beach (Ps) had been evaluated. The NiO-Ps catalyst was prepared using wet impregnation method with Ps to Ni (NO3)2·6H2O weight ratio of 1:1. The catalyst was calcined at a temperature of 400 °C for 5 h under flow of 20 mL min-1 of N2 gas. The ODS-DBT process was carried out using NiO-Ps catalyst on solution of n-hexane with a sulfur content of 500 ppm under variations of temperature, time, and H2O2 volume. The results of XRD and FTIR indicated the main minerals of Ps were quartz, alumina, and magnetite. The Ps and NiO-Ps had crystallinities of 59.97 and 70.32% with crystal sizes of 16.32 and 10.95 nm. The SEM-EDX and TEM analysis showed the surface of Ps was flat and NiO-Ps was rough. The BET-nitrogen absorption-desorption indicated the Ps and NiO-Ps were mesoporous materials with average pore diameters of 11.98 and 24.01 nm, total pore volumes of 0.008 and 0.057 cm3 g-1, and specific surface areas of 2.611 and 9.502 m2 g-1. The Ps and NiO-Ps have acidity values of 1.14 and 1.74 mmol g-1. The optimum desulfurization using NiO-Ps catalyst in the ODS-DBT was 79.40% obtained at a temperature, time, and H2O2 volume of 60 °C, 30 min, and 0.42 mL.

Facile Construction of Supported Polyoxometalate Ionic Liquids for Deep Oxidative Desulfurization of Fuel

Facile Construction of Supported Polyoxometalate Ionic Liquids for Deep Oxidative Desulfurization of Fuel

Hydrophobic Modification of Halloysite Nanotubes Loaded with a Small Amount of Tungsten Oxide for Efficient Oxidative Desulfurization.

Transition metal oxides can be used as efficient multiphase catalysts in the field of catalysis. In this study, a hydrophobic halloysite nanotube (HNT) catalyst was designed and prepared with a low loading. Tungsten oxide was immobilized on the inner surface of the HNT, through electrostatic adsorption and calcination. Furthermore, a dual-functional W/HMT/M catalyst was prepared by hydrophobic modification of the outer surface of HNT through a harmless and nontoxic method. The catalyst was applied in the oxidative desulfurization (ODS) of dibenzothiophene (DBT), and characterized by inductively coupled plasma (ICP), contact angle tests, and other methods. Systematic characterization further confirmed that W/HNT/M has a low loading (0.48 wt %) and a relatively high contact angle of 92.6°. Oxidative desulfurization experiments demonstrated that the high contact angle corresponds to good hydrophobicity. The low loading and high activity of the catalyst enabled it to achieve a removal efficiency of 100% for DBT under conditions of 60 °C and an O/S = 4. The hydrophobic surface of HNT allowed better dispersion in the oil phase, while its hydrophilic inner cavity could adsorb H2O2 and the converted dibenzothiophene sulfoxide, thereby reducing the subsequent extraction steps after oxidative desulfurization and enhancing the reaction environment for reactants and active oxygen. W/HNT/M maintained high activity for at least 5 cycles. Additionally, the potential mechanism of the catalyst in the aqueous ODS reaction was proposed. This study demonstrates that HNT-supported metal oxides have desulfurization potential and provides ideas for improving ODS catalytic activity of the ODS through low loading, high activity, and unique hydrophobicity design.

Constructing frustrated Lewis pairs on Mo-doped Fe2O3 catalyst to enhance oxidative desulfurization efficiency

The emission of sulfur oxides will not only cause a series of environmental pollution but also threaten human health. At present, oxidative desulfurization is considered one of the technologies to achieve high-efficiency conversion of sulfur-containing compounds. Herein, the special frustrated Lewis pairs (FLPs) for efficient oxidative desulfurization are created by regulating surface doping in a redox iron-based oxide. According to experimental results, the Lewis acidic sites can be considered as the iron atoms adjacent to the molybdenum dopant, while the doped metal proximal to the oxygen vacancies serves as Lewis basic sites to create FLPs in redox iron-based oxide. This reactivity of FLPs is further adapted to the chemical activation of molecular oxygen and aromatic sulfur-containing compounds. The Fe2O3-FLP catalyst can achieve 100 % sulfur removal at 3 h and maintains 96.9 % after seven cycles, higher than other previously reported iron-based oxidative desulfurization catalysts. In addition, the design of FLPs offers a promising approach for developing high-efficiency catalysts in the oxidative desulfurization process.

Development of silver dichromate-geopolymer composite: An innovative catalyst for simultaneous desulfurization and denitrogenation for cleaner petroleum fuel

Rising global energy demands necessitate cleaner fuel technologies due to stringent environmental regulations. Emerging techniques like oxidative desulfurization and denitrogenation offer advantages over traditional hydrotreatment by selectively oxidizing sulfur and nitrogen compounds without damaging hydrocarbon structures. This research employs nano-crystalline silver dichromate-geopolymer composite catalysts prepared by direct precipitation, sonochemical, surfactant-assisted and surfactant assisted sonochemical routes for oxidizing sulfur and nitrogen compounds in fuel oil. Surfactant assisted preparation aided in generating catalysts with controlled size, while sonochemical synthesis facilitated uniform dispersion of the particles. The uniform dispersion, controlled particle size, and low agglomeration along with unclogged pores aided the sonochemically prepared catalyst in demonstrating superior catalytic performance over other counterparts in individual sulfur oxidation tests. In contrast, due to the high rate of oxidation and high affinity to occupy active sites, the catalyst prepared by surfactant assisted sonochemical route performed better than its sonochemical counterpart in individual nitrogen compound oxidation tests. The prepared catalysts were thoroughly characterized by different analytical characterization techniques. Single component oxidation resulted in 80.86 and 98.94% conversion of sulfur and nitrogen, while simultaneous oxidation resulted in 58.41% sulfur oxidation and 95.69% nitrogen conversion. Due to the cavitation effect, efficient mixing and a high local temperature and pressure created due to the introduction of ultrasound, the conversion rose to 88.02 and 98.02% for sulfur and nitrogen, respectively. Post oxidation, the oxidation products were removed by extraction, leading to 100% removal of nitrogen and 85% removal of sulfur. The proposed mechanism suggested the oxidation of both the compounds to occur through the formation of active Cr(VI)-peroxo species.

Uncovering structure-activity relationships in Brønsted acidic deep eutectic solvents for extractive and oxidative desulfurization

Modeling the structure-activity relationships (SARs) of deep eutectic solvents (DESs) is crucial for upgrading their catalytic performance in targeted reactions. Herein, a series of Brønsted acidic DESs are developed for the SARs research at molecular and atomic levels. Experimental and theoretical results suggest that the catalytic activity increases with the decreasing distances between O atom of active sites in DESs and S atom in sulfur compounds, and the R2 between EODS efficiency and the valid distances of O···S is above 0.9. Such geometric configuration can be optimized by altering the composition of DESs, which in turn substantially triggers the reaction acceleration between active intermediates and substrates. The resulting DES (TEAC/2BSA) achieved deep desulfurization for various sulfur compounds based on the optimal valid distances of O···S. This work contributes to a deep understanding of the reaction mechanism and enables the effective screening of task-specific DESs.

Oxidative desulfurization catalyzed by magnetically recoverable CoFe2O4 nano-particles

In this study, the magnetic CoFe2O4 was fabricated and utilized as catalysts to activate peroxymonosulfate (PMS) for removal of dibenzothiophene (DBT) in model oil with the extraction-coupled catalytic combined with oxidation desulfurization system (ECODS). The prepared magnetic CoFe2O4 was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Vibrating Sample Magnetometer VSM etc. The results showed that the prepared magnetic CoFe2O4 with a large specific surface area and exhibited excellent magnetism, phase composition, crystallinity and uniform distribution of the elements. The sulfur removal of DBT in n-octane was 95 % in 60 min at 40 °C under the conditions: 6 mL of model oil (600 ppm), O/S = 3:1 and 125 mg of CoFe2O4 powder. The possible mechanism of desulfurization was proposed by GC–MS. In conclusion, CoFe2O4 magnetic nanoparticles function well in both desulfurization and catalysis for PMS.

Metal-based Ionic Liquids and Solid-loaded Catalysts in Fuel Oil Desulfurization: A Review

Abstract: Metal-based ionic liquids (MILs) have the advantages of designability, efficiency, stability, and regenerative cycle and can efficiently convert thiophene and its derivatives, which are important for the production of "ultra-low sulfur" oils. This paper provides an overview of the research progress of MILs in the field of fuel desulfurization, focusing on the current status of MILs and solid-loaded MILs catalysts in extractive desulfurization, oxidative desulfurization, extraction-catalyzed oxidative desulfurization, and catalytic-adsorption desulfurization processes. For MILs, the anion and cation can be altered by design so as to impart specific functions. Loading is one of the effective ways to solidify MILs, and the combination of MILs with different carriers can not only reduce the usage while ensuring the catalytic activity but also improve the reusability of the catalyst. The combination of MILs with specially structured carriers also allows solution-free adsorption and removal of oxidation products. Compared with conventional MILs, polymetallic-based ionic liquids (PMILs) exhibit ultrahigh catalytic activity and are one of the most promising materials available, but are still in their infancy in the field of fuel catalysis, and researchers are needed to enrich the gap in this field. Finally, some problems faced by various types of MILs are pointed out in order to design new functional MILs catalysts with better properties in the future and promote the further development of MILs in the field of fuel catalysis.

Preparation of Ni/ZnCo2O4@ZnO composite metal oxide adsorbent and its adsorption desulfurization and regeneration performance

Metal Co was introduced into ZnO by co-precipitation to form composite metal oxides as the desulfurization agent with different Co contents, with which the desulfurization activity and regeneration performance were investigated. The systematic characterization of the structure and properties of the desulfurization agent using XRD, TEM, N2 adsorption and desorption, XPS and H2-TPR confirmed that the composite metal oxide desulfurization agent had the Ni/ZnCo2O4@ZnO structure. The formation of ZnCo2O4 in the composite metal oxides desulfurization agent facilitated the particle size reduction, dispersion enhancement and specific surface area increase of the desulfurization agent, which also acted as an adsorbent for H2S indicated by the XRD analysis, improving the sulfur adsorption capacity of the desulfurization agent. The desulfurization performance of all the composite metal oxide desulfurization agents was higher than that of Ni/ZnO, in which the desulfurization agent NZCo-3 with a molar ratio of Zn:Co of 1:1 exhibited the optimal desulfurization performance, and the desulfurization rate was 100% at a reaction temperature of 300 °C, a hydrogen pressure of 3 MPa, a mass-air velocity of 2.2 h–1, and a hydrogen-oil ratio of 300, and the excellent desulfurization performance was maintained after 6 cycles. The results of this study provide new ideas for the rational design of Ni/ZnO desulfurization agent to improve its desulfurization and regeneration performance.

Achieving Ultra-Low-Sulfur Model Diesel Through Defective Keggin-Type Heteropolyoxometalate Catalysts

Various Keggin-type heteropolyoxometalate catalysts with structural defects and surface acidity were synthesized by immobilizing 12-phosphotungstic acid (HPW) on mesoporous SBA−15, to produce near-zero-sulfur diesel fuel. As the calcination temperature increased, the W=O and the corner-shared W–O–W bonds in the Keggin unit partially broke, creating oxygen defects, as evidenced by the Rietveld refinement and in situ FTIR characterization. All the catalysts contained Lewis (L) and Brønsted (B) acid sites, with L acidity predominant. The relative intensity of the IR band (I980) of W=O bond inversely correlated with the number of L acid sites as the calcination temperature varied, suggesting that oxygen defects contributed to the Lewis acid sites formation. In the oxidation of dibenzothiophene (DBT) in a model diesel within a biphasic system, DBT conversion exceeded 99% under the optimal reaction conditions (reaction temperature 70 °C, reaction time 60 min, H2O2/sulfur molar ratio 8, H2O2/formic acid molar ratio 1.5, catalyst concentration 2 mg/mL). The influence of fuel composition and addition of indole and 4,6-DMDBT on DBT oxidation were also evaluated. Indole and cyclohexene negatively impacted the DBT oxidative removal. Oxygen defects served as active centers for competitive adsorption of sulfur compound and oxidant. Both L and B acid sites were involved in transferring O atom from peroxophosphotungstate complex to sulfur in DBT, resulting in DBTO2 sulfone, which was immediately extracted by polar acetonitrile. This study confirms that structural defects and surface acidity are crucial in the deep oxidative desulfurization (ODS) reaction, and in enabling the simultaneous oxidation and separation of refractory organosulfur compounds in a highly efficient model diesel.