Ternary choline chloride/benzene sulfonic acid/ethylene glycol deep eutectic solvents for oxidative desulfurization at room temperature

Deep eutectic solvents (DESs) have been extensively studied as promising green solvents to attain a better removal efficiency of sulfide. A new DES system formed from choline chloride (ChCl), benzene sulfonic acid (BSA), and ethylene glycol (EG) as a class of ternary DESs was prepared and used in the oxidative desulfurization (ODS) of different sulfides. Ternary DESs have distinct advantages such as volatility and high activity compared with organic acid-based binary DESs. Under the optimum conditions with VDES/VOil = 1 : 5, O/S (molar ratio of oxygen to sulfur) = 5, and T = 25 °C, the desulfurization efficiencies of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT) were all achieved to 100% in 2 h. Through experimental and density functional theory (DFT) calculation methods, this new system as a class of ternary DESs shows good stability and excellent desulfurization performance at room temperature. The investigation of this study could supply a new idea of ternary DESs for oxidative desulfurization.

Combined Heterogeneous Catalyst Based on Titanium Oxide for Highly Efficient Oxidative Desulfurization of Model Fuels

In this work, new heterogeneous Mo-containing catalysts based on sulfonic titanium dioxide were developed for the oxidation of sulfur-containing model feed. The synergistic effect of molybdenum and sulfonic group modifiers allows for enhancing catalytic activity in dibenzothiophene oxidative transformation, and a strong interaction between support and active component for thus obtained catalysts provides increased stability for leaching. For the selected optimal conditions, the Mo/TiO₂-SO₃H catalyst exhibited 100% DBT conversion for 10 min (1 wt % catalyst, molar ratio of H₂O₂:DBT, 2:1; 80 °C). Complete oxidation of DBT in the presence of the synthesized catalyst is achieved when using a stoichiometric amount of oxidizing agent, which indicates its high selectivity. The enhanced stability for metal leaching was proved in recycling tests, where the catalyst was operated for seven oxidation cycles without regeneration with retainable activity in DBT-containing model feed oxidation with hydrogen peroxide under mild reaction conditions. In 30 min of the reaction (H₂O₂:S = 2:1 (mol), 0.5% catalyst, 5 mL of acetonitrile, 80 °C), it was possible to reduce the content of sulfur compounds in the diesel fraction by 88% (from 5600 to 600 ppm).

Highly Efficient Catalytic Oxidative Desulfurization of Dibenzothiophene using Layered Double Hydroxide Modified Polyoxometalate Catalyst

Layered double hydroxide-modified polyoxometalate (ZnAl-PW) was prepared and used for the oxidative desulfurization of dibenzothiophene. XRD patterns of ZnAl-LDH and PW are still present in ZnAl-PW. The bands of ZnAl-PW in wavenumber 3276, 1637, 1363, 1050, 952, 887, and 667 cm-1. The typical surface of ZnAl-LDH and ZnAl-PW can be observed not smooth in different sized with irregular shapes. The average diameter distribution of ZnAl-LDH and ZnAl-PW is 14 nm and 47 nm, respectively. For dibenzothiophene with 500 ppm, conversion on ZnAl-LDH, PW, and ZnAl-PW was 94.71%, 95.88%, and 99.16%, respectively. Conversion of dibenzothiophene in line with the acidity of ZnAl-LDH, PW, and ZnAl-PW were 0.399, 1.635, and 3.023 mmol/gram, respectively. The most effective catalyst dosage for the desulfurization of dibenzothiophene on ZnAl-LDH, PW, and ZnAl-PW is 0.25 g. The unchanged dibenzothiophene concentration indicates a heterogeneous system. ZnAl-LDH, PW, and ZnAl-PW are truly heterogeneous catalysts. After 3 cycles of oxidative desulfurization, the percentage conversion of dibenzothiophene on ZnAl-LDH, PW, and ZnAl-PW were 77.42 %, 65.98%, and 86.38%, respectively. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Catalytic Oxidative Desulfurization of Dibenzothiophene Utilizing Composite Based Zn/Al Layered Double Hydroxide

In this study, the Zn/Al-TiO2 and Zn/Al-ZnO was successfully synthesized. The catalysts were characterized by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscope—Energy Dispersive X-ray Spectroscopy (SEM-EDS). The typical diffraction peaks of Zn/Al-LDH, TiO2, and ZnO still appear in the Zn/Al-TiO2 and Zn/Al-ZnO composites, indicating that the composite preparation did not change the form of precursors. FTIR spectra of Zn/Al-TiO2 and Zn/Al-ZnO showed absorption band at 3448, 1627, 1381, 832, 779, and 686 cm-1. The catalysts have an irregular structure where the percent mass of Ti and Zn on the composite at 10.6% and 55.6%, respectively. The acidity of Zn/Al-LDH composite increased after being composed with TiO2 and ZnO. The percentage conversion dibenzothiophene on Zn/Al-ZnO, Zn/Al-TiO2, ZnO, Zn/Al-LDH, and TiO2 was 99.38%, 96.01%, 95.36%, 94.71%, and 91.92%, respectively. The heterogeneous systems of catalytic reaction was used for reusability. After 3 cycles catalytic reactions at 50 oC for 30 min, the percentage conversion of dibenzothiophene on Zn/Al-LDH, TiO2, ZnO, Zn/Al-TiO2, and Zn/Al-ZnO were 77.42%, 83.19%, 82.34%, 84.91%, and 89.71 %, respectively. The composites of Zn/Al-TiO2 and Zn/Al-ZnO have better reusability test than Zn/Al-LDH, TiO2, and ZnO, which proofing that Zn/Al-TiO2 and Zn/Al-ZnO have a stable structure. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Ultrafast oxidative desulfurization of diesel fuel catalyzed by a polyoxometalate-based catalyst immobilized on functionalized Y-SBA-15

Y-SBA-15 was synthesized by doping yttrium (Y) into SBA-15 using a solvent-free solid-state grinding method, and 1-butyl-3-methylimidazolium phosphomolybdic salt ([Bmim]₃PMo₁₂O₄₀, abbreviated as [Bmim]PMoO) was also synthesized. [Bmim]PMoO/Y-SBA-15 was prepared and used for oxidative desulfurization (ODS). The physicochemical characteristics of the catalyst have been characterized by FT-IR, XRD, N₂ adsorption-desorption, FESEM, TEM, XPS, contact angle testing, EPR, etc. A lipophilic surface is beneficial for making the catalyst well disperse in an oil phase, and a hydrophilic core can help to store aqueous oxidants. Therefore, the amphiphilic catalyst 25[Bmim]PMoO/10Y-SBA-15 exhibited high catalytic activity in dibenzothiophene (DBT) ODS, and sulfur compounds can be removed completely within 40 min under the following conditions: V_Oil = 10 mL, m_catalyst = 0.1 g, m_[Bmim]PMoO : m_{[Bmim]PMoO/10Y-SBA-15} = 25%, and O/S = 4 (molar ratio). In addition, the concentration of aromatics exerted little effect on the DBT ODS. Sulfur compounds in real diesel might be reduced to 8 μg g^-1. The hydroxyl radical ˙OH and superoxide radical ˙O₂^- play crucial roles in the ODS reaction, and the ODS reaction mechanism was also proposed.

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

The ceaseless increase of pollution cases due to the tremendous consumption of fossil fuels has steered the world towards an environmental crisis and necessitated urgency to curtail noxious sulfur oxide emissions. Since the world is moving toward green chemistry, a fuel desulfurization process driven by clean technology is of paramount significance in the field of environmental remediation. Among the novel desulfurization techniques, the oxidative desulfurization (ODS) process has been intensively studied and is highlighted as the rising star to effectuate sulfur-free fuels due to its mild reaction conditions and remarkable desulfurization performances in the past decade. This critical review emphasizes the latest advances in thermal catalytic ODS and photocatalytic ODS related to the design and synthesis routes of myriad materials. This encompasses the engineering of metal oxides, ionic liquids, deep eutectic solvents, polyoxometalates, metal-organic frameworks, metal-free materials and their hybrids in the customization of advantageous properties in terms of morphology, topography, composition and electronic states. The essential connection between catalyst characteristics and performances in ODS will be critically discussed along with corresponding reaction mechanisms to provide thorough insight for shaping future research directions. The impacts of oxidant type, solvent type, temperature and other pivotal factors on the effectiveness of ODS are outlined. Finally, a summary of confronted challenges and future outlooks in the journey to ODS application is presented.

A facile sol–gel method based on urea–SnCl2 deep eutectic solvents for the synthesis of SnO2/SiO2 with high oxidation desulfurization activity

The n%-SnO2/SiO2 (n = 2, 4, 6) supported catalyst was prepared by the sol–gel and calcination method. Compared with the traditional impregnation method, the catalyst prepared by sol–gel method has higher oxidative desulfurization activity.