Oxidative desulfurization of dibenzothiophene catalyzed by peroxotungstate on functionalized MCM-41 materials using hydrogen peroxide as oxidant

Heterogeneous catalytic oxidative desulfurization of dibenzothiophene of metal oxide-Mg/Al layered double hydroxide

Mg/Al-TiO2 and Mg/Al-ZnO were successfully prepared for dibenzothiophene catalytic oxidative desulfurization. XRD, FTIR, TEM, and BET analyses were utilized to characterize the catalyst. In composites, the distinctive XRD patterns of precursors are still observable. FTIR spectra of the absorption bands were at 3448, 1627, 1381, 601, and 547 cm-1. The TEM pictures of the sample also revealed the almost spherical and hexagonal platelets of Mg/Al-LDH and its composite. Mg/Al LDH, Mg/Al-TiO2, and Mg/Al-ZnO had typical pore sizes of 35.78 nm, 52.81 nm, and 38.37 nm, respectively. The graph of nitrogen isotherms Mg/Al LDH, Mg/Al-TiO2, and Mg/Al-ZnO followed type IV isotherms. In addition, the conversion rates on Mg/Al-ZnO, Mg/Al-TiO2, ZnO, Mg/Al-LDH, and TiO2 were 99.34%, 99.50%, 91.20%, 96.29%, and 88.06%, respectively. This work presents alternative materials for the oxidative desulfurization of dibenzothiophene in practical applications.

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). 

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal-Organic Framework

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW₄ active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H₂O₂ as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF₆, 2:1 model diesel/[BMIM]PF₆). High recycling and reusing capacity was also found for PW₄@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time.

Solvent-Free Desulfurization System to Produce Low-Sulfur Diesel Using Hybrid Monovacant Keggin-Type Catalyst

Two quaternary ammonium catalysts based on the monovacant polyoxotungstate ([PW₁₁O₃₉]⁷⁻, abbreviated as PW₁₁) were prepared and characterized. The desulfurization performances of the PW₁₁-based hybrids (of tetrabutylammonium and trimethyloctadecylammonium, abbreviated as TBA[PW₁₁] and ODA[PW₁₁], respectively), the corresponding potassium salt (K₇PW₁₁O₃₉, abbreviated as KPW₁₁) and the peroxo-compound (TBA-PO₄[WO(O₂)₂], abbreviated as TBA[PW₄]) were compared as catalysts for the oxidative desulfurization of a multicomponent model diesel (2000 ppm S). The oxidative desulfurization studies (ODS) were performed using solvent-free systems and aqueous H₂O₂ as oxidant. The nature of the cation in the PW₁₁ catalyst showed to have an important influence on the catalytic performance. In fact, the PW₁₁-hybrid catalysts showed higher catalytic efficiency than the peroxo-compound TBA[PW₄], known as Venturello compound. TBA[PW₁₁] revealed a remarkable desulfurization performance with 96.5% of sulfur compounds removed in the first 130 min. The reusability and stability of the catalyst were also investigated for ten consecutive ODS cycles without loss of activity. A treated clean diesel could be recovered without sulfur compounds by performing a final liquid/liquid extraction diesel/EtOH:H₂O mixture (1:1) after the catalytic oxidative step.

Deep oxidative desulfurization of model fuels catalyzed by polyoxometalates anchored on amine-functionalized ceria doped MCM-41 with molecular oxygen

The synergistic effect between the vanadium-substituted POM and ceria doped MCM-41 results in extraordinary catalytic activity for oxidative desulfurization.

An overview of conventional and alternative technologies for the production of ultra-low-sulfur fuels

Environmental concerns have given a great deal of attention for the production of ultra-low-sulfur fuels. The conventional hydrodesulfurization (HDS) process has high operating cost and also encounters difficulty in removing sulfur compound with steric hindrance. Consequently, various research efforts have been made to overcome the limitation of conventional HDS process and exploring the alternative technologies for deep desulfurization. The alternative processes being explored for the production of ultra-low-sulfur content fuel are adsorptive desulfurization (ADS), biodesulfurization (BDS), oxidative desulfurization (ODS), and extractive desulfurization (EDS). The present article provided the comprehensive information on the basic principle, reaction mechanism, workability, advantages, and disadvantages of conventional and alternative technologies. This review article aims to provide valuable insight into the recent advances made in conventional HDS process and alternative techniques. For deep desulfurization of liquid fuels, integration of conventional HDS with an alternative technique is also proposed.

Polyoxometalate as an effective catalyst for the oxidative desulfurization of liquid fuels: a critical review

In order to meet the stringent environmental and industrial legislation on fuel specifications, sulfur compounds have to be removed efficiently from fuels. The requirement to produce ultralow-sulfur fuels (S < 10 ppm) has stimulated many works in the area of conventional hydro-desulfurization (HDS) method. Oxidative desulfurization (ODS), as an alternative or complementary technology to HDS for deep desulfurization, is conducted with high selectivity and reactivity to sterically hindered S compounds under mild reaction conditions. In the ODS process, using an appropriate oxidant in the presence of a catalyst, organic sulfur compounds can be oxidized selectively to their corresponding sulfoxides and sulfones, which can be easily removed by different separation methods. Having great catalytic characteristics, polyoxometalate materials have been utilized as a vital class of catalysts for deep desulfurization of fuels. In the past few decades, ODS of fuels using polyoxometalate as catalyst has drawn much attention, and various studies have been carried out in this area. Here, we give a critical review for the removal of sulfur compounds from liquid fuels (mostly from diesel and model fuels) by ODS via homogeneous and heterogeneous polyoxometalate catalysts.

Sulfur compounds reactivity in the ODS of model and real feeds on W–SBA based catalysts

W based catalysts were synthesized by dry impregnation of SBA-15 mesoporous silica with phosphotungstic acid (HPW) solution with W contents between 5 and 20%, the HPW compound being preserved after calcination. The catalysts performance and the reactivity of various sulfide compounds were evaluated in the oxidative desulfurization (ODS) of model solutions and of real diesels, with sulfur contents ranging from 50 to 2000 ppm. The reactivity of benzothiophene and dibenzothiophene compounds was different in the ODS of model solutions but globally identical in the ODS of SRGO. The monitoring of the concentration of a range of alkyl DBT compounds (with alkyl groups from C2 to C5) in LGO confirmed the importance of the steric hindrance of alkyl substituents in the 4,6 position near the S atom, as well as of the size of the alkyl groups. Among the xW/SBA series, the catalyst with the highest loading showed the best performance in the ODS of LGO and SRGO while the catalysts efficiency could not be discriminated in the ODS of model solutions. In the ODS of both model solutions and real feeds, the W/SBA catalyst was found to be much more efficient than a catalyst obtained by impregnation of a commercial silica with similar loading, highlighting the beneficial use of a mesoporous support with high surface area and pore volume that allowed well-dispersed tungsten species to be obtained. The quantity of sulfones precipitated and/or retained on the catalyst depended on the feed and was found to be higher in the ODS of model solution than in the ODS of real feeds. The precipitated/retained sulfones on the support may induce catalyst deactivation, which highlights the importance of the textural properties of the support. This detailed study points out the difficulty of extrapolating results obtained in the ODS of model solution to the ODS of real feeds.

Comparison of model and real feedstocks oxidative desulfurization on tungsten based catalysts supported on SBA.

Oxidative desulfurization of dibenzothiophene catalyzed by α-MnO2 nanosheets on palygorskite using hydrogen peroxide as oxidant

Palygorskite (Pal)-supported α-MnO₂ nanosheets (Ns-MnPal) combine the adsorption features of Pal with the catalytic properties of α-MnO₂ nanosheets. They were prepared and examined in the catalytic oxidative desulfurization (ODS) of dibenzothiophene (DBT) from a model oil employing 30 wt% H₂O₂ as the oxidant under mild conditions. The supported catalyst was fabricated by the solvothermal method, and effective immobilization of α-MnO₂ nanosheets was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption. The influence of various solvents, solvent volume, reaction temperature, reaction time, catalyst amount and H₂O₂/sulfur molar ratio on ODS was investigated. Using 20 mL of acetonitrile as a solvent, maximum sulfur removal of 97.7% was achieved for ODS of DBT in 1.5 h using a Ns-MnPal/oil ratio of 0.2 g L⁻¹, reaction temperature of 50 °C and H₂O₂/sulfur molar ratio of 4. As solid catalysts, supported α-MnO₂ nanosheets could be separated from the reaction readily. The catalyst was recycled seven times and showed no significant loss in activity.

Palygorskite (Pal)-supported α-MnO₂ nanosheets (Ns-MnPal) combine the adsorption features of Pal with the catalytic properties of α-MnO₂ nanosheets.

Ultrasound-assisted oxidative desulfurization and denitrogenation of liquid hydrocarbon fuels: A critical review

Nowadays, a continuously worldwide concern for development of process to produce ultra-low sulfur and nitrogen fuels have been emerged. Typical hydrodesulfurization and hydrodenitrogenation technology deals with important difficulties such as high pressure and temperature operating condition, failure to treat some recalcitrant compounds and limitations to meet the stringent environmental regulations. In contrary an advanced oxidation process that is ultrasound assisted oxidative desulfurization and denitrogenation satisfies latest environmental regulations in much milder conditions with more efficiency. The present work deals with a comprehensive review on findings and development in the ultrasound assisted oxidative desulfurization and denitrogenation (UAOD) during the last decades. The role of individual parameters namely temperature, residence time, ultrasound power and frequency, pH, initial concentration and types of sulfur and nitrogen compounds on the efficiency are described. What's more another treatment properties that is role of phase transfer agent (PTA) and solvents of extraction step, reaction kinetics, mechanism of the ultrasound, fuel properties and recovery in UAOD are reviewed. Finally, the required future works to mature this technology are suggested.

Oxidative desulfurization of dibenzothiophene using a catalyst of molybdenum supported on modified medicinal stone

In this paper, the performance of catalytic oxidative desulfurization from model oil was studied using a catalyst of molybdenum supported on modified medicinal stone (Mo/MMS).

Performances, kinetics and mechanisms of catalytic oxidative desulfurization from oils

Ultra-deep desulfurization technologies are critical for cleaner oils and consequent better air quality.