Catalyst For Oxidative Desulfurization Research Articles

Boosting tungsten -based catalyst activity for aerobic oxidative desulfurization of gas oil by cerium

This study is aimed at investigating the effect of tungsten-based catalysts for aerobic oxidative desulfurization (AODS) for gas oil. Two catalysts tungsten loaded on activated carbon (W/AC) and cerium-tungsten load on activated carbon (Ce–W/AC) were prepared, and they are characterized by Fourier transform infrared spectroscopy FTIR, X-ray diffraction (XRD), Scanning electronic microscopy (SEM), Energy dispersive spectroscopy EDX, and thermal behavior was examined by thermal graphometry analysis (TGA), the surface area was measure by Brunauer-Emmett-Teller (BET) method. The experiments were conducted in a lab-scale reactor. The primary investigation shows that Ce–W/AC was more active than W/AC. The second part examines the effect of reaction temperature, air flow rate, and catalyst dosage on sulfur removal efficiency by using Ce–W/AC, the ranges for the studied parameter are 150–200 °C, 20–60 mL/min, and 0.5–1 g for reaction temperature, air flow rate, and catalyst dosage respectively. The experiments were designed according to the Taguchi method. The experiments results show the sulfur removal efficiency ranged between 72.3 and 99.9. The findings demonstrate that increasing the reaction temperature leads to an increase in sulfur removal efficiency, while the increase in sulfur removal efficiency with air flow rate and catalyst dosage did not continue because it started decreasing after it reached a maximum value According to analysis variance ANOVA demonstrated that the effect of the studied variables ordered the following: reaction temperature air flow rate and finally catalyst dosage via their F-value where these values are 12.27, 4.09, and 0.16 for reaction temperature, air flow rate, and catalyst dosage respectively.

Tungsten oxide nanoparticles encapsulated by porous carbon for boosting H2S selective oxidation performance

Effective advancements for H2S removal are desperately expected to meet security and ecological necessities as natural guidelines on H2S emissions. Selective catalytic oxidation, as a green technology, has attracted attention owing to its direct conversion of H2S to S without thermodynamic constraints. Herein, we report a carbon-encapsulated WO3 (C@WO3–300) catalyst with nearly 100 % H2S conversion and 99 % S selectivity. Importantly, it likewise accomplishes noteworthy catalytic stability (over 120 h of continuous operation) and water resistance. Excellent durability may be attributed to the ideal porosity of C@WO3, which facilitates the adsorption and activation of H2S and O2. Additionally, the abundant lone pair electrons of carbon support can optimize the chemical environment of WO3-based catalysts and thereby benefit the O2 activation. This study provides a new avenue for the rational design of efficient and durable catalysts for continuous catalytic oxidative desulfurization.

Eco-friendly catalyst in ultrasonic-assisted oxidative desulfurization of dibenzothiophene compound

10 W t.% WO3@activated carbon was prepared from apple peel and used as a catalyst in ultrasonic-assisted oxidative desulfurization of dibenzothiophene@octane in the presence of H2O2 as an oxidant. The physical characteristics of the prepared catalyst were investigated using X-ray diffraction, N2-adsorption-desorption, and scanning electron microscope. The reaction time, oxidant dose, catalyst dose, and sulfur compound concentration were studied to reach 99 % dibenzothiophene removal at ambient conditions and after four cycles the efficiency of dibenzothiophene removal can reach 97.7 %. The kinetic parameters were studied and indicate the ultrasonic-assisted oxidative desulfurization reaction is pseudo-second order.

Synthesis of boron nitride nanorod and its performance as a metal-free catalyst for oxidative desulfurization of diesel fuel

In order to reduce the sulfur compounds in diesel fuel, boron nitride (BN) has been employed as a novel metal free catalyst in the present research. This nanocatalyst was synthesized via template-free approach followed by heating treatment at 900 °C in nitrogen atmosphere that the characteristics of the sample were identified by the XRD, FTIR, Raman Spectroscopy, FESEM TEM, AFM and N2 adsorption–desorption isotherms. The results of structural and morphological analysis represented that BN has been successfully synthesized. The efficacy of the main operating parameters on the process was studied by using response surface methodology based on the Box–Behnken design (BBD) method. The prepared catalyst showed high efficiency in oxidative desulfurization of diesel fuel with initial sulfur content of 8040 ppm S. From statistical analysis a significant quadratic model was obtained to predict the sulfur removal as a function of efficient parameters. The maximum efficiency of 72.4% was achieved under optimized conditions at O/S molar ratio of 10.2, temperature of 71 °C, reaction time of 113 min and catalyst dosage 0.36 g. Also, the reusability of the BN was studied and the result showed little reduction in activity of the catalyst after 10 times regeneration. Moreover, a plausible mechanism was proposed for oxidation of sulfur compounds on the surface of the catalyst. The present study shows that BN materials can be selected as promising metal-free catalysts for desulfurization process.

Preparation of Anderson-type CoMo6-2NH2@ECOF for highly active catalysis on aerobic oxidative desulfurization of fuel under O2

Deep desulfurization with high-efficiency is imperia for environmental demands with increasing stringent standard of sulfur content in fuels. To develop high efficiency heterogeneous catalyst for aerobic oxidative desulfurization (AODS) of fuel, an Anderson-type CoMo6-2NH2 (POM) as active site, which was considered to be very effective in catalyzing the activation of O2, was successfully anchored on the sub-stoichiometric ECOF as a carrier by Schiff-base condensation reaction between –NH2 groups in CoMo6-2NH2 and –CHO groups in ECOF. The anchoring of CoMo6-2NH2 on ECOF by covalent bond resulted in the heterogenization of CoMo6-2NH2 enabled CoMo6-2NH2@ECOF to be recyclable during the AODS process. When CoMo6-2NH2@ECOF was applied as catalyst for AODS of fuel with surfactant (OTAC) under O2, it exhibited excellent catalytic activity with almost 100 % removal rates under 95 °C for 6 h. Moreover, the catalyst can be recycled 7 times without significant loss of catalytic activity. Further, the structure-activity relationship was investigated and the reaction mechanism of AODS of fuel was verified by ESR, XPS analysis and selective quenching experiments.

Efficient room-temperature oxidation of dibenzothiophene over mesoporous WO3@ZrO2-TiO2 composites derived from polymer-oriented self-assembly strategy

Deep removal of thiophenic sulfur compounds in fuel oil remains an enormous challenge to achieve ultra-clean diesel production. Herein, a polyoxometalate-based inorganic-organic hybrid derived mesoporous WO3@ZrO2-TiO2 composites has been prepared by a simple polymer-oriented self-assembly strategy using polyethyleneimine (PEI) as the structure-directing agent. It exhibits that the existence of mesoporous pore channels, Zr doped TiO2 matrix, and highly dispersed WO3 active sites on the ZrO2-TiO2 framework can facilitate the adsorption-oxidation process of thiophene-type sulfide and provide more accessible active sites. The as-prepared mesoporous WO3@ZrO2-TiO2 composite shows good catalytic activity for dibenzothiophene (DBT) at room temperature, removing 500 ppm of DBT from simulated oil within 80 min, making it a suitable alternative catalyst for deep oxidative desulfurization.

Agricultural waste-based microporous catalysts for oxidative desulfurization of highly sour heavy gas oil

In recent years, the use of abundant and low-cost biomaterials such as agricultural wastes in the preparation of activated carbon has been receiving a lot of attention. Besides, the conventional middle and heavy fuel cuts require a substantial and cost-effective sweetening process because sulfur in transportation fuel was found as one of the main causes of air pollution. The present work explored the preparation and characterization of microporous activated carbon (AC) catalysts prepared from olive stone by tubular furnace (Fe/AC1) and microwave (Fe/AC2) heating methods using H3PO4 (85 wt%) as chemical activating agents. The kinetics of the oxidative desulfurization process (ODS) of a highly sour diesel fuel (sulfur content = 7361 ppm) was determined. The effect of the heating method on the texture and morphological structure, surface area, and surface chemistry of the carbons produced was investigated. Fe/AC1 was prepared in a horizontal tabular furnace at 650 °C calcination temperature and 90 min residence time under a nitrogen atmosphere, while Fe/AC2 was performed in a microwave reactor with 565 W and 7 min microwave power and irradiation time respectively. The catalysts were characterized by N2- adsorption-desorption, SEM-EDX, FTIR, XRD, XRF, TGA, PSD, and elemental analysis. It was found that the use of a tubular furnace for heating the olive seeds resulted in a higher surface area and yield. Also, the characterizations of the Fe/AC1 catalyst showed that it has a large surface area of 1175 m2/g and micropore volume of 0.6954 cm3/g whereas Fe/AC2 had a surface area of 854 m2/g and micropore volume of 0.6936 cm3/g. Moreover, SEM-EDX results indicated that Fe/AC1 was dispersed uniformly better than Fe/AC2. Also, TGA/DTA results revealed better results for Fe/AC1 than Fe/AC2 making it favorable in ODS experiments. The difference in texture and chemical properties is caused by the heating methods. The desulfurization removal was investigated under different temperatures (80, 90, 100, 110 °C) and reaction time (30–90 min). The kinetics of the ODS were conducted over the efficient Fe/AC1 catalyst prepared. It was shown that the ODS reaction followed pseudo-first-order kinetics with a fairly low activation energy over the catalyst was 40.71 kJ/mol.

Boron Nitride Nanofibers as Catalysts for High-Efficiency Aerobic Oxidative Desulfurization

Boron Nitride Nanofibers as Catalysts for High-Efficiency Aerobic Oxidative Desulfurization

Three-layer coated composite materials PMoV2@UiO-66-X@mSiO2: Efficient oxidative desulfurization catalysts

In this article, composite materials PMoV2@UiO-66-X (X = H, NH2, NO2, SO3H) are prepared by using hydrothermal synthesis method, and then the surfaces of the composite materials are coated with mSiO2 shell to obtain three-layer coated catalysts PMoV2@UiO-66-X@mSiO2. The prepared catalysts were characterized by FT-IR, XRD, N2 adsorption desorption isotherms, SEM, and TEM. The catalytic oxidation desulfurization performance of the catalyst was studied using GC–MS, and the optimal reaction conditions of the catalysts were explored, including temperature, stirring rate, catalyst dosage, and oxidant dosage. The results indicate that at 800 ppm of simulated fuel, PMoV2@UiO-66-NO2@mSiO2 has the highest catalytic activity, with a total desulfurization efficiency of 98 % under optimal conditions. After eight cycles, the efficiency can still reach 94 %, which is attributed to the strong acidity provided by PMoV2, the electron donating effect of the –NO2 group, and the stable core–shell structure after coating with mSiO2.The paper further confirmed the high catalytic activity of the catalyst through UV–Vis analysis.

Magnetically recyclable high-entropy metal oxide catalyst for aerobic catalytic oxidative desulfurization

High-entropy metal oxide catalysts have demonstrated exceptional performance in activating oxygen for catalytic oxidation reactions. However, ensuring their ease of cyclic usage is crucial to broadening their applications. To address this challenge, a magnetic and recyclable high-entropy metal oxide catalyst is designed and its potential in catalytic oxidative desulfurization of fuel oils with oxygen as the oxidant is also investigated. Through a mechanochemical-assisted calcination method, the magnetic high-entropy metal oxide catalyst (HEMO-900) is successfully synthesized, and the structure of the HEMO-900 catalyst is comprehensively characterized. In addition, it is found that the high-entropy structure facilitates charge modulation of the active components, thereby enhancing the oxygen activation performance. The HEMO-900 catalyst exhibits exceptional oxygen activation ability and catalytic oxidative desulfurization performance, and 96.9% of sulfur removal is achieved under optimal conditions. In addition, it achieves profound desulfurization of various fuel samples by efficiently oxidizing and eliminating diverse aromatic sulfur compounds. Additionally, the catalyst demonstrates outstanding magnetically recyclable properties, enabling rapid separation and recovery from the fuel oil phase through the application of an external magnetic field, making the HEMO-900 catalyst maintained a remarkable sulfur removal efficiency of 91.1% even in the 5th cycle. Therefore, this magnetically recyclable HEMO-900 catalyst possesses significantly promising research and application prospects in the field of catalytic oxidative desulfurization of fuel oils with oxygen as the oxidant, as well as some other heterogeneous catalysis.

Metallic cobalt-anchored carbon with non-metallic heteroatom decoration: Remarkably effective oxidative desulfurization catalyst

The discovery of low-cost, highly effective, and novel catalytic materials for oxidative desulfurization (ODS) of liquid fuel is an important topic in the field of heterogeneous catalysis from both academic and industrial viewpoints. Different metallic active component supported on porous carbon was found as effective catalysts for ODS reactions and the contribution of the secondary or non-metallic heteroatom decoration on the carbon was also assumed. However, the precise role of the doped heteroatom(s) on boosting the ODS process is unknown. Here, a new approach to prepare a series of cobalt-anchored porous carbon (Co@C) with different heteroatom co-dopants (i.e., N, P, and B) and their effects on boosting oxidative desulfurization (ODS) from fuel were firstly instigated. The Co@nitroneneous carbons with P or B co-dopants could be derived via the carbonization of a bimetallic MOF with extra N, P, and B sources. A newly designed/developed Co@C catalyst exhibited high intrinsic activities in ODS. Importantly, Co@C having suitable N and P contents had an extremely low Ea (21 KJ·mol-1) and the highest TOF (104 h-1), among the studied/reported materials, for the oxidation of dibenzothiophene. We also firstly demonstrate the precise role of doped heteroatoms in Co@C in accelerating ODS by the synergy between doped heteroatoms and the reduction of the HOMO-LUMO energy gap of the catalyst. This approach can pave the way for tuning the catalytic performance through atom-level surface modification of carbonaceous catalysts.

Enthalpy-driven synthesis of magnetic high entropy oxide catalyst for efficient oxidative desulfurization and high-value product recovery

High entropy metal oxides (HEOs) have shown remarkable catalytic potential owing to their multifaceted and tunable chemical composition, coupled with their exceptional thermodynamic stability. Specifically, magnetic HEOs demonstrate enhanced effectiveness in terms of catalyst separation and recovery owing to their magnetic properties. Nevertheless, current synthesis methods for magnetic HEOs often involve high-temperature conditions (typically > 1100 °C) to maximize the contribution of mixing entropy (ΔSmix) in the Gibbs equation (ΔGmix = ΔHmix - TΔSmix). Herein, unlike previous approaches, a reduction in the mixing enthalpy (ΔHmix) is proposed to result in a negative Gibbs free energy for the crystallization of HEOs. Based on this principle, a magnetic high entropy oxide, CoCrFeMnMoOx (MHEO), is successfully synthesized, at a relatively low temperature (900 °C). Notably, the MHEO catalyst demonstrated outstanding catalytic activity in the oxidative desulfurization (ODS) system utilizing O2 as the oxidant, achieving a rapid and complete sulfur removal of 100% within 3 h. Moreover, it demonstrates remarkable cycling durability, allowing for continuous operation over 20 cycles without significant loss in ODS efficiency. Furthermore, the magnetic properties of the MHEO catalyst facilitated the efficient separation and recovery of both the catalyst and high-value products. These findings offer significant insights into the design of high entropy catalysts and contribute to the advancement of sustainable green development.

Preparation of porous hollow spherical MoOX/C catalyst for efficient extraction and oxidative desulfurization

Preparation of porous hollow spherical MoOX/C catalyst for efficient extraction and oxidative desulfurization

N-doped carbon nanotube encapsulated nZVI as a high-performance bifunctional catalyst for oxidative desulfurization

N-doped carbon nanotube encapsulated nZVI as a high-performance bifunctional catalyst for oxidative desulfurization

Synthesis of POM@Porphyrin COF heterogeneous catalyst for oxidative desulfurization of thio compounds

Sulfur compounds cause substantial environmental pollution problems, and their immediate removal is urgently needed to keep the environment clean. Fuel desulfurization is necessary due to the severe impacts of sulfur on humans, wildlife, and crops when emitted into the atmosphere during fuel combustion. Fuels with high sulfur contents used in automobiles and factories are the primary source of atmospheric sulfur. A new covalent organic framework (COF) MnTP@ZnAdCOF [(N(C4H9)4]12[{NHC(CH2O)3}4(CO)4C44H24N4Mn(OCOCH3)][ZnMo6O18]4 is synthesized and characterized thoroughly using FT-IR, UV/visible, 1HNMR, TGA, PXRD, SEM-EDX, cyclic voltammetry and fluorescence spectroscopy. Herein, an environmentally safe and cost-effective approach for the ODS of thiobenzoic acid is reported using H2O2 as an oxidant and MnTP@ZnAdCOF as a heterogenous catalyst under mild reaction conditions. Desulphurization results of the catalyst are confirmed by the RP-HPLC technique using acetonitrile and water in a 50:50 M ratio as a mobile phase. Active intermediates [(Por)(OAc)Mn-OOH]−, [(Por)(OAc)MnIVO] and Mo(O2) are formed due to oxidation of Mn and Mo metal in the presence of H2O2 considered responsible for the excellent catalytic efficiency of MnTP@ZnAdCOF catalyst up to 98% desulphurization efficiency was observed. Incredible catalytic conversion of dibenzothiophene, thiobenzoic acid and the mixture of different Sulphur containing compounds to sulfoxide is observed at 25 ℃ temperature. The H2O2/S molar ratio of 5:1 is an outstanding achievement that can be utilized for the oxidation of sulfur compounds present in diesel to reduce the sulfur contents of fuel.

Natural deep eutectic solvents of γ-valerolactone and formic acid for oxidative desulfurization with superior efficiency

Deep eutectic solvents (DESs) are widely used in oxidative desulfurization (ODS) to produce clean fuel. However, some DESs with good ODS efficiencies are generally consisted of harmful components, and the ODS efficiencies of most DESs with green components need to be further improved. Herein, a DES with two natural compounds of γ-valerolactone (γ-Val) and formic acid (FA) was prepared and used in ODS. The hydrogen bond interaction of DES was characterized by FT-IR, 1H NMR, DSC, and calculated by density functional theory (DFT) computation. The radical quenching experiments, EPR, and kinetic study were carried out to investigate the active radical and apparent activation energy of ODS process. The desulfurization efficiencies of γ-Val and FA (molar ratio 1: 4) DES was capable of reaching 100% of dibenzothiophene (DBT) removal within 100 min at an energy saving way of room temperature (25 °C) with a low O/S molar ratio of 2. When the temperature was raised to 70 °C and the O/S molar ratio was raised to 5, 100% sulfur removal of dibenzothiophene, 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT) could be achieved in 4 min, 6 min, and 10 min respectively. DFT calculations revealed that the introduction of γ-Val could reduce the transition state energy barrier of ODS compared with a single FA ODS process. This work provides a novel high ODS efficiency DES with natural compounds, indicating the potential application of green DESs in ODS catalysts.

Tailored monolithic catalyst and reactor by direct photo-curing 3D printing for oxidative desulfurization of fuels

Structured monolithic catalysts have attracted growing attention in the petrochemical industry due to significant advantages of reusability, easy scale-up, and high heat and mass transfer rate. 3D printing offers enormous flexibility in accurately regulating the configuration of monolithic catalysts to realize the strengthening of the reaction process. However, this remains challenging in terms of reliable manufacturing, high resolution, and the distribution of active sites. Here, we report a direct photo-curing 3D printing based method for manufacturing precise monolithic catalysts for oxidative desulfurization of fuels. Numerous molybdenum oxide nanoparticles with a high density of oxygen vacancies are spatially distributed in three-dimensional Al2O3 by 3D printing technology and post-treatment, thus favoring the catalytic reaction. This 3D-MoOx/Al2O3 exhibits excellent catalytic performance with a 99.2 % conversion of dibenzothiophene. Furthermore, this tailored catalyst is 3D-printed to manufacture a monolithic agitating impeller as a stirring reactor, which plays a dual role in mixing and catalysis. The study provides an effective strategy for precisely manufacturing structured catalysts with excellent catalytic activity and can be readily applied to a range of chemical reactions.

Mesoporous SnO2–MoO3 catalyst for diesel oxidative desulfurization: Impact of the SnO2/MoO3 ratio on catalytic efficiency

Vehicular SOx emissions have a huge detrimental impact on public health, catalytic converters, and the environment. Developing strategies to remove sulfur from diesel and thus safeguard the above is imperative. A series of SnO2–MoO3 mixed oxides and mono oxides MoO3 and SnO2 were prepared by soft template method, calcined at 450 °C and successfully tested in model diesel oxidative desulfurisation (ODS). The impact of the SnO2/MoO3 mole ratio (hereinafter denoted as Sn/Mo) on catalytic efficiency was investigated, among other catalytic parameters. The obtained samples were analyzed using X-ray diffraction (XRD), Raman spectrocscopy, scanning electron microscopy (SEM), N2-physisorption and titration method for acidic properties. The study demonstrates that mixing SnO2 and MoO3 improves acidic sites, crystallinity, and morphological properties of pure SnO2. The addition of MoO3 increased oxygen vacancies and the surface area of SnO2. High acidic site densities of 49.3, 47.4, and 46.7 mEqg−1 were observed for the catalysts with 2:1, 1:1, and 1:2 Sn/Mo mole ratio, respectively. The catalytic efficiency increased with an increase in Sn content with the highest catalytic efficiency of 99.8% for the dibenzothiophene (DBT) oxidation achieved in 30 min for Sn/Mo (2:1) catalyst compared to 92 and 70% for Sn/Mo 1:1 and 1:2 catalysts, respectively. The rate constant for the reaction was 0.057 min−1, which is eight times that of MoO3; 0.007 min−1 and three times that of SnO2; 0.017 min−1. The ODS mechanism utilizing the SnO2–MoO3 catalyst was proposed. The prepared SnO2–MoO3 catalyst demonstrated a high potential for industrial desulfurisation applications.

Molybdenum-based metal–organic frameworks as highly efficient and stable catalysts for fast oxidative desulfurization of fuel oil

Heterogeneous catalysts are usually constructed by immobilizing active species on appropriate supports. However, the dispersibility is difficult to precisely control. In this work, three representative Mo-based MOFs (Mo-MOFs) were constructed by assembling various organic linkers and MoO3, where the Mo atoms are homogeneously dispersed due to the coordination. The results illustrated that the obtained Mo-MOF-PI synthesized with 2-propyl imidazole as the ligands exhibited an extremely fast reaction rate, achieving 99.4% sulfur removal of DBT within only 12 min. Compared to other similar catalysts, Mo-MOF-PI showed much higher catalytic activity with a turnover frequency value of 19.2 h−1. Moreover, it can be reused at least 20 times without a dramatic reduction in catalytic performance. Thus, the as-prepared Mo-MOF catalysts show great potential in large-scale industrial applications.

Encapsulation of ionic liquid, phosphotungstic acid inside the nanocages of MIL-101(Cr): Effective and reusable catalyst for efficient solvent-free oxidative desulfurization from fuel oil

Oxidative desulfurization from fuel oil is one of the important methods for deep desulfurization. The development of efficient oxidative desulfurization catalysts is crucial for improving the desulfurization performance. Successful encapsulation of phosphotungstic acid (HPW) and ionic liquid (BMImBr) inside the mesoporous cages of MIL-101(Cr) was accomplished through a combination of “bottle around ship” and “ship in bottle” methods. The obtained BMImPW@MIL-101(Cr) composite was characterized by XRD, FTIR, BET, SEM, XPS and ICP methods. Results indicated that the BMImPW@MIL-101(Cr) composites with PW3− loading of 23.1–50.7 wt% were obtained, demonstrating that the “bottle around ship” method is beneficial to make full use of nanocages of MIL-101(Cr) to obtain expected high loading of active PW3−. The BMImPW@MIL-101(Cr) exhibits excellent reusability with no evidence of leaching of active PW3− and BMIm+, and well-preserved structure after successive cycles of regeneration and reuse. The significantly improved stability of BMImPW@MIL-101(Cr) as compared to HPW@MIL-101(Cr) is possibly because the leaching of the active PW3−− sites can be greatly suppressed by forming large size of BMImPW owing to introduction of BMIm+ cation. The BMImPW@MIL-101(Cr) exhibited excellent catalytic activity for solvent free oxidative desulfurization of refractory sulfides. The enhanced oxidative desulfurization activity as compared to HPW@MIL-101(Cr) can be explained by the intimate contact of sulfides with active PW3− sites owing the strong attraction of BMIm+ cation with the sulfides.