Catalyst For Oxidative Desulfurization Research Articles

Metal-free oxidative desulfurization with molecular oxygen by using N-enriched porous carbons derived from ionic liquid-loaded covalent-organic polymer

A microporous triazine polymer (MCTP) was prepared and loaded, for the first time, with an N-containing ionic liquid (IL) through a ship-in-a-bottle method. The composite material, IL@MCTP, was pyrolyzed under high temperature to get N-enriched carbonaceous materials. The obtained carbons (denoted ICDCs) were utilized as a metal-free catalyst for the aerobic oxidative desulfurization (ODS) of organic sulfur compounds like dibenzothiophene from a model fuel. The reactivity of ICDCs in ODS was dependent on the nitrogen content and porosity of the carbons. One selected material (ICDC(8)), because of high nitrogen content and adequate porosity, showed a remarkable performance in ODS or removal of dibenzothiophene with a very low activation energy of 23.7 kJ/mol. Radical scavenger experiments and ESR analysis revealed the important role of superoxide anion radicals (•O2−) in oxidation. A plausible reaction mechanism to suggest an important role of nitrogen species in ICDCs to activate O2 (via adsorption on C with a partial positive charge) was proposed. The ODS also can be carried out with air, and the catalyst was reusable for up to the fifth cycle by simple solvent washing. The ICDCs can be a competitive and environment-friendly (metal-free) ODS catalyst, especially using cheap oxidants like air or O2.

Enhancing the oxidative desulfurization efficiency of cobalt-loaded-porous carbon catalyst via nitrogen doping on carbon support

Melamine (M)-incorporated bimetallic (Zn/Co)-azolate framework-6s (M( x )@BM6s) (with wide M-contents) composites were firstly synthesized via an in-situ method and used as a precursor to derive Co/N-enriched porous carbon (M( x )@BMC6s) via pyrolysis. Very small Co-nanoparticles (4–10 nm) uniformly distributed on highly porous carbon with much N-doping were obtained from M( x )@BM6s. The developed Co-based materials with high N-content were used as catalysts for heterogeneous oxidative desulfurization (ODS) of liquid model fuel, critical for the environment and the petroleum industry . M( x )@BMC6s (with various N-contents), especially the M( 10 )@BMC6 (obtained from M( 10 )@BM6 with 10% M), were more competitive in ODS than orther tested Co-based catalysts (without or with less N-sites) and comparable to the reported catalysts to date. For example, the turnover frequency of M( 10 )@BMC6 was 61.1 h ˗1 and ∼10 times that of Co/activated carbon. Additionally, the good reactivity of M( 10 )@BMC6 with adequate reusability might be understood by the good dispersion of small Co-nanoparticles. Importantly, dominant role of the doped N-species on carbon, by enhancing the synergy between Co- and N-species, was firstly suggested in this study. Finally, incorporation of N-sites in the carbon support for Co-nanoparticles can enhance the ODS performance, thus being suggested as an effective way to develop oxidation catalysts with outstanding performance. • Melamine incorporated bimetallic-azolate framework-6s were firstly prepared. • Co-nanoparticles well dispersed on N-enriched carbon were prepared from melamine/MOF. • Oxidative desulfurization (ODS) activity was increased by N-dopant on the carbon support. • The reusable M( 10 )@BMC6 had ∼ 10 times that of Co/activated carbon in ODS. • ODS reaction was explained with the facile formation of ⋅OH or 1 O 2 because of Co and N.

From agro-waste to encapsulated carbon catalyst for improving stability of naphtha desulfurization

The deactivation of the oxidative desulfurization (ODS) catalysts is a challenge and is a major concern in industrial catalytic processes. In this work, an activated carbon (AC) was prepared from agricultural waste and modified to withstand the ODS activity loss over time. The AC was impregnated with manganese and coated with aluminum oxide to prolong the activity lifetime. The catalysts were characterized by nitrogen adsorption-desorption, scanning electron microscope, energy dispersive X-ray, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transition electron microscope (TEM). The BET surface areas of the examined AC materials were 814.48 m2/g, 784.76 m2/g, and 755.03 m2/g for the AC, Mn/AC, and coated Mn/AC catalysts, respectively with a dominance of microporous pore size. The TGA showed that the coating layer retards the degradation of the active metal and suppresses phase transitions. XRD showed no change in the structure of the catalyst with a coating layer, and from the TEM analysis, the coating layer thickness was 3.6 nm. The kinetics of the ODS catalysts were investigated. It was shown that the ODS reaction follows the first-order kinetics and is not influenced by the coating layer. The activity decay was also investigated. It is found that the activation energy of the deactivation reaction over the coated catalyst was higher than the uncoated catalyst.

Ultrafine W2C well-dispersed on N-doped graphene: Extraordinary catalyst for ultrafast oxidative desulfurization of high sulfur liquid fuels

A ternary nanocomposite comprising phosphotungstic acid (PW12), polyethyleneimine (PEI), and graphene oxide (GO), i.e., PW12-PEI/GO, was developed as a precursor to obtain the W2C/N-rGO catalyst upon in-situ carbonization. W2C/N-rGO was applied in the deep oxidative desulfurization (ODS) of liquid fuel, and exhibited extraordinary performance due to the ultrafine W2C nanoparticles (～3–5 nm) evenly dispersed on N-rGO and the electron-donating effect of N-rGO on W2C. 4000 ppm of DBT in model oil could be completely removed within only 10 min with a remarkably high turnover frequency (168 h−1) and the lower activation energy (30.9 kJ·mol−1). Radical experiments and density functional theory calculations indicate that the ODS reaction proceeds mainly via a HO• radical mechanism. Moreover, W2C/N-rGO could be recycled for 6 successive cycles with no obvious loss of performance.

Enhanced Oxygen Activation Achieved by Robust Single Chromium Atom-Derived Catalysts in Aerobic Oxidative Desulfurization

Enhanced Oxygen Activation Achieved by Robust Single Chromium Atom-Derived Catalysts in Aerobic Oxidative Desulfurization

Facial synthesis of mesoporous {Mo132}/BiOCl for the efficient oxidative desulfurization of fuel

The Keplerate nanoball iso-polyoxomolybdate {Mo132} supported on BiOCl was prepared and assessed as a green, innovative, and low-cost oxidative desulfurization catalyst for dibenzothiophene-containing model oil (DBT). The XRD, FT-IR, Raman, SEM, TEM, BET, and XPS characterize the prepared catalysts. The optimum operating parameters were identified by evaluating factors such as reaction time, catalyst quantity, oxygen to sulfur molar ratio, and temperature. Experiments indicated that the catalyst was greatly efficient in removing DBT, with a sulfur removal rate up to 100 % at optimum conditions (catalyst dosage = 5 g/L, O/S = 10, time = 180 min, and temperature = 40 °C) utilizing hydrogen peroxide (H2O2) as oxidizing agent and acetonitrile as extracting solvent. Furthermore, {Mo132}/BiOCl showed high stability and catalytic activity like that of the fresh one after four cycles. ODS activity of the catalyst was evaluated for various thiophenes (thiophene, BT, 4,6-DMDBT, and DBT) derivative and feed at optimum conditions. The proposed mechanism for catalytic oxidation of DBT in the existence of {Mo132}/BiOCl nanocomposite was studied.

Phosphotungestic acid and manganese containing periodic mesoporous organosilica with imidazolium ionic liquid framework: A robust and durable nanocomposite for desulfurization of aromatic sulfur in diesel fraction

As sulfur compounds produced by the combustion of fossil fuels are one of the main elements in air pollution, some strict legislation has been issued that specifies the sulfur ratios of different fuels. Therefore, periodic mesoporous organosilicas (PMO) composed of 1,3- bis(trimethoxysilylpropyl)imidazolium chloride ionic liquid, 1,2- bis(trimethoxysilyl)ethane, and phosphotungstic acid or permanganate as counter ions of imidazolium moieties in the framework of PMO-IL were fabricated to obtain highly reactive -MnO4 or -HPW12O40 based heterogeneous catalysts. The synthesized materials were characterized by FT-IR, N2 adsorption–desorption, low and wide-XRD, XPS, TGA, and HRTEM. The surface area was of 615, 425 and 347 m2 g–1 for PMO-IL, HPW12O40–PMO-IL and MnO4- PMO-IL, respectively. The desulfurization was studied on three types of aromatic sulfur models. The results revealed that MnO4-PMO-IL and HPW12O40– PMO-IL outperform other catalysts in the oxidative desulfurization process of three kinds of aromatic sulfur compounds; comprising benzothiophene, dibenzothiophene, and 4, 6-dimethyldibenzothiophene even at smaller O/S ratio. The MnO4–PMO-IL catalyst showed the maximum efficiency in reducing sulfur at 50 °C, as it achieved sulfur reduction rates of 93.2, 92.7, and 98.8% after 90 min, while the HPW12O40– PMO-IL catalyst showed a reduction of sulfur by 85.1, 94.3 and 98% after 120 min for BT, DBT, and 4,6-DMDBT compounds, respectively. The two catalysts can be suggested as effective catalysts for oxidative desulfurization of fuel. Furthermore, our research showed that the catalyst might be retrieved and reused at least nine times without a noticeable loss in performance.

Encapsulation of Sandwich POM in MIL-101 as Efficient Oxidative Desulfurization Catalyst of DBT

Encapsulation of Sandwich POM in MIL-101 as Efficient Oxidative Desulfurization Catalyst of DBT

N-hydroxyphthalimide anchored on hexagonal boron nitride as a metal-free heterogeneous catalyst for deep oxidative desulfurization

A metal-free N-hydroxyphthalimide/hexagonal boron nitride (NHPI/h-BN) catalytic system was developed for deep oxidative desulfurization (ODS) of fuel oils. Detailed experiments find that the heterogenization process of loading NHPI on h-BN not only benefits to the dispersion and utilization of NHPI, but also can significantly promote the catalytic performance. By employing NHPI/h-BN as the catalyst, azodiisobutyronitrile (AIBN) as the metal-free initiator, a 95% conversion of dibenzothiophene (DBT) can be acquired under the reaction conditions of 120 °C and atmospheric pressure with molecular oxygen (O2) as oxidant. Moreover, the heterogenization is convenient for the regeneration of the catalyst with >94% DBT conversion after being recycled seven times. Characterizations illustrate that the promoted catalytic activity along with the regenerability originate from the interactions between NHPI and h-BN. The catalytic mechanism study shows that molecular oxygen is readily activated by the NHPI/h-BN to form a superoxide radical (O2•−), which oxidize DBT to DBTO2 for desulfurization.

High-Performance Heterogeneous Oxidative Desulfurization Catalyst with Brønsted Acid Sites

A new heterogeneous catalyst containing two types of active sites, sulfo group and ammonium heptamolybdate, on ASKG silica gel support was synthesized. The influence of oxidation conditions (temperature, reactant ratio, reaction time) on the conversion of a model substrate, dibenzothiophene (DBT), was examined. Conditions were found for exhaustive oxidation of DBT. The catalyst synthesized is stable under the oxidation conditions and preserves its activity in five oxidation cycles. The combination of two types of active sites not only considerably enhances the catalyst performance but also reduces to a minimum the possible washout of molybdenum compounds from the support surface.

Cobalt-based sandwich-type polyoxometalate supported on amino-silane decorated magnetic graphene oxide: A recoverable catalyst for extractive-catalytic oxidative desulfurization of model oil

In order to produce ultra-low sulfur fuel, a sandwich-type polyoxometalate (K10[Co4(H2O)2(PW9O34)2]10- (Co4-POM) was covalently immobilized on amino-modified magnetic graphene oxide, and employed as a novel heterogeneous catalyst in an extractive- catalytic oxidative desulfurization system (ECODS). The (Co4-POM@APTES-(Fe3O4/GO)) nanocomposites with various Co4-POM content were prepared. The obtained samples were characterized by XRD, FT-IR, SEM, EDX, N2 adsorption, and VSM techniques. Meanwhile, the effects of Co4-POM load percentage, reaction temperature, catalyst dosage, and H2O2/DBT molar ratio on desulfurization efficiency of the prepared catalyst were investigated. The highest catalytic activity was observed for the sample with 30 wt% Co4-POM content. Dibenzothiophene (DBT) could be completely removed within at 50 ℃ using 4 g catalyst L−1 fuel, and H2O2/DBT molar ratio of 4. In addition, BT and 4,6-DMDBT could be completely removed under the optimized conditions, which suggested a promising prospect of the catalyst for industrial applications. The nanocomposite could be easily separated and reused by utilizing an external magnetic field without any substantial decline in its catalytic activity even after five runs. The kinetic data were fitted to a pseudo-first-order model. Finally, a reaction mechanism for the catalytic oxidation of DBT in the presence of Co4-POM@APTES-(Fe3O4/GO) was proposed.

Polyoxometalate/Cellulose Nanofibrils Aerogels for Highly Efficient Oxidative Desulfurization.

Polyoxometalate (POM) presents great potential in oxidative desulfurization (ODS) reaction. However, the high dissolubility of POM in common solvents makes it difficult to recycle. Besides, the small specific surface area of POM also limits the interaction between them and the substrate. Depositing polyoxometalates onto three-dimensional (3D) network structured materials could largely expand the application of POM. Here, the surfaces of cellulose nanofibrils (CNFs) were modified with very few (3-Aminopropyl) trimethoxysilane (APTS) to endow positive charges on the surfaces of CNFs, and then phosphotungstic acid (PTA) was loaded to obtain the aerogel A-CNF/PTA as the ODS catalyst. FT-IR indicated the successful deposition of PTA onto aminosilane modified CNF surfaces. UV-VIS further suggested the stability of PTA in the aerogels. BET and SEM results suggested the increased specific surface area and the relatively uniform 3D network structure of the prepared aerogels. TGA analysis indicated that the thermal stability of the aerogel A-CNF/PTA50% was a little higher than that of the pure CNF aerogel. Most importantly, the aerogel A-CNF/PTA50% showed good catalytic performance for ODS. Catalysis results showed that the substrate conversion rate of the aerogel A-CNF/PTA50% reached 100% within 120 min at room temperature. Even after five cycles, the substrate conversion rate of the aerogel A-CNF/PTA50% still reached 91.2% during the dynamic catalytic process. This work provides a scalable and facile way to stably deposit POM onto 3D structured materials.

Polyoxometalates Immobilized on Covalent Triazine Framework as Efficient Catalysts for Deep Oxidative Desulfurization

AbstractThe immobilized polyoxometalates (POMs) with evenly dispersed catalytic sites, amphiphilic surface, and excellent recyclability are highly desired in many important reactions. Herein, PMo12@CTF has been successfully fabricated by the electrostatic assembly of H3PMo12O40 (PMo12) with porous cationic covalent triazine framework (CTF), where PMo12 are evenly dispersed on the support. The synthesized PMo12@CTF is highly active for oxidative desulfurization of diesel fuel and dibenzothiophene (DBT) can be completely converted in 2 h under mild conditions (40 °C) in a biphasic system. Impressively, the catalytic activity of heterogeneous PMo12@CTF (conversion: 100 %) is much higher than that of homogeneous PMo12 (conversion: 20 %). The control experiments and contact angle measurements reveal that the CTF endows PMo12@CTF with large surface area and amphiphilic feature and the catalyst can effectively contact with both oxidant H2O2 in extraction phase and DBT in oil phase. Moreover, PMo12@CTF is robust and its catalytic activity is basically maintained after ten cycles.

Promoting Effect of P in MoV Oxide-based Catalysts for Oxidative Desulfurization of Dibenzothiophene Compounds

Promoting Effect of P in MoV Oxide-based Catalysts for Oxidative Desulfurization of Dibenzothiophene Compounds

Ce2(MoO4)3 as an efficient catalyst for aerobic oxidative desulfurization of fuels

Ce 2 (MoO 4 ) 3 was synthesized by a simple reflux method using cerium nitrate hexahydrate and ammonium molybdate as reactants. The as-prepared Ce 2 (MoO 4 ) 3 was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The removal of dibenzothiophene (DBT) in model oil was studied using Ce 2 (MoO 4 ) 3 as catalyst and oxygen as oxidant. The reaction factors such as reaction temperature, amount of catalyst, and sulfide type on sulfur removal were researched. The results prove that both Ce 3+ and MoO 4 2- play significant role in the conversion from DBT to DBTO 2 . The Ce 2 (MoO 4 ) 3 catalyst has an excellent performance for the sulfur removal of DBT. Under the optimum reaction conditions, sulfur removal of 99.6% was obtained. After recycling five times, no significant loss in catalyst activity of Ce 2 (MoO 4 ) 3 . Mechanism of aerobic oxidative desulfurization was proposed based on the experiment of free radical capture and infrared characterization.

Dichloro and dimethyl dioxomolybdenum(VI)-bipyridine complexes as catalysts for oxidative desulfurization of dibenzothiophene derivatives under extractive conditions

The complexes [MoO2Me2(2,2′-bipyridine)] (5), [MoO2X2(4,4′-dimethyl-2,2′-bipyridine)] (X = Cl (2), Me (6)), [MoO2Me2(4,4′-di‑tert‑butyl‑2,2′-bipyridine)] (7) and [MoO2X2(4,4′-dinonyl-2,2′-bipyridine)] (X = Cl (4), Me (8)) have been prepared and examined as catalysts in extractive and catalytic oxidative desulfurization (ECODS) of a simulated diesel fuel (3000 ppm S) containing dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. The molecular structures of 6 and 8 were characterized by 1H NMR, FT-IR and FT-Raman, and X-ray crystallography. The ECODS reaction conditions were optimized for complex 5 by comparing different extraction solvents (MeCN, the ionic liquid (IL) 1‑butyl‑3-methylimidazolium hexafluorophosphate ([BMIM]PF6), polyethylene glycol (PEG) and two PEG-based deep eutectic solvents), and by varying the catalyst and oxidant (H2O2) amounts, and diesel/solvent volume ratio. Under the optimal conditions with [BMIM]PF6 as the extraction solvent, the quantitative elimination of all sulfur compounds from the model diesel was achieved within 3 h at 70 °C. A comparison of initial ECODS rates for complexes 2, 4, 6 and 8 indicated that the equatorial N,N-chelate ligand was more important than the axial ligand (X) for the desulfurization catalytic performance, with the best results being obtained for the IL-soluble complexes 4 and 8. The IL-entrapped catalyst from 4 showed a good capacity to be reused in consecutive desulfurization cycles.

New Type of Catalyst for Efficient Aerobic Oxidative Desulfurization Based On Tungsten Carbide Synthesized by the Microwave Method.

Herein, we present a new type of high-performance catalyst for aerobic oxidation of organosulfur compounds based on tungsten carbide. The synthesis of tungsten carbide was performed via microwave irradiation of the precursors, which makes it possible to obtain a catalyst in just 15 min. The synthesized catalyst was investigated by a variety of physicochemical methods: X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and N2 adsorption/desorption. It was shown that active centers containing tungsten in the transition oxidation state (+4) play a key role in the activation of oxygen. The main factors influencing the conversion of dibenzothiophene (DBT) were investigated. It should be noted that 100% conversion of DBT can be achieved under relatively mild conditions: 120 °C, 3 h, 6 bar, and 0.5% wt catalyst. The catalyst retained its activity for at least six oxidation/regeneration cycles. The simplicity and speed of synthesis of the proposed catalyst in combination with its high activity and stability open broad prospects for its further use both for oxidative desulfurization and for other reactions of aerobic oxidation of organic substrates.

Simple and Green Preparation of ZnO Blended with Highly Magnetic Silica Sand from Parangtritis Beach as Catalyst for Oxidative Desulfurization of Dibenzothiophene

Simple and green preparation of ZnO blended with Parangtritis beach sand (BS) catalysts for oxidative desulfurization of dibenzothiophene (ODS-DBT) has been conducted. The ZnO-BS catalysts were prepared by blending ZnO with beach sand under a weight ratio of 1:1, 1:2, and 1:4, and then heated by microwave (MW) at 540 watts for 30 min, resulting in BS-MW, ZnO-MW, ZnO-BS-1-MW, ZnO-BS-2-MW, and ZnO-BS-4-MW, respectively. As a comparison, the ZnO-BS-1 was also heated by oven at 100 °C for 30 min produced ZnO-BS-1-OV. Each product was characterized by XRF, XRD, FTIR, acidity test by NH3 vapor adsorption, SAA, SEM-EDX, TEM, and magneticity test by an external magnetic field. Furthermore, each material was applied for ODS-DBT, and its product was analyzed by UV-Vis spectrophotometer and FTIR. The results showed that ZnO-BS-1-OV had the highest acidity of 2.3486 mmol/g and produced the highest DBT removal efficiency through the ODS reaction of 81.59%. The use of catalysts in ODS-DBT does not affect the main structure of the treated fuel. Therefore, the combination of ZnO with BS can provide good performance in ODS activity and facilitate the separation of catalysts after the reaction due to its magnetic iron oxide content.

VO2 uniformly supported by 3D g-C3N4: A highly effective catalyst for deep oxidative desulfurization

A supported catalyst VO2/3D g-C3N4 was prepared by calcination and hydrothermal reduction method. Characterizations proved that the synthesized carrier g-C3N4 is a three-dimensional material with a porous structure. The loading process was to the benefit of the uniform dispersion of the VO2, while the shortcoming of easy agglomeration was overcome and the catalytic activity was improved. Through characterization and activity testing, the composition, morphology and desulfurization performance of VO2/3D g-C3N4 were analyzed. Experimental results showed that 10% VO2/3D g-C3N4 could activate molecular oxygen under milder conditions, which could further oxidize sulfur compounds in the model oil into easily removable sulfones, and deep desulfurization was achieved. The free radical elimination experiments, ESR, and GC–MS analyses were taken to find out the possible desulfurization mechanism. Molecular oxygen was activated into superoxide radical, which efficiently oxidized dibenzothiophene (DBT) to the DBT sulfone (DBTO2). Furthermore, 10% VO2/3D g-C3N4 still had high desulfurization efficiencies after 10 cycles.

Ionic Liquid-Based Polyoxometalate Incorporated at ZIF-8: A Sustainable Catalyst to Combine Desulfurization and Denitrogenation Processes

An effective and sustainable process capable of simultaneously execute desulfurization and denitrogenation of fuels is in fact an actual necessity in the refinery industry. The key to achieve this goal is the parallel oxidation of sulfur and nitrogen compounds present in fuels, which is only achieved by an active and recovered catalyst. A novel heterogeneous catalyst was successfully prepared by the encapsulation of an imidazolium-based polyoxometalate (POM) into a ZIF-8 framework ([BMIM]PMo12@ZIF-8). This composite material revealed exceptional catalytic efficiency to concurrently proceed with the oxidative desulfurization and denitrogenation of a multicomponent model fuel containing various sulfur and nitrogen compounds. A complete removal of all these compounds was achieved after only one hour and the catalyst system was able to be reused for ten consecutive cycles without loss of efficiency. In fact, an ionic liquid POM was incorporated in the ZIF-8 for the first time, and this composite compound was originally applied as a catalyst for simultaneous oxidative desulfurization and denitrogenation processes.