Heterogeneous Oxidative Desulfurization Research Articles

Multifunctional Aryl Sulfonium Decavanadates: Tuning the Photochromic and Heterogeneous Oxidative Desulfurization Catalytic Properties Using Salicylaldehyde-type Functional Moieties on Counterions.

Multifunctional materials based on polyoxovanadates (POVs) have rarely been reported. Herein, we used aryl sulfonium counterions (ASCIs) bearing a salicylaldehyde-type functionality to tune the properties of decavanadate ([V10O28]6-)-based hybrids for their application in photochromism and heterogeneous oxidative desulfurization (ODS) catalysis. The counterions FHPDS ((3-formyl-4-hydroxyphenyl)dimethylsulfonium), DFHPDS ((3,5-diformyl-4-hydroxyphenyl)dimethylsulfonium), and EFPDS ((4-ethoxy-3-formylphenyl)dimethylsulfonium) were clubbed with the decavanadate cluster to generate the hybrids (FHPDS)4[H2V10O28](H2O)4 (HY1), (DFHPDS)4[H2V10O28](H2O)3 (HY2), and (EFPDS)4[H2V10O28](H2O)6 (HY3). The photochromic properties of these hybrids were tested under 365 nm irradiation, which showed a color change from yellow to green. Different hybrids exhibited different photocoloration half-life (t1/2) values in the range of 0.77-28.38 min, suggesting the dependence of the photocoloration properties upon functional groups on the counterions. The hybrid HY2, having a 2,6-diformyl phenol moiety on the ASCI, exhibited an impressive t1/2 of 0.77 min. UP to 70% reversibility of photocoloration was achieved for the best photochromic hybrid HY2 in 48 h at 70 °C under an oxygen atmosphere. Theoretical and experimental data suggested that some of these aryl sulfonium POVs follow a different e--h+ stabilization mechanism than traditional sulfonium POM hybrids. Further, the salicylaldehyde-type ASCIs control the solubility of the decavanadate hybrids, which enables their application as heterogeneous catalysts for the selective oxidation of various sulfides. The nature of the substituents on the ASCIs also affected their catalytic activities; the counterion that facilitates the reversible V4+/V5+ switching enhances the catalytic ODS efficiency of the hybrids. Using HY2 as the catalyst, up to 99% conversion and 96% selectivity toward sulfones were achieved in dibenzothiophene (DBT) oxidation. The present study suggests a new promising approach for controlling POVs' photoresponsive and catalytic properties by using ASCIs bearing salicylaldehyde-type functional moieties.

Heterogeneous oxidative desulfurization of fuels using amphiphilic mesoporous phosphomolybdate-based poly(ionic liquid) over a wide temperature range

Four new types of amphiphilic polyoxometalate-based poly(ionic liquid) (PDB-PMo, PDO-PMo, PDD-PMo and PDH-PMo) were prepared by ion exchange between poly(ionic liquid) (PIL) and H3PMo12O40 (HPMo), where PIL are copolymerized by hydrophilic 3,3′-methylenebis(1-vinylimidazol) bromine and hydrophobic [3–alkyl–1–vinylimidazolium] bromine (alkyl = C4, PDBBr; alkyl = C8, PDOBr; alkyl = C12, PDDBr and alkyl = C16, PDHBr). Among them, the desulfurization rate of PDD-PMo can reach 100% within a wide temperature range of 0–50 °C, especially at 0 °C, DBT can be completely removed within 100 min. The influences of reaction temperature, molar ratio of H2O2/S, catalyst dosage and different sulfur-containing compounds were investigated. The kinetic study shows that the apparent activation energy of the DBT oxidation reaction is 36.73 ± 1.42 kJ/mol. In addition, EPR analysis and the free radical quenching experiment proved that both active radicals O2•− and HO• played an active role in the oxidative desulfurization (ODS) reaction system and proposed a reasonable reaction mechanism. The introduction of hydrophilic IL monomer is also an efficient strategy to construct amphiphilic polyoxometalate-based poly(ionic liquid), which further implements ultra-deep desulfurization.

Designing polyoxometalate based hybrid catalysts for efficient removal of hazardous sulfur from fuel via heterogeneous oxidative desulfurization

Hydrodesulfurization is a common but less effective technique to remove sulfur content of oils due to severe operating conditions of temperature, pressure and cost. Oxidative desulfurization(ODS) is preferable due to low cost and mild operating conditions. Coupling of the extractive catalytic desulfurization with the ODS give rise to extractive catalytic oxidative desulfurization(ECODS), a more promising for the elimination of sulfur contents of fuel oil. Herein we present by polyoxometalate based hybrids, [H2TPP][K5BVW11O40]•2CH3CN•2H2O (1), [H2TPP]2[K3BVW11O40]•CH3CN•3H2O (2), and [H2TPP]3[KBVW11O40]•2CH3CN (3) for efficient ECODS of hazardous model fuel. These were synthesized by facile method and characterized by elemental analysis, inductive couple plasma, powder X-ray diffraction analysis, thermo-gravimetric/differential thermal analysis, fourier transform infrared, and UV–visible analysis. These polyoxometalate based hybrids contain cations [H2TPP]2+(organic) and [BVW11O40]7−(inorganic) with stoichiometric ratios(i.e., 1:1, 2:1, 3:1). The stoichiometry of these hybrids was also established by Job’s analysis which agreed well with the results of TG-DTA and elemental analyses. Interestingly, an increase in catalytic efficiency is observed with increase of organic cations. The maximum ∼99.5 % conversion of dibenzothiophene at 60 °C after 2 h has been achieved with hybrid 3 which could be employed up to ten cycles without a significant decrease in efficiency.

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.

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.

Phosphomolybdic ionic liquid supported hydroxyapatite for heterogeneous oxidative desulfurization of fuels

With the continual air pollution and environmental issues caused by the combustions of sulfur-containing fuels, the desulfurization in transport fuels becomes a crucial topic worldwide. In this study, a kind of phosphomolybdic ionic liquid–supported hydroxyapatite was successfully designed and employed as a catalyst for heterogeneous oxidative desulfurization in fuel. The prepared catalysts were characterized via Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET), which confirmed that phosphomolybdic ionic liquid was successfully immobilized on hydroxyapatite. With the prepared sample n-[Pmim]PMo/HAP, the sulfur removal could reach 97.2% under mild conditions. Furthermore, the supported catalyst has excellent recyclability and utilization foreground.

A Lacunary Polyoxovanadate Precursor and Transition‐Metal‐Sandwiched Derivatives for Catalytic Oxidation of Sulfides

A SeO3 centered lacunary Keggin-type heteropolyoxovanadate (hetero-POV) K6H2[SeV10O28(SeO3)3]·14H2O (1) was isolated by one-pot reaction of KVO3 and SeO2 under acidic condition. X-ray studies revealed that it comprised a single {VO5}-capped trivacant B-α-type Keggin ion [SeV9O33(VO)]14- with its lacunary sites decorated by three {SeO3} pyramids. Interestingly, this new basic hetero-POV building block was further used as precursor to assembly with different transtion metal (TM) ions, yielding a series of TM-sandwiched POVs K6H8[(SeV10O28(SeO3)3)2(M(H2O)4)]·24H2O (M2+ = Mn2+ (2), Co2+ (3), Zn2+ (4)). All four compounds were characterised by single-crystal X-ray structure analysis, IR, XPS, EPR, and 51V NMR spectroscopy. Importantly, three TM-sandwiched derivatives exhibited effective catalytic activity for the heterogeneous oxidative desulfurization of sulfides at room temperature.

Fast heterogeneous oxidative desulfurization of dibenzothiophene from ionic liquids supported urchin-liked meso-silica

As air pollution and green-house effect have caused numerous environmental problems in past decades, and increasing investigations have been focused on reducing the emission of harmful gas such as SOx. Oxidative desulfurization of fuel is considered as a promising method for its high efficiency and mild condition. Herein, ionic liquids supported urchin-liked meso-silica were facilely prepared and applied for heterogeneous oxidative desulfurization, which had a good dispersion of polyoxometalate ionic liquids. With the prepared materials, sulfur compounds can be efficiently removed. Moreover, the oxidation product was analyzed by GC-MS to further investigate reaction mechanism.

Heterogeneous oxidative desulfurization catalysed by titanium grafted mesoporous silica nanoparticles containing tethered hydrophobic ionic liquid: A dual activation mechanism

In this study, heterogeneous catalysts containing ionic liquid and/or titanium have been prepared and used for oxidative desulfurization. For the synthesis of hybrid mesoporous silica nanoparticles (ILBF4-MSN), a grafting method has been employed with the ionic liquid 1-octyl-3-(3-(triethoxysilyl)propyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate (ILBF4) which contains a long alkyl chain. Titanium hybrid mesoporous silica nanoparticles (ILBF4-x%TiCp2-MSN) and mesoporous silica nanoparticles containing titanium (TiCp2-MSN) have also been prepared using titanocene dichloride. The catalyst containing ionic liquid and titanium, ILBF4-3%TiCp2-MSN exhibited the highest desulfurization efficiency (99.1%) in model oil with high concentration of DBT and using H2O2 as oxidant. In addition, the effect of immobilization of the ionic liquid on titanium materials has been investigated by solid-state 13C, 47/49Ti and 19F NMR spectroscopy and solid state electrochemical techniques. The titanium species and ionic liquid play an important role in the oxidative desulfurization reaction since they might activate synergistically sulfur derivatives and enhance the process.

Synthesis of highly dispersed phosphotungstic acid encapsulated in MIL-100(Fe) catalyst and its performance in heterogeneous oxidative desulfurization

Highly efficient HPW(x)/MIL-100(Fe) catalysts with different phosphotungstic acid (HPW) loading (x, wt%) were successfully synthesized by a one-step hydrothermal method and characterized by XRD, SEM, FTIR, and BET. The influences of HPW loading, catalyst dosage, temperature, and O/S molar ratio on oxidative desulfurization (ODS) were investigated. The results indicated that the HPW(x)/MIL-100(Fe) retained the structure of its parent MIL-100(Fe). The MIL-100(Fe) presented a high surface area, which is beneficial to dispersion of HPW. The HPW(x)/MIL-100(Fe) with HPW loading of 40% exhibited excellent ODS activity. At a temperature of 50 °C, a catalyst dosage of 0.06 g, and an O/S molar ratio of 4, 100% desulfurization was achieved within 90 min for benzothiophene, dibenzothiophene, and 4,6-dimethyl-dibenzothiophene. The high catalytic activity of HPW(x)/MIL-100(Fe) can be attributed to highly dispersed HPW active sites with a high specific surface area.

Polyoxometalate-based silica-supported ionic liquids for heterogeneous oxidative desulfurization in fuels

With the aim of deep desulfurization, silica-supported polyoxometalate-based ionic liquids were successfully prepared by a one-pot hydrothermal process and employed in heterogeneous oxidative desulfurization of various sulfur compounds. The compositions and structures of the hybrid samples were characterized by various methods such as FT-IR, XPS, Raman, UV–Vis, wide-angle XRD and N2 adsorption–desorption. The experimental results indicated that the hybrid materials presented a high dispersion of tungsten species and excellent catalytic activity for the removal of 4,6-dimethyldibenzothiophene without any organic solvent as extractant, and the sulfur removal could reach 100.0% under mild conditions. The catalytic performance on various substrates was also investigated in detail. After cycling seven cycles, the sulfur removal of the heterogeneous system still reached 93.0%. The GC-MS analysis results demonstrated that the sulfur compound was first adsorbed by the catalyst and subsequently oxidized to its corresponding sulfone.

Ionic liquid-supported 3DOM silica for efficient heterogeneous oxidative desulfurization

DBT is absorbed by IL-3DOM SiO2 and then oxidized to DBTO2 in the presence of H2O2.

A Polyoxovanadate-Resorcin[4]arene-Based Porous Metal-Organic Framework as an Efficient Multifunctional Catalyst for the Cycloaddition of CO2 with Epoxides and the Selective Oxidation of Sulfides.

In this work, we report a new polyoxovanadate-resorcin[4]arene-based metal-organic framework (PMOF), [Co2L0.5V4O12]·3DMF·5H2O (1), assembled with a newly functionalized wheel-like resorcin[4]arene ligand (L). 1 features an elegant porous motif and represents a rare example of PMOFs composed of both a resorcin[4]arene ligand and polyoxovanadate. Remarkably, 1 shows open V sites in the channel, which makes 1 an efficient heterogeneous Lewis acid catalyst for the cycloaddition of carbon dioxide to epoxides with high conversion and selectivity. Strikingly, 1 also exhibits high catalytic activity for the heterogeneous oxidative desulfurization of sulfides. Particularly, the heterogeneous catalyst 1 can be easily separated and reused with good catalytic activity.

Heterogeneous oxidative desulfurization for model fuels using novel PW-coupled polyionic liquids with carbon chains of different lengths

Abstract Novel PW-coupled polyionic liquids with different alkyl chain lengths, poly(1-n-ethyl-3-vinylimidazolium bromide) (PEVImPW), poly(1-n-butyl-3-vinylimidazolium phosphotungstate) (PBVImPW), poly (1-n-octyl-3-vinylimidazolium phosphotungstate) (POVImPW), and poly(1-n-dodecyl-3-vinylimidazolium phosphotungstate) (PDVImPW), have been successfully synthesized and characterized by FTIR, XRD, TG, 13C NMR, 31P NMR, ICP and CHN elemental analysis. The obtained catalysts have been applied in heterogeneous oxidative desulfurization (ODS) processes. Their ODS performances have been studied. The results indicated PBVImPW was revealed to be a highly efficient catalyst and the benzothiophene removal of 99% was achieved in 2.5 h, 50 °C. The catalyst could be recycled four times.

Heterogeneous oxidative desulfurization of diesel fuel catalyzed by mesoporous polyoxometallate-based polymeric hybrid

In this work, the simple preparation of novel polymer supported polyoxometallates (POMs) catalysts has been reported. Soluble task-specific cross-linked poly (ionic liquid) (PIL) was prepared with N,​N-​dimethyl-​dodecyl-​(4-​vinylbenzyl) ammonium chloride and divinylbenzene as co-monomers. The as-prepared cationic PILs were assembled with different commercial POMs to form the interlinked mesoporous catalysts, and the formation mechanism was provided. The catalytic oxidation activities of the catalysts were closely related to the formation pathway of their corresponding peroxide active species. The catalyst with H2W12O4210− as counterion, which exhibited the best activity in the oxidation of benzothiophene (BT) and dibenzothiophene (DBT) to sulfones in model oil with hydrogen peroxide (H2O2, 30wt%) as oxidant, was characterized by different techniques and systematically studied for its sulfur removal performance. As for the oxidative desulfurization of a real diesel, it was observed that almost all of the original sulfur compounds could be completely converted, and the catalyst could be reused for at least eight cycles without noticeable changes in both catalytic activity and chemical structure. In the end, a catalytic mechanism was put forward with the assistant of Raman analysis.

Fabrication and characterization of tungsten-containing mesoporous silica for heterogeneous oxidative desulfurization

A series of functional, tungsten-containing mesoporous silica materials (W-SiO2) have been fabricated directly from an ionic liquid that contained imidazole and polyoxometalate, which acted as mesoporous template and metal source respectively. These materials were then characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectra (FTIR), diffuse reflectance spectra (DRS), and N2 adsorption-desorption, which were found to contain tungsten species that were effectively dispersed throughout the structure. The as-prepared materials W-SiO2 were also found to possess a mesoporous structure. The pore diameters of the respective sample W-SiO2-20 determined from the TEM images ranged from 2 to 4 nm, which was close to the average pore size determined from the nitrogen desorption isotherm (2.9 nm). The materials were evaluated as catalysts for the heterogeneous oxidative desulfurization of dibenzothiophene (DBT), which is able to achieve deep desulfurization within 40 min under the optimal conditions (Catalyst (W-SiO2-20) = 0.01 g, temperature = 60 °C, oxidant (H2O2) = 20 µL). For the removal of different organic sulfur compounds within oil, the ability of the catalyst (W-SiO2-20) under the same conditions to remove sulfur compounds decreased in the order: 4,6-dimethyldibenzothiophene > Dibenzothiophene > Benzothiophene > 1-dodecanethiol. Additionally, they did not require organic solvents as an extractant in the heterogeneous oxidative desulfurization process. After seven separate catalytic cycles, the desulfurization efficiency was still as high as 90.3%. From the gas chromatography-mass spectrometer analysis, DBT was entirely oxidized to its corresponding sulfone DBTO2 after reaction. A mechanism for the heterogeneous desulfurization reaction was proposed.

Heterogeneous oxidative desulfurization of diesel oil by hydrogen peroxide: Catalysis of an amphipathic hybrid material supported on SiO2

Abstract Here we described a catalytic system for oxidation of benzothiophene (BT), dibenzothiophene (DBT), or 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) in model oil by catalysis using a hybrid material ([Bmim] 3 PW 12 O 40 ) supported on SiO 2 . The [Bmim] 3 PW 12 O 40 was synthesized by reacting H 3 PW 12 O 40 with 1-butyl-3-methyl imidazolium bromide. The experimental results demonstrated that the SiO 2 -supported catalyst with 20 wt.% [Bmim] 3 PW 12 O 40 exhibited a high catalytic activity, achieving the DBT, 4,6-DMDBT, and BT conversions of 100%, 100%, and 71.6% at 50 °C, atmospheric pressure, and H 2 O 2 /DBT molar ratio of 3.0 in 100 min. The catalyst was recycled conveniently by filtration and reused for seven times without a significant decrease on the activity. The reused catalyst can recover the oxidation activity only by drying at 100 °C for 4 h. This extraction and catalytic oxidative desulfurization (ECODS) system can remove 98.2% sulfur-contenting compounds from the diesel oil with sulfur-containing of 445 mg/L.