Synthesis and characterization of new hybrid inorganic–organic polymer nanocomposite as efficient catalyst for oxidative desulfurization of real fuel

Sulfur-containing compounds are responsible for much air pollution, and therefore eliminating these compounds is of importance. Herein, a hybrid organic–inorganic recyclable nanocatalyst (TBA-PW₁₁Ni@PANI) was synthesized successfully to investigate its effects on the catalytic oxidative desulfurization (CODS) process of real gasoline/model fuel. To this end, the Keggin-based mono-lacunary polyoxometalate [PW₁₁NiO₃₉] was prepared and modified with quaternary cation tetrabutylammonium (TBA). Then, this was further immobilized on polyaniline (PANI) via the sol–gel method. The synthesized nanocomposite was characterized using various techniques. The high dispersion of polyoxometalate on PANI was confirmed. Also, it was found that the crystalline structure remained unaltered after immobilization. In addition, the effects of various parameters such as dosage and temperature on the CODS of model fuel in the presence of H₂O₂–acetic acid (1:2 v/v) were studied in detail. Moreover, the kinetics of the CODS process was also studied and a mechanism proposed. According to the results, TBA-PW₁₁Ni@PANI showed an efficiency of up to 97% with 0.1 g at 35°C (optimum values) which implies its good catalytic functionality in the CODS process. Finally, the TBA-PW₁₁Ni@PANI catalyst displayed long-term stability and good reusability after five runs.     

Facile synthesis of inorganic–organic Fe2W18Fe4@NiO@CTS hybrid nanocatalyst induced efficient performance in oxidative desulfurization of real fuel

In this work, a new nanocatalyst, Fe₂W₁₈Fe₄@NiO@CTS, was synthesized by the reaction of sandwich‐type polyoxometalate (Fe₂W₁₈Fe₄), nickel oxide (NiO), and chitosan (CTS) via sol–gel method. The assembled nanocatalyst was systematically characterized by FT‐IR, UV–vis, XRD, SEM, and EDX analysis. The catalytic activity of Fe₂W₁₈Fe₄@NiO@CTS was tested on oxidative desulfurization (ODS) of real gasoline and model fuels. The experimental results revealed that the levels of sulfur content and mercaptan compounds of gasoline were lowered with 97% efficiency. Also, the Fe₂W₁₈Fe₄@NiO@CTS nanocatalyst demonstrated an outstanding catalytic performance for the oxidation of dibenzothiophene (DBT) in the model fuel. The major factors that influence the desulfurization efficiency and the kinetic study of the ODS reactions were fully detailed and discussed. The probable ODS pathway was proposed via the electrophilic mechanism on the basis of the electrophilic characteristic of the metal‐oxo‐peroxo intermediates. The prepared nanocatalyst could be reused for 5 successive runs without any appreciable loss in its catalytic activity. As a result, the current study suggested the potential application of the Fe₂W₁₈Fe₄@NiO@CTS hybrid nanocatalyst as an ideal candidate for removal of sulfur compounds from fuel.     

Desulfurization of model and real fuels by extraction and oxidation processes using an indenylmolybdenum tricarbonyl pre-catalyst

Regulations on the permissible levels of sulfur in transportation fuels are becoming ever more strict, with a global shift towards “zero sulfur” fuels, and the revamp of existing hydrodesulfurization (HDS) facilities to meet these lower caps is cost-prohibitive. Metal-catalyzed sulfoxidation chemistry is viewed as an economically viable desulfurization strategy that could complement conventional HDS technology. In the present work, the complex [η⁵-IndMo(CO)₃Me] ( 1 ) (Ind = indenyl) was employed in the catalytic oxidative desulfurization (CODS) of model and real liquid fuels, using aqueous hydrogen peroxide (H₂O₂) as oxidant. After optimization of the CODS reaction parameters (diesel/H₂O₂ ratio, catalyst amount, temperature), a high-sulfur (2000 ppm) model diesel containing benzothiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene could be completely desulfurized within 2 hr under solvent-free conditions or in the presence of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) as extraction solvent. The catalyst formed under solvent-free conditions could be recycled without a significant decrease in desulfurization activity. The high performance of the CODS system was verified in the sulfur removal from a commercial untreated diesel fuel with a sulfur content of 2300 ppm, and a jet fuel with a sulfur content of 1100 ppm. Solvent-free CODS in combination with initial/final extraction gave desulfurization efficiencies of 70% for the diesel fuel and 55% for the jet fuel. CODS with [BMIM]PF₆ in combination with initial/final extraction led to a sulfur removal of 95.9% for the diesel fuel, which is one of the best results yet reported for ODS of commercial diesels.     

磷钼杂多酸离子液体催化氧化脱硫

 合成了新型的磷钼杂多酸离子液体 [hmim]3PMo12O40, 并将其用于室温离子液体 1-甲基咪唑四氟硼酸盐 ([hmim]BF4) 为溶剂的模拟油品氧化脱硫反应. 结果表明, 在温和的反应条件下, 过氧化氢与硫摩尔比为 4:1 时, 二苯并噻吩脱硫率为 90%, 二苯硫醚、苯甲硫醚和二乙硫醚的脱除率可达 100%. 离子液体催化体系循环使用 4 次后, 脱硫率没有明显下降.     

Methane Carboxylation Using Electrochemically Activated Carbon Dioxide

Direct synthesis of CH₃COOH from CH₄ and CO₂ is an appealing approach for the utilization of two potent greenhouse gases that are notoriously difficult to activate. In this Communication, we report an integrated route to enable this reaction. Recognizing the thermodynamic stability of CO₂, our strategy sought to first activate CO₂ to produce CO (through electrochemical CO₂ reduction) and O₂ (through water oxidation), followed by oxidative CH₄ carbonylation catalyzed by Rh single atom catalysts supported on zeolite. The net result was CH₄ carboxylation with 100 % atom economy. CH₃COOH was obtained at a high selectivity (>80 %) and good yield (ca. 3.2 mmol g⁻¹_cat in 3 h). Isotope labelling experiments confirmed that CH₃COOH is produced through the coupling of CH₄ and CO₂. This work represents the first successful integration of CO/O₂ production with oxidative carbonylation reaction. The result is expected to inspire more carboxylation reactions utilizing preactivated CO₂ that take advantage of both products from the reduction and oxidation processes, thus achieving high atom efficiency in the synthesis.     

Synthesis and non-parametric evaluation studies on high performance of catalytic oxidation-extraction desulfurization of gasoline using the novel TBAPW11Zn@TiO2@PAni nanocomposite

In this work, the new catalyst (assigned as TBAPW₁₁Zn@TiO₂@PAni) was successfully designed and synthesized on the basis of quaternary ammonium salt of zinc monosubstituted phosphotungstate [(n-C₄H₉)₄N][PW₁₁ZnO₃₉] (TBAPW₁₁Zn), titanium dioxide (TiO₂), and polyaniline (PAni). This study reports the catalytic oxidation-extraction desulfurization (ECODS) of sulfur-containing molecules from real and the simulated (Th, BT, and DBT) gasoline using new organic–inorganic hybrid catalyst (TBAPW₁₁Zn@TiO₂@PAni). The ECODS results were shown that the concentration of sulfur compounds (SCs) of real gasoline was lowered from 0.4992 to 0.0122 wt.% with 97% efficiency at 35 °C after 1 h. Furthermore, the synthesized heterogeneous nanocatalyst showed high stability and reusability after five times without significant loss of activity. The high performance of TBAPW₁₁Zn@TiO₂@PAni/H₂O₂/CH₃CO₂H system can be a promising route with a superb potential in the generation of ultra-low-sulfur gasoline. Also the Mann–Whitney U-test results show that there is not a significant difference between the mean of sulfur percentage for DBT & BT, BT & Th and DBT & Th in the presence of the catalyst. Based on the Kruskal–Wallis test results, we can conclude that the temperature, time and amount of catalyst have a significant effect on ECODS efficiency of TBAPW₁₁Zn@TiO₂@PAni nanocomposite.     

Highly stable polyoxometalate‐resorcin[4]arene‐based inorganic‐organic complexes for catalytic oxidation desulfurization

Self‐assembly of a resorcin[4]arene‐based ligand (TMR4A) with metal salts and H₃PMo₁₂O₄₀·xH₂O offers two isostructural complexes, namely, [Ni₂Cl(TMR4A)₂(CH₃CN)₂]·[PMo₁₂O₄₀]·4CH₃CN ( 1 ) and [Co₂Cl(TMR4A)₂(CH₃CN)₂]·[PMo₁₂O₄₀]·4CH₃CN ( 2 ). In both 1 and 2 , one Cl^? anion bridges two metal cations, and each metal cation is further chelated by four 2‐mercaptopyridine N‐oxide groups of one TMR4A, producing a [M₂Cl(TMR4A)₂]³⁺ dimer (M = Ni or Co). The negative [PMo₁₂O₄₀]^3? as a counter‐anion balances the positive charge. Markedly, 1 and 2 exhibit high stability in aqueous solutions with different pH values and in organic solvents. Remarkably, the efficient heterogeneous catalytic capability for oxidative desulfurization was studied by suing 1 and 2 as recycled catalysts. Moreover, the electrochemical behaviors of the two compounds were discussed as well.     

Radiation stability of trivalent antimony in the presence of organic acids

The gamma ray induced oxidation of Sb(III) in sulfuric acid solutions was studied. A simplified method depending on selective extraction of the different valency states and radiometric counting was elaborated for oxidation yield determination. The effect of increasing amounts of HCOOH, CH₃COOH, NH₂CH₂COOH, CH₃CHOH COOH and H₂C₂O₄ on G[-Sb(III)] was examined. The study enabled a determination of rate constant values for reactions of the used additives with the OH radical in the working solutions.     

Synthesis and characterization of new organic–inorganic nanohybrid film (TBA)PWFe/PVA/CTS as an efficient and reusable amphiphilic catalyst for ODS of real fuel

In this work, we report a new catalytic oxidative desulfurization (CODS) system based on (TBA)PWFe/PVA/CTS nanohybrid film as a highly active catalyst. The nanohybrid material was successfully fabricated by the composition of tetra (n‐butyl) ammonium salt of Fe‐substituted phosphotungstate, ((n‐C₄H₉)₄N)₄[PW₁₁Fe(H₂O)O₃₉] abbreviated as (TBA)PWFe, polyvinyl alcohol (PVA), and chitosan (CTS). The composite was characterized using various analytical techniques including FT‐IR, UV–vis, XRD, and SEM. The results revealed the hydrogen‐bonding interaction between inorganic (TBA)PWFe clusters and organic polymers. The catalytic activity of (TBA)PWFe/PVA/CTS was evaluated in the CODS of real gas oil. Also, the solutions of heterocyclic thiophenic compounds (HTCs) in n‐heptane were tasted as simulated fuels. It was found that the removal efficiency of HTCs in the presence of (TBA)PWFe/PVA/CTS catalyst reached as high as 95% at 60 °C after 2 h. The significant catalytic performance of the nanohybrid film might be attributed to its amphiphilicity and multifunctional active sites, which enhances adsorption and oxidation of sulfur compounds. Moreover, the (TBA)PWFe/PVA/CTS composite can be easily recovered and reused by simple filtration, making it a suitable catalyst for cleaner processing.     

Photocatalytic desulfurization of thiophene base on molecular oxygen and zinc phthalocyanine/g-C3N4

Oxidative desulfurization is considered to be one of the promising new methods for super-deep desulfurization of fuel oil. Herein, zinc phthalocyanine/g-C₃N₄ (g-C₃N₄/ZnTcPc) composites were synthesized by a facile in situ hydrothermal technique, utilizing g-C₃N₄, Zn(CH₃COO)₂ and 1,2,4-benzenetricarboxylic anhydride as the precursors. The crystal structure, morphology and chemical environment of the catalysts were respectively confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the resulting g-C₃N₄/ZnTcPc composites was evaluated by desulfurization of thiophene in fuel under visible light with molecular O₂ as the oxidant. Compared with pure g-C₃N₄ and ZnTcPc, g-C₃N₄/ZnTcPc presented a significantly enhanced photocatalytic activity for the degradation of thiophene in fuel under visible irradiation. Sulfur content of model gasoline (800 ppm) after desulfurization for 90 min was decreased to 125 ppm. The possible preparation pathway of g-C₃N₄/ZnTcPc has been proposed according to the results of XRD and TEM. The formation mechanism of g-C₃N₄/ZnTcPc–O₂ complex is proposed to be desulfurization by molecular oxygen.

     

Deep oxidative desulfurization of dibenzothiophene with molybdovanadophosphoric heteropolyacid-based catalysts

Three hydrophobic Keggin-type heteropolyacid catalysts, [C₃H₃N₂(CH₃)(C₂H₄)]₅PMo₁₀V₂O₄₀ ([C₂mim]PMoV), [C₃H₃N₂(CH₃)(C₄H₈)]₅PMo₁₀V₂O₄₀ ([C₄mim]PMoV) and [C₃H₃N₂(CH₃)(C₆H₁₂)]₅PMo₁₀V₂O₄₀ ([C₆mim]PMoV), were synthesized by reacting molybdovanadophosphoric acid with imidazolium bromides, and characterized by spectroscopic methods. Their use as catalysts in the extractive catalytic oxidative desulfurization process using hydrogen peroxide as the oxidant and acetonitrile as phase transfer agent was studied. The catalytic properties decreased in the order: [C₆mim]PMoV > [C₄mim]PMoV > [C₂mim]PMoV. The main factors influencing the rate of removal of dibenzothiophene (DBT) were investigated, including reaction temperature, the amounts of catalyst, H₂O₂ and acetonitrile. Nearly 100 % sulfur removal rate was achieved under optimal conditions. The catalyst could be recycled six times with only a slight decrease in activity. A reaction mechanism for DBT oxidation is proposed, in which the Keggin anions first obtain active oxygen from H₂O₂, then the DBT is oxidized to dibenzothiophene sulfones.     

A novel hybrid material based on two symmetrically independent Keggin polyoxoanions: [NH3-CH(CH3)COOH][H3O]8[PMo12O40]3.4NH3CH(CH3)COO

Novel polyoxometalate-based organic-inorganic hybrid [NH₃-CH(CH₃)COOH][H₃O]₈[PMo₁₂O₄₀]₃.4NH₃CH(CH₃)COO was synthesized and characterized by ³¹P, ¹H, ¹³C NMR and IR spectroscopies, elemental analysis and single crystal X-ray determination. Two of the PMo₁₂O₄₀ ^3? anions in the title hybrid are symmetrically equivalent. They are crystallographically independent from the third PMo₁₂O₄₀ ^3? polyoxoanion, in the case of various interactions with neighboring components in the crystal network (i.e. ⁺NH_3-CH(CH₃)-COOH and H₃O⁺ cations, ₊NH₃CH(CH₃)COO^? zwitterions and polyoxoanions). The compound crystallizes in an orthorhombic C222 space group with a = 16.0392(16) Å, b = 34.480(4) Å, c = 12.8968(13) Å and Z = 2.     

Heterogenized magnetic graphene oxide-supported N6-Schiff base Cu (II) complex as an exclusive nanocatalyst for synthesis of new pyrido[2,3-d]pyrimidine-7-carbonitrile derivatives

In this article, the synthesis of a novel and highly efficient recyclable and reusable heterogeneous nanocatalyst has been reported via the functionalizing of the Fe₃O₄-magnetized graphene oxide nanosheets with the N₆-Schiff base Cu (II) complex (GO/Fe₃O₄@SPNC). The structure of this novel nanocatalyst was determined by different analytical techniques such as FTIR, FE-SEM, TEM, TGA-DTG, and VSM. The catalytic activity of the synthesized GO/Fe₃O₄@SPNC nanocatalyst was explored for the synthesis of several new 2H-pyrido[3′,2′:6,7]pyrano[2,3-d]pyrimidine-7-carbonitrile derivatives with excellent yields. All new derivatives were fully identified by various spectral (¹H NMR, ¹³C NMR, FT-IR, ESI-MS) analyses. In addition, this nanocatalyst carried out satisfactory catalytic maintenance of activity and high chemical stability in the titled reactions after seven-time of recycling without substantial loss of leaching.     

Molybdovanadophosphoric Acid Catalyzed Oxidation of Hydrocarbons by H2O2 to Oxygenates

Heteropoly acids of the general formula H_3+x[PMo_12-xV_xO₄₀] (where x = 1,2,3) catalyzed the oxidation of aromatic hydrocarbons at 65°C with H₂O₂ to give oxygenated products. Among the catalysts, H₄[PMo₁₁VO₄₀] was found to be a more active catalyst and its activities have been reported in the oxidation of cyclohexane, methyl cyclohexane, naphthalene, 1-methyl naphthalene and biphenyl.     

Synthesis, crystal structure and properties of a charge-transfer compound [(CH3)3CNH3]3[PMo12O40] · 2H2O

A charge-transfer compound [(CH₃)₃CNH₃]₃[PMo₁₂O₄₀] · 2H₂O was synthesized and characterized by IR, UV, ESR, diffusion reflectance electronic spectrum, cyclic voltammogram and X-ray crystallography. Oxygen atoms of the polyoxometalate anion, N atoms of organic substrates (CH₃)₃CNH₂ and O atoms of water molecules are involved in hydrogen bonding. The solid reflectance electronic spectra and IR data indicate the presence of interaction between the [PMo₁₂O₄₀]³⁻ and the organic substrates in the solid state. Photosensitivity to ultraviolet light was assessed for the compound, showing that charge-transfer resulted from oxidation of the organic substrates and the reduction of the heteropolyanion.     

Isatin‐SO3H coated on amino propyl modified magnetic nanoparticles (Fe3O4@APTES@isatin‐SO3H) as a recyclable magnetic nanoparticle for the simple and rapid synthesis of pyrano[2,3‐d] pyrimidines derivatives

Isatin‐SO₃H coated on amino propyl modified magnetic nanoparticles (Fe₃O₄@APTES@isatin‐SO₃H) is found to be a novel, efficient, and reusable magnetic nanocatalyst, and characterized by FT‐IR, SEM, TEM, XRD, EDX, VSM, and TGA analysis. The magnetic nanocatalyst demonstrated outstanding performance in synthesis of pyrano[2,3‐d] pyrimidines derivatives via one‐pot three‐component reaction of various aromatic aldehydes 1, malononitrile 2, and barbituric acid 3 under reflux conditions in mixture of H₂O:EtOH (1:1) as solvent. Easy workup procedure, short reaction time, high yield, simple preparation and easy recovery of the catalyst, mild reaction conditions are some advantages of this work.     

Oxidation of natural rubber using a sodium tungstate/acetic acid/hydrogen peroxide catalytic system

A catalytic system based on Na₂WO₄/CH₃COOH/H₂O₂ effectively oxidizes natural rubber (NR) to prepare telechelic epoxidised liquid natural rubber (TELNR). The Na₂WO₄/CH₃COOH/H₂O₂ catalytic system possesses a much higher epoxidation efficiency than the traditional CH₃COOH/H₂O₂ system: the epoxidation degree (X_epoxy) of products increases from merely 5.6% (CH₃COOH/H₂O₂) to values as high as 52.1% (Na₂WO₄/CH₃COOH/H₂O₂) by reacting for 24 h at 60 °C. Moreover, this catalytic system also induces hydrolytic degradation so that the weight average molecular weight of NR decreases, e.g., from 14.10 × 10⁵ Da (NR) to 0.57 × 10⁵ Da (TELNR) after reacting for 30 h.The catalytic process probably proceeds via a mononuclear tungsten peroxo-species with coordinated peracetyl/acetyl group, as suggested by ESI-MS measurements. During oxidation, the tungstic anion [W(CH₃COOO)(O)(O₂)₂]⁻ not only catalyzes NR epoxidation, but also induces a further oxidation of epoxy groups to form ketones and aldehydes.     

Mn(III) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalyst for selective oxidation of thiols to disulfides

A manganese(III) complex, [Mn(phox)₂(CH₃OH)₂]ClO₄ (phox?=?2-(2′-hydroxyphenyl)oxazoline), was immobilized on silica-coated magnetic Fe₃O₄ nanoparticles through the amino propyl linkage using a grafting process in dichloromethane. The resulting Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The nanocatalyst was recycled several times. Leaching and recycling experiments revealed that the nanocatalyst can be recovered, recycled, and reused more than five times, without the loss of catalytic activity and magnetic properties. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000. The heterogeneous Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticle shows more selectivity for the formation of disulfides in comparison with the homogeneous manganese complex.     

Hydrothermal syntheses, crystal structures, and properties of two polyoxometalates [Cd(2,2′-bpy)3]2[PMoVMoVI 11O40] and [H3PMo12O40]·3(4,4′-bpy)·4H2O

Two Keggin-type phosphododecamolybdate compounds [Cd(2,2′-bpy)₃]₂[PMo^VMo^VI ₁₁O₄₀] (1) and [H₃PMo₁₂O₄₀]·3(4,4′-bpy)·4H₂O (2) (bpy=bipyridine) were prepared by the hydrothermal method for the first time and characterized by elemental analyses, X-ray single-crystal diffraction, ESR spectra, and IR spectra, showing that compound 1 consists of a mixed valence Keggin polyanion [PMo^VMo^VI ₁₁O₄₀]⁴⁻ and two isolated coordinated cations [Cd(2,2′-bpy)₃]²⁺, while compound 2 is an intermolecular compound based on organic substrate 4,4′-bpy and heteropoly acid unit H₃PMo₁₂O₄₀. Furthermore, both the compounds show strong photoluminescence properties in the solid state at room temperature. The catalytic activities of the two compounds were also determined by the oxidation of benzaldehyde to benzoic acid using H₂O₂ as oxidant in a liquid–solid triphase system.     

Oxychlorination of methane to methyl chloride at 300°C in the system palladium(II) complexes-heteropolyacids-silica gel

The activity of systems, applied to silica gel from chloride solutions, in the oxychlorination of CH₄ to CH₃Cl at 300° Cincreases in the order H₃[PMo₁₂O₄₀]9[PMo₆V₆O_40]2(PdCl₂-H₉[PMo₆V₆O₄₀] (or H₃[PMo₁₂O₄₀]))<(PdCl₂-Na_nH_9–n[PMo₆V₆O₄₀]). Additions of NaCl (molar ratio of the components NaClSiO₂7100) lead to an increase in the yield of CH₃Cl. The mechanisms of CH₄ oxidation have been discussed which are electrophilic with the participation of Pd(II) complexes and involve chlorides with the participation of surface Cl atoms.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 1, pp. 29–33, January–February, 1995.