Oxygen Sulfide Research Articles

Selective Late-Stage Oxygenation of Sulfides with Ground-State Oxygen by Uranyl Photocatalysis.

Oxygenation is a fundamental transformation in synthesis. Herein, we describe the selective late-stage oxygenation of sulfur-containing complex molecules with ground-state oxygen under ambient conditions. The high oxidation potential of the active uranyl cation (UO22+ ) enabled the efficient synthesis of sulfones. The ligand-to-metal charge transfer process (LMCT) from O 2p to U 5f within the O=U=O group, which generates a UV center and an oxygen radical, is assumed to be affected by the solvent and additives, and can be tuned to promote selective sulfoxidation. This tunable strategy enabled the batch synthesis of 32 pharmaceuticals and analogues by late-stage oxygenation in an atom- and step-efficient manner.

Surface decorated cobalt sulfide as efficient catalyst for oxygen evolution reaction and its intrinsic activity

Here, we report an efficient surface decorated, e.g. oxidation and nitrogen doped, cobalt sulfide (O-N-Co9S8) oxygen electrocatalyst, which shows excellent activity especially for oxygen evolution reaction (OER), and good stability over 900 charge-discharge cycles at 10 mA cm−2 in Zinc-air battery. Moreover, we found that O-N-Co9S8 was completely converted into Co3O4 after OER, showing oxide is actual active phase. Density functional theory calculations reveal the continuous exposure of oxidized surface Co sites during O-N-Co9S8 → Co3O4 is essential for its high OER activity. These Co sites promote the kinetics for OH∗ transformation to O∗ and also ensure fast O2 desorption. Once Co3O4 is generated, the high activity is contributed by its resulting characteristic surfaces. Thus, we propose and demonstrate that oxides in-situ generated during OER are more active than the directly calcined oxides. This work advances fundamental insight of metal chalcogenides “catalysts” and guides the design of active OER catalysts.

Oxygenation of sulfides catalysed by SBA‐15‐immobilized molybdenum(VI) complex of a bis(phenol) diamine ligand using aqueous hydrogen peroxide as a green oxidant

A highly efficient and reusable molybdenum‐based catalyst has been synthesized by covalent grafting of a bis(phenol) diamine ligand, namely 2‐(((2‐bromoethyl)(2‐((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)amino)ethyl)amino)methyl)‐4,6‐di‐tert‐butylphenol, onto functionalized ordered mesoporous silica (SBA‐15) followed by complexation with MoO2(acac)2. The resulting organic–inorganic hybrid material was found to be a highly effective catalyst for oxygenation of various sulfides to their corresponding sulfoxides or sulfones. The catalyst was characterized using transmission and scanning electron microscopies, X‐ray photoelectron, Fourier transform infrared and atomic absorption spectroscopies, Brunauer–Emmett–Teller surface area analysis and thermogravimetric analysis. Mild reaction conditions, high selectivity and easy recovery and reusability of the catalyst render the presented protocol very useful for addressing industrial needs and environmental concerns.

Heptamolybdate: a highly active sulfide oxygenation catalyst.

The sulfide oxygenation activities of both heptamolybdate ([Mo7O24]6-, [1]6-) and its peroxo adduct [Mo7O22(O2)2]6- ([2]6-) were examined in this contribution. [Mo7O22(O2)2]6- was prepared in a yield of 65% from (NH4)6[Mo7O24] (1a) upon treatment of 10 equiv. of H2O2 and structurally identified through single crystal X-ray diffraction study. (nBu4N)6[Mo7O22(O2)2] (2b) is an efficient catalyst for the sequential oxygenation of methyl phenyl sulfide (MPS) by H2O2 to the corresponding sulfoxide and subsequently sulfone with a 100% utility of H2O2. Surprisingly, (nBu4N)6[Mo7O24] (1b) is a significantly faster catalyst than 2b for MPS oxygenation under identical conditions. The pseudo-first order kcat constants from initial rate kinetics are 54 M-1 s-1 and 19 M-1 s-1 for 1b and 2b, respectively. Electrospray ionization mass spectrometry (ESI-MS) investigation of 1b under the catalytic reaction conditions revealed that [Mo2O11]2- is likely the main active species in sulfide oxygenation by H2O2.

A Membrane-Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalyst.

Polymer electrolyte membranes employed in contemporary fuel cells severely limit device design and restrict catalyst choice, but are essential for preventing short-circuiting reactions at unselective anode and cathode catalysts. Herein, we report that nickel sulfide Ni3 S2 is a highly selective catalyst for the oxygen reduction reaction in the presence of 1.0 m formate. We combine this selective cathode with a carbon-supported palladium (Pd/C) anode to establish a membrane-free, room-temperature formate fuel cell that operates under benign neutral pH conditions. Proof-of-concept cells display open circuit voltages of approximately 0.7 V and peak power values greater than 1 mW cm-2 , significantly outperforming the identical device employing an unselective platinum (Pt) cathode. The work establishes the power of selective catalysis to enable versatile membrane-free fuel cells.

A Membrane‐Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalyst

AbstractPolymer electrolyte membranes employed in contemporary fuel cells severely limit device design and restrict catalyst choice, but are essential for preventing short‐circuiting reactions at unselective anode and cathode catalysts. Herein, we report that nickel sulfide Ni3S2 is a highly selective catalyst for the oxygen reduction reaction in the presence of 1.0 m formate. We combine this selective cathode with a carbon‐supported palladium (Pd/C) anode to establish a membrane‐free, room‐temperature formate fuel cell that operates under benign neutral pH conditions. Proof‐of‐concept cells display open circuit voltages of approximately 0.7 V and peak power values greater than 1 mW cm−2, significantly outperforming the identical device employing an unselective platinum (Pt) cathode. The work establishes the power of selective catalysis to enable versatile membrane‐free fuel cells.

Inside Cover: A Membrane‐Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalyst (Angew. Chem. Int. Ed. 26/2017)

Inside Cover: A Membrane‐Free Neutral pH Formate Fuel Cell Enabled by a Selective Nickel Sulfide Oxygen Reduction Catalyst (Angew. Chem. Int. Ed. 26/2017)

Two titanium(iv)-oxo-clusters: synthesis, structures, characterization and recycling catalytic activity in the oxygenation of sulfides

Two 5-sulfosalicylic acid (H3ssal) and 1,10-phenanthroline (Phen) substituted titanium-oxo-clusters, [Ti6O8 (Hssal)2(Phen)6(H2O)4]·4OH·21H2O (TOC-1) and [Ti4O4(Hssal)4(Phen)4]·18H2O·4NH3 (TOC-2), have been synthesized and fully characterized by single crystal X-ray diffraction, FT-IR spectroscopy, elemental analysis, thermogravimetric analysis and fluorescence analysis. The structure of TOC-1 is a hexanuclear cluster containing a {Ti6(μ2-O)8} core, where all titanium ions can be described in a distorted octahedral geometry with both 1,10-phenanthroline and 5-sulfosalicylate serving as chelating ligands, while TOC-2 consists of a tetranuclear {Ti4(μ2-O)4} skeleton forming an approximate plane quadrilateral where both 5-sulfosalicylate and 1,10-phenanthroline ligands chelate to the titanium atom and the oxygen atom bridges two titanium atoms. Moreover, catalytic activity for the selective oxidation of sulfides, methyl phenyl sulfide (MPS) and phenyl sulfide (PPS), has also been explored. The results showed that TOCs 1 and 2 exhibit excellent catalytic performance in the oxidation of sulfides to sulfoxides with H2O2 as an oxidant. In particular, TOC-1 is an efficient homogeneous catalyst and very interestingly it can be recovered by filtration upon cooling and then reused at least four times without losing activity, which is very rare in the oxygenation of organic sulfides.

Assessment of sulfide production risk in soil during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification process.

This study aimed to determine the potential of sulfide generation during infiltration through soil of domestic wastewater treated by a sulfur-utilizing denitrification process. Three types of soil with different permeability rates (K s = 0.028, 0.0013, and 0.00015cm/s) were investigated to evaluate the potential risk of sulfur generation during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system. These soils were thoroughly characterized and tested to assess their capacity to be used as drainages for wastewaters. Experiments were conducted under two operating modes (saturated and unsaturated). Sulfate, sulfide, and chemical oxygen demand (COD) levels were determined over a period of 100days. Despite the high concentration of sulfates (200mg/L) under anaerobic conditions (ORP = -297mV), no significant amount of sulfide was generated in the aqueous (<0.2mg/L) or gaseous (<0.15ppm) phases. Furthermore, the soil permeability did not have a noticeable effect on the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system due to low contents of organic matter (i.e., dissolved organic carbon, DOC). The autotrophic denitrification process used to treat the domestic wastewater allowed the reduction of the concentration of biochemical oxygen demand (BOD5) below 5mg/L, of DOC below 7mg/L, and of COD below 100mg/L.

Characterisation and comparison of corrosion products originated in steel pipelines transporting sour gas and crude oil

In this work, X-ray diffraction and Mössbauer spectroscopy techniques were used to characterise and carry out a comparison of the corrosion products obtained during the pigging activities in two sour-hydrocarbon-transporting pipelines located in the Gulf of Mexico: the first one being a gas pipeline and the other one a crude oil pipeline. The results indicate that for these specific conditions, there are differences between the corrosion products formed in each pipeline. Iron sulphides and oxides were the main corrosion products and their presence is directly related to the operating conditions prevailing in the pipelines as well as to the hydrocarbon quality. As for the sour gas pipeline, higher concentrations of greigite and pyrite were observed, whereas more proportions of magnetite, mackinawite and marcasite were found in the sour crude oil pipeline. The most important parameters in the formation of the different types of corrosion products are the water content, hydrogen sulphide concentration and oxygen presence in the system.

Photocatalytic Oxygenation of Sulfide and Alkenes by Trinuclear Ruthenium Clusters.

Trinuclear Ru cluster photocatalysts that contain two Ru(II) photosensitizers and a Ru(II) reaction center are prepared, and their activity in the photocatalytic oxygenation of a sufide and alkenes is investigated. Photoirradiation (visible light) and the use of a Co salt ([Co(NH3)5Cl]Cl2, as an electron acceptor) are found to be essential for these catalytic reactions. The O atom of the water solvent (pH 6.8) is transferred to the substrate by a stepwise electron transfer and deprotonation of an aqua ligand at the reaction center. Through these processes, the aqua ligand coordinated at the reaction center is converted to a Ru(V)═O species, which is the active intermediate in the sulfide and alkene oxygenation.

Photoredox catalysis for oxygenation/deoxygenation between sulfides and sulfoxides by visible-light-responsive polyoxometalates

We report the visible-light-responsive photoredox catalysis of a lacunary silicotungstate for selective aerobic oxygenation of sulfides and deoxygenation of sulfoxides.

Molybdenum-doped α-MnO2 as an efficient reusable heterogeneous catalyst for aerobic sulfide oxygenation

In the presence of Mo6+-doped α-MnO2 (Mo–MnO2), various sulfides could efficiently be oxidized to the corresponding sulfoxides as the major products. In addition, Mo–MnO2 could repeatedly be reused.

Dirhodium(II)-Catalyzed Sulfide Oxygenations: Catalyst Removal by Coprecipitation with Sulfoxides.

The dirhodium(II) carboxylate complex Rh2(esp)2 (esp = α,α,α',α'-tetramethyl-1,3-benzenedipropanoate) was shown to catalyze the sulfoxidation of organic sulfides using tert-butyl hydroperoxide as the oxidant. Due to the unique structure of Rh2(esp)2 and its stable Rh2(II,II) catalyst resting state, the rhodium catalyst is able to precipitate as a Rh2(esp)2-sulfoxide complex following the reaction which makes separation of the catalyst from the products very convenient. The precipitated Rh2(esp)2-sulfoxide complexes could be reused to catalyze sulfide oxygenation reactions without considerable loss of activity. Mechanistic studies suggest that the axial ligands fine-tune the redox potential of the dirhodium(II,II) compounds and determine the predominant catalyst species in the oxidation reaction.

Influence of Plastic Waste for Refuse-Derived Fuel on Downdraft Gasification

The potential of syngas production from used- and unused-plastic-waste Refuse-Derived Fuels (RDFs) by downdraft type fixed bed gasification technology is investigated. The purpose of this study is to investigate the syngas compositions of used- and unused-plastic-waste RDFs in the downdraft type fixed bed gasification system. It is found that used- and unused-plastic-waste RDFs can be successfully converted to generate the syngas consisting of carbon monoxide, carbon dioxide, hydrocarbon, hydrogen sulfide oxygen and water vapor. The performance of the downdraft type fixed bed gasification system is evaluated in terms of the composition of syngas and the rate of carbon monoxide production. The result can be concluded that syngas produced from the used- and unused-plastic-waste RDFs is the same. The HHV (Higher Heating Value) of the syngas from the unused-plastic-waste RDF (781kJ/Nm3) is slightly higher than that of the used one (500kJ/Nm3). It is also suggested that the gasification of used- and unused-plastic-waste RDFs is a clean alternative to fossil fuels. Moreover, the syngas can be directly used in the internal gas combustion engines.

Peroxo-dimolybdate catalyst for the oxygenation of organic sulfides by hydrogen peroxide

The reaction between Na2MoO4 and hydrogen peroxide at pH around 6.5 resulted in a novel peroxo-dimolybdate anion [{MoO(O2)2}2(μ-O)]2−, which was isolated as a tetrabutylammonium salt (1). X-ray single crystal diffraction study of 1 revealed that there are two η2-peroxo ligands for each Mo center and a single μ-oxo bridge linking two Mo(VI) centers. Compound 1 can function as a stoichiometric oxidant for the oxygenation of organic sulfides and donate up two active oxygen atoms. Furthermore, 1 catalyzes organic sulfide oxygenation by hydrogen peroxide with 100% utility. The catalytic proficiency of 1 was examined with the oxygenation reactions of substrates including benzyl phenyl sulfide, methyl phenyl sulfide and 4-bromo thioanisole with TOF of 240, 550 and 740h−1, respectively. Based on the initial rate study of several para-substituted thioanisoles, a reactivity constant (ρ) of −1.06 was obtained, which implies an electron deficient transition state. The initial rate study using thioanisole as the substrate also revealed that the reaction is first order in catalyst but zero order in hydrogen peroxide. Based on these results, a mechanism for the activation of hydrogen peroxide is proposed. The DFT calculations of model catalyst and substrate resulted in an activation energy of 75kJmol−1 for the transition state, and a reaction free energy of −69kJmol−1.

Facile control of the charge density and photocatalytic activity of an anionic indium porphyrin framework via in situ metalation.

An anionic indium porphyrin framework (UNLPF-10) consisting of rare Williams β-tetrakaidecahedral cages was constructed using an octatopic ligand linked with 4-connected [In(COO)4](-) SBUs. Remarkably, the extent of indium metalation of porphyrin macrocycles in UNLPF-10 can be facilely tuned in situ depending on the M/L ratio during synthesis, resulting in a controllable framework charge density and photocatalytic activity toward the selective oxygenation of sulfides.

Diruthenium(II,III) tetracarboxylates catalyzed H2O2 oxygenation of organic sulfides

Diruthenium(II,III) tetracarboxylates, Ru2(OAc)4Cl (A), Ru2(esp)2Cl (B, esp=tetramethyl-1,3-benzenedipropionate) and Ru2(3-HB)4Cl (C, 3-HB=3-hydroxybenzoate) were investigated for activating hydrogen peroxide in organic sulfide oxygenation. The speciation of the substrate and potential products, sulfoxide and sulfone, were investigated for each catalyst. With methyl phenyl sulfide as the substrate, A simultaneously produces sulfoxide and sulfone, B yields the highest turnover with complete conversion to sulfoxide at 6min before sulfone appears, and C facilitates complete conversion to sulfoxide in 20min but little subsequent conversion to sulfone. The dependence of the initial reaction rate on catalyst and H2O2 concentrations were investigated. A small set of other sulfides were subjected to catalytic reactions with C, and all reactions resulted in near quantitative conversion. Finally, the sulfide oxygenation activity and stability towards hydrogen peroxide of the diphosphonate complex Na4[Ru2(hedp)2(H2O)Cl] (D, hedp=1-hydroxyethylidenediphosphonate) was investigated, and D was found to be an effective catalyst, which retains its activity over an extended period of time due to its robustness at the (III,III) oxidation state.

Polyoxometalate [γ-SiW10O34(H2O)2]4− on MCM-41 as catalysts for sulfide oxygenation with hydrogen peroxide

The polyoxometalate (POM) catalyst, [γ-SiW10O34(H2O)2]4−, was introduced into the pores of both as-synthesized (I) and amine functionalized MCM-41 (II). The resultant catalysts were characterized with powder X-ray diffraction, nitrogen sorption, and diffuse-reflectance UV–vis spectroscopy. Both catalysts were tested for reusability through repeated catalytic conversions of methyl phenyl sulfide to methyl phenyl sulfone with hydrogen peroxide. While the physisorbed catalyst (I) exhibits steadily decreasing turnover frequency (TOF), the POM catalyst supported on MCM-41 functionalized with a protonated amine (II) exhibits markedly improved reusability. This chemisorbed catalyst effectively showed no change in TOF between the second (21) and the sixth reactions (22). Additionally, sulfoxidations with catalyst II were investigated with a small set of substrates focusing on compounds including dibenzothiophene, which serves as a model refractory sulfide.

Diverse silver(i) sulfobenzoate coordination polymers and their recycling property as homogeneous catalyst in oxygenation of sulfide

Four silver sulfobenzoate coordination polymers with bpmb ligands were prepared. The variable positions of sulfonate groups on benzene rings gave rise to different coordination polymers and variable chemical properties.