Aerobic Oxidation Of Sulfides Research Articles

Decavanadates anchored into micropores of graphene-like boron nitride: Efficient heterogeneous catalysts for aerobic oxidative desulfurization

Catalytic aerobic oxidation of aromatic sulfides to their corresponding sulfones could provide a novel route for producing fuels with ultra-low sulfur content, solving the increasingly severe air pollution problems. In this work, a series of heterogeneous catalysts were synthesized by anchoring decavanadate ionic liquids (ILs) into the micropores of graphene-like hexagonal boron nitride (g-BN). The as-prepared catalysts could inherit both the catalytic ability of polyoxometalate ILs (POM-ILs) and the separation efficiency of g-BN. Besides, the usage amount of POM-ILs could be reduced sharply. Under the optimized reaction conditions, sulfur removal of dibenzothiophene (DBT), as one of the most stubborn residuals in oil refining process, could rise up to 99.8% (≤1 ppm) in this proposed adsorptive and aerobic oxidative desulfurization (AAODS) process. In addition, excellent sulfur removal with oils of different sulfide concentrations, substrates and aromatics/olefins addition could also be achieved. Moreover, renewable recycling performance with 99.4% sulfur removal was observed after 6 times recycle. Finally, a possible reaction process was proposed depending on the experiment evidence from different aspects.

The effect of oxygen availability on long‐distance electron transport in marine sediments

AbstractCable bacteria are long, multicellular, filamentous bacteria that can conduct electrons over centimeter distances in marine and freshwater sediments. Recent studies indicate that cable bacteria are widely present in many coastal environments, where they exert a major influence on the biogeochemistry of the sediment. Their energy metabolism can be based on the aerobic oxidation of sulfide, and hence to better understand their natural occurrence and distribution, we examined the growth and activity of cable bacteria in relation to bottom water oxygenation. To this end, we conducted laboratory sediment incubations at four different O2 levels in the overlying water (10%, 20%, 40%, and 100% air saturation). The abundance of cable bacteria was determined by fluorescence in situ hybridization, while their activity was assessed via microsensor profiling and geochemical pore‐water analysis. Cable bacteria did not develop in the 10% air saturation O2 incubation but were present and active at all higher O2 levels. These data show that microbial long‐distance electron transport can occur under a wide range of bottom water O2 concentrations. However, the growth rate was notably slower at lower oxygen concentrations, suggesting a reduced metabolic activity of the population when the O2 supply becomes restricted. Finally, in response to lower O2 levels, cable bacteria filaments appear to partially emerge out of the sediment and extend into the overlying water, thus likely enhancing their oxygen supply.

Hollow Anatase TiO2 Octahedrons with Exposed High-Index {102} Facets for Improved Dye-Sensitized Photoredox Catalysis Activity.

The high activity of exposed facets and large surface area have significant effects on the performance of photocatalysts because most of the photoreactivity properties of materials are related to surface processes. The strategy of combining high-index facets and a hollow structure into one material will provide a new way for designing effective photocatalysts, possessing active exposed facets and a large surface area at the same time. However, fabricating one material with both high-index facets and a hollow structure is still a great challenge due to their thermodynamic instability. Here, hollow anatase TiO2 octahedrons exposed with high-index (102) facets (HTO-102) were successfully fabricated for the first time by a facile hydrothermal method using HF and H2O2 as morphology controlling agents. Compared with two other catalysts (a solid sharp octahedron with (101) facets (SSO-101) and a hollow sharp octahedron with (101) facets (HSO-101)), HTO-102 particles exhibit a better photochemical activity for the selective aerobic oxidation of organic sulfides under visible-light irradiation. Experimental results and theoretical calculations indicate that the excellent photocatalytic activity of HTO-102 particles is mainly due to the synergistic effects of its hollow structure and exposed high-index (102) facets.

Differential depth distribution of microbial function and putative symbionts through sediment-hosted aquifers in the deep terrestrial subsurface

An enormous diversity of previously unknown bacteria and archaea has been discovered recently, yet their functional capacities and distributions in the terrestrial subsurface remain uncertain. Here, we continually sampled a CO2-driven geyser (Colorado Plateau, Utah, USA) over its 5-day eruption cycle to test the hypothesis that stratified, sandstone-hosted aquifers sampled over three phases of the eruption cycle have microbial communities that differ both in membership and function. Genome-resolved metagenomics, single-cell genomics and geochemical analyses confirmed this hypothesis and linked microorganisms to groundwater compositions from different depths. Autotrophic Candidatus “Altiarchaeum sp.” and phylogenetically deep-branching nanoarchaea dominate the deepest groundwater. A nanoarchaeon with limited metabolic capacity is inferred to be a potential symbiont of the Ca. “Altiarchaeum”. Candidate Phyla Radiation bacteria are also present in the deepest groundwater and they are relatively abundant in water from intermediate depths. During the recovery phase of the geyser, microaerophilic Fe- and S-oxidizers have high in situ genome replication rates. Autotrophic Sulfurimonas sustained by aerobic sulfide oxidation and with the capacity for N2 fixation dominate the shallow aquifer. Overall, 104 different phylum-level lineages are present in water from these subsurface environments, with uncultivated archaea and bacteria partitioned to the deeper subsurface.

Preparation of gold clusters on metal oxides by deposition-precipitation with microwave drying and their catalytic performance for CO and sulfide oxidation

Gold clusters and small nanoparticles supported on metal oxides could be prepared by deposition-precipitation followed by microwave irradiation as a drying method and then calcination. The drying method influenced the size of the Au particles. Au(III) was partly reduced during conventional oven drying, resulting in Au aggregates. In contrast, Au(III) was preserved during microwave drying owing to rapid and uniform heating, and the Au diameter was minimized to 1.4 nm on Al2O3. This method can be applied to several metal oxide supports having different microwave absorption efficiencies, such as MnO2, Al2O3, and TiO2. These catalysts exhibited higher catalytic activities for CO oxidation at low temperature and for selective aerobic oxidation of sulfide than those prepared by conventional methods.

The sulfur depot in the rhizosphere of a common wetland plant, Juncus effusus, can support long-term dynamics of inorganic sulfur transformations

The sulfur cycle in the rhizosphere of constructed wetlands is frequently interlaced with transformations of carbon and nitrogen. Knowledge about the manifold sulfur transformations may thus aid in improving treatment performance of constructed wetlands. In this study, two laboratory-scale constructed wetland models (planted fixed bed reactors; PFR1 and PFR2) were used to investigate inorganic sulfur transformations at various total loads of sulfate and organic carbon. Sulfate, sulfide and elemental sulfur were the most abundant sulfur compounds detected, thus providing evidence for the simultaneous occurrence of dissimilatory sulfate reduction and sulfide oxidation. This co-occurrence was likely enabled by oxygen micro-gradients in the root-near environment, i.e. aerobic sulfide and elemental sulfur oxidation took place mostly at the roots while sulfate and elemental sulfur reduction occurred in the pore water under reduced redox conditions. The rhizosphere was found to be first sink, then source for sulfur during the course of the experiment. Immobilization of reduced sulfur was triggered by catabolism of organic matter coupled to dissimilatory sulfate reduction and the subsequent partial oxidation of generated sulfide. Good plant status was critical for sulfur deposition in the systems. Without externally provided sulfate the sulfur depot of the rhizosphere was a prolonged source for sulfur, which was remobilized into the pore water. Oscillations between sulfide and sulfur (PFR1) or sulfide and sulfate (PFR2) suggested a dynamic interplay between plants and various microbial guilds, i.e. dissimilatory sulfate and sulfur reducers on one side and sulfide and sulfur oxidizers on the other.

ChemInform Abstract: Visible‐Light‐Induced Photoredox Catalysis of Dye‐Sensitized Titanium Dioxide: Selective Aerobic Oxidation of Organic Sulfides.

AbstractThe title reaction provides sulfoxides together with small amounts of the corresponding sulfones.

Visible-Light-Induced Photoredox Catalysis of Dye-Sensitized Titanium Dioxide: Selective Aerobic Oxidation of Organic Sulfides.

TiO2 photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by the fact that TiO2 can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal-free dye onto the surface of TiO2. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O2. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible-light photoredox catalysis.

Visible‐Light‐Induced Photoredox Catalysis of Dye‐Sensitized Titanium Dioxide: Selective Aerobic Oxidation of Organic Sulfides

AbstractTiO2 photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by the fact that TiO2 can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal‐free dye onto the surface of TiO2. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO [(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl] ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O2. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible‐light photoredox catalysis.

Linkages between mineralogy, fluid chemistry, and microbial communities within hydrothermal chimneys from the Endeavour Segment, Juan de Fuca Ridge.

Rock and fluid samples were collected from three hydrothermal chimneys at the Endeavour Segment, Juan de Fuca Ridge to evaluate linkages among mineralogy, fluid chemistry, and microbial community composition within the chimneys. Mössbauer, midinfrared thermal emission, and visible-near infrared spectroscopies were utilized for the first time to characterize vent mineralogy, in addition to thin-section petrography, X-ray diffraction, and elemental analyses. A 282°C venting chimney from the Bastille edifice was composed primarily of sulfide minerals such as chalcopyrite, marcasite, and sphalerite. In contrast, samples from a 300°C venting chimney from the Dante edifice and a 321°C venting chimney from the Hot Harold edifice contained a high abundance of the sulfate mineral anhydrite. Geochemical modeling of mixed vent fluids suggested the oxic-anoxic transition zone was above 100°C at all three vents, and that the thermodynamic energy available for autotrophic microbial redox reactions favored aerobic sulfide and methane oxidation. As predicted, microbes within the Dante and Hot Harold chimneys were most closely related to mesophilic and thermophilic aerobes of the Betaproteobacteria and Gammaproteobacteria and sulfide-oxidizing autotrophic Epsilonproteobacteria. However, most of the microbes within the Bastille chimney were most closely related to mesophilic and thermophilic anaerobes of the Deltaproteobacteria, especially sulfate reducers, and anaerobic hyperthermophilic archaea. The predominance of anaerobes in the Bastille chimney indicated that other environmental factors promote anoxic conditions. Possibilities include the maturity or fluid flow characteristics of the chimney, abiotic Fe2+ and S2- oxidation in the vent fluids, or O2 depletion by aerobic respiration on the chimney outer wall.

Respirometric characterization of aerobic sulfide, thiosulfate and elemental sulfur oxidation by S-oxidizing biomass

Respirometry was used to reveal the mechanisms involved in aerobic biological sulfide oxidation and to characterize the kinetics and stoichiometry of a microbial culture obtained from a desulfurizing biotrickling filter. Physical–chemical processes such as stripping and chemical oxidation of hydrogen sulfide were characterized since they contributed significantly to the conversions observed in respirometric tests. Mass transfer coefficient for hydrogen sulfide and the kinetic parameters for chemical oxidation of sulfide with oxygen were estimated. The stoichiometry of the process was determined and the different steps in the sulfide oxidation process were identified. The conversion scheme proposed includes intermediate production of elemental sulfur and thiosulfate and the subsequent oxidation of both compounds to sulfate. A kinetic model describing each of the reactions observed during sulfide oxidation was calibrated and validated. The product selectivity was found to be independent of the dissolved oxygen to hydrogen sulfide concentration ratio in the medium at sulfide concentrations ranging from 3 to 30 mg S L−1. Sulfide was preferentially consumed (SOURmax = 49.2 mg DO g−1 VSS min−1) and oxidized to elemental sulfur at dissolved oxygen concentrations above 0.8 mg DO L−1. Substrate inhibition of sulfide oxidation was observed (Ki,S2− = 42.4 mg S L−1). Intracellular sulfur accumulation also affected negatively the sulfide oxidation rate. The maximum fraction of elemental sulfur accumulated inside cells was estimated (25.6% w/w) and a shrinking particle equation was included in the kinetic model to describe elemental sulfur oxidation. The microbial diversity obtained through pyrosequencing analysis revealed that Thiothrix sp. was the main species present in the culture (>95%).

ChemInform Abstract: Fe(NO3)3·9H2O‐Catalyzed Aerobic Oxidation of Sulfides to Sulfoxides under Mild Conditions with the Aid of Trifluoroethanol.

Abstract Selective oxidation of sulfides to sulfoxides was successfully performed by employing readily available Fe(NO 3 ) 3 ·9H 2 O as the active catalyst with oxygen as the oxidant in 2,2,2-trifluoroethanol (TFE) without the formation of sulfones. Nitrate anion could play a crucial role in promoting the reaction due to the oxidation capacity under acidic media. High yields of sulfoxides were exclusively obtained from the corresponding sulfides. Furthermore, both aromatic and aliphatic sulfides gave moderate to high yields of sulfoxides with this protocol.

ChemInform Abstract: Synergistic Photocatalytic Aerobic Oxidation of Sulfides and Amines on TiO2 under Visible‐Light Irradiation.

AbstractTiO2 acts as a photocatalyst in the synergistic aerobic oxidation of aryl sulfides and benzylamines.

ChemInform Abstract: Efficient and Convenient Oxidation of Sulfides to Sulfoxides with Molecular Oxygen Catalyzed by Mn(OAc)2 in Ionic Liquid [C12mim][NO3

A simple, efficient, and eco-friendly procedure for aerobic oxidation of sulfides catalyzed by Mn(OAc)2/[C12mim][NO3] has been developed. The reactions afford the target products in good to high yields and no over-oxidation was observed. The products can be easily separated, and the catalytic system can be recycled without loss of catalytic activity.

Closing the Nutrient Cycle in Two-Stage Anaerobic Digestion of Industrial Waste Streams

Industrial waste streams from brewing industries and distilleries provide a valuable but largely unused alternative substrate for biogas production by anaerobic digestion. High sulfur loads in the feed caused by acidic pretreatment to enhance bioavailability are responsible for H2S formation during anaerobic digestion. Microbiological oxidation of H2S provides an elegant technique to remove this toxic gas compound. Moreover, it allows for recovery of sulfuric acid, the final product of aerobic sulfide oxidation, as demonstrated in this study. Two-stage anaerobic digestion of brewer’s spent grains, the major byproduct in the brewing industry, allows for the release of up to 78% of total H2S formed in the first pre-acidification stage. Desulfurization of such pre-acidification gas in continuous acidic biofiltration with immobilized sulfur-oxidizing bacteria resulted in a maximum H2S elimination capacity of 473 g m–3 h–1 at an empty bed retention time of 91 s. Complete H2S removal was achieved at inlet conce...

Synergistic photocatalytic aerobic oxidation of sulfides and amines on TiO2 under visible-light irradiation.

Selective photocatalytic aerobic oxidation, which can be conducted under ambient conditions, is of great importance towards achieving sustainable chemistry. However, its practical applications are undermined by several challenges, such as low selectivity, sluggish reaction rates, and the requirement of UV light irradiation. Herein, we report a new concept of synergistic photocatalytic oxidation, for which two seemingly irrelevant reactions can be achieved in one photocatalytic system through the synergistic interplay of reactants and catalyst. As proof of concept, two challenging reactions, the aerobic oxidation of sulfide and the aerobic oxidative formylation of amine with methanol, were employed to demonstrate such synergistic photocatalytic aerobic oxidation under visible-light irradiation. This work could pave the way for highly selective photoredox catalysis via rational design based on mechanistic insight.

Tertiary amine mediated aerobic oxidation of sulfides into sulfoxides by visible-light photoredox catalysis on TiO2.

The selective oxidation of sulfides into sulfoxides receives much attention due to industrial and biological applications. However, the realization of this reaction with molecular oxygen at room temperature, which is of importance towards green and sustainable chemistry, remains challenging. Herein, we develop a strategy to achieve the aerobic oxidation of sulfides into sulfoxides by exploring the synergy between a tertiary amine and titanium dioxide via visible-light photoredox catalysis. Specifically, titanium dioxide can interact with triethylamine (TEA) to form a visible-light harvesting surface complex, preluding the ensuing selective redox reaction. Moreover, TEA, whose stability was demonstrated by a turnover number of 32, plays a critical role as a redox mediator by shuttling electrons during the oxidation of sulfide. This work suggests that the addition of a redox mediator is highly functional in establishing visible-light-induced reactions via heterogeneous photoredox catalysis.

Fe(NO3)3·9H2O-catalyzed aerobic oxidation of sulfides to sulfoxides under mild conditions with the aid of trifluoroethanol

Abstract Selective oxidation of sulfides to sulfoxides was successfully performed by employing readily available Fe(NO 3 ) 3 ·9H 2 O as the active catalyst with oxygen as the oxidant in 2,2,2-trifluoroethanol (TFE) without the formation of sulfones. Nitrate anion could play a crucial role in promoting the reaction due to the oxidation capacity under acidic media. High yields of sulfoxides were exclusively obtained from the corresponding sulfides. Furthermore, both aromatic and aliphatic sulfides gave moderate to high yields of sulfoxides with this protocol.

Flavin-Functionalized Gold Nanoparticles as an Efficient Catalyst for Aerobic Organic Transformations

Monolayer-protected gold clusters functionalized with synthetic flavins were synthesized and their catalytic activity in aerobic organic transformations investigated. Gold nanoparticles with 5-ethyl-3-(8-thiooctyl)lumiflavinium perchlorate acts as an efficient catalyst for the aerobic oxidation of organic sulfides to the corresponding sulfoxides upon treatment with hydrazine at room temperature and under atmospheric pressure in oxygen. With a catalytic amount of gold nanoparticles with 3-(8-thiooctyl)lumiflavin, diimide reduction of various olefins can be performed with hydrazine at room temperature under atmospheric pressure in air with greater yields of product alkanes than with non-supported 3-methyllumiflavin catalyst under the same conditions. Kinetic studies revealed that the monolayer-protected gold cluster-catalyzed reactions proceeded faster than those with non-supported catalysts over the full substrate concentration range for the hydrogenation of olefins and at lower substrate concentrations for sulfoxidation. This positive effect was rationalized by assuming a Michaelis–Menten-type mechanism in which the specific inclusion of substrates into the enzyme-like reaction cavities was a key factor in the high efficiency of the supported flavin catalysts.

ChemInform Abstract: PyHBr3/TBN/H2O as Catalytic System for the Oxidation of Sulfides to Sulfoxides with Air as the Oxidant.

AbstractThe title catalyst system allows the aerobic oxidation of sulfides to sulfoxides under very mild and transitions metal free conditions.