Organic Sulfur Compounds Research Articles

Catalytic Asymmetric Reactions of Ketimines and Alkenes via [2 + 2] Cycloaddition: Chemical Reactivity Controlled by Switching a Heteroatom.

Azetidine units are commonly found in natural products and biologically active drugs. The [2 + 2] cycloaddition of imines and alkenes has been extensively used in the synthesis of such structures, while enantioselective approaches remain elusive. Herein, an efficient B(C6F5)3/chiral phosphoric acid-catalyzed asymmetric [2 + 2] cycloaddition of ketimines and aryl vinyl selenides was presented, delivering valuable chiral azetidines with excellent stereoselectivities (>20:1 dr and up to 96:4 er). What's even more interesting was that when a "Se" atom was switched to an "S" atom, the reaction proceeded through a [2 + 2] cycloaddition/ring-opening cascade process, affording a range of chiral thioacetals with high enantioselectivities (up to 98:2 er), which were also important organic sulfur compounds. Mechanistic experiments, coupled with density functional theory (DFT) calculations, shed light on a mechanism involving stepwise [2 + 2] cycloaddition and ring-opening processes, with the initial alkenylation step identified as crucial for achieving stereoselective control.

Regulation of freshwater filamentous green algae (Cladophora) and its impact on malodorous volatile organic sulfur compound (DMS) by biomanipulation

When improving the water quality of natural bodies such as lakes, the explosive growth of filamentous green alga Cladophora can limit the growth of submerged macrophytes and prevent the water from shifting to a clear state. During the decay of Cladophora, it can cause various water quality issues such as reduced dissolved oxygen, increased nutrient levels and water odor. Biomanipulation, involving the introduction of a suitable density of aquatic animals into the water, can reduce the biomass of filamentous algae. We hypothesized that stocking appropriate densities of aquatic animals could reduce filamentous algal biomass and at the same time reduce the concentration of odorants in the water. Our study investigated the impact of stocking swamp shrimp (Macrobrachium nipponense), rosy bitterling (Rhodeus ocellatus), and silver carp (Hypophthalmichthys molitrix) at low (30 g/m3), medium (60 g/m3) and high (120 g/m3) densities on water quality, biomass of primary producers (such as Cladophora, submerged macrophyte and algae) and malodorous volatile organic sulfur compound dimethyl sulfide (DMS) in the water, respectively. It was found that the swamp shrimp treatment groups and the rosy bitterling high-density groups effectively inhibited the growth of filamentous green algae cover, in which the rosy bitterling high-density group reduced the filamentous green algae mat coverage by 29.65 % compared with the control group. Additionally, the high-density swamp shrimp and rosy bitterling groups notably promoted the growth of submerged macrophytes (Vallisneria denseserrulata), and significantly reduced the concentration of the malodorous DMS in the water. Overall, stocking swamp shrimp and rosy bitterling can benefit the restoration of aquatic ecology and the maintenance of clear water. However, it is essential to consider potential changes in water quality resulting from excessive stocking density. Therefore, the appropriate density and proportion of stocking should be determined in conjunction with the specific scale of the aquatic ecological restoration project.

Molecular characteristics of sea spray aerosols during aging with the participation of marine volatile organic compounds

Sea spray aerosols (SSAs) are one of the largest natural sources of aerosols globally, known to affect the earth's radiation budget and to play a pivotal role in air quality and climate. The physical and chemical properties of organic components in SSA change during long-distance atmospheric transport over the ocean. To characterize the evolution of organic components during the aging process of SSA, in this study, we use a flow reactor to simulate the oxidation processes of SSA produced by authentic seawater via OH radicals (in the presence of organic gases evaporated from seawater) and to present the molecular signatures of the nascent and aged SSA. We found, under our experimental conditions, that oxidation of headspace organic gases during aging leads to significant formation of new particles and changes in the chemical constituents of SSA. In the nascent and aged SSA samples, we retained 129 and 340 products, respectively. The formation of high O/C and low carbon-number products was observed during the aging process, corresponding to functionalization and fragmentation reactions. Moreover, the significant contributions of compounds containing multiple nitrogen atoms and sulfate groups were observed in aged SSA for the first time, which can be attributed to the accretion reaction driven by OH heterogeneous oxidation and the formation of organic sulfur compounds, respectively. These findings provide additional insights into the atmospheric transformation of organic components in marine aerosols, which is important for understanding the global carbon cycle.

PetroSulfur: A Gas Chromatography and Mass Spectrometry Database of Organic Sulfur Compounds in Petroleum

PetroSulfur: A Gas Chromatography and Mass Spectrometry Database of Organic Sulfur Compounds in Petroleum

Application of sulfur isotopes of volatile organic sulfur compounds to determine the natural gas secondary alterations and possible sources in the Tarim Basin, NW China

Currently, there are very limited methods for direct gas-source rock correlation studies. Herein, we applied sulfur isotope analyses of individual volatile organic sulfur compounds (VOSC) in natural gases and dibenzothiophenes (DBTs) in the associated oils from Ordovician reservoirs in Shunbei and Tahe areas of the Tarim Basin, and coupled them with characteristics of gaseous hydrocarbons to elucidate gas-source correlation and secondary alterations in the reservoirs. The results show that the VOSCs in some of the gas samples have reached isotopic equilibrium with the associated H2S but with distinct sulfur isotope compositions, suggesting that they may be related to the thermal cracking of kerogen and/or oil, or altered by thermochemical sulfate reduction (TSR). The δ34S values of VOSCs in the gases unaffected by TSR range from +14.9 to +21.3‰, which are correlated well with the Cambrian source rock kerogen and DBTs from its derived oils, indicating the gases may have a Cambrian source. Few gas samples from the Tahe area exhibit higher δ34S values of VOSCs (from +22.9 to +31.6‰) but with no evidence for TSR alteration in the associated oils. This suggests that exogenous TSR-H2S was charged into the reservoirs, and altered the δ34S values of the VOSCs. The sulfur isotopes of VOSCs in a gas sample range from +27.3 to +34.8‰ which are close to the Cambrian anhydrite but are not in isotopic equilibrium with the associated H2S. This suggests that the VOSCs have interacted with recently migrated H2S produced by TSR and the increasing concentrations of H2S might have prevented the system from reaching isotopic equilibrium with the VOSC. Thus, VOSC can provide an additional layer of information when interpreting gas generation and migration processes within a complex basin such as the Tarim Basin.

Zeolitic Framework Ta and MoO3 Confined in Beta Zeolite Cooperatively Enhance Activity and Stability for Oxidative Desulfurization.

Oxidative desulfurization (ODS), as a novel desulfurization technique of fuel oil, possesses high desulfurization efficiency for aromatic sulfide and low cost, making it a promising approach. The key to the technology lies in the rational design of catalysts with high activity and stability. Polyoxometalates, which are environmentally friendly, cost-effective, and abundantly available, face constraints in the development of ODS applications due to their low specific surface area and difficulty in regeneration. Introducing metal oxides into carriers with large specific surface areas to obtain heterogeneous catalysts is an effective solution to this problem. Beta zeolites, with regular three-dimensional channel systems, large specific surface area, and superior thermal/hydrothermal stability, are usually used as carriers. In this work, we developed a strategy to enhance zeolite carrier utilization efficiency by introducing Ta5+ species into the rigid framework of zeolites containing confined MoO3. The Ta species in the zeolite framework and the confined MoO3 produce a synergistic effect, exhibiting extremely high catalytic activity for the aerobic oxidative desulfurization of various organic aromatic sulfur compounds under mild conditions (90 °C and atmospheric pressure) in a deep eutectic solvent, surpassing common heterogeneous catalysts for oxidative desulfurization. Moreover, it can resist the adverse effects of interferents, such as naphthalene and indole. Additionally, the confined nature of Beta zeolite endows it with exceptional stability, demonstrating distinctive recyclability.

Size-dependent influences of nano- and micro-plastics exposure on feeding, antioxidant systems, and organic sulfur compounds in ciliate Uronema marinum

Protozoa play a pivotal role in the microbial cycle, and ciliated protozoan grazing habits are associated with dimethyl sulfide (DMS) cycle. Many studies have explored the impacts of nanoplastics (NPs) and microplastics (MPs) on ecotoxicological effects of ciliates. However, limited research exists on NPs and MPs influences on the production of organic sulfur compounds. The impact of NPs and MPs on the production of dimethyl sulfoxide (DMSO) and carbonyl sulfide (COS) remains unclear. Therefore, we examined the impacts of three concentrations (1 × 105, 5 × 105, and 1 × 106 items/mL) of polystyrene (PS) NPs (50 nm) and MPs (1 and 5 μm) on the ecotoxicology and DMS/dimethylsulfoniopropionate (DMSP)/DMSO/COS production in the ciliate Uronema marinum. NPs and MPs exposure were found to reduce the abundance, growth rate, volume, and biomass of U. marinum. Additionally, NPs and MPs increased the superoxide anion radical (O2˙─) production rates and malondialdehyde (MDA) contents (24 h), leading to a decline in glutathione (GSH) content and an ascend in superoxide dismutase (SOD) activity to mitigate the effects of reactive oxygen species (ROS). Exposure to PS NPs and MPs decreased the ingestion rates of algae by 7.5–14.4%, resulting in decreases in DMS production by 56.8–85.4%, with no significant impact on DMSO production. The results suggest a distinct pathway for the production of DMSO or COS compared to DMS. These findings help us to understand the NPs and MPs impacts on the marine ecosystem and organic sulfur compound yield, potentially influencing the global climate.

Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Removal of sulfur compounds from transportation fuels is a requirement in the worldwide effort to reduce emissions from transportation fuels. Refineries use the hydrodesulfurisation (HDS) process to reduce sulfur compounds in fuels. However, the HDS process requires high hydrogen pressure and temperature, making it costly. An alternative to the HDS process is oxidative desulfurisation via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurise transportation fuels via solvent extraction due to their low-cost. In our study, DESs were synthesised using phenylacetic acid (PAA) and salicylic acid (SAA) as hydrogen bond acceptors (HBAs) and tetraethylene glycol (TTEG) as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterised by using Fourier transform infrared (FTIR) spectroscopy. Physicochemical properties of DESs, such as density, viscosity and refractive index, were also measured. The synthesised DESs were used to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesised DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30°C using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68% and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidised. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low temperature 30°C using combined extractive catalytic oxidative desulfurisation. Hence, the DES synthesised using SAA and TTEG in the molar ratio of 1:2 works better as an extraction solvent for removing organic sulfur compounds from fuels at low temperatures.

Gas-phase reaction of CH4 and H2S – Evidence from pyrolysis experiments and case study from the Sichuan Basin

The application of routine geochemical analyses for identification of dry natural gas sources and post generation processes poses a challenge as its hydrocarbon composition is typically dominated by CH4 (∼≥99 %) while the presence of non-hydrocarbons may be limited. In particular, the possibility of dry gas interaction with H2S at reservoir conditions (low temperatures, high pressures, millions of years residence time) is not established as previous studies of this reaction focused on conditions typical for industrial reactors (high temperature, ambient pressure, residence time of seconds). To address these issues, we studied the molecular and isotopic (δ34S) composition of volatile organic sulfur compounds (VOSC) formed during pyrolysis experiments between CH4 and H2S at 360 °C (4–96 h), reaching %Ro equivalent of 0.80–1.25 which represents thermally mature oil and gas reservoirs. The results demonstrated that methanethiol (MeSH) is the main product of the reaction, while its δ34S value suggest equilibrium isotopic effect with its parent H2S. Subsequent analysis of the molecular and isotopic (δ13C, δ2H, δ34S) composition of thermogenic, H2S containing, dry natural gases from the Jiannan gas field in China revealed the presence of short thiols and sulfides dominated by MeSH. The δ34S of the VOSC identified suggests they all formed by gas-phase reaction of alkanes (mainly CH4) with the associated H2S.This study demonstrates the applicability of VOSC as a proxy for identification of interaction between H2S and dry gas and identification of H2S sources within a gas reservoir or a basin.

The stable sulfur isotope and abundance fluxes of reduced inorganic sulfur and organic sulfur phases recorded in the Permian-Triassic transition of the Meishan type section

Sulfur cycle fluxes implicated in the Permian-Triassic mass extinction have traditionally been studied by the sulfur phase abundances in sedimentary rocks and the stable sulfur isotopic value (δ34S) of seawater sulfate inferred from mineral sulfate analyses. This information might be complemented by studies of the reduced inorganic sulfur and organic sulfur produced following bacterial sulfate reduction. To explore this potential the δ34S and concentration analyses of total reduced inorganic sulfur (TRIS) and organic sulfur – separately in the forms of kerogen (Ker) and individual organosulfur compounds, specifically dibenzothiophenes (DBTs) – has been conducted on sediments across the Late Permian to Early Triassic marine type section of Meishan-1 (South China). The relatively steady δ34S profiles (e.g., < 5 ‰ variation) of all sulfur phases measured through much of the late Permian were indicative of a primary seawater sulfate control, but other biogeochemical modulators caused prominent δ34S fluctuations of TRIS and DBT adjacent to the extinction event. The late Triassic δ34STRIS profile of Meishan-1 displayed a notable 34S enrichment (+15 ‰ increase) in bed 22–24 sediments concomitant with lower δ34SDBT values (−7 ‰ decrease), whereas co-eval δ34SKerS values remained relatively constant. The contrasting δ34SDBT and δ34SKerS data suggests the dynamic behavior of specific diagenetic sulfurisation processes may be resolved by the δ34S of discrete organic sulfur compounds (i.e., dibenzothiophenes, DBTs), but dissipated by the sulfurisation collective represented by the bulk kerogen fraction. The inverse isotopic trend observed between DBT and TRIS resulted in negative Δδ34SDBT-TRIS values identifying an organic sulfurisation pathway(s) with an unusual preference over pyrite (FeS2) for the lighter stable sulfur isotope. A redox control of the δ34SDBTs and δ34STRIS deviations in the bed 22–24 extinction interval was confirmed by coincident variation in TRIS/(TRIS + KerS) and pyrite (Py) and highly reactive (HR) iron ratios (FePy/FeHR). The iron (Fe) speciation data indicated a transition to ferruginous conditions, ruling out Fe2+ limitation as a factor in the bias against 34S evident in DBT formation. The 34S depletion of the DBTs promoted by the ferruginous setting may arise from the rapid and irreversible reaction of organic substrates with labile sulfur anions (e.g. HS-) or be supported by an especially localised sediment–water depositional microenvironment. Our study highlights the potential of incorporating stable sulfur isotope analytics of reduced and organic sulfur phases, particularly of specific organic compounds, into a holistic assessment of the dynamic sulfur biochemical periods of Earth’s past.

Holed up, but thriving: Impact of multitrophic cryoconite communities on glacier elemental cycles

Cryoconite holes (water and sediment-filled depressions), found on glacier surfaces worldwide, serve as reservoirs of microbes, carbon, trace elements, and nutrients, transferring these components downstream via glacier hydrological networks. Through targeted amplicon sequencing of carbon and nitrogen cycling genes, coupled with functional inference-based methods, we explore the functional diversity of these mini-ecosystems within Antarctica and the Himalayas. These regions showcase distinct environmental gradients and experience varying rates of environmental change influenced by global climatic shifts. Analysis revealed a diverse array of photosynthetic microorganisms, including Stramenopiles, Cyanobacteria, Rhizobiales, Burkholderiales, and photosynthetic purple sulfur Proteobacteria. Functional inference highlighted the high potential for carbohydrate, amino acid, and lipid metabolism in the Himalayan region, where organic carbon concentrations surpassed those in Antarctica by up to 2 orders of magnitude. Nitrogen cycling processes, including fixation, nitrification, and denitrification, are evident, with Antarctic cryoconite exhibiting a pronounced capacity for nitrogen fixation, potentially compensating for the limited nitrate concentrations in this region. Processes associated with the respiration of elemental sulfur and inorganic sulfur compounds such as sulfate, sulfite, thiosulfate, and sulfide suggest the presence of a complete sulfur cycle. The Himalayan region exhibits a higher potential for sulfur cycling, likely due to the abundant sulfate ions and sulfur-bearing minerals in this region. The capability for complete iron cycling through iron oxidation and reduction reactions was also predicted. Methanogenic archaea that produce methane during organic matter decomposition and methanotrophic bacteria that utilize methane as carbon and energy sources co-exist in the cryoconite, suggesting that these niches support the complete cycling of methane. Additionally, the presence of various microfauna suggests the existence of a complex food web. Collectively, these results indicate that cryoconite holes are self-sustaining ecosystems that drive elemental cycles on glaciers and potentially control carbon, nitrogen, sulfur, and iron exports downstream.

Novel insights into dimethylsulfoniopropionate cleavage by deep subseafloor fungi

Dimethylsulfoniopropionate (DMSP), a key organic sulfur compound in marine and subseafloor sediments, is degraded by phytoplankton and bacteria, resulting in the release of the climate-active volatile gas dimethylsulfide (DMS). However, it remains unclear if dominant eukaryotic fungi in subseafloor sediments possess specific abilities and metabolic mechanisms for DMSP degradation and DMS formation. Our study provides the first evidence that fungi from coal-bearing sediments ∼2 km below the seafloor, such as Aspergillus spp., Chaetomium globosum, Cladosporium sphaerospermum, and Penicillium funiculosum, can degrade DMSP and produce DMS. In Aspergillus sydowii 29R-4-F02, which exhibited the highest DMSP-dependent DMS production rate (16.95 pmol/μg protein/min), two DMSP lyase genes, dddP and dddW, were identified. Remarkably, the dddW gene, previously observed only in bacteria, was found to be crucial for fungal DMSP cleavage. These findings not only extend the list of fungi capable of degrading DMSP, but also enhance our understanding of DMSP lyase diversity and the role of fungi in DMSP decomposition in subseafloor sedimentary ecosystems.

Effect of jujube powder addition on the aroma profile of quinoa snacks (QS).

Quinoa is a full-nutrition food; however, its poor flavor and small size make it not the best food option for direct consumption. In this study, a quinoa snack (QS, a cake) was developed, and the aroma profile of the products was improved by adding jujube fruit powder (made from dried jujube fruits, from 5% to 30%). Gas chromatography mass spectrum (GC-MS) combined with electronic nose (e-nose) was applied for characterizing the aroma profiles of QS samples. Results showed a total of 26 aroma compounds were identified in QS samples by GC-MS, and 3-methylbutanol (from 1525 μg/kg in QS-30 to 3487 μg/kg in QS-0), ethanol (from 1126 μg/kg in QS-0 to 3581 μg/kg in QS-30), hexanal (from 125.6 μg/kg in QS-30 to 984.1 μg/kg in QS-0), and acetaldehyde (from 531.9 μg/kg in QS-30 to 191.1 μg/kg in QS-0) were common. The e-nose response of W1S (sensitive to methane, from 17.50 of QS-0 to 93.85 of QS-30) and W1W (sensitive to sulfur-organic compounds of e-nose, from 15.57 of QS-0 to 39.50 of QS-30) were significantly higher, and significant differences were presented among QS samples. In conclusion, the aroma profile of the QS sample was significantly (p < .05) enhanced by the addition of jujube powder, and QS-30 with the highest jujube content (30%) presented the strongest aroma profile. Moreover, QS samples with different additions of jujube powders could be well distinguished by principal component analysis (PCA), and the combination of e-nose and GC-MS was effective in the volatile profile analysis of QS samples.

Biogenic Sulfur Gases as Biosignatures on Temperate Sub-Neptune Waterworlds

Theoretical predictions and observational data indicate a class of sub-Neptune exoplanets may have water-rich interiors covered by hydrogen-dominated atmospheres. Provided suitable climate conditions, such planets could host surface liquid oceans. Motivated by recent JWST observations of K2-18 b, we self-consistently model the photochemistry and potential detectability of biogenic sulfur gases in the atmospheres of temperate sub-Neptune waterworlds for the first time. On Earth today, organic sulfur compounds produced by marine biota are rapidly destroyed by photochemical processes before they can accumulate to significant levels. Domagal-Goldman et al. suggest that detectable biogenic sulfur signatures could emerge in Archean-like atmospheres with higher biological production or low UV flux. In this study, we explore biogenic sulfur across a wide range of biological fluxes and stellar UV environments. Critically, the main photochemical sinks are absent on the nightside of tidally locked planets. To address this, we further perform experiments with a 3D general circulation model and a 2D photochemical model (VULCAN 2D) to simulate the global distribution of biogenic gases to investigate their terminator concentrations as seen via transmission spectroscopy. Our models indicate that biogenic sulfur gases can rise to potentially detectable levels on hydrogen-rich water worlds, but only for enhanced global biosulfur flux (≳20 times modern Earth’s flux). We find that it is challenging to identify DMS at 3.4 μm where it strongly overlaps with CH4, whereas it is more plausible to detect DMS and companion byproducts, ethylene (C2H4) and ethane (C2H6), in the mid-infrared between 9 and 13 μm.

Potential of diallyl sulfide from bulbs of Allium parvum to inhibit the growth and biofilm formation in Malassezia furfur MTCC 1374

The bulbs of Allium parvum are used as a flavoring agent in diet and are conventionally assumed to treat skin infections. The current study evaluates the phytochemicals from organic extract of A. parvum and their antifungal activity against biofilm-forming dermatophytic fungi Malassezia furfur MTCC 1374, yeast found in the normal flora of the skin, causes superficial infections, systemic infections like pulmonary infections, fungemia, etc., and implant-associated infection by biofilm formation. Biofilm formation enables the fungi to escape from antifungal agents and renders resistance to antifungal agents. The phytochemical assay for the organic extract of the onion bulb documented that A. parvum contains phenol (58 + 0.1 mg GAE/g), flavonoids (112 + 0.12 mg QE/g), saponins (1.45 + 0.1 mg AE/g), and tannins (4.1 + 0.03 g TA/g). The FT-IR and GC-MS analysis revealed the presence of specific compounds, alkaloids such as glycosides and quinolones, plant flavonoids such as 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl-ester, phenolics, saponins such as butanoic acid and gluconic acid, and organic sulfur compounds such as diallyl sulfide, thiopyran tetrahydro-ester, allyl methyl trisulfide, and allyl methyl di sulfide. These compounds inhibited the growth of M. furfur at a minimum inhibitory concentration (MIC) value of 6.25 mg/ml and its biofilm at a minimum biofilm inhibitory concentration (MBIC) value of 12.5 mg/ml. Further studies required to explore the possible mechanism in controlling the biofilm, so, as to recommend as fungal control agent in medical sector.

Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components.

Boundary lubrication characteristics are strongly dependent on tribochemical reactions at the contact interface. There are multiple factors that contribute to the activity of tribochemical reactions and the complexity of this phenomenon. Here, we focused on nascent surfaces created by friction and aimed to clarify their chemical properties. To achieve this, we first developed a method based on a mass spectrometer that can sensitively detect molecular adsorption and reactions on a nascent surface. We used various organic compounds as adsorbates and friction materials such as steel, aluminum, gold, and ceramics and examined adsorption of the organic compounds on the nascent surfaces. The adsorption properties of the additives differed between steel metal oxide and nascent steel surfaces. For example, polar organic phosphates, which are extreme-pressure additives, were more easily adsorbed on oxide surfaces, whereas nonpolar organic sulfur compounds were more easily adsorbed on nascent steel surfaces. Alcohols and ethers also adsorbed on nascent aluminum surfaces, whereas olefins and benzene did not. Nascent gold surfaces showed high catalytic activity. Saturated hydrocarbons and fluorinated compounds, which are chemically inert, were also adsorbed on nascent ceramic surfaces, showing high activity. Hydrocarbon oils decomposed through the influence of frictional heat on a nascent steel surface to generate hydrogen and methane. We applied reactive molecular dynamics to simulate the adsorption phenomenon on iron surfaces. As a result, the adsorption energy obtained by simulation and the experimentally determined adsorption activity correlated well. Thus, adsorption and reaction behaviors on nascent surfaces inferred by our method were theoretically supported. On the basis of the chemical properties of the nascent surfaces obtained here, it is possible to explain boundary lubrication phenomena.

Screening ionic liquids based on COSMO-SAC model for extracting organic sulfur from coal and mechanism study

Screening suitable ionic liquids（ILs） for removing organic sulfur compounds from coal and discovering new, effective and environmentally friendly coal desulfurization additives is crucial. The solubility properties (SP) of six organic sulfur model compounds (OSMCs) in imidazole ILs were calculated based on the COSMO-SAC model. The results showed that 2-thiophenecarboxylic acid and 2-aminophenyl phenyl sulfone exhibited favorable solubility properties in certain ILs. The solubility properties of partial imidazole ILs consisting of [Cl]- were significantly better than other anions. Through the σ -profiles analysis of ILs anions, cations and OSMCs, it showed that [Cl]- had a higher tendency to be hydrogen bond acceptor than other anions. The polar groups in OSMCs increased the hydrogen bond donor or acceptor sites for interactions with ILs, while extended the optional range of ILs for hydrogen bond interactions with OSMCs. The extraction efficiencies of 2-thiophenecarboxylic acid by ILs were above 25%, with [DMIM][Cl] displaying the highest efficiency at 47.5%. Meanwhile, [DMIM][Cl] was the most effective extractant for removing all OSMCs except benzothiophene, which was basically consistent with the calculation results. Electrostatic potential analysis was used to obtain the sites where OSMCs are the most likely to form hydrogen bond interactions with [DMIM][Cl]. And characterization of hydrogen bond formation between ILs and OSMCs was obtained by FTIR analysis. The hydrogen bond formed by p-thiocresol with [DMIM][Cl] is weak, and the hydrogen bonds formed by 2-thiophenecarboxylic acid, 2-aminophenyl phenyl sulfone with [DMIM][Cl] are relatively strong. The analysis of intermolecular hydrogen bond interactions verified the mechanism underlying the excellent extraction performance for specific OSMCs by the selected ILs.

The Impact of Sulfur-Containing Inorganic Compounds during the Depolymerization of Lignin by Hydrothermal Liquefaction of Black Liquor.

Lignin is a promising resource for the sustainable production of platform chemicals and biofuels. The paper industry produces large quantities of lignin every year, mostly dissolved in a black liquor. With the help of hydrothermal liquefaction, black liquor can be used directly as a feedstock to depolymerize the lignin to desired products. However, because various cooking chemicals (e.g., NaHS, NaOH) used in the Kraft process, dominant in the paper industry, are also dissolved in the black liquor, it is necessary to study in detail their influence on the process as well as their fate. In this work, the focus was on the fate of sulfur and the influence of sulfide (HS-). For this purpose, hydrothermal liquefaction experiments (250-400 °C) were carried out with black liquor and self-prepared model black liquor with different sulfide concentrations (0-3 g·L-1 HS-) in batch reactors (V = 25 mL), and the products were analyzed to understand the chemical pathways involving sulfur. It was found that the inorganic sulfur compounds react with organic matter to produce organic sulfur compounds. Dimethyl sulfide is the most abundant of these products. The HS- concentration correlates with the amount of dimethyl sulfide produced. Because methanethiol has also been qualitatively detected, the reaction mechanism of Karnofski et al. for the formation of dimethyl sulfide in the Kraft process also applies to the hydrothermal liquefaction of black liquor. Increased sulfide concentration in the feed leads to an accelerated depolymerization of lignin. In contrast, the yields of some aromatic monomers decrease slightly, possibly as a result of repolymerization reactions also occurring more quickly.

Characterize the Growth and Metabolism of Acidithiobacillus ferrooxidans under Electroautotrophic and Chemoautotrophic Conditions.

Acidophiles are capable of surviving in extreme environments with low pH. Acidithiobacillus ferrooxidans is a typical acidophilic bacterium that has been extensively studied when grown chemoautotrophically, i.e., when it derives energy from oxidation of Fe2+ or reduced inorganic sulfur compounds (RISCs). Although it is also known to grow with electrons supplied by solid electrodes serving as the sole source of energy, the understanding of its electroautotrophic growth is still limited. This study aimed to compare the growth characteristics of A. ferrooxidans under electroautotrophic (ea) and chemoautotrophic (ca) conditions, with an attempt to elucidate the possible mechanism(s) of extracellular electron flow into the cells. Jarosite was identified by Raman spectroscopy, and it accumulated when A. ferrooxidans used Fe2+ as the electron donor, but negligible mineral deposition occurred during electroautotrophic growth. Scanning electron microscopy (SEM) showed that A. ferrooxidans possesses more pili and extracellular polymeric substances (EPSs) under electroautotrophic conditions. A total of 493 differentially expressed genes (DEGs) were identified, with 297 genes being down-regulated and 196 genes being up-regulated in ea versus ca conditions. The genes known to be essential for chemoautotrophic growth showed a decreased expression in the electroautotrophic condition; meanwhile, there was an increased expression of genes related to direct electron transfer across the cell's outer/inner membranes and transmembrane proteins such as pilin and porin. Joint analysis of DEGs and differentially expressed metabolites (DEMs) showed that galactose metabolism is enhanced during electroautotrophic growth, inducing A. ferrooxidans to produce more EPSs, which aids the cells in adhering to the solid electrode during their growth. These results suggested that electroautotrophy and chemoautotrophy of A. ferrooxidans have different extracellular electron uptake (EEU) pathways, and a model of EEU during electroautotrophic growth is proposed. The use of extracellular electrons as the sole energy source triggers A. ferrooxidans to adopt metabolic and subsequently phenotypic modifications.

Effect of different pretreatments on the hydrolysis efficiency and flavor of squid viscera (Dosidicus gigas)

In order to better utilize the proteins in squid viscera (Dosidicus gigas), the effects of different pretreatments on the degree of hydrolysis (DH) and volatile compounds of hydrolysates were studied. The DH was used as an indicator to select alkaline protease as the optimal protease from 8 types of proteases. The hydrolysis conditions of alkaline protease and the flavor of the hydrolysates were investigated through single-factor, response surface methodology, and pretreatment-assisted hydrolysis experiments. The results showed that alkaline protease had the highest DH (42.08 ± 0.58%), with enzyme dosage of 1.5%, hydrolysis temperature of 45 °C, hydrolysis time of 5 h, and liquid-solid ratio of 4:1. The DH of the ultrasound group was significantly higher than other groups, with the highest DH (45.67 ± 0.34%) after ultrasound for 40 min (U40). The proportion of molecular weight < 1 kDa and the content of free amino acids (1613.64 mg/100 g) were the highest at U40. The electronic nose results indicated that the composition of organic sulfur and aliphatic compounds in U40 showed significant differences compared to other products. The U40 sample had the highest type and content of volatile compounds (especially benzaldehyde), which was more conducive to the volatilization of flavor substances. In conclusion, U40 pretreatment can effectively improve the DH and flavor of hydrolysates.