Methanethiol Research Articles

Design, Synthesis, in vitro and in silico Study of 5-(Methylthio)-4-(H)-1,2,4-triazole-2-amine and its Derivatives

In this work, design and synthesis of 5-(methylthio)-4-(H)-1,2,4-triazole-2-amine and its derivatives were carried out using N-cyano-carbonimidodithioic acid dimethyl ester and methane thiol hydrazine monohydrate to obtain an excellent yield of the desired core molecule. It was observed that free -NH2 group available at 2nd position, which itself acts as a pharmacophore useful to connect with alkyl/aryl substituted isocyanate and form urea moiety as a bridge between 5-(methylthio)-4-(H)-1,2,4-triazole and alkyl/aryl substituent which exhibited the antimicrobial and docking activities of the synthesized molecules. The QSAR, toxicokinetics, docking studies with selected antimicrobial PDBs are useful in silico study of derivatives. In this study, it is emphasised that the results obtained in vitro and in silico correspond with each other and provide a better understanding of how and where medications exert their effects at the molecular level. This is based on the fact that the results were found using the same drug.

Odour impact assessment using kinetics and optimization: case studies on removal of multiple volatile organo-sulphur compounds from sewage wastewater using porous functional materials.

Expanding industries and booming population have led to the increase in the installation of wastewater and sewer systems, even in close proximity to residential areas. Emissions from these installations particularly volatile organo-sulphur compounds (VOSCs) such as methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), dimethyl sulphide (CH3SCH3) and carbon disulphide (CS2) are a nuisance to people even when present in small concentration. Strategies for removal involve addition of chemicals or other chemical processes which are generally expensive. Biofilters, on the other hand, consume large amount of energy and wash waters. Hence keeping commercialization in mind, it is important to develop a strategy which would be cost-effective and at the same time be effective to remove most of the odorous compounds present in these systems. In the present research work, granular activated carbons (GAC) are functionalized with alkali solution to improve the adsorption capacity. Liquid phase batch adsorption is performed with GAC and various functionalized activated carbons (FACs) with the help of raw sewage water from a local sewage water treatment plant. Concentration of odour was evaluated by two methods-olfactometry-based analysis for sensory measurement and GCMS-based analysis for analytical estimation of a specific odorous compound. The adsorption capacities of the functionalized GACs are higher primarily because of complex formation at the surface of modified GACs. Pseudo-second-order kinetic model agreed well with experimental results with the rate constant being 0.0191mg/l min and 0.0153mg/l min for methyl and ethyl mercaptan adsorption onto FAC-NH3. Boyd's film diffusion along with rate kinetic model supported that chemical adsorption forms the rate-limiting step. Response surface methodology (RSM) was used to optimize the removal of VOSCs with respect to different process parameters like adsorbent amount and time. The olfactometry removal of overall odour was also optimized taking 6 factors in the Box Behnken design. Variance of analysis results indicated that all the models displayed considerable goodness of fit with R2 values close to 1. Methyl mercaptan turned out to be the highest contributor to the overall odour as confirmed both from experimental and optimization study. The optimized olfactometry odour removal (77.4%) along with CH3SH removal (80.34%), C2H5SH removal (59.16%), CH3SCH3 removal (63.21%) and CS2 removal (71.95%) was found at optimum process conditions, with amount of adsorbent of 10.29g, adsorption time of 2.92h. This result indicates that methyl mercaptan (CH3SH) is the highest odour contributing component out of the studied VOSCs. The results show promising potential for the use of activated carbon as an adsorbent for removal of odorous compounds from STPs.

Electron Transfer Trade-offs in MOF-Derived Cobalt-Embedded Nitrogen-Doped Carbon Nanotubes Boost Catalytic Ozonation for Gaseous Sulfur-Containing VOC Elimination

High-performance and robust catalysts act as core drivers for catalytic ozonation to eliminate gaseous sulfur-containing volatile organic compounds (VOCs). Herein, nitrogen-doped carbon nanotubes embedded with Co species (Co@NCNT) are synthesized by thermolysis of a ZIF-67/melamine mixture. The carbon-confinement effects in Co@NCNT not only improve the stability of Co species but also regulate the electronic structure of Co─C bonds, consequently synergistically improving the catalytic ozonation performance. The experimental results indicate that the Co@NCNT catalyst could still remove ∼86% of odorous methyl mercaptan (CH3SH) after running for 60 h at 25 °C under an initial concentration of 50 ppm CH3SH and 40 ppm ozone, relative humidity of 60%, and space velocity of 600,000 mL h–1 g–1, outdistancing reported values under comparable reaction conditions. Detailed characterization and theoretical simulations reveal that the electronic metal–support interaction of Co─C bonds in Co@NCNT significantly adjusts the electronic structure of Co species, thereby promoting ozone-specific adsorption/activation to convert the surface atomic oxygen (*Oad) and ·OH/1O2/·O2–. Also, the electrons obtained from CH3SH in the electron-poor center transferred through the C─Co bond bridge to maintain the redox cycle of ≡Co0/2+ → ≡Co3+ → ≡Co0/2+ and realize the efficient and stable removal of CH3SH into CO2/SO42–/H2O. This work demonstrates that MOF-derived materials with tunable electronic structures achieve the stable removal efficiency for gaseous sulfur-containing VOCs via electron transfer trade-offs and provide potential candidate catalysts for the application of air purification.

Effects of dietary supplementation of diacylglycerol on growth performance, nutrient digestibility, fecal noxious gas emission, and hematology parameters in weaned piglets

A total of 120 21-day-old weaned piglets ((Yorkshire × Landrace) × Duroc) were used to evaluate the effects of dietary supplementation of diacylglycerol (DAG) on the growth performance, nutrient digestibility, fecal noxious gas emission, and hematology parameters in a 42-day experiment. All pigs were randomly assigned to three groups based on the initial body weight (6.47 ± 0.45 kg). There were eight replicate pens per treatment and five pigs (three barrows and two gilts) per pen. The DAG in the levels of 0%, 0.05%, or 0.10% was used as supplement to the corn–soybean meal-based basal diet. Piglets fed the diet supplemented with graded levels of DAG linearly increased the average daily gain (ADG) during days 22–42 ( P = 0.027) and 1–42 ( P = 0.048). In addition, a tendency in the linear reduction of fecal ammonia ( P = 0.095), hydrogen sulfide ( P = 0.078), and methyl mercaptan ( P = 0.085) emission was observed by increasing the DAG levels in the diet. However, feeding pigs with DAG-containing diet had no significant effects on the nutrient digestibility and hematology parameters. Therefore, the suitable dose of DAG used in the diet of weaned piglets was at 0.10% to improve ADG and reduce fecal gas emission.

The tongue biofilm metatranscriptome identifies metabolic pathways associated with the presence or absence of halitosis

Intra-oral halitosis usually results from the production of volatile sulfur compounds, such as methyl mercaptan and hydrogen sulfide, by the tongue microbiota. There are currently no reports on the microbial gene-expression profiles of the tongue microbiota in halitosis. In this study, we performed RNAseq of tongue coating samples from individuals with and without halitosis. The activity of Streptococcus (including S. parasanguinis), Veillonella (including V. dispar) and Rothia (including R. mucilaginosa) was associated with halitosis-free individuals while Prevotella (including P. shahi), Fusobacterium (including F. nucleatum) and Leptotrichia were associated with halitosis. Interestingly, the metatranscriptome of patients that only had halitosis levels of methyl mercaptan was similar to that of halitosis-free individuals. Finally, gene expression profiles showed a significant over-expression of genes involved in L-cysteine and L-homocysteine synthesis, as well as nitrate reduction genes, in halitosis-free individuals and an over-expression of genes responsible for cysteine degradation into hydrogen sulfide in halitosis patients.

Improvement of the technology of disposal of pig waste products at the industrial complex

The aim. To determine the degree of completeness of air purification and the suitability of the developed experimental samples of the chamber for its use to reduce the content of polluting gases during the removal of air from the premises of the industrial complex. Methods. The research was conducted on the basis of the pig farm of Agroprime Holding LLC of the Odesa region. The determination of the level of methyl mercaptan (mg/m3) in air emissions outside the premises was carried out using a portable gas analyzer Dräger X-am 5600. The determination of the level of ammonia (mg/m3), hydrogen sulfide (mg/m3) was carried out using a portable multi-component gas analyzer ANKAT - 7664 Micro. The measurement of the content of polluting gases in the air before and after passing the air through the purification chamber was carried out in the pig fattening shop of the pig complex. The concentration level of ammonia and hydrogen sulfide was recorded using a certified and certified device: a multicomponent individual alarm-analyzer of gases "DOZOR-S-M". The results. It was established that the level of hydrogen sulfide in the air of the room at a height of 0.5 m from the floor was 3.34 mg/m3, above the manure bath – 9.72, at the entrance to the upper filter from below - 2.46, at the entrance to the upper filter from the side – 3.03, at the exit from the air exchange shafts on the roof – 2.83, and at the entrance to the side filter – 5.66 mg/m3. The level of ammonia at a height of 0.5 m from the floor was 1.84 mg/m3, above the manure bath – 5.28, at the entrance to the upper filter from below – 1.34, at the entrance to the upper filter from the side – 1.64, at the exit from the air exchange ventilation shaft on the roof – 1.54, at the entrance to the side filter – 3.08 mg/m3. Hydrogen sulfide and ammonia were not detected at the exit from the ventilation ducts, where air purification chambers were installed. Conclusions. The obtained results indicate that, during the tests, the air contaminated with foul-smelling gases, after passing through the purification chamber, was completely freed from gases, and the presence of ammonia and hydrogen sulfide was not detected either by apparatus or organoleptically. Purification of polluted indoor air with the help of a developed chamber makes it possible to completely remove ammonia and hydrogen sulfide. Therefore, it is possible to ventilate the premises without polluting the environment. Key words: pig complex, pig farm, air pollution, hydrogen sulfide, ammonia, air purification, ecological state of the environment

Template-free hydrothermal synthesis of hollow alumina microspheres and its excellent catalytic properties for thiolation

In view of the important industrial application value of alumina supports in the field of oil refining and reforming, it is of great significance to develop a simple and economical synthesis method for the hierarchical porous alumina. Herein, the hollow microsphere alumina was hydrothermally synthesized without template. The surface of the hollow microsphere alumina supports has a raised fluffy structure, the microsphere diameter is about 5 ∼ 8 μm, and the thickness of the shell is about 1 μm. The morphology evolution process from solid microspheres to core–shell microspheres with spindle-shaped nanoclusters, and then to hollow fluffy microspheres with protruding surface was observed by investigating the effect of hydrothermal synthesis temperature on the morphology of microspheres. Because of its specific morphology and surface characteristics, the microsphere can better disperse the active component KW to prepare KW/Al2O3 catalyst and used in the thiolation to methyl mercaptan. Compared with our previously used catalysts prepared from commercial alumina, this KW/Al2O3 catalyst was not only able to greatly reduce the amount of active component, but also exhibited higher CH3SH selectivity. On the 10KW/Al catalyst, the CH3SH selectivity reached 66.2 % at 340 °C, which was about 10 % higher than that of the previous commercial alumina catalyst. This work can provide theoretical basis and practical guidance for the reasonable design of new alumina support and high efficiency methyl mercaptan catalyst.

A preliminary evaluation on mixed probiotics as an antimicrobial spraying agent in growing pig barn

The purpose of this study is to examine whether spraying an anti-microbial agent into the slurry pit will reduce the noxious odor substances from piggery barns. For this, a total of 200 crossbred ([Landrace × Yorkshire] × Duroc) growing pigs with an initial average body weight (BW) of 23.58 ± 1.47 kg were selected and housed in two different rooms, i.e. control (CON) and treatment (TRT). Each room has 100 pigs (60 gilts and 40 borrows). For a period of 42 days, all pigs were fed with corn-soybean meal-based basal diet. Later the noxious odor substances were measured by the following methods. First, fecal samples were randomly collected and stored in sealed and unsealed containers, and sprayed with the non-anti-microbial agent (NAMA) (saline water) and multi-bacterial spraying (MBS) agent (200 :1, mixing ratio-fecal sample : probiotic), Second, the slurry pit of CON and TRT rooms were directly sprayed with NAMA and MBS, respectively. The fecal sample that was stored in sealed and un-sealed containers and sprayed with MBS significantly reduced NH3 and CO2 concentration at the end of day 7. However, at the end of day 42, the fecal sample showed a lower H2S, methyl mercaptans, acetic acid, and CO2 concentration compared to the unsealed container. Moreover, at the end of days 7, 14, 21, 28, 35, and 42 compared to the CON room and TRT room slurry pit emits lower concentrations of NH3, acetic acid, H2S, and methyl mercaptans, and CO2 into the atmosphere. Based on the current findings, we infer that spraying anti-microbial agents on pig dung would be one of the better approaches to suppress the odor emission from the barn in the future.

A new air cleaning technology to synergistically reduce odor and bioaerosol emissions from livestock houses

Odor and bioaerosols have serious impacts on the biological safety of animal production and the ecological environment. Thus, it is particularly important to explore synergistic air cleaning technology to solve these problems. In this study, a pilot-scale air cleaning equipment were applied to an experimental manure storage house to determine the removal efficiency of gaseous pollution using four treatments groups. These treatment groups include acid scrubbing + caustic scrubbing (AC), acid scrubbing + caustic scrubbing + photocatalytic oxidation (ACP), acid scrubbing + caustic scrubbing + biological scrubbing (ACB), and acid scrubbing + caustic scrubbing + biological scrubbing + photocatalytic oxidation (ACBP). Results showed that ACP can synergistically remove odor and bioaerosol, with ammonia, odor concentrations, hydrogen sulfide, methyl mercaptan, methyl sulfide, bacterial aerosol, and fugal aerosol removal efficiencies of 89.1 %, 76.3 %, 100 %, 94.2 %, 91.2 %, 75.6 %, and 83.6 %, respectively. Furthermore, ACBP has the highest removal efficiency of 79.2 % for odor concentration, but this combination has a low inactivation efficiency (< 25 %) for bacterial aerosols. Moreover, adding biological scrubbing before photocatalytic can reduce the conversion from aromatic hydrocarbons to Oxygenated VOCs. Findings of this study provide a theoretical basis and technical support for the application of air cleaning technology in livestock houses.

Experimental investigation of waste tyres pyrolysis gas desulfurization through absorption in alkanolamines solutions

Pyrolysis of waste tyres produces harmful hydrogen sulfide and other mercaptan compounds as by-products. The current study is concerned with the purification of hydrogen-rich pyrolysis gas from hydrogen sulfide gas that is present in a great amount (up to 5.1% mol at 420 °C), and mercaptans that are also problematic impurities. The method proposed is absorption by alkanolamines which is one of the most economical methods applied in natural gas sweetening. However, it has not been adopted in waste tyre pyrolysis gas purification yet. Two organic absorbents were tested, diethanolamine (DEA), N-methyldiethanolamine (MDEA) as well as theirs blends, at various concentrations. The application of 30 wt% DEA in water reduced H2S emission by 98%. In turn, 40 wt% MDEA aqueous solutions reduced H2S emission by 97%. The best results were produced when 30 wt% DEA was mixed with 40 wt% of MDEA (1:1 vol ratio) which allowed a removal of 99% of H2S from the pyrolysis gas. Moreover, the maximum H2S emission was 7 ppm, and a level below 5 ppm was kept for 99% of experiments duration. Finally, the application of this mixture also reduced significantly the concentrations of other sulfur-containing compounds such as methyl mercaptan and carbonyl sulfide (a minimum of 98%), ethyl mercaptan (∼90%), and carbon disulphide (by more than 99%). Thus, aqueous solvent mixture of 30 wt% DEA with 40 wt% of MDEA (1:1 v/v) can be recommended as a potential desulfurization method for waste tyres pyrolysis gas.

Synthesis of amine grafted Cu-BTC and its application in regenerable adsorption of ultra-low concentration methyl mercaptan

Purification of volatile sulfur compounds is a hot topic since these malodorous gases with low odor thresholds are generated in both community and industry. Adsorption is an effective method, but adsorbent regeneration is usually difficult because of the strong bond between adsorbent and malodorous gases. In this work, an amine-grafted metal–organic framework was synthesized and applied in cyclic adsorption of ultra-low concentration methyl mercaptan (MM). As a result, MM was effectively purified to below 50 ppb for 1062 min, resulting in a breakthrough capacity of 84.9 mg/g. In comparison, the breakthrough time and capacity without grafting amine were 777 min and 58.6 mg/g, respectively. After detailed characterizations, Cu2+ site and amine group were both attributed to MM removal. Although Cu2+ site was unregenerable, the amine group was regenerable with a capacity of 17.9–19.4 mg/g since the N-H bond was weak between amine and MM. In addition, competitive gases CO and CO2 only decreased the breakthrough time and capacity by 10%. The main result of this work is in favor of applying a regenerable adsorbent for purification of ultra-low concentration malodorous gas.

Unraveling the Synergistic Reaction and the Deactivation Mechanism for the Catalytic Degradation of Double Components of Sulfur-Containing VOCs over ZSM-5-Based Materials.

The competitive adsorption behavior, the synergistic catalytic reaction, and deactivation mechanisms under double components of sulfur-containing volatile organic compounds (VOCs) are a bridge to solve their actual pollution problems. However, they are still unknown. Herein, simultaneous catalytic decomposition of methyl mercaptan (CH3SH) and ethyl mercaptan (C2H5SH) is investigated over lanthanum (La)-modified ZSM-5, and kinetic and thermodynamic results confirm a great difference in the adsorption property and catalytic transformation behavior. Meanwhile, the new synergistic reaction and deactivation mechanisms are revealed at the molecular level by combining with in situ diffuse reflectance infrared spectroscopy (in situ DRIFTS) and density functional theory (DFT) calculations. The CH3CH2* and SH* groups are presented in decomposing C2H5SH, while the new species of CH2*, active H* and S*, instead of CH3* and SH*, are proved as the key elementary groups in decomposing CH3SH. The competitive recombining of SH* in C2H5SH with highly active H* in dimethyl sulfide (CH3SCH3), an intermediate in decomposing CH3SH, would aggravate the deposition of carbon and sulfur. La/ZSM-5 exhibits potential environmental application due to the excellent stability of 200 h and water resistance. This work gives an understanding of the adsorption, catalysis, reaction, and deactivation mechanisms for decomposing double components of sulfur-containing VOCs.

Iron carbon particle dosing for odor control in sewers: Laboratory tests

Treatment of malodor in the sewer system is a priority in many municipalities for human health concerns, sewer pipe corrosion prevention. In this study, the removal effects of iron-carbon (Fe–C) particles on the inhibition of sulfide in the liquid phase, as well as hydrogen sulfide (H2S) and methyl mercaptan (MeSH) in the headspace were investigated using laboratory-scale reactors simulating gravity-flow sewer system. The results indicated that the sulfide in the liquid phase can be reduced from 15.1 to 16.5 mg S/L to 0.05 and 0.14 mg S/L after 70 g/L and 50 g/L Fe–C particles dosing. The flux of H2S and MeSH in the headspace was also inhibited, and its flux decreased by up to 99%. Meanwhile, the microbial community structures of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) in the sediment surface and water were also analyzed, and the results revealed that the relative abundance of SRB in the water and sediment surface was inhibited greatly after adding Fe–C particles, especially for Sulfurospirillum, Clostridium, and Desulfovibrio, while Fe–C particles promoted the growth of SOB. Moreover, the surface deposition was collected and analyzed through X-ray photoelectron spectroscopy (XPS), and the results indicated that sulfide can be removed by co-precipitation with ferrous ions formed through micro-electrolysis of Fe–C. This study provides a new approach to control the in-situ odor pollution for sewage systems.

The influence of lanthanum (La) promoter on Mo/Al2O3 for the catalytic synthesis of methyl mercaptan (CH3SH) from COS/H2/H2S

The cooperative transition of sulfur-containing pollutants of COS/H2S/H2 to the chemical feedstock of methyl mercaptan (CH3SH) catalyzed by Mo-based catalysts has good application prospects. However, the role of rare earth elements as promoters in this reaction system has not been investigated currently. In this study, the effects of the rare earth of lanthanum (La) on the catalytic performance of Mo-based catalysts were investigated by XRD, Raman, TEM, H2-TPR, and XPS characterizations. The results showed that the addition of La species led to the formation of larger particle size and lower sulfidation degree of Mo species, but the higher, rather than lower, catalytic activity was obtained. This unusual phenomenon is confirmed to be due to the generation of La2(MoO4)3 crystals covered with surface MoS2 layers caused by the interaction of Mo oxide and La species at the sulfidation atmosphere. The presence of La2(MoO4)3 changes the electronic and chemical environment of MoS2 in the catalyst, which lead a positive effect on the catalytic activity, outweighing the negative effect caused by the larger particle size of Mo species and the reduced sulfidation.

Photoluminescence in halogeno copper(Ⅰ) methyl thiolate polymers via in situ DMSO decomposition reaction

Five halogeno-copper thiolate coordination polymers, Cu12Cl6(SCH3)6(DMSO) 1, Cu3X(SCH3)2 (2, 4), and Cu2X(SCH3) (X = Br, I) (3, 5) were solvothermally prepared by employing DMSO, which is used as a thiolate source via in situ decomposition. The X-ray crystallographic data revealed one type of 3D network structure composed of Atlas spheres. Additionally, two types of 2D layered bromo/iodo isostructural complexes were found, and the differences between these two types are attributed to the different connection modes of their Cu3X2(SCH3)2 chains. Sharing the halogen atoms in Cu3X2(SCH3)2 chain or bridging the chains via additional copper atoms could lead to the formation of different layers with a Cu:X:SCH3 ratio of 3:1:2 or 2:1:1, respectively. The absorption and emission spectral data described the influence of the ratio and species of halogen elements in copper thiolate complexes. From the spectroscopic studies, long-lived phosphorescence was detected, the characteristic lifetime of which depends on the crystal internal structures as well as the constituent halogen atoms.

Emission of volatile sulphur compounds during swine manure composting: Source identification, odour mitigation and assessment

This study aimed to identify the sources of volatile sulphur compounds (VSCs) and evaluate their mitigation by ferric oxide (Fe2O3) during swine manure composting. Four chemicals, including l-cysteine, l-methionine, sodium sulphite, and sodium sulphate, were further added to simulate organic and inorganic sulphur-containing substances in swine manure to track VSC sources during composting. Results show that sulphur simulants induced the emission of six common VSCs, including methyl sulphide (Me2S), dimethyl sulphide (Me2SS), carbonyl sulphide (COS), carbon disulphide (CS2), methyl mercaptan (MeSH), and ethyl mercaptan (EtSH), during swine manure composting. Of them, COS, CS2, MeSH and Me2SS were predominantly contributed by the biodegradation of methionine and cysteine, while Me2S and EtSH were dominated by the reduction of sulphite and sulphate. Further Fe2O3 addition at 1.5 % of total wet weight of composting materials immobilized elemental sulphur and inhibited sulphate reduction to reduce the emission of VSCs by 46.7–80.9 %. Furthermore, odour assessment indicated that adding Fe2O3 into composting piles significantly reduced the odour intensity level to below 4, the odour value of VSCs by 47.1–81.3 %, and thus the non-carcinogenic risk by 68.4 %.

Temporal and Spatial Variation in Odor Pollution and Membrane Barrier Effect in Municipal Solid Waste Landfill

In order to explore the source characteristics as well as the temporal and spatial variations in odor pollution in municipal waste landfills, gas samples were collected from a landfill in an eastern coastal area of China throughout winter and summer. The total concentration of malodorous substances reached 60000 μg·m-3. There were more types of odor pollutants detected in summer than in winter, the average concentration was 30-300 times higher than that in winter, and the concentration of sulfur compounds increased by 4.7-136.7 times in summer. Oxygenated compounds had the highest concentration, and the total concentration of sulfur compounds accounted for less than 10% of malodorous substances. However, sulfur compounds contributed more than 90% to the theoretical odor concentration. Sulfur compounds such as methyl mercaptan and propane mercaptan were the key odorants in the landfill. After the landfill unit was covered, the concentration of odorous substances and the theoretical odor concentration on the surface of the landfill showed an increasing trend with time, indicating that the covering had a certain odor barrier effect; however, the landfill unit still had a large odor release potential. The similarity analysis showed that the odorous gas accumulated in the unit with temporary cover and without an exhaust system could be released to the environment through the overlapping gap of the membrane and the location of membrane rupture, resulting in more serious odor pollution around the landfill at night than that during the day.

Study on adsorption of low-concentration methyl mercaptan by starch-based activated carbon.

The development of a low-concentration methyl mercaptan adsorbing material for an efficient decontamination has become a hot research topic. In this study, carbonization activation was employed with starch and urea as carbon and nitrogen sources, respectively, to prepare a type of starch-based activated carbon. Subsequently, the product was used to adsorb low-concentration methyl mercaptan. Based on sorption experiments and molecular simulations, the underlying mechanism of the adsorption effect of the adsorbent's pore structure and surface oxygen- and nitrogen-containing functional groups on methyl mercaptan molecules were discussed. The results indicated that when the methyl mercaptan equilibrium concentration was 0.197mg/L, the adsorption capacity of SUAC-16-2 for methyl mercaptan was 78.16mg/g. Its adsorption performance was better than that of its previously reported counterparts. The well-developed microporous structure of SUAC-16-2 promoted the adsorption of methyl mercaptan. In addition, methyl mercaptan molecules could be broken down to produce CH3S- and H+ by the effect of the surface functional groups. Adjacent carbon atoms containing nitrogen and oxygen functional groups could better adsorb CH3S- and H+, and further strengthen the methyl mercaptan adsorption performance of activated carbon. The study could help to develop new technology for treatment of low concentration of methyl mercaptan in the air.

Analysis of volatile organic compounds from deep airway in the lung through intubation sampling.

Exhaled volatile organic compounds (VOCs) have been widely applied for the study of disease biomarkers. Oral exhalation and nasal exhalation are two of the most common sampling methods. However, VOCs released from food residues and bacteria in the mouth or upper respiratory tract were also sampled and usually mistaken as that produced from body metabolism. In this study, exhalation from deep airway was first directly collected through intubation sampling and analyzed. The exhalation samples of 35 subjects were collected through a catheter, which was inserted into the trachea or bronchus through the mouth and upper respiratory tract. Then, the VOCs in these samples were detected by proton transfer reaction mass spectrometry (PTR-MS). In addition, fast gas chromatography proton transfer reaction mass spectrometry (FGC-PTR-MS) was used to further determine the VOCs with the same mass-to-charge ratios. The results showed that there was methanol, acetonitrile, ethanol, methyl mercaptan, acetone, isoprene, and phenol in the deep airway. Compared with that in oral exhalation, ethanol, methyl mercaptan, and phenol had lower concentrations. In detail, the median concentrations of ethanol, methyl mercaptan, and phenol were 7.3, 0.6, and 23.9 ppbv, while those in the oral exhalation were 80.0, 5.1, and 71.3 ppbv, respectively, which meant the three VOCs mainly originated from the food residues and bacteria in the mouth or upper respiratory tract, rather than body metabolism. The research results in our study can provide references for expiratory VOC research based on oral and nasal exhalation samplings, which are more feasible in clinical practice.

Deep desulfurization of alkylated oil by alumina adsorbents: characteristics and mechanism study

Deep desulfurization of alkylated oil is the primary problem that has long plagued the petroleum refining industry. In this study, alkaline alumina adsorbent microspheres were synthesized by carbonization–hot oil column pelletization method. The adsorption desulfurization performance of as-synthesized adsorbent and three commercial alumina-based adsorbents were systematically evaluated and compared. The results showed that alkaline alumina adsorbent had the optimal adsorption performance with a saturated adsorption capacity of 8.604 mg/g. Meanwhile, FTIR and sulfur speciation analysis indicated that the alkaline alumina adsorbent could deeply remove various sulfides (methyl mercaptan, dimethyl disulfide, hexacarbon sulfide, dibenzothiophene, etc.) from alkylated oil. Furthermore, the adsorption kinetics study manifested that the adsorption of sulfide was dominated by chemical adsorption, supplemented by physical adsorption, and accompanied by competitive adsorption among different sulfides. In addition, the regeneration experiment showed that nitrogen (90 °C) could realize the stable regeneration of the alkaline alumina adsorbent. To ensure stable regeneration performance in the industry, it is recommended that the alkaline alumina adsorbent be regenerated once with nitrogen at 90 °C. This study will provide theoretical support for the process optimization of deep desulfurization of alkylated oil and contribute to the high-quality production of clean fuels worldwide.