Saturated And Unsaturated Research Articles

Real-time evolution characteristics and potential reactions of contaminants in commuter bus cabin air

Despite the increasing use of motor vehicles, the impact of airborne pollutants and their health risks inside public transportation, such as commuter buses, is not well understood. This study assessed air quality inside an urban commuter bus by continuously monitoring PM10, PM2.5, and CO concentrations during both driving and parking periods. Our findings revealed that the ventilation system of the bus significantly reduced the infiltration of outdoor particulate matter and water vapor. However, CO concentrations were considerably higher inside the bus than outside, primarily due to vehicular self-emission. The ineffection of the ventilation system to remove CO potentially increases long-term exposure risks for passengers. The study identified ozone as a key oxidant in the cabin. Besides vehicle emissions, C3-C10 saturated aldehydes and carbonyl compounds were detected, including acetone, propanal, and hexanal. The presence of 6-MHO, an oxidation product of squalene, suggests that passengers contribute to VOCs load through direct emissions or skin surface reactions. Additionally, human respiration was found to significantly contribute to isoprene levels, estimated at 81.7 %. This research underscores the need for further investigation into the cumulative effects of stable compounds in cabin air and provides insights for developing healthier public transportation systems.

Recent Advances in Ligand-Controlled Regio- or Stereodivergent Transition-Metal-Catalyzed Hydroelementation (H[E]) (E = H, B, Si, Ge) of C–C Unsaturated Systems

AbstractReductive functionalization of C–C unsaturated systems, including alkenes and alkynes, with a range of hydroelements (H[E]) is one of the most fundamental and highly practical methods for the synthesis of functionalized hydrocarbons. Since the resultant hydrocarbon products have strong applicability as synthetic intermediates, numerous homogeneous organo(metallic) catalysts have been intensively utilized to date for reductive functionalization reactions. In particular, well-defined transition-metal-based catalysts capable of controlling the regio- or stereoselectivity of a product by harnessing the addition of H[E] (E = H, B, Si, Ge) into Cα–Cβ unsaturated bonds have drawn special attention. In this review, we describe recent examples of transition-metal catalytic systems (M = Fe, Co, Rh, Pd, Ni) for regio- or stereodivergent hydroelementation reactions of (conjugated) alkenes, alkynes, and allenes to give a pair of isomeric products in high selectivities from the same starting compounds simply by variation of the ligand. Mechanistic aspects of the ligand-controlled selectivity divergence are discussed in detail on the basis of experimental observations and/or computational insights.1 Introduction2 Hydroelementation of Alkenes and Alkynes3 Hydroelementation of Conjugated Dienes and Diynes4 Hydroelementation of Allenes5 Summary and Outlook

Unravelling the role of silver in addressing the nitrate radical induced photocatalytic oxidation of olefins to epoxides or carbonyl compounds

Nitrate radicals possess the unique capability to add to unsaturated bonds, leading to the formation of carbon-centred radicals evolving to organic compounds, which cannot be achieved through more common reactive oxygen centred species. Therefore, the possibility of generating nitrate radicals through heterogeneous photocatalysis endows this technology with unprecedented possibilities in the field of green organic synthesis. In particular, previous research showcased the promising potential of nitrate radicals in selectively conducting the photocatalytic oxidative cleavage of limonene to limononaldehyde. However, the role of silver ions, required for the reaction to occur, remained uncertain. This study aims at elucidating the role of silver in determining conversion of limonene and selectivity towards the corresponding oxidized compounds. In particular, it has been demonstrated that silver ions efficiently scavenge photogenerated electrons, thus making molecular oxygen available for the nitrate radical induced production of limononaldehyde, obtained with selectivity values up to 60%. In this study it is shown that, nitrate radical formation is as well boosted by silver nanoparticles, in the absence of silver ions. However, in this case, the consequent oxidation of limonene produced both 1,2-limonene epoxide and limononaldehyde. Notably, in the absence of silver ions, molecular oxygen is the main electron scavenger and its lower availability for the oxidative cleavage mechanism addresses the reaction towards the epoxide. Ab initio calculations, confirmed this hypothesis, showing that, while formation of limononaldehyde is thermodynamically and kinetically favoured, formation of the epoxide is kinetically limited. Therefore, its formation takes place when the formation of limononaldehyde is hindered by factors such as the reduced availability of molecular oxygen. The identification of key parameters governing the process offers possibilities to tune the selectivity of the reaction towards oxidative cleavage or epoxidation. Moreover, it allows to further optimize this reaction, which may become an appealing and versatile method of chemicals green synthesis.

РАЗРАБОТКА МЕТОДА ИДЕНТИФИКАЦИИ И ОЦЕНКА КОЛИЧЕСТВЕННОГО СОДЕРЖАНИЯ ЭФИРНОГО МАСЛА В ХВОЕ МОЖЖЕВЕЛЬНИКА ОБЫКНОВЕННОГО

The aim of the study is to develop methods for the identification of terpenoids and to assess the quantitative content of essential oil in the conifers of juniper, fresh and dried by air-shade drying. The object of the study were samples of needles of juniper. The raw materials were used fresh and dried. To carry out qualitative reactions, well-known methods were selected, which are most often used in the analysis of essential oil raw materials. The identification of essential oil components was carried out by TLC method on Silufol plates. A-pinene solution was used as a standard. The quantitative content of essential oil in the raw material was determined by steam distillation in accordance with the OFS method.1.5.3.00010.15. Determination of the essential oil content in medicinal plant raw materials and medicinal herbal preparations. The authors proposed qualitative reactions for the identification of terpenoids in raw materials, which can be used to form the "Authenticity" section for a new type of raw material-needles of juniper. A-pinene was identified by the TLC method. A quantitative assessment of the essential oil content in fresh and dried raw materials was carried out. A decrease in the content of essential oil during drying of raw materials was revealed. Qualitative reactions were selected experimentally to confirm the presence of terpenoids in alcoholic extracts from juniper needles, as well as unsaturated compounds in essential oil obtained by steam distillation. The TLC method identified a-pinene in the analyzed samples. The presence of additional 11 adsorption zones in the samples of essential oil obtained from fresh raw materials and 9 in samples from dried raw materials was also revealed. The results obtained indicate changes in the composition of the terpenoid fraction occurring during the drying process and actualize further research in this direction. Assessment of the quantitative content of essential oil in the raw material, carried out according to the method 2 of the OFS.1.5.3.00010.15 "Determination of the essential oil content in medicinal plant raw materials and medicinal plant preparations", showed a decrease in the essential oil content in all dried samples compared with fresh raw materials. The data obtained during the experiment allow us to recommend the inclusion of an essential oil content of at least 1% in the quality indicators of juniper needles, as well as optimize the drying mode to better ensure the preservation of essential oil in raw materials.

Photo-induced oxidative esterification via aldehyde and alkyl halides using dimethyl carbonate as green solvent

For a practical and environmentally benign strategy, we have devised an innovative approach for esterification in green dimethyl carbonate (DMC). Moreover, we employed a compatible system comprising abundantly available aldehydes and halides catalyzed using simple and commercial eosin Y under photocatalytic conditions. This strategy offers merits such as readily accessible feedstocks, remarkable functional tolerance and transition metal–free conditions, which allows to access wide scope of substrates with 34 examples and up to 93 % yield. Notably, cinnamaldehyde and 3-phenylpropiolaldehyde could accomplish this transformation while preserving CC unsaturated bonds. The density functional theory calculations (DFT) reveal that this transformation might undergo photoexcitation of the aldehyde to produce an acyl radical, which could further oxidatively esterify with halides to generate corresponding esters.

Modification Structure of Cinnamaldehyde with Primary Amines by Reflux and Sonication Methods in the Presence of Sulfuric Acid as a Catalyst

Cinnamon is one of the most valuable natural resources that sustains life and exists freely in nature. Cinnamaldehyde is the primary compound in cinnamon oil. It has a unique structure that contains a benzene ring, an aldehyde group, and an unsaturated double bond. Cinnamaldehyde has been structurally modified to improve biological activity. In this research, cinnamaldehyde and nitrophenyl amines were reacted with sulfuric acid as a catalyst by refluxing and sonication. UV-Vis Spectroscopy, FT-IR, 1H-NMR, and 13C-NMR were used to validate the chemical structures. Thin-layer chromatography (TLC) revealed a new single spot formed by the reaction of cinnamaldehyde and 4-amino-2-nitrophenol. By refluxing for 2 hours or sonicating for 30 minutes, a novel imine chemical, 4-nitro-2-((3-phenylallylidene)amino)phenol, was effectively synthesized with a yield of 75.21% or 83.71%, respectively. This imine was obtained as a dark red powder with a melting point of 237 °C. Meanwhile, only sonication produced a novel product from the reaction of cinnamaldehyde and 4-nitroaniline. However, the structural elucidation has not yet been performed because the yield was so low. Surprisingly, there was no reaction between cinnamaldehyde and 2,4-dinitroaniline. It was most likely owing to the amine’s bulky structure and the presence of two nitro groups in the amine as electron-withdrawing groups that reduced the nucleophilicity of the amine. We demonstrated that sonication is a suitable approach for imine synthesis, as it is commonly utilized in organic compound synthesis protocols.

General Methods for the Analysis of Chemical Properties of Fuels

This article is the third in a series of articles focused on presenting common methods for evaluating conventional and alternative fuels. The first two articles of the series were devoted to the determination of elements and non-hydrocarbon compounds in fuels [1]) and the determination of the physical properties of fuels [2]). This text presents an overview of the chemical properties determined for individual fuels. The chemical properties, acidity and alkalinity of fuels, content of unsaturated compounds, aniline point, water content, oxidation stability, and corrosive properties of fuels are presented in this article. The main goal of the article is to provide a comprehensive overview of which fuels are monitored, why they are monitored, and what methods are used for this monitoring. The emphasis is mainly on standardized parameters and tests, but in some cases, non-standardized tests are also discussed, or (additional) determinations not required by standards. For conventional and alternative fuels, several physical chemical, or other properties are used to evaluate the quality of these fuels. In this article, we present an overview of the chemical properties that are monitored for liquid and gaseous conventional and alternative fuels. These are acidity and alkalinity, content of unsaturated compounds, aniline point, water content, oxidation stability, and corrosive effects of fuels. In the article, we present the testing methods that are used to monitor these properties. Furthermore, we also present the reasons why these properties are monitored for individual fuels. Emphasis is placed on standardized parameters and tests, i.e., those prescribed by the relevant standards for individual fuels. However, parameters and alternative methods are also discussed, which are not prescribed by any standard for the respective fuels, but are supplementary determinations. The determination of elements and hydrocarbon and non-hydrocarbon compounds in fuels potentially falls within the scope of this article. However, since two separate articles [1] were devoted to these parameters, they will not be discussed here

Investigation on the steam gasification mechanism of different chars using isotopic tracing method

Gasification can provide syn-gas for consequent chemical production from carbon resources. The control of CO2 emission produced from gasification calls for the lower temperature and the more biomass char for the feed compared with traditional gasification, and the mechanism for steam gasification of different chars is more important. The gasification behaviors of four biomass chars and four coal chars are studied. The mechanism is probed using H216O/H218O period step tracing method coupled with various solid-state analyses on char structures. The increment of intermediates with increasing conversion demonstrate other slow step exists during gasification, and the solid state spectra of chars after and before gasification demonstrates that the condensation of poly-aromatic clusters in chars occurs accompanied with gasification. The addition reactions of radicals generated from gasifying agents and unsaturated carbon bonds C = C in chars is the slower step during gasification and enhancing the addition of radicals to unsaturated C = C bonds may be helpful for the higher gasification rate.

Recognition of screening out hierarchical toxic contaminants tuned by quantified pseudo-components from complex engineering co-combustion

Co-combustion of industrial and municipal solid wastes has emerged as the most promising disposal technology, yet its effect on unknown contaminants generation remains rarely revealed due to waste complexity. Hence, six batches of large-scale engineering experiments were designed in an incinerator of 650 t/d, which overcame the inauthenticity and deviation of laboratory tests. 953–1772 non-targeted compounds were screened in fly ash. Targeting the impact of co-combustion, a pseudo-component matrix model was innovatively integrated to quantitatively extract nine components from complex wastes grouped into biomass and plastic. Thus, the influence was evaluated across eight dimensions, covering molecular characteristics and toxicity. The effect of co-combustion with biomass pseudo-components was insignificant. However, co-combustion with high ratios of plastic pseudo-components induced higher potential risks, significantly promoting the formation of unsaturated hydrocarbons, highly unsaturated compounds (DBE≥15), and cyclic compounds by 19 %− 49 %, 17 %− 31 %, and 7 %− 27 %, respectively. Especially, blending with high ratios of PET plastic pseudo-components produced more species of contaminants. Unique 2 Level I toxicants, bromomethyl benzene and benzofuran-2-carbaldehyde, as well as 4 Level II toxicants, were locked, receiving no concern in previous combustion. The results highlighted risks during high proportion plastics co-combustion, which can help pollution reduction by tuning source wastes to enable healthy co-combustion.

Atomic-scale understanding on the influence of sliding angle on the interfacial structure and friction behavior of textured amorphous carbon films

Textured amorphous carbon (T:a-C) films have received great attention in the fields of hard drives, MEMS, and NEMS due to their excellent tribological properties. However, there is still a lack of research on the dependence of its friction behavior on different sliding angles. Especially, owing to the limitations of in-situ characterization in capturing the friction interface information, the potential friction mechanisms are still unclear. Hence, in this work T:a-C film with a rectangular shape was constructed and the impact of different sliding angles on friction behavior under dry friction condition was mainly explored through reactive molecular dynamics simulation. Results unveil that the friction properties of T:a-C films are closely dependent on the sliding angle. When the sliding angle increases from 0° to 45°, the decrease in the number of CC covalent bonds at the friction interface weakens the interfacial crosslinking effect, leading to a decrease in the friction coefficient by 20.11 %. However, as the sliding angle further increases from 45° to 90°, an increase in friction coefficient is observed, which is due to the increase of unsaturated bond content, weakening the interface passivation effect. These results reveal the friction mechanism of T:a-C films, induced by sliding angle, and effectively guide the design and technical application of textured a-C films.

Selective Hydrogenation of Unsaturated Vinyl Ethers in Two‐Chamber Gauge‐Reactor

AbstractA pressure gauge was incorporated into a two‐chamber glass H‐tube to continuously monitor the pressure inside a reactor when working with gases. The ex situ generated H2, D2, acetylene and CO2 were tested in pressure gauge reactors, and calibration curves were plotted. A series of unsaturated compounds with two or more double C=C bonds accessible for hydrogenation were synthesized for hydrogenation. The hydrogenation proceeded well due to constant pressure control, and the desired products were isolated in good yields. The same hydrogenation procedures were then carried out using steel autoclaves to verify the results and compare them. Surprisingly, almost the same results were obtained, confirming the effectiveness of self‐made glass reactors. The hydrogenation mechanism was further investigated using D‐labeled reagents. The kinetics of hydrogenation was studied both in manometric glass reactors and in steel autoclaves, which showed a similar nature of the main process in both reaction units. Thus, the created reactors can be effectively used in barometric transformations instead of steel autoclaves in appropriate cases.

Nitro-functionalization on MIL-53(Fe) for PCMX degradation: Elevating Fenton-like catalytic propelled by abundant reaction sites and iron cycle

To address the issue of excessive residues of 4-chloro-3,5-dimethylphenol (PCMX) in the water environment. In a one-step solvothermal process, iron-based metal-organic frameworks (Fe-MOFs) material MIL-53(Fe) undergoes a synthetic modification strategy. 2-Nitroterephthalic acid as an organic ligand reacted with Fe3+ in a solvothermal process lasting 18 h to yield the nitro-functionalized MIL-53(Fe)–NO2(18h). The objective was to augment the abundance of Fe central unsaturated coordination sites (Fe CUCs) and expedite the Fe(III)/Fe(II) redox cycle, thereby enhancing the heterogeneous Fenton-like treatment capability of pollutants. MIL-53(Fe)–NO2(18h) has excellent hydrogen peroxide (H2O2) catalytic activity and PCMX degradation across a broad pH spectrum (4.0∼8.0). Almost complete removal of PCMX was achieved within 30 min, while pseudo-first-order kinetic rate constants (kobs) increased 4.37 times over MIL-53(Fe). The confirmation of increased Fe CUCs abundance in MIL-53(Fe)–NO2(18h) was achieved through Lewis acidity, oxygen vacancies (OVs) signals, and Fe–O coordination characterization results. Density functional theory (DFT) calculations revealed that Fe CUCs in MIL-53(Fe)–NO2(18h) exhibits heightened affinity for H2O2 adsorption, showcasing stronger charge transfer and enhanced H2O2 dissociation ability. The Fe(III)/Fe(II) redox cycle, a driving force of Fenton-like reactions, was notably improved in the nitro-modified materials. These enhancements significantly expedited the Fenton-like process, resulting in the generation of increased amounts of reactive oxygen species (ROSs), with hydroxyl radicals (OH·) being pivotal components in degradation. The MIL-53(Fe)–NO2(18h)/H2O2 system has demonstrated versatility in treating a variety of emerging contaminants, achieving removal efficiencies exceeding 99.7% for other antibiotics and endocrine disruptors within 60 min. Furthermore, MIL-53(Fe)–NO2(18h) demonstrated outstanding reusability and adaptability in actual water environments. This study introduces a straightforward and environmentally friendly strategy for remediating environmental pollution using Fe-MOF-catalysed heterogeneous Fenton-like technology.

Regional differences in molecular characteristics of atmospheric water-soluble organic carbon over northern China: Comparison of remote, rural, and urban environments

Atmospheric water-soluble organic carbon (WSOC) is a critical component of airborne particulates. It significantly affects the Earth's energy balance, air quality, and human health. Despite its importance, the molecular composition and sources of WSOC remain unclear, particularly in non-urban areas. In this study, we collected total suspended particulate (TSP) samples from three sites in northern China: Erenhot (remote site), Zhangbei (rural site), and Jinan (urban site). The WSOC components were analyzed using high-performance liquid chromatography coupled with high-resolution mass spectrometry. The results showed that the formula numbers of identified compounds exhibited a decreasing trend of Jinan (2647) > Zhangbei (2046) > Erenhot (1399). Among the assigned formulas, CHO compounds were the most abundant category for all three sites, accounting for 33 %–38 % of the identified compounds, followed by the CHON compounds with contributions of 27 %–30 %. In the remote site of Erenhot, CHO compounds were dominated by oxidized unsaturated organic compounds, and CHON compounds were mainly low-oxygenated aliphatic compounds, suggesting a significant influence of primary emissions. In contrast, the urban site of Jinan showed higher contributions of CHO and CHON compounds with elevated oxidation degrees, indicating the influence of more extensive secondary oxidation processes. Atmospheric WSOC in Erenhot and Zhangbei had abundant reduced sulfur-containing species, likely from coal or diesel combustion, while that in Jinan was characterized by aliphatic organosulfates and nitrooxy-organosulfates, which are mainly associated with traffic emissions and biogenetic sources, respectively. These findings reveal significant differences in the molecular composition of WSOC in different atmospheric environments and improve our understanding of the chemical properties, potential sources, and transformations of organic aerosols.

A sustainable rapeseed oil-based bio-additive designed for hard asphalt binders: Performance, environmental, and economic assessment

The inherent properties of hard asphalt binder give it both mechanical and economic benefits, rendering it a naturally advantageous material for preventing permanent deformation at higher temperatures. However, its poor resistance to thermal and fatigue cracking limits its application in the paving industry. This study aimed to improve the low-temperature and fatigue performance of hard asphalt binders by using the newly developed vegetable oil-based sub-epoxidized rapeseed oil (SERO). Two SEROs with epoxidation degree of 49.1% and 98.1% were synthesized through an oxidation reaction, respectively. Subsequently, the microstructural characteristics of SEROs were examined by Fourier transform infrared spectroscopy (FTIR) and Hydrogen nuclear magnetic resonance tests. The anti-oxidative aging properties of SERO modified hard asphalt binders were investigated through the utilization of mass loss and aging index. Additionally, the comprehensive rheological properties of SERO modified hard asphalt binders were explored via dynamic shear rheometer and bending beam rheometer tests. Furthermore, the modification mechanism of SERO on hard asphalt binders was confirmed through the quantitative analysis using the FTIR test. The findings suggested the improvement in anti-volatilization and anti-oxidative aging performance of bio-modified hard asphalt binders, which was positively related to the epoxidation degree of SERO. A notable softening effect of SERO on the hard asphalt binders was observed, which enhanced their resistance to thermal and fatigue cracking at lower and intermediate temperatures. The epoxy groups within SERO engaged in ring-opening reactions, forming a new oxygen bridge bond by combining with the unsaturated double bond presented in the asphalt. Consequently, this process resulted in the formation of cross-linked structures within bio-modified hard asphalt binders, thereby enhancing the elasticity. Notably, this phenomenon was most conspicuous in the SERO-H modified 50# binder. Finally, the environmental and economic assessment of SERO modified hard asphalt binders were conducted by the techno-economic method and the emission factors technique. The data revealed that the production of one ton of SERO modified hard asphalt binders could reduce the production costs by about 30%, energy consumption and CO2 emissions by around 20% in contrast to styrene–butadiene–styrene block copolymer modified asphalt binders. Hence, the substantial economic and environmental advantages make SERO an attractive bio-renewable additive for sustainable pavements.

Synthesis of Multisubstituted 2,3-Allenamides via Palladium-Catalyzed Carbonylation of Propargylic Esters.

2,3-Allenamides are an important class of unsaturated group-substituted carbonyl compounds. A palladium-catalyzed aminocarbonylation of propargyl acetates with amines for the synthesized tri-/tetrasubstituted 2,3-allenamides has been developed. A broad range of tri-/tetrasubstituted 2,3-allenamides have been prepared from propargyl acetates in good to excellent yields. The reaction featured mild reaction conditions and good functional group tolerance. The applicability of this methodology was further highlighted by the late-stage modification of several natural products and pharmaceuticals.

Zr-decorated hyper-cross-linked polymers for highly selective upgrading of furfural to furfuryl alcohol

In the present study, the ultra-large specific surface area Zr-decorated hyper-cross-linked polymers (HP) were firstly developed for the catalytic production of furfuryl alcohol (FOL) from furfural (FAL) using isopropanol as both the hydrogen source and solvent. Comprehensive characterizations were performed to uncover the basic physicochemical properties. The as-prepared Zr/HP showed large specific surface area of ∼1000 m2/g, good dispersion of Zr species, plentiful acidity and basicity. 2.5Zr/HP presented the highest activity in the FAL-to-FOL transformation, wherein 97.4 % FAL conversion and 92.9 % FOL yield were achieved within 2 h at 160 °C. The recycling experiments revealed that the as-fabricated Zr-decorated hyper-cross-linked polymers presented good recyclability without significant loss of reactivity even after two consecutive cycles, owing to the strong interaction between hyper-cross-linked polymers and grafted Zr species. Kinetical analysis verified that the activation energy for transfer hydrogenation of FAL could be lowered to a certain degree, especially in the case of lower Zr loadings. More gratifyingly, the Zr-decorated hyper-cross-linked polymers were capable of catalyzing other unsaturated compounds with high conversion rates. In addition, the plausible pathway for the FAL-to-FOL transformation over Zr-decorated hyper-cross-linked polymers was proposed.

Sustainable depolymerization of lignin into aromatic compounds using amphiphilic Anderson-type polyoxometalate catalysts

Lignin serves as a primary abundant source of renewable aromatic compounds. Achieving efficient breakdown of lignin and retaining its aromatic properties is highly desirable but remains a challenging task. To address this challenge, we synthesized Anderson-type polyoxometalate (POM) catalysts, particularly [CTAC]2[CoMo6]. We then investigated the effectiveness of the POM catalysts in the oxidative depolymerization of larch lignin. Under conditions of 160 °C, 1.0 MPa oxygen atmosphere, and a catalyst-to-substrate ratio of 1:5, we achieved a monomer yield of phenolic compounds at 12.43 wt%. The unsaturated coordination sites of Mo5+ within the catalysts were identified as active sites, facilitating enhanced O2 adsorption and activation. The enhanced O2 adsorption significantly influenced the production of aromatic monomers from lignin. We observed that the catalysts effectively cleaved CC bonds in β-O-4 dimer compounds using lignin dimer model compounds. Notably, the [CTAC]2[CoMo6] catalyst exhibited excellent stability across five cycles, maintaining its high efficiency in lignin depolymerization. This indicates that Anderson-type POM-based catalysts exhibit potential for sustainable conversion of biomass into valuable compounds and for enhancing lignin valorization processes.

Polysulfides for presulfiding of hydrogenation catalysts: synthesis, mechanism and applications

Presulfiding agents are widely used in oil refining and chemical industry, how to produce safe and efficient presulfiding agent by more environmentally friendly synthesis process are still problems to be solved. In this study, the organic polysulfide FSA-55 was synthesized by a practical one-pot process using isobutene and sulfur as raw materials and organic amine as a catalysts. The product components were analyzed and the possible catalytic reaction pathways in the thermal conversion of sulfides were elucidated. The amine catalysts showed a catalytic activities in inducing the ring opening of the cyclic molecular structure of sulfur at high temperature, thereby releasing the reactive sulfur radicals, which react with unsaturated double bonds through addition reactions. Different molecular structures of polysulfide were generated through molecular rearrangement and cyclization reactions. The suitability of the product as a presulfiding agent was investigated by analyzing the thermal properties and studying the presulfiding effect on hydrogenation catalysts. The polysulfide has a wide decomposition temperature range (100–260 °C), which can effectively avoid the occurrence of concentrated exothermic phenomena during presulfiding of hydrogenation catalysts. The presulfiding degree of the catalysts can reach 58.32%, which shows the great potential of oil processing as a presulfiding agent.

Direct detection of monoterpenes in evacuated air atmospheres by glow discharge plasma source for mass spectrometry

Some compounds, including the monoterpenes, are difficult to be analyzed by chemical ionization mass spectrometry (CI-MS) mass spectrometry because of having distinct chemical features of unsaturated bonds in relatively large molecule, which is responsible for occurring fragmentation of molecular ions. A direct detection of monoterpenes, including monocyclic, bicyclic and oxygenated (acyclic), was carried out using a soft plasma ionization (SPI) source combined with a q-mass spectrometer (q-MS). Detectable signals for monoterpenes were examined in an ambient air discharge plasma when varying the discharge parameters, such as discharge pressure (0.4–3.0 kPa) and sample/carrier pressure ratio (R = 5–100%). Furthermore, to consider the ionization reactions in detail, nitrogen gas was also used as the discharge gas (carrier gas). Monoterpenes, including cross-linked bicyclic (α-pinene and β-pinene) and oxygenated (linalool, geraniol, nerol and eucalyptol), in which their simple spectrum patterns can be obtained with little or no fragmentation at an ambient air pressure of several kPa, has successfully conducted by the pulsed dc SPI-MS. To our knowledge, this is the first report demonstrating that the spectrum pattern of monoterpenes could be directly detected without any complicated fragmentation of analyte ions in the SPI source.

How the addition of atomic hydrogen to a multiple bond can be catalyzed by water molecules.

Observational data show complex organic molecules in the interstellar medium (ISM). Hydrogenation of small unsaturated carbon double bond could be one way for molecular complexification. It is important to understand how such reactivity occurs in the very cold and low-pressure ISM. Yet, there is water ice in the ISM, either as grain or as mantle around grains. Therefore, the addition of atomic hydrogen on double-bonded carbon in a series of seven molecules have been studied and it was found that water catalyzes this reaction. The origin of the catalysis is a weak charge transfer between the π MO of the unsaturated molecule and H atom, allowing a stabilizing interaction with H2O. This mechanism is rationalized using the non-covalent interaction and the quantum theory of atoms in molecules approaches.