Search

Heterogeneous chemistry of oxidized carbons in aerosol phase is known to significantly contribute to secondary organic aerosol (SOA) burdens. The UNIfied Partitioning Aerosol phase Reaction (UNIPAR) model was developed to process the multiphase chemistry of various oxygenated organics into SOA mass predictions in the presence of salted aqueous phase. In this study, the UNIPAR model simulated the SOA formation from gasoline fuel, which is a major contributor to the observed concentration of SOA in urban areas. The oxygenated products, predicted by the explicit mechanism, were lumped according to their volatility and reactivity and linked to stoichiometric coefficients which were dynamically constructed by predetermined mathematical equations at different NOx levels and degrees of gas aging. To improve the model feasibility in regional scales, the UNIPAR model was coupled with the Carbon Bond 6 (CB6r3) mechanism. CB6r3 estimated the hydrocarbon consumption and the concentration of radicals (i.e., RO2 and HO2) to process atmospheric aging of gas products. The organic species concentrations, estimated by stoichiometric coefficient array and the consumption of hydrocarbons, were applied to form gasoline SOA via multiphase partitioning and aerosol-phase reactions. To improve the gasoline SOA potential in ambient air, model parameters were also corrected for gas–wall partitioning (GWP). The simulated gasoline SOA mass was evaluated against observed data obtained in the University of Florida Atmospheric PHotochemical Outdoor Reactor (UF-APHOR) chamber under varying sunlight, NOx levels, aerosol acidity, humidity, temperature, and concentrations of aqueous salts and gasoline vapor. Overall, gasoline SOA was dominantly produced via aerosol-phase reaction, regardless of the seed conditions owing to heterogeneous reactions of reactive multifunctional organic products. Both the measured and simulated gasoline SOA was sensitive to seed conditions showing a significant increase in SOA mass with increasing aerosol acidity and water content. A considerable difference in SOA mass appeared between two inorganic aerosol states (dry aerosol vs. wet aerosol) suggesting a large difference in SOA formation potential between arid (western United States) and humid regions (eastern United States). Additionally, aqueous reactions of organic products increased the sensitivity of gasoline SOA formation to NOx levels as well as temperature. The impact of the chamber wall on SOA formation was generally significant, and it appeared to be higher in the absence of wet salts. Based on the evaluation of UNIPAR against chamber data from 10 aromatic hydrocarbons and gasoline fuel, we conclude that the UNIPAR model with both heterogeneous reactions and the model parameters corrected for GWP can improve the ability to accurately estimate SOA mass in regional scales.

Secondary organic aerosol (SOA) formed from vehicle exhaust contributes substantially to the atmospheric particulate matter in urban air but there still remain uncertainties in the simulation of the SOA by air quality models. This omission is due partly to uncertainties about the differences in SOA formation between vehicle types, exhaust aftertreatment devices, and oxidation conditions in the air. In this work, smog chamber experiments were conducted to investigate SOA formation from diluted exhaust gases emitted by two light-duty gasoline vehicles and one passenger and one medium-duty diesel vehicles. Emissions were aged in the smog chamber under light (ultraviolet) and dark (with high O3) conditions. In these experiments, there were considerable emissions of elemental carbon and primary organic aerosol by a gasoline direct-injection vehicle and a diesel truck, but the corresponding emissions were relatively small from a gasoline vehicle with port fuel injection and a passenger diesel vehicle. However, significant amounts of SOA were produced from all four vehicles. Box model simulations indicated that OH exposure was higher and the ratio of NO to peroxy radicals (HO2 + RO2) was lower under dark conditions in the presence of high added O3 than under light conditions. The higher concentrations and yields of SOA under dark conditions than under light conditions could partly be explained by the lower NO/(HO2 + RO2) ratios under dark conditions. Simulations with a volatility basis-set model indicated that aromatic compounds were the dominant precursors of SOA from gasoline vehicles (64–84%), whereas unspeciated intermediate-volatility organic compounds (IVOC) were the dominant precursors for the production of SOA from diesel vehicles (75–87%). The observed O : C ratios were higher for gasoline SOA (0.7–0.8) than diesel SOA (0.3–0.4), and this difference was explained by the differences in their precursors. SOA formed under the light and dark conditions was similar in the dominant precursors and oxidants, as well as the O : C ratios, but different in the NO/(HO2 + RO2) ratios during the oxidation processes. Thus, we cannot conclude that SOA formed under the light and dark conditions has similar chemical composition, and their characteristics should be further examined in future studies.

Cyclohexanone is widely used in coatings, pesticides, dyes, lubricants, and other industries due to its high solubility and low volatility, but designing highly active and stable heterogeneous cata...

Hybrid Reactive Distillation Configurations (HRDCs), with single feed/multi-side draws having both reactive and non-reactive sections, can be effectively used to get the desired selectivity in multi-reaction systems. Our previous research (Hasan et al., 2013a,b, 2014, 2015; Singh et al., 2018, 2019, 2021) was focused on finding designs of hybrid RD columns of desired selectivity for complex reaction schemes without inerts. In the present work, we extend the approach to cover a wider range of multi-reaction schemes and include systems with inerts present in feed as well as inert forming multi-azeotropes in the column. Using the concepts of attainable region and graphical simulation approach, we developed algorithms that are capable of finding at least one feasible design of hybrid RD configuration successfully that give the desired selectivity in the systems under study. Further, the effect of inert percentage in feed and volatility of inert on the design of hybrid RD columns is also investigated. The developed methodology allows us to find the maximum allowable percentage of inerts in feed to obtain a feasible design of hybrid RD column. The methodologies developed here are applicable to any number of inerts present in the feed, any number of total components, inerts of any volatility, inerts forming multi-azeotropes with any of the reactant, product/desired product. However, they are limited to single feed configurations and to the multi-reaction schemes with a maximum of three products undergoing further side reactions wherein the reactant(s) is/are of intermediate volatility.

We observe the impact of bouncing and floating of water drops on a pool of immiscible volatile oil pools at low Weber numbers. The residence time of the impacting drop ranges from a few milliseconds to a few seconds before it sinks into the lighter oil phase. It is hypothesized that the confined evaporation from the volatile oil pool replenishes the thin film draining and results in prolonged floating and delayed sinking of drops into the oil pool. Water drops are released from a low height to impact on volatile hydrocarbon oil deep pools of various volatilities. The floating dynamics and residence times are captured using high-speed imaging. A theoretical model for the residence time has been developed to evaluate the hypothesis. The drop residence time is found to be directly proportional to the volatility of the oil pool in accordance with the hypothesis. The mathematical model incorporating the coupled confined evaporation and film draining dynamics is found to be in well agreement with the experimentally observed residence time. The bouncing-sinking regime map has been developed based on the experimental data.

Palm biodiesel-ethanol blends could be the better automotive fuel over palm biodiesel alone owing to the high oxygen content and high volatility of ethanol. The evaporation and burning characteristics of palm biodiesel with 10%, 20%, and 30% ethanol by volume concentration respectively, were investigated by using the droplet experiment. Rapid bubble growth and bubble explosions during the heating stage were observed to be substantial for the palm biodiesel droplet added with 30% volume of ethanol (BE30). Adding ethanol in palm biodiesel increased the ignition delay and burn-rate constant by up to 38.6% and 23.2%, respectively whereas, the evaporation duration and burning period decreased by up to 20.6% and 22.5%, respectively. Overall, the relatively shorter evaporation duration and higher burn-rate found for the BE30 droplet could promote high thermal efficiency and has the potential to achieve ultra-low carbon monoxide (CO) and unburned hydrocarbons (UHCs) emissions in diesel and gas turbine engines.

Thermogravimetry, differential scanning calorimetry, and flow methods were used to investigate thermal properties of a series of cobalt(II) β-iminoketonates [R2C(NR1)CHC(O)R2]. The consecutive order of their volatility was determined. The complexes do not decompose up to melting and do not undergo phase transitions. For the complex (R1 = Н, R2 = Me) the temperature dependence of sublimation ln (p/p0) = 32.02 ‒ 16822/T(K) at 402.6‒433.7 K was measured and the values of ΔsublH°Т* = 140±4 kJ/mol and ΔsublS°Т* = 266±10 J/(K·mol) were calculated.

1,3-Butadiene has wide industrial application with main focus on production of butadiene-based polymers. The accurate determination of 1,3-butadiene is complicated by its high volatility. The aim of this study was to develop the method for determination of 1,3-butadiene migrated from butadiene-based polymers to air and water based on thermal desorption–gas chromatography–mass spectrometry. Purge-and-trap method was used for transferring analyte from water to gas phase followed by trapping on multi-bed sorbent tube (Carbopack B+X). The calibration plots for air and water with coefficients of determination R 2 > 0.99 were obtained in ranges 2–20, 10–200 and 50–1000 ng. The limits of detection and quantification of 1,3-butadiene were 0.02 ng and 0.06 ng, respectively. The accuracy of the developed method expressed in spike recoveries was in the range from 92 to 101% for air, and from 94 to 95% for water, with relative standard deviations below 10% for both matrices. The developed method was successfully applied for determination of 1,3-butadiene migration level from personal protective equipment (shoes) to air and water. The concentrations of 1,3-butadiene migrated to water and air were 0.044 µg L−1 and 0.91 µg m−3, respectively.

The high volatility, water‐immiscibility, and light/oxygen‐sensitivity of most aroma compounds represent a challenge to their incorporation in liquid consumer products. Current encapsulation methods entail the use of petroleum‐based materials, initiators, and crosslinkers as well as mixing, heating, and purification steps. Hence, more efficient and eco‐friendly approaches to encapsulation must be sought. Herein, we propose a simple method by making use of a pre‐formed amphiphilic polymer and employing the Hansen Solubility Parameters approach to determine which fragrances could be encapsulated by spontaneous coacervation in water. The coacervates do not precipitate as solids but they remain suspended as colloidally stable liquid microcapsules, as demonstrated by fluorescence correlation spectroscopy. The effective encapsulation of fragrance is proven through confocal Raman spectroscopy, while the structure of the capsules is investigated by means of cryo FIB/SEM, confocal laser scanning microscopy, and small‐angle X‐ray scattering., The use of a PEG‐g‐PVAc amphiphilic graft copolymer together with hydrophobic fragrances in aqueous medium leads to the spontaneous formation of colloidally stable suspensions of liquid coacervate droplets. Arrows indicate the local turbulences sustaining the spontaneous mixing of the components. The bottom panel shows the confocal Raman microspectroscopy mapping of a multicompartment coacervate droplet with carvone as fragrance.

Polonium is formed in relatively large quantities in lead-bismuth eutectic (LBE) cooled nuclear systems. Because of its radiotoxicity and volatility, a good understanding of the chemical equilibria governing polonium release from LBE is required. In this work, a set of thermochemical data is derived for the chemical species involved in the equilibrium between a solution of polonium in LBE and its vapor in inert conditions. The data were obtained by matching thermochemical models with experimental vapor pressure measurements and ab initio results. The dilute-limit activity coefficient of dissolved polonium in LBE is estimated, as well as the solubility of solid lead polonide in LBE. The results indicate that polonium evaporates from LBE according to the experimentally determined Henry’s law, up to dissolved polonium concentrations well above that expected in LBE cooled nuclear systems.

Biofuels can contribute to reducing greenhouse gas emissions and bridging the gap between production and consumption. Ethanol is a renewable source of energy. It can reduce oil dependence and also can be appropriately used in gasoline as a blend. The high cost of dry ethanol has turned the researcher's attention to the more economic hydrous ethanol. However many works were focused on its impact on the engine performance and the exhaust emissions; few works were interested in the phase stability of those blends. This work aims to study the impact of blending cyclohexanol (CH) into hydrous ethanol-gasoline blends as a stabilizing agent. Four dual-alcohol (E5-3CH, E10-3CH, E15-3CH, and E20-3CH) blends were investigated besides their single hydrous ethanol (E0, E5, E10, E15, and E20) blends. The tests involved; water tolerance, distillation curve, and vapor pressure. Vapor lock protection potential, the area under the distillation curve (AUDC), and the area due to azeotrope formation (ADAF) were calculated. The obtained results show that cyclohexanol significantly increases the water tolerance of hydrous ethanol-gasoline blends. The blends of E5 and E10 which were separated at 30 °C converted into miscible and clear samples when they were blended with 3 vol% of cyclohexanol. These samples can also tolerate additional water. For E20, the addition of 3 vol% of cyclohexanol increased the water tolerance by about six times. Also, it was found that cyclohexanol does not have any negative effect on the volatility properties of the fuel blends. It was found that blending CH into the hydrous ethanol blends causes a significant increase in the AUDC and consequently, the area due to azeotrope formation (ADAF) decrease.

High-pour point and high-viscosity crude oil can be gathered and transported below the pour point during a high water-cut period. However, oil under these conditions can easily aggregate, thereby blocking the pipeline. In this study, a comprehensive field experimental pipeline system (368 m long and 64 mm internal diameter (ID)) was developed to investigate the pipeline blockage mechanism. The changes in the pressure, temperature, and oil–water morphology during cooling experiments were studied. The pipe flow regime under different flow rates of water-blending conditions was divided into blockage, transition, and safe operation modes. The blocking mode was divided into stable development, rising volatility, and fast congestion periods. The rheological change of non-Newtonian crude oil during the cooling process was the dominant mechanism of blockage that caused successive decreases in the oil–water interface until the water phase channel was blocked, finally causing a surge in the flow resistance and pressure drop. The correlation equation of the single well temperature limits as functions of fluid flow rate and water-cut was established, and the error between the prediction results and experiments was between 0.12–0.20 °C. The prediction method for the minimum water-blending flow rate was combined with heat transfer analysis, and the corresponding temperature limit was less than the pour point of crude oil at approximately 1–10 °C (liquid flow rate: 5–30 m3/d, water-cut: 80%–90%). The investigations conducted in this study further ascertained the crucial impact of non-isothermal and non-Newtonian characteristics on the low-temperature oil–water two-phase flow.

This study was a successful endeavor to develop and investigate the suitability of a bioadhesive wound-healing gel based on gelatin for first-aid purposes. Polyethylene glycol (PEG) was used to prepare a denser phase of gelatin chains, and diethyl ether (DEE) was used to introduce high volatility to the solution. The prepared solution was stable in the storage container but rapidly formed (within 3 s) a protective and bioadhesive gel around the wound surface by being sprayed over the wound. Besides, it also suppressed pain and showed moderate antimicrobial activity against S. aureus. It was also found highly biocompatible and non-toxic. All the results revealed that the prepared solution could be an effective candidate for treating minor injuries or burn, especially for a first-aid purpose. [Image: see text]

One of the highlights of green chemistry is the development of techniques and procedures with low environmental impact. In the last years, deep eutectic solvents (DES) have become an important alternative to conventional organic solvents. For a period ionic liquids have provoked remarkable interest, but they have been displaced by DES because they show easier preparation methods, lower prices, many of them are biodegradable and compatible with biological systems. In addition, they show adjustable physicochemical properties, high thermal stability, low volatility and are compatible with water. In this paper is reviewed the state of the art of the use of DES paying special attention to the role of reaction media in organic synthesis., Deep eutectic solvents are an interesting alternative to conventional solvents, both as a reaction medium and for many processes and technologies used in chemistry and related sciences. They are easily prepared, versatile, many of them can be obtained from renewable sources and can be designed and adapted for specific processes. For all these reasons, they have been studied intensively in recent years and their interest is constantly growing. This paper reviews some of the most prominent applications and which are the fields of interest that may be a focus of applications in the near future.

With regard to the radioactive waste vitrification technology, literature data on the behavior of technetium and its release into the gas phase are reviewed. In various types of spent nuclear fuel (SNF), the content of technetium varies from 16 to 1350 g per 1 ton of SNF. In nitric acid solutions, technetium exists mainly in the form of pertechnetate anions TcO4– and, when heated, is released into the gas phase in the form of Тс2О7 and НТсО4. The volatility of technetium during vitrification varies from fractions of a percent to 70%. Two directions of technological solutions for capturing technetium from the gas phase are described: low-temperature methods using liquid-type apparatus and high-temperature methods with capturing onto zeolite and aluminosilicate filters.

The volatilities of the components of the saturated vapors of molten UCl4–NaCl–KCl mixtures containing 2.0, 5.0, 12.2, 25.1, 32.9, and 49.7 mol % UCl4 are measured by a transpiration technique in the temperature range 880–1200 K. The chemical composition of the saturated vapors is determined. The vapor phase is most likely to contain the binary NaUCl5 and KUCl5 compounds, which make a significant contribution to the total vapor pressure over the molten mixtures. The molten mixtures are found to exhibit negative deviations from ideal behavior.

Introduction (problem statement and relevance). Hydrocarbon emissions from vaporizationtank fuel contribute significantly to the total emissions of hazardous substances from vehicles equipped with spark ignition engines. To meet the established standards for limiting hydrocarbon emissions caused by evaporation, all modern vehicles use fuel vapor recovery systems, the optimal parameters of which require the availability and application of mathematical models and methods for their determination.The purpose of the research was to develop a model of vapor generation processes in the car fuel tank and a methodology for determining the main quantitative parameters of the vapor-air mixture.Methodology and research methods. The analysis of the processes of vapor generation in the fuel tank was carried out. It was shown that the mass of hydrocarbons generated in the steam space was directly proportional to its volume and did not depend on the amount of fuel in the tank.Scientific novelty and results. New analytical dependences of the vaporization amount on the saturated vapor pressure, barometric pressure, initial fuel temperature and fuel heating during parking have been obtained.Practical significance. A formula was obtained to estimate the temperature of gasoline boiling starting in the tank, depending on the altitude above sea level and the volatility of gasoline, determined by the pressure of saturated vapors. Using the new equations, the vaporization analysis in real situations (parking, idling, refueling, explosive concentration of vapors) was carried out.

Roasted coffee oil (RCO) is rich in volatile organic compounds (VOCs), but the VOCs’ volatility and the presence of unsaturated fatty acids make RCO unstable. The microencapsulation process can extend RCO properties by transforming the liquid RCO into stable powders for further application in coffee brews to better result in-cup. In this work, a central composite rotational design was used to study the effect of the emulsification process and discuss the effect of added microcapsules to instant coffees on the time-resolved release of VOCs upon reconstitutions. Capsules were produced by complex coacervation loaded with RCO, and ultrasound-assisted (US) emulsification was used to obtain stable coffee oil–loaded emulsions. VOC release was monitored by proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF–MS). High encapsulation efficiency (EE) (> 80%) was obtained even at a high load (100%) of RCO. EE was only affected by US power while particle mean size (D43) was strongly affected by US power and the RCO concentration. The presence of microcapsules affected the VOC release from the moment of reconstitution. The microcapsules accelerated the VOC release in soluble coffee, while in instant cappuccino, an opposite effect was observed. A zero-order model described well the mechanism of VOC release during the first 300 s. The diffusional exponent values of the Korsmeyer–Peppas equation explained a zero-order transport during the first seconds of release (burst effect) and a non-Fickian release mechanism when the release slowed down. Such findings shed new light on the development of instant coffees in order to improve their sensorial properties.

A model of the formation of surrogate organic aerosol (OA) in the atmosphere upon the condensation of different volatility component is considered. The model takes into account the physical and chemical properties of individual components, determining their partial pressures over particles (Pi, atm) and hygroscopicity. The organic compounds (OCs) (components of surrogate particles) are taken to be organic peroxides and nitrates IALD, ISNP, and INPN, which are chemical transformation products of biogenic isoprene and α-pinene. The results of calculations (using the AIOMFAC model) reveal a complex character of the changes in activity coefficients (γi) of components for variations in the composition of OA. The surrogate particles were found to be significantly hygroscopic. The equilibrium composition of particles calculated from these data for the background atmosphere and taking into account their hygroscopicity and γi of components shows clearly expressed deviations from that found under the approximation that physical and chemical properties of particle ingredients are independent, which should be taken into account in the construction of models for the formation of real secondary OA in the atmosphere.

Gases, vapors, liquid sprays, aerosols and other forms of ignitable fluids dispersed into the atmosphere, under certain circumstances, may encounter a hot surface. When investigating a fire, it may be necessary to determine in such cases if the hot surface was a competent ignition source. The paper reviews the available experimental data and findings on this topic and gives appropriate advice. It is shown that, unlike the autoignition temperature (AIT), which is only slightly dependent on test conditions, the hot-surface ignition temperature (HSIT) is highly dependent on the test environment conditions. The primary variable affecting the outcome is the degree of ‘enclosedness.’ If the degree of enclosedness is not extreme, a standard recommendation is that the hot-surface ignition temperature might be assumed to be 200°C higher than the AIT. But for conditions of significant enclosedness, the actual ignition temperature is more influenced by the fuel’s volatility (which is related to its flash point) than its AIT value. Higher volatility fuels are harder, not easier, to ignite from a hot surface. Since gasoline is the most volatile of the common automotive-use ignitable liquids, it turns out to be the one which is the hardest to ignite by a hot surface. Nonetheless, in some cases, vehicular engine compartment temperatures can become high enough for gasoline to get ignited. When conducting HSIT tests, it is important to be cognizant of the probabilistic nature of the ignition problem.

Multizonal thermodynamic equilibrium calculation is one of the methods used in estimating or explaining the fate of elements such as heavy metals during waste incinerations and probably only one method that can estimate the fate of trace elements, but the ability of the calculation as a fate-estimation tool was not fully examined. This study examines the performance of multizonal thermodynamic equilibrium calculation applied to waste incineration by comparing the calculated results with the results from the incineration test and literature information. High temperature behaviors of the heavy metals were also reviewed to correctly understand their gas phase speciation in the incinerator, and the thermodynamic data of gaseous Cd species were modified to better reproduce the high temperature vaporization behavior. The calculation represented the high volatility of Hg, Cd, Pb, and low volatility of Cr in the incineration, whereas the measured high volatility of Zn and As could not be obtained by the calculation. The calculation succeeded in reproducing the possible gas phase chemical speciation of heavy metals in the incinerator expected from the review on the high temperature properties, whereas the calculated fly ash speciation does not match with the measured speciation. Possible reasons for these inconsistencies were considered.

Aerosol microphysical processes are essential for the next generation of global and regional climate and air quality models to determine particle size distribution. The contribution of organic aerosols (OAs) to particle formation, mass, and number concentration is one of the major uncertainties in current models. A new global–regional nested aerosol model was developed to simulate detailed microphysical processes. The model combines an advanced particle microphysics (APM) module and a volatility basis set (VBS) OA module to calculate the kinetic condensation of low-volatility organic compounds and equilibrium partitioning of semi-volatile organic compounds in a 3-D framework using global–regional nested domain. In addition to the condensation of sulfuric acid, the equilibrium partitioning of nitrate and ammonium, and the coagulation process of particles, the microphysical processes of the OAs are realistically represented in our new model. The model uses high-resolution size bins to calculate the size distribution of new particles formed through nucleation and subsequent growth. The multi-scale nesting enables the model to perform high-resolution simulations of the particle formation processes in the urban atmosphere in the background of regional and global environments. By using the nested domains, the model reasonably reproduced the OA components obtained from the analysis of aerosol mass spectrometry measurements through positive matrix factorization and the particle number size distribution in the megacity of Beijing during a period of approximately a month. Anthropogenic organic species accounted for 67 % of the OAs of secondary particles formed by nucleation and subsequent growth, which is considerably larger than that of biogenic OAs. On the global scale, the model well predicted the particle number concentration in various environments. The microphysical module combined with the VBS simulated the universal distribution of organic components among the different aerosol populations. The model results strongly suggest the importance of anthropogenic organic species in aerosol particle formation and growth at polluted urban sites and over the whole globe. Aerosol microphysical processes are essential for the next generation of global and regional climate and air quality models to determine particle size distribution. The contribution of organic aerosols (OAs) to particle formation, mass, and number concentration is one of the major uncertainties in current models. A new global-regional nested aerosol model was developed to simulate detailed microphysical processes. The model combines an advanced particle microphysics (APM) module and a volatility basis set (VBS) OA module to calculate the kinetic condensation of low-volatility organic compounds and equilibrium partitioning of semi-volatile organic compounds in a 3-D framework using global-regional nested domain In addition to the condensation of sulfuric acid, the equilibrium partitioning of nitrate and ammonium, and the coagulation process of particles, the microphysical processes of the OAs are realistically represented in our new model. The model uses high-resolution size bins to calculate the size distribution of new particles formed through nucleation and subsequent growth. The multi-scale nesting enables the model to perform high-resolution simulations of the particle formation processes in the urban atmosphere in the background of regional and global environments. By using the nested domains, the model reasonably reproduced the OA components obtained from the analysis of aerosol mass spectrometry measurements through positive matrix factorization and the particle number size distribution in the megacity of Beijing during a period of approximately a month. Anthropogenic organic species accounted for 67 % of the OAs of secondary particles formed by nucleation and subsequent growth, which is considerably larger than that of biogenic OAs. On the global scale, the model well predicted the particle number concentration in various environments. The microphysical module combined with the VBS simulated the universal distribution of organic components among the different aerosol populations. The model results strongly suggest the importance of anthropogenic organic species in aerosol particle formation and growth at polluted urban sites and over the whole globe.

The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on‐line gas phase chromatography technique, in the temperature range 350–600 °C. Under the exactly same chemical conditions, comparative studies with the lighter homologues of Group 5 in the Periodic Table clearly indicate the volatility sequence being NbOCl3 > TaOCl3 ≥ DbOCl3. From the obtained experimental results, thermochemical data for DbOCl3 were derived. The present study delivers reliable experimental information for theoretical calculations on chemical properties of transactinides., Dubnium obeys Mendeleev's periodicity. Fifty years after the discovery of this element, its chemical behavior was experimentally revisited. From the gas chromatographic investigation of the volatile oxychloride compound, a trend of decreasing volatility along Group 5 elements was deduced, in agreement with the expectations by the laws established in the Periodic Table.

A novel method of using anion-functionalized ionic liquids (ILs) with high NO absorption capacity and reversibility for the capture and in situ oxidation of low-concentration NO was established. For the mixed gas containing 0.25% NO, the accumulation rate of nitric acid in these ILs was significantly higher than that in the conventional ILs; after absorption and oxidation reached equilibrium, the molar ratio of HNO₃ to [P₄₄₄₆][PhSO₃] was 0.86, which was 5 times as high as that of the conventional IL. Therefore, the problems of low efficiency and poor reversibility of traditional ILs in the absorption and oxidation process were solved. Through absorption and oxidation experiments, quantum chemical calculation, NMR, and time-resolved in situ ATR-FTIR spectroscopic investigation, the results demonstrated that such a high accumulation rate of HNO₃ originated from high uptake of NO through multiple-site interaction. Moreover, high reversibility is attributed to low volatility of conjugated acid of anions and decreased basicity of O sites on anions. We believe that such highly efficient and reversible conversion of low-concentration NO to HNO₃ by ILs provides a new strategy for improving atomic economy of fossil fuel combustion, that is, converting post-combustion pollutants to good valuable chemicals.

A layered graphene oxide/ethylenediamine (GO/EDA) composite film was developed by exposing aqueous GO liquid crystal (GOLC) coating to EDA vapor and its effects on the gas barrier performance of GO film were systematically investigated. When a GO/EDA coating with a thickness of approximately 1 μm was applied to a neat polyethylene terephthalate (PET) film, the resultant film was highly impermeable to gas molecules, particularly reducing the gas permeance up to 99.6% for He and 98.5% for H2 in comparison to the neat PET film. The gas barrier properties can be attributed to the long diffusion length through stacked GO nanosheets. The EDA can crosslink oxygen-containing groups of GO, enhancing the mechanical properties of the GO/EDA coating with hardness and elastic modulus values up to 1.14 and 28.7 GPa, respectively. By the synergistic effect of the viscoelastic properties of GOLC and the volatility of EDA, this coating method can be applied to complex geometries and EDA intercalation can be spontaneously achieved through the scaffold of the GOLC.

Fragrances are frequently added to a variety of products, including food, cosmetics and health products. However, the high volatility and instability of essence limit its application in some fields. In this study, mesoporous silica nanoparticles (MSNs) were prepared to encapsulate eugenol, which could reduce the volatilization of the fragrance molecules. A facile approach was presented to synthesize MSNs with three different pore diameters for encapsulating eugenol. In addition, the properties of MSNs including mean particle size, morphology, encapsulating efficiency and release tendency were characterized. Results showed that the larger the pore diameters of MSNs, the more aromatic molecules were adsorbed. Furthermore, the release mechanism was described as the smaller the pore diameters of MSNs, the slower the release of eugenol.

Treatment of 3 equiv of the potassium salts derived from the β-amino ketones 1-(dimethylamino)-3,3-dimethylbutan-2-one (L1H), 3,3-dimethyl-1-(pyrrolidin-1-yl)butan-2-one (L2H), and 3,3-dimethyl-1-(...

Volatility and viscosity have substantial impacts on gas–particle partitioning, formation and evolution of aerosol and hence the predictions of aerosol-related air quality and climate effects. Here aerosol volatility and viscosity at a rural site (Gucheng) and an urban site (Beijing) in the North China Plain (NCP) in summer and winter were investigated by using a thermodenuder coupled with a high-resolution aerosol mass spectrometer. The effective saturation concentration (C*) of organic aerosol (OA) in summer was smaller than that in winter (0.55 µg m−3 vs. 0.71–0.75 µg m−3), indicating that OA in winter in the NCP is more volatile due to enhanced primary emissions from coal combustion and biomass burning. The volatility distributions varied and were largely different among different OA factors. In particular, we found that hydrocarbon-like OA (HOA) contained more nonvolatile compounds compared to coal-combustion-related OA. The more oxidized oxygenated OA (MO-OOA) showed overall lower volatility than less oxidized OOA (LO-OOA) in both summer and winter, yet the volatility of MO-OOA was found to be relative humidity (RH) dependent showing more volatile properties at higher RH. Our results demonstrated the different composition and chemical formation pathways of MO-OOA under different RH levels. The glass transition temperature (Tg) and viscosity of OA in summer and winter are estimated using the recently developed parameterization formula. Our results showed that the Tg of OA in summer in Beijing (291.5 K) was higher than that in winter (289.7–290.0 K), while it varied greatly among different OA factors. The viscosity suggested that OA existed mainly as solid in winter in Beijing (RH = 29 ± 17 %), but as semisolids in Beijing in summer (RH = 48 ± 25 %) and Gucheng in winter (RH = 68 ± 24 %). These results have the important implication that kinetically limited gas–particle partitioning may need to be considered when simulating secondary OA formation in the NCP.

Ionic liquids (ILs) are molten salts composed of a large organic cation and an organic/inorganic anion. Due to their ionic character, most ILs present advantageous properties over conventional solvents, such as negligible volatility at atmospheric conditions and high thermal and chemical stabilities. The wide variety of IL anion–cation combinations allows these solvents to be designed to display a strong solvation ability for a myriad of active pharmaceutical ingredients (APIs) and (bio)polymers. Given these properties, ILs have been used as solvents and as formulation components in different areas of drug delivery, as well as novel liquid forms of APIs (API-ILs) applied in different stages of development of novel drug delivery systems. Furthermore, their combination with polymers and biopolymers has enabled the design of drug delivery systems for new therapeutic routes of administration.

Cooking emissions account for a major fraction of urban organic aerosol. It is therefore important to understand the atmospheric evolution in the physical and chemical properties of organic compounds emitted from cooking activities. In this work, we investigate the formation of secondary organic aerosol (SOA) from oxidation of gas-phase organic compounds from heated cooking oil. The chemical composition of cooking SOA is analyzed using thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS). While the particle-phase composition of SOA is a highly complex mixture, we adopt a new method to achieve molecular speciation of the SOA. All the GC-elutable material is classified by the constituent functional groups, allowing us to provide a molecular description of its chemical evolution upon oxidative aging. Our results demonstrate an increase in average oxidation state (from −0.6 to −0.24) and decrease in average carbon number (from 5.2 to 4.9) with increasing photochemical aging of cooking oil, suggesting that fragmentation reactions are key processes in the oxidative aging of cooking emissions within 2 d equivalent of ambient oxidant exposure. Moreover, we estimate that aldehyde precursors from cooking emissions account for a majority of the SOA formation and oxidation products. Overall, our results provide insights into the atmospheric evolution of cooking SOA, a majority of which is derived from gas-phase oxidation of aldehydes.

Measurements of particle-size transformations due to changes in temperature, relative humidity, and other environmental factors are essential for understanding aerosol properties, such as its hygroscopicity and volatility. The commonly used measurement techniques, such as tandem differential mobility analyzer (TDMA) and single-particle levitation techniques, allow measurements of only one initial size at a time, which makes their applications to highly dynamic aerosol systems problematic. In this paper, we evaluate the Heisler method developed in the second half of 1970s that uses measurements of size distributions of a polydisperse aerosol before and after it undergoes a growth or evaporation. The Heisler method is based on preservation of particle number concentration and allows simultaneous determination of particle-size changes across the whole measured size distribution. In this paper, we evaluated the Heisler method using numerical techniques and compared it with TDMA measurements during experiments with adipic acid aerosol. We show that the Heisler method is sensitive to counting statistics and that significant errors (over 50%) can occur if there are particles that can grow or evaporate in or out of the measured size range. Otherwise, the Heisler method gives results within 5% of those obtained with TDMA measurements, providing a faster alternative to the TDMA technique.

Photothermal effect has shown great promise in manipulating the droplet evaporation. In this work, the evaporation of a propylene glycol–water binary droplet on the hydrophobic surface induced by the photothermal effect of a focused infrared laser with a wavelength of 1550 nm was experimentally investigated. Dynamic evaporation behaviors were discussed through the visualization method and image processing technique. Experimental results showed that the photothermally induced evaporation of such a binary droplet could be divided into two stages: the first stage dominated by the evaporation of water with more volatility represented by rapid variations of the droplet volume and geometric parameters and the second stage dominated by the evaporation of propylene glycol with less volatility represented by a smaller slope. Correspondingly, the binary droplet evaporation first experienced the mixed mode greatly related to the more volatile component, and then the constant contact radius mode greatly related to the less volatile component. In addition, the effects of the initial composition and input laser power were also discussed. This work provides a deep understanding of the photothermal effect of a focused light-caused evaporation behaviors of the propylene glycol–water binary droplets and a potential route to accommodate various applications using the evaporation of the binary droplet.

Organoselenium compounds with perspective application as Se precursors for atomic layer deposition have been reviewed. The originally limited portfolio of available Se precursors such as H2Se and diethyl(di)selenide has recently been extended by bis trialkylsilyl)selenides, bis(trialkylstannyl)selenides, cyclic selenides, and tetrakis(N,N-dimethyldithiocarbamate)-selenium. Their structural aspects, property tuning, fundamental properties, and preparations are discussed. It turned out that symmetric four- and six-membered cyclic silyl selenides possess well-balanced reactivity/stability, facile and cost-effective synthesis starting from inexpensive and readily available chlorosilanes, improved resistance toward air and moisture, easy handling, sufficient volatility, thermal resistance, and complete gas-to-solid phase exchange reaction with MoCl5, affording MoSe2 nanostructures. These properties make them the most promising Se precursor developed for atomic layer deposition so far. Jsou představeny organoselenové sloučeniny s perspektivními aplikacemi jako selenové prekurzory pro depozice atomárních vrstev. Nabídka dostupných Se prekurzorů byla rozšířena o bis(trialkylsilyl)selenidy, bis(trialkylstannyl)seleniys, cyklické selenidy a tetrakis(N,N-dimethyldithiokarbamate)-selenium. Jsou diskutovány strukturní aspekty, základní vlastnosti, způsoby přípravy a ladění vlastností sloučenin.

Increasing evidence from experimental studies suggests that the losses of semi-volatile vapors to chamber walls could be responsible for the underestimation of organic aerosol (OA) in air quality models that use parameters obtained from chamber experiments. In this study, a box model with a volatility basis set (VBS) scheme was developed, and the secondary organic aerosol (SOA) yields with vapor wall loss correction were optimized by a genetic algorithm based on advanced chamber experimental data for biomass burning. The vapor wall loss correction increases the SOA yields by a factor of 1.9–4.9 and leads to better agreement with measured OA for 14 chamber experiments under different temperatures and emission loads. To investigate the influence of vapor wall loss correction on regional OA simulations, the optimized parameterizations (SOA yields, emissions of intermediate-volatility organic compounds from biomass burning, and enthalpy of vaporization) were implemented in the regional air quality model CAMx (Comprehensive Air Quality Model with extensions). The model results from the VBS schemes with standard (VBS_BASE) and vapor-wall-loss-corrected parameters (VBS_WLS), as well as the traditional two-product approach, were compared and evaluated by OA measurements from five Aerodyne aerosol chemical speciation monitor (ACSM) or aerosol mass spectrometer (AMS) stations in the winter of 2011. An additional reference scenario, VBS_noWLS, was also developed using the same parameterization as VBS_WLS except for the SOA yields, which were optimized by assuming there is no vapor wall loss. The VBS_WLS generally shows the best performance for predicting OA among all OA schemes and reduces the mean fractional bias from −72.9 % (VBS_BASE) to −1.6 % for the winter OA. In Europe, the VBS_WLS produces the highest domain average OA in winter (2.3 µg m−3), which is 106.6 % and 26.2 % higher than VBS_BASE and VBS_noWLS, respectively. Compared to VBS_noWLS, VBS_WLS leads to an increase in SOA by up to ∼80 % (in the Balkans). VBS_WLS also leads to better agreement between the modeled SOA fraction in OA (fSOA) and the estimated values in the literature. The substantial influence of vapor wall loss correction on modeled OA in Europe highlights the importance of further improvements in parameterizations based on laboratory studies for a wider range of chamber conditions and field observations with higher spatial and temporal coverage.

Proton-transfer-reaction mass spectrometry (PTR-MS) is widely used in atmospheric sciences for measuring volatile organic compounds in real time. In the most widely used type of PTR-MS instruments, air is directly introduced into a chemical ionization reactor via an inlet capillary system. The reactor has a volumetric exchange time of ∼0.1 s, enabling PTR-MS analyzers to measure at a frequency of 10 Hz. The time response does, however, deteriorate if low-volatility analytes interact with surfaces in the inlet or in the instrument. Herein, we present the extended volatility range (EVR) PTR-MS instrument which mitigates this issue. In the EVR configuration, inlet capillaries are made of passivated stainless steel, and all wetted metal parts in the chemical ionization reactor are surface-passivated with a functionalized hydrogenated amorphous silicon coating. Heating the entire setup (up to 120 ∘C) further improves the time-response performance. We carried out time-response performance tests on a set of 29 analytes having saturation mass concentrations C0 in the range between 10−3 and 105 µg m−3. The 1/e-signal decay times after instant removal of the analyte from the sampling flow were between 0.2 and 90 s for gaseous analytes. We also tested the EVR PTR-MS instrument in combination with the chemical analysis of aerosols online (CHARON) particle inlet, and 1/e-signal decay times were in the range between 5 and 35 s for particulate analytes. We show on a set of example compounds that the time-response performance of the EVR PTR-MS instrument is comparable to that of the fastest flow tube chemical ionization mass spectrometers that are currently in use. The fast time response can be used for rapid (∼1 min equilibration time) switching between gas and particle measurements. The CHARON EVR PTR-MS instrument can thus be used for real-time monitoring of both gaseous and particulate organics in the atmosphere. Finally, we show that the CHARON EVR PTR-MS instrument also rapidly detects highly oxygenated species (with up to eight oxygen atoms) in particles formed by limonene ozonolysis.

Bis(trifluoromethylsulfonyl)imidic dicationic liquids containing a disiloxane linker between the imidazole cations have been synthesized. Their thermal stability was estimated, and their melting points, viscosity, and volatility in vacuo were measured. The opportunity to use these ionic liquids as heat transfer agents in a dynamic vacuum has been shown.

A lab-scale (0.03 m di, 0.4 m H) bubble column is investigated as a means of achieving low-temperature evaporation of process streams containing dissolved pharmaceutical APIs in batch and continuous modes. A thermodynamic model is developed from first principles which predicts the rate of evaporation of pure solvents, using a dry stream of air bubbles as the driving force for the mass transfer from a liquid to a gas phase. This model is validated experimentally, and it is demonstrated that saturation is achieved almost instantaneously between liquid and the gas, highlighting the efficiency and potential of this method. Maintaining the bubble flow in the homogeneous regime, various rates of solvent evaporation were achieved based on the solvent's characteristic volatility and fixed process variables. All modelling prediction rates of evaporation of pure solvents are within satisfactory errors of experimental measurements (

In the present work, we performed chassis dynamometer experiments to investigate the emissions and secondary organic aerosol (SOA) formation potential of intermediate-volatility organic compounds (IVOCs) from an on-road Chinese gasoline vehicle. High IVOC emission factors (EFs) and distinct volatility distribution were recognized. The IVOC EFs for the China V vehicle ranged from 12.1 to 226.3 mg per kilogram fuel, with a median value of 83.7 mg per kilogram fuel, which was higher than that from US vehicles. Besides, a large discrepancy in volatility distribution and chemical composition of IVOCs from Chinese gasoline vehicle exhaust was discovered, with larger contributions of B14–B16 compounds (retention time bins corresponding to C14-C16 n-alkanes) and a higher percentage of n-alkanes. Further we investigated the possible reasons that influence the IVOC EFs and volatility distribution and found that fuel type, starting mode, operating cycles and acceleration rates did have an impact on the IVOC EF. When using E10 (ethanol volume ratio of 10 %, v/v) as fuel, the IVOC EF of the tested vehicle was lower than that using commercial China standard V fuel. The average IVOC-to-THC (total hydrocarbon) ratios for gasoline-fueled and E10-fueled gasoline vehicles were 0.07±0.01 and 0.11±0.02, respectively. Cold-start operation had higher IVOC EFs than hot-start operation. The China Light-Duty Vehicle Test Cycle (CLTC) produced 70 % higher IVOCs than those from the Worldwide Harmonized Light Vehicles Test Cycle (WLTC). We found that the tested vehicle emitted more IVOCs at lower acceleration rates, which leads to high EFs under CLTC. The only factor that may influence the volatility distribution and compound composition is the engine aftertreatment system, which has compound and volatility selectivity in exhaust purification. These distinct characteristics in EFs and volatility may result in higher SOA formation potential in China. Using published yield data and a surrogate equivalent method, we estimated SOA formation under different OA (organic aerosol) loading and NOx conditions. Results showed that under low- and high-NOx conditions at different OA loadings, IVOCs contributed more than 80 % of the predicted SOA. Furthermore, we built up a parameterization method to simply estimate the vehicular SOA based on our bottom-up measurement of VOCs (volatile organic compounds) and IVOCs, which would provide another dimension of information when considering the vehicular contribution to the ambient OA. Our results indicate that vehicular IVOCs contribute significantly to SOA, implying the importance of reducing IVOCs when making air pollution controlling policies in urban areas of China.

Multiple additive manufacturing techniques have been developed in recent years to produce structures with tunable physical, chemical, and mechanical properties and defined architecture. Solution electrospinning, although an older and more established technique, normally cannot achieve the pattern resolution and tunability of these newer manufacturing techniques. In this study, we present solution electrowriting as a method to produce fibrous conduits from various polymers with tunable patterns, dimensions, and scaffold porosity. We demonstrate the importance of solvent selection during solution electrowriting and discuss how solvent polarity and volatility can be exploited to controllably alter the structure of the resulting scaffolds. The technique can be readily implemented with equipment for conventional electrospinning and offers versatility, control, and customization that is uncommon in the solution electrospinning field.

Global warming is one of the arch challenges of this era mainly caused by the increasing concentration of carbon dioxide in the atmosphere. Methanation process utilizes carbon dioxide and hydrogen to produce methane gas as an energy-rich fuel. To supply the hydrogen for the methanation process, LOHC could be used as a medium for long-range hydrogen transportation. However, the heat of reaction is needed to recover hydrogen from the LOHC medium. In this study, a new method to utilize the heat from the methanation process for dehydrogenation and optimum conditions are calculated for various LOHC materials. The new process designed uses an Air-Brayton cycle to generate the required high pressure as well as compensate for the LOHC dehydrogenation thermal energy requirement using a proportionate amount of methane produced. Also, the performance of various LOHC materials is compared in the proposed process. The simulation is performed via Aspen Plus® simulator. Dibenzyltoluene is found to be the best selection among the selected LOHC materials for use in this process with a system efficiency of 46.7% with a 100% medium recovery. Pyrrole group LOHC exhibits lower dehydrogenation temperature and energy requirement however are prone to bond scission and generally toxic. Toluene has high volatility resulting in its maximum recovery limited to 96.2% at an elevated pressure of 7 bar decreasing to 84.5% at 1 bar and 30 °C with a system efficiency of 49.08% and a low CVA of 36.74%, while NEC has 63.78% CVA with 55.64% efficiency and DBT has 54.12% CVA with 47.99% efficiency.

Chamber experiments showing “pure biogenic nucleation” have shown an important role for covalently bound organic association products (“dimers”). These form from peroxy-radical (RO2) cross reactions. Chamber experiments at low-NOx conditions often have quite high hydrocarbon reactant concentrations and relatively low concentrations of oxygenated volatile organic compounds (OVOCs). This can skew the radical chemistry in chambers relative to the real atmosphere, favoring RO2 and disfavoring HO2 radicals. RO2 cross reaction kinetics are in turn highly uncertain. Here we explore the implications of the RO2 to HO2 ratio in chamber experiments as well as the implications of uncertain RO2 cross reaction kinetics and the potential for added CO to mimic more atmospheric radical conditions. We treat a plausible range of RO2 rate coefficients under both typical chamber conditions and atmospheric conditions to see how dimerization is affected by high concentrations of OVOCs, and thus lower RO2 : HO2 relative to smog chamber experiments. We find that if RO2 reactions are fast, relatively high yields of low volatility dimers can participate in new particle formation. The results are highly sensitive to both the (uncertain) RO2 kinetics as well as RO2 : HO2, suggesting both that low-NOx chamber results should be extrapolated to the atmosphere with caution but also that the atmosphere itself may be highly sensitive to the specific (and rich) mixture of organic compounds and thus peroxy radicals.

The use of fluorination as a rapid separation technique for quantification of trace-mass, short-lived isotopes is illustrated. Single crystal 238UO2 was exposed to a 14 MeV neutron source to produce mixed fission and activation products. Selective removal of trace volatile fluorides from non-volatile ones produced two results of interest. A decrease in background produced better detection and quantification of select analytes across the gamma spectrum. Second, at the very low burnup condition described, the volatility behaviors of common isotopes were altered relative to their well-established behaviors in higher burnup metal and metal oxide fuels.

A novel, high yield (91 ± 5%) photochemical vapor generation (PVG) method is reported for Os, achieved via photo-reduction reactions in a 1% CH₃COOH medium containing 50 mg L⁻¹ Fe³/²⁺. A sample flow rate of 2 mL min⁻¹ delivered to a flow-through photoreactor provided a 21 s irradiation time prior to passage of the volatile product to an inductively coupled plasma mass spectrometer for detection at m/z 192. A method detection limit of 0.16 pg mL⁻¹ was achieved, a 10-fold enhancement over that obtained using parallel photo-oxidation synthesis of OsO₄ from a 5% HNO₃ medium. Precision of replicate measurement was 4% (RSD) at 10 ng mL⁻¹. Although the identity of the product has not yet been ascertained by GC-MS, based on the chemistry of Os and the reaction conditions, as well as its difference in volatility from OsO₄, a carbonyl or alkyl-substituted carbonyl is suspected e.g., Osᵥᵥ(CO)ₓ(CH₃)ᵧHz.

Bio-based ionogels with versatile properties are highly desired for practical applications. Herein, we designed a novel self-healing, anti-freezing, and self-adhesive ionogel with excellent sensor capability. The ionogel was obtained by cross-linking amino groups (chitosan) and aldehyde groups (dextran oxide) to form Schiff-base bonds in the ionic liquids (EMIMOAc) with TA. Ionogels inherited the superior electrical conductivity of ionic liquids (IG2, 1.1 mS cm−1). Due to the dynamic reaction of Schiff-base bonds, the obtained IG2 possessed self-healing properties (self-healing efficiency = 89%). The presence of TA also provided the ionogel with excellent self-adhesive properties (IG2/TA, adhesive strength to hogskin = 8.05 kPa). Owing to the low freezing point and low vapor pressure of ionic liquids, ionogels were endowed with anti-freeze properties and resistance to solvent volatility. Moreover, the ionogel can act as a strain sensor, and exhibited excellent sensitivity and sensing performance. Our work provided a green and effective method in preparation of the high performance ionogel sensor, which could accommodate future practical industrial applications.

High volatility would lead to a highly flammable hazard, explosion danger, low regeneration efficiency and air pollution. Eutectic solvents (ESs) are assumed to be nonvolatile; however, the assumption is not correct. Here, we, for the first time, find that superbase-derived ESs are highly volatile. Even at room temperature (i.e., 25 °C) and atmospheric pressure, the mass loss of ESs could reach as high as 43.5% after 20 h of exposure. Superbase-derived ESs are promising solvents for CO2 capture, and they are also highly volatile after CO2 capture. We found that typical ethylene glycol : 1,8-diazabicyclo[5.4.0]undec-7-ene (EG : DBU (4 : 1)) has a three-stage volatilizing mechanism. EG and DBU volatilize first by breaking weak hydrogen-bonding interactions (1st stage), followed by the destruction of strong hydrogen-bonding interactions (2nd stage), and finally by destroying much stronger hydrogen-bonding interactions (3rd stage). This work presents a new horizon that ESs and their mixture with CO2 are highly volatile, which is helpful for mitigating laboratory explosion, combustion hazards, air pollution and designing new types of ESs with negligible volatility.

To improve the ablation performance of carbon/carbon (C/C) composite materials, a WSi2–ZrSi2 composite-reinforced ZrxHf1–xC/SiC coating was prepared on the substrate surface via patterning strengthening method. The results show that this coating can protect the substrate from failure for 300 s under an oxyacetylene flame at 2600 °C. Owing to the presence of W, an extremely dense oxide layer was formed on the surface of the coating during initial ablation, which progressively led to the expulsion of the product of oxidation (WO3) from the inner layer, as well as to holes and cracks on healing the coating surface, thereby significantly improving the ablation performance of the C/C composites. In addition, the excellent ablative performance and mechanism of the coating were analysed using volatility diagrams.

Cyclic monoterpenes (CMTs) are intractable natural products with high volatility and strong odors so that there has been no molecular receptor capable of selectively and tightly trapping CMTs in both solution and the solid state. We herein report that a polyaromatic capsule acts as a functional nanoflask for CMTs with the following five features: (i) the capsule can selectively bind menthone from mixtures with other saturated CMTs in water. In contrast, (ii) treatment of the capsule with mixtures of menthone and π-conjugated CMTs gives rise to ternary host–guest complexes with high pair-selectivity. Notably, (iii) the encapsulated menthone displays unusual isomerization from a typical chair conformer to otherwise unstable conformers upon heating. (iv) The selective binding of volatilized CMTs is demonstrated by the capsule even in the solid state at atmospheric pressure. Furthermore, (v) the volatilities of CMTs are significantly suppressed at elevated temperatures by the capsule upon encapsulation in solution as well as in the solid state., A polyaromatic capsule demonstrated its unique host functions toward cyclic monoterpenes, i.e., selective binding in water, pair-selective encapsulation, unusual isomerization, selective binding in the solid state, and remarkable volatility suppression.

Molecular composition, viscosity, and liquid–liquid phase separation (LLPS) were investigated for secondary organic aerosol (SOA) derived from synthetic mixtures of volatile organic compounds (VOCs) representing emission profiles for Scots pine trees under healthy and aphid-herbivory stress conditions. Model “healthy plant SOA” and “stressed plant SOA” were generated in a 5 m3 environmental smog chamber by photooxidation of the mixtures at 50% relative humidity (RH). SOA from photooxidation of α-pinene was also prepared for comparison. Molecular composition was determined with high resolution mass spectrometry, viscosity was determined with the poke-flow technique, and liquid–liquid phase separation was investigated with optical microscopy. The stressed plant SOA had increased abundance of higher molecular weight species, reflecting a greater fraction of sesquiterpenes in the stressed VOC mixture compared to the healthy plant VOC mixture. LLPS occurred in both the healthy and stressed plant SOA; however, stressed plant SOA exhibited phase separation over a broader humidity range than healthy plant SOA, with LLPS persisting down to 23 ± 11% RH. At RH ≤25%, both stressed and healthy plant SOA viscosity exceeded 108 Pa s, a value similar to that of tar pitch. At 40% and 50% RH, stressed plant SOA had the highest viscosity, followed by healthy plant SOA and then α-pinene SOA in descending order. The observed peak abundances in the mass spectra were also used to estimate the SOA viscosity as a function of RH and volatility. The predicted viscosity of the healthy plant SOA was lower than that of the stressed plant SOA driven by both the higher glass transition temperatures and lower hygroscopicity of the organic molecules making up stressed plant SOA. These findings suggest that plant stress influences the physicochemical properties of biogenic SOA. Furthermore, a complex mixture of VOCs resulted in a higher SOA viscosity compared to SOA generated from α-pinene alone at ≥25% RH, highlighting the importance of studying properties of SOA generated from more realistic multi-component VOC mixtures.

This work uses an annular co-flow spray burner as a laboratory test method for evaluating one of the important jet fuel figures of merit, namely lean blowout (LBO), and investigates the coupling of physical and chemical properties affecting this phenomenon. Previous work has shown that relative trends in LBO from different fuels in a real gas turbine are well reflected in this burner setup. Representative characteristics for fuel heat of combustion, volatility, atomization, and pressure are used to produce correlations predicting the LBO for this spray burner, thus these characteristics are considered important toward the prediction of LBO in real gas turbine combustors. The results of this testing are compared to general relations for spray flames as published in prior literature; it is found that equivalence ratio at LBO is positively correlated to fuel flow rates and effective evaporation, and inversely correlated to combustion pressure, heat of combustion, and spray droplet diameter. Using simultaneous OH Planar Laser Induced Fluorescence and Mie scattering imaging of the spray and flame structure, the liquid loading in the flame region is also analyzed for surrogate jet fuels which have comparable derived cetane number (DCN) but have very different compositions. Characteristics that can affect the amount of liquid fuel entering the flame region in near-LBO conditions are discussed. The use of surrogates allows for discussion of the competing effects of volatility and reactivity of fuel components. It is found that the most stable flames occur when the interplay of fuel atomization/volatility and reactivity result in substantial penetration of fuel droplets containing components with high DCN.

A zero-mean flow fan-stirred chamber is used to gather data on suspended fuel droplet evaporation at turbulence intensities, q1/2, approaching 4.30 m/s. This research is driven by the oft-cited but unconfirmed belief that the droplet evaporation rate, K, eventually plateaus with increasing turbulence kinetic energy. Further motivation comes from numerous real-world examples, including combustion systems, where droplets are exposed to turbulence intensities far beyond the experimental capabilities reported in the literature to date. Decane, ethanol, and heptane fuels are selected and grouped into two categories based on the similarity of their vapor pressures, Pv, and mass diffusivity coefficients, DAB, in an effort to discern which thermophysical properties are important to vaporization enhancement, or lack thereof, in high turbulence. Individual droplets with constant initial diameters, d0, of 500 µm are placed in the central region of a highly homogeneous and isotropic turbulent flow field using a novel multi-fiber intersection technique. Neither alkane fuel exhibits any sign of reduced effect of turbulence, as K/K0 remains a strongly linear function of turbulence intensity throughout the test conditions. Conversely, the normalized evaporation rate of ethanol begins to plateau at the higher levels of intensity. Although equalizing the vapor pressures of ethanol and heptane was sufficient to match K/K0 values at low intensity, their divergence as q1/2 increases implies that the thermodynamically-predicted vapor quantity at the droplet surface does not enforce an upper limit on turbulence effectiveness at moderately elevated temperatures. This is confirmed by decane, which has the lowest volatility and yet experiences the greatest improvement in evaporation rate at the highest levels of turbulence.