Mixed Vapors Research Articles

Influence of sulfurization process in tin sulfide and sulfur mixed vapors on the morphology of Cu2SnS3 thin films

Abstract Cu2SnS3 (CTS) is expected to be an absorber material for next-generation solar cells because it is composed of nontoxic, low-cost elements and has an absorption coefficient of >104 cm−1. In this study, the effects of sulfurization in tin sulfide (Sn x S y ) and S mixed vapors on various properties of CTS were investigated by using a 3-zone tube furnace to suppress carrier recombination at the grain boundaries and control the composition of the CTS. The CTS deposited via sulfurization in S vapor only (1-zone CTS) contained different monoclinic and tetragonal CTS structures. The grain size of the CTS thin films deposited via sulfurization in Sn x S y and S mixed vapors was not increased. On the other hand, crystal structure analysis revealed that the CTS had grown to single-phase monoclinic CTS. The results suggest that precipitation in Sn x S y and S mixed vapors contributes to the growth of monoclinic CTS with suitable power-generation characteristics. This finding is important for realizing high-efficiency CTS-based solar cells.

Experimental research on condensation flow and heat transfer characteristics of immiscible binary mixed vapors on different wettability wall surfaces

In the process of biomass gasification syngas waste heat recovery, water and organic compounds in the syngas will condense at the same time, resulting in immiscible condensates adhering to the wall, which can reduce the heat exchanger heat transfer efficiency and working life. Changing the wettability of the wall surface can affect the condensate flow state on the wall surface, thus affecting the condensation heat transfer performance. Water and organic cyclohexane were used as immiscible working fluids in this paper, the condensation flow and heat transfer characteristics of the mixed vapors on hydrophilic, super-hydrophilic, and super-hydrophobic wall surfaces were experimentally investigated. The results showed that cyclohexane in immiscible condensates existed as a liquid film on hydrophilic, super-hydrophilic, and super-hydrophobic wall surfaces, while the water existed in droplets on the hydrophilic and super-hydrophobic wall surfaces, and there were two forms of channels and droplets on the super-hydrophilic wall surface. The condensation heat transfer coefficient on the super-hydrophobic wall surface was higher than that on the hydrophilic wall surface and the super-hydrophilic wall surface, with a maximum of 34% higher than hydrophilic and 45% higher than super-hydrophilic, which was related to the smaller droplet departure diameter on the super-hydrophobic surface. In addition, the super-hydrophilic wall surface had better heat transfer performance than the hydrophilic wall surface only when the immiscible condensate was a "film-channel" flow pattern. The results can provide guidance for enhancing the condensation heat transfer of the water and organic compounds binary mixed vapors.

Highly selective removal of thiophene from benzene by cucurbit[6]uril in both mixed vapors and solutions

The efficient separation of a benzene and thiophene mixture was realized both in mixed vapors and solutions by using cucurbit[6]uril as an adsorbent.

Water/Vapor Assisted Fabrication of Large-Area Superprotonic Conductive Covalent Organic Framework Membranes.

Fabrication of large-area ionic covalent organic framework membranes (iCOMs) remains a grand challenge. Herein, the authors report the liquid water and water vapor-assisted fabrication of large-area superprotonic conductive iCOMs. A mixed monomer solution containing 1,3,5-triformylphloroglucinol (TFP) in 1,4-dioxane and p-diaminobenzenesulfonic acid (DABA) in water is first polymerized to obtain a pristine membrane which subsequently underwent crystallization process in mixed vapors containing water vapor. During the polymerization stage, water played a role of a diluting agent, weakening the Coulombic repulsion between sulfonic acid groups. During the crystallization stage, water vapor played a role of a structure-directing agent to facilitate the formation of highly crystalline, large-area iCOMs. The resulting membranes achieved a proton conductivity value of 0.76 S cm-1 at 90 °C under 100% relative humidity, which is among the highest ever reported. Using liquid water and water vapor as versatile additives open a novel avenue to the fabrication of large-area membranes from covalent organic frameworks and other kinds of crystalline organic framework materials.

Modeling analysis of non-azeotropic and immiscible binary mixed vapors condensation under natural convection

A calculation model describing the condensation heat and mass transfer process of non-azeotropic immiscible binary mixed vapors on the vertical wall under natural convection conditions was developed in this study. The model includes the two possible condensation modes of mixed vapors on the vertical wall as well as the conversion conditions between them. Cyclohexane and water were used as non-azeotropic immiscible mixtures. The reliability of the model was verified first, then the influence of vapor mass concentration and wall subcooling on the condensation mode and heat and mass transfer of the mixed vapors were analyzed. The results showed that the maximum deviation between the model results and the experimental results was less than 21%, confirming that the model was reliable. When the mixed vapors mass concentration was nearly eutectic or the wall subcooling was large, the condensation Mode B (Co-condensation) was more likely to occur than Mode A (Single condensation) due to the decrease in vapor-liquid interface temperature. The condensation mode may change from B to A as the wall length increased along the gravity direction of the condensation wall, and the condensation heat transfer coefficient and mass flux decreased. The thermal resistance of the vapor and liquid phases during condensation was also calculated. In Mode A, regulation of the thermal resistance of the vapor-liquid two phases can be achieved by adjusting the vertical length of the condensation wall and the vapor mass concentration. Condensation Mode B can only be realized by adjusting the wall subcooling. The results of this work may provide a workable reference for condensation heat transfer and enhancement of non-azeotropic immiscible mixed vapors in industrial environments.

Chemical recycling of plastic waste to monomers: Effect of catalyst contact time, acidity and pore size on olefin recovery in ex-situ catalytic pyrolysis of polyolefin waste

The catalytic upgrading of post-consumer mixed polyolefinic waste pyrolysis vapors has been studied over five different solid acid catalysts to understand the effect of vapor-catalyst contact time and catalyst properties on the recovery of light olefins (C2-C4). HZSM-5 with Si/Al ratio of 11 and 27 produced the highest light olefins yields (83.4 wt% and 72.1 wt%, respectively) at a very short contact time of ∼5 ms while extending the contact time (≥23 ms) decreased the olefin yields and resulted in higher yields of aromatics (∼30.0 wt% and ∼40.0 wt%, respectively). Short contact time (5 ms) was not sufficient for HZSM-22 to crack pyrolysis vapors to C2-C4 olefins (8.0 wt%) but increasing contact time improved C2-C4 yields to 53.5 wt% without increased production of aromatics, which may be attributed to its small pore size (shape selectivity). SAPO-34, SAPO-11, and Al-MCM-41 were not selective to light olefins at any studied contact time.

Experimental study on condensation flow patterns and heat transfer characteristics of non-azeotropic and immiscible binary mixed vapors

The condensation phenomenon of non-azeotropic and immiscible mixed vapors always occurs in the waste heat recovery process of biomass gasification gas. During the condensation process, the immiscible condensation products, such as tar and water, have a different flow pattern from the pure working fluid, which can affect the waste heat recovery efficiency and the service life of the heat exchanger. However, the relationship between the flow pattern of immiscible condensates and condensation heat transfer is not clear at present. In this paper, water and cyclohexane were used as non-azeotropic and immiscible working fluids. The effects of different mixed vapors mass ratios, cooling water inlet temperatures, and vapor mass flow rates on the condensation heat transfer characteristics of the binary mixed vapors on the vertical wall were studied. And the condensate flow patterns were combined for analysis and discussion. The experimental results showed that the condensation on the wall surface of the mixed vapors presented a film-drop flow pattern comparing with the filmwise condensation of water vapor or cyclohexane vapor. The film-drop flow pattern was manifested as that the cyclohexane condensate was attached on the condensation wall in the form of liquid film, and the water condensate was attached on the cyclohexane film in the form of droplets. And the flow of water droplets on the cyclohexane liquid film can enhance the condensation heat transfer of the mixed vapors. In addition, different from water vapor and cyclohexane vapor, the heat transfer coefficient of the mixed vapors decreased with the increase of the cooling water inlet temperature, which was related to the film-drop condensation flow pattern.

Poly(sulfobetaine)-Based Diblock Copolymer Thin Films in Water/Acetone Atmosphere: Modulation of Water Hydration and Co-nonsolvency-Triggered Film Contraction.

The water swelling and subsequent solvent exchange including co-nonsolvency behavior of thin films of a doubly thermo-responsive diblock copolymer (DBC) are studied via spectral reflectance, time-of-flight neutron reflectometry, and Fourier transform infrared spectroscopy. The DBC consists of a thermo-responsive zwitterionic (poly(4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate)) (PSBP) block, featuring an upper critical solution temperature transition in aqueous media but being insoluble in acetone, and a nonionic poly(N-isopropylmethacrylamide) (PNIPMAM) block, featuring a lower critical solution temperature transition in water, while being soluble in acetone. Homogeneous DBC films of 50-100 nm thickness are first swollen in saturated water vapor (H2O or D2O), before they are subjected to a contraction process by exposure to mixed saturated water/acetone vapor (H2O or D2O/acetone-d6 = 9:1 v/v). The affinity of the DBC film toward H2O is stronger than for D2O, as inferred from the higher film thickness in the swollen state and the higher absorbed water content, thus revealing a pronounced isotope sensitivity. During the co-solvent-induced switching by mixed water/acetone vapor, a two-step film contraction is observed, which is attributed to the delayed expulsion of water molecules and uptake of acetone molecules. The swelling kinetics are compared for both mixed vapors (H2O/acetone-d6 and D2O/acetone-d6) and with those of the related homopolymer films. Moreover, the concomitant variations of the local environment around the hydrophilic groups located in the PSBP and PNIPMAM blocks are followed. The first contraction step turns out to be dominated by the behavior of the PSBP block, whereas the second one is dominated by the PNIPMAM block. The unusual swelling and contraction behavior of the latter block is attributed to its co-nonsolvency behavior. Furthermore, we observe cooperative hydration effects in the DBC films, that is, both polymer blocks influence each other's solvation behavior.

Catalytic fast pyrolysis of Arundo donax in a two-stage fixed bed reactor over metal-modified HZSM-5 catalysts

Various types of mono- and bi-metallic modified HZSM-5 catalysts such as Mo-, Fe-, Zn-, Cu-, Mo–Fe-, Mo–Zn-, and Mo–Cu-modified HZSM-5 were prepared via impregnation and were characterized by scanning electron microscope (SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and pyridine adsorption infrared spectroscopy (Py-IR) analysis. Online catalytic upgrading of Arundo donax pyrolysis vapors was performed using modified zeolite catalysts in a two-stage fixed bed reactor to investigate the catalytic performance. Results showed that loading of Mo, Fe, Zn and Cu were well-dispersed, the channels and acidity of zeolites were modified. Impregnation of HZSM-5 with metals resulted in relatively lower yield of oxygenates and nitrogen-containing compounds in bio-oil as compared to the reference condition without catalyst. Moreover, the addition of metals significantly favored the catalytic selectivity towards aromatics especially monocyclic aromatic hydrocarbons (MAHs). Mo-M/HZSM-5 catalysts was the best catalyst and exhibited the optimal de-oxygenation potential (from 62.66% to 18.03%), denitrification (from 6.53% to 0.43%) and produced maximum MAHs content approximately 28.77%. Among the bimetallic modified zeolite catalysts, Mo–Zn/HZSM-5 exhibited strong catalytic effect in oxygen-free aromatization of the mixed pyrolysis vapors containing methane and propane. In the presence of Mo–Zn/HZSM-5 catalyst, the content of oxygen in bio-oil decreased from 36.07 wt% to 15.05 wt%, and the calorific value reached a maximum value of 34.12 MJ kg−1. Mo–Zn/HZSM-5 has been identified as a superior catalyst for improving the value of Arundo donax pyrolysis to make bio-oil.

KCs Molecular Bands in the Visible Region

We measured light absorption of potassium and cesium mixed vapors at temperatures 360–660°C in the visible spectral region 380–780 nm. By comparison with the absorption of pure potassium or cesium vapors, we concluded that the spectral phenomena observed in the mixture peaking at 539 nm, 562 nm (and 700 nm) are new KCs molecular bands. Quantum mechanical calculations of the KCs molecular bands in the visible and near-infrared spectral region were performed using available theoretical potential curves for the KCs molecule. Using these calculations, we identified the three observed molecular bands as 31Π–X, 41Σ+–X, and 11Π–X electronic transitions of KCs molecule, respectively.

High-Temperature Optical Spectra of Diatomic Molecules: Influence of the Avoided Level Crossing

In this study, we analyzed the light absorption by diatomic molecules or colliding atoms in a spectral region dominated by an avoided crossing of adiabatic state levels or crossing of the corresponding diabatic state levels. Our attention was focused on the low-resolution spectrum at a higher gas temperature under local thermodynamic equilibrium conditions. The absorption measurements of mixed vapors of potassium (≈80%) and cesium (≈20%) were made in the temperature range of 542–715 K and the infrared spectral range 900–1250 nm. In this area, the main spectral contributions were the broad A 1 Σ ( u ) + ( 0 ( u ) + ) − X 1 Σ ( g ) + ( 0 ( g ) + ) bands of K2, Cs2, and KCs molecules. There was a crossing of A 1 Σ ( u ) + ( 0 ( u ) + ) and b 3 Π ( u ) ( 0 ( u ) + ) state potential curves and the coupling of this state was due to the matrix element ⟨ A 1 Σ ( u ) + ( 0 ( u ) + ) | H s o | b 3 Π ( u ) ( 0 ( u ) + ) ⟩ of the spin–orbit interaction. Using data for relevant electronic potential curves and transition dipole moments existing in the literature, the spectra of the A 1 Σ ( u ) + ( 0 ( u ) + ) − X 1 Σ ( g ) + ( 0 ( g ) + ) molecular bands of K2, Cs2, and KCs molecules were calculated. Full quantum mechanical and semi-quantum coupled channel calculations were done and compared with their non-coherent adiabatic or diabatic approximations. Through the comparison of our theoretical and experimental spectra, we identified all observed spectral features and determined the atoms’ number density and gas temperature.

Selective adsorption of carbon dioxide from mixed vapors by blockage of methane in graphene nanoribbons

We study numerically the adsorption of a mixture of $$\hbox {CO}_{2}$$ and $$\hbox {CH}_{4}$$ on a graphite substrate covered by graphene nanoribbons (NRs). The NRs are flat and parallel to the graphite surface, at a variable distance ranging from 6 to 14 A. We show that the NRs-graphite substrate acts as an effective filter for $$\hbox {CO}_{2}$$ . Our study is based on molecular dynamics simulations. Methane is considered a spherical molecule, and carbon dioxide is represented as a linear rigid body. Graphite is modeled as a continuous material, while the NRs are approached atomistically. We observe that when the NRs are placed 6 A above the graphite surface, methane is blocked out, while $$\hbox {CO}_{2}$$ molecules can diffuse and be collected in between the NRs and the graphite surface. Consequently, the selectivity of $$\hbox {CO}_{2}$$ is extremely high. We also observe that the initial rate of adsorption of $$\hbox {CO}_{2}$$ is much higher than $$\hbox {CH}_{4}$$ . Overall we show that the filter can be optimized by controlling the gap between NRs and the NRs-graphite separation.

KCs molecular bands in the visible region-=SUP=-*-=/SUP=-

We measured light absorption of potassium and cesium mixed vapors at temperatures 360-660o in the visible spectral region 380-780 nm. By comparison with the absorption of pure potassium or cesium vapors, we concluded that the spectral phenomena observed in the mixture peaking at 539 nm, 562 nm (and 700 nm) are new KCs molecular bands. Quantum mechanical calculations of the KCs molecular bands in the visible and near-infrared spectral region were performed using available theoretical potential curves for the KCs molecule. Using these calculations, we identified the three observed molecular bands as 31-X, 41Sigma+-X and 11- X electronic transitions of KCs molecule respectively. Key words: potassium and cesium mixed vapors, absorption spectra, KCs molecular bands, quantum mechanical calculations.

Swelling and plasticization of PDMS and PTMSP in methanol and dimethyl carbonate vapors and liquids: Volume, mechanical properties, Raman spectra

The swelling and plasticization of polydimethylsiloxane (PDMS), a rubbery polymeric network, and poly[(trimethylsilyl)propyne] (PTMSP), a glassy polymer, in methanol and dimethyl carbonate (DMC) vapors (a) and liquids (b) was studied using visible-light microscopy (ad a), dynamic mechanical analysis (DMA, ad a) and confocal Raman microscopy (ad b). The properties of swollen PDMS were found to be as expected: Volume swelling followed volume additivity and swelling in mixed vapors was predictable from single component swelling data, elastic moduli followed the scaling law and Raman spectra of pure and swollen PDMS were indistinguishable. On the contrary, swollen PTMSP showed pronouncedly lower volume changes than those expected from volume additivity and non-predictable swelling in mixed vapors, preferential saturation of the nonequilibrium packing defects of the polymer, an initial plateau for the storage modulus and pronounced spectral changes when swollen with the liquids. The initially rigid physical structure of PTMSP was found to be relaxed when the concentration of the volatile compound in the polymer exceeded the capacity of the first adsorption layer, which is one of the parameters of the Guggenheim, Anderson, de Boer (GAB) model of multilayer adsorption. Hence, the general mechanism for sorption of volatile compounds in glassy polymers is likely adsorption and gradual physical relaxation.

ZIF filled PDMS mixed matrix membranes for separation of solvent vapors from nitrogen

The efficiency of chemical processes can be improved by recovering high value volatile organic compounds (VOCs). For this purpose PDMS based mixed matrix membranes were prepared by using ZIF-7, ZIF-8, ZIF-67, ZIF-71 and ZIF-L as filler for VOC removal from permanent gases. Membranes were characterized by separating pure or mixed solvent vapors of methanol (MeOH), ethanol (EtOH), isopropanol (IPA), n-propanol (PrOH) and ethyl acetate (EtAc) from nitrogen. The total VOC permeability and VOC/N2 selectivity increased with the incorporation of ZIF-L and ZIF-71, while other ZIFs had limited influence on the separation performance of membranes. ZIF-L (20% wt.)/PDMS membrane exhibited total VOC permeability of 9874 Barrer and VOC/N2 selectivity of 45 in the separation of ethanol and IPA vapor from nitrogen in a mixture with molar composition of EtOH:IPA:N2 = 10:10:980. Those values were higher than the permeability and selectivity of pure PDMS by 60 and 33%, respectively. ZIF-L filled PDMS membrane was also used for the separation of multicomponent mixtures and showed total VOC permeability of 10215 Barrer and VOC/N2 selectivity of 72 in the separation of ethanol, isopropanol, ethyl acetate and water vapor mixture from nitrogen. A method was also proposed to compare the separation performance of membranes with each other and with the performance of membranes reported in the literature based on the dew point temperature of membrane streams.

Synergistic Sorption of Mixed Solvents in Wood Cell Walls: Experimental and Theoretical Approach

The behavior of poplar wood and its components in water‐ethanol mixtures is investigated through a coupled experimental and theoretical approach including physico‐chemical and dynamic mechanical analyses and molecular dynamics simulations. Affinity for water‐ethanol vapors, measured by isothermal gravimetric sorption experiments, features a maximum for mixed vapors. The longitudinal viscoelastic behavior of the same wood upon immersion in ethanol‐water solutions, measured by dynamic mechanical analysis, features a minimum in storage modulus and a maximum damping upon immersion in solutions of intermediate composition. Optical microscopy observation of solvent‐saturated samples evidences inter‐ and intra‐cellular disbonding in pure ethanol and ethanol aqueous solutions. Molecular dynamics simulations provide information on interactions of water‐ethanol solutions with models of cellulose microfibers and lignin. The relative solvation of cellulose microfibers by water and ethanol shows a nearly linear variation with the composition of the solution. In contrast, the accessibility of lignin dimers to the solvent presents a maximum at intermediate ethanol concentrations, in correspondence with a conformational transition of the dimer towards an extended conformation. The modelization of the interactions of cellulose and lignin in water‐ethanol solutions indicates a minimum of adhesion of the two components of wood in the presence of solutions with intermediate concentrations.

Vapor detection through dynamic process of molecule desorption from butterfly wings

Abstract This work explores an alternative vapor sensing mechanism through analyzing dynamic desorption process from butterfly wings for the differentiation of both individual and mixed vapors quantitatively. Morpho butterfly wings have been used in differentiating individual vapors, but it is challenging to use them for the differentiation of mixed vapor quantitatively. This paper demonstrates the use of Morpho butterfly wings for the sensitive and selective detection of closely related vapors in mixtures. Principal components analysis (PCA) is used to process the reflectance spectra of the wing scales during dynamic desorption of different vapors. With the desorption-based detection mechanism, individual vapors with different concentrations and mixed vapors with different mixing ratios can be differentiated using the butterfly wing based sensors. Both the original butterfly wings and butterfly wings with surface modification show the capability in distinguishing vapors in mixtures, which may offer a guideline for further improving selectivity and sensitivity of bioinspired sensors.

Mixed Vapor Generation Device for delivery of homemade explosives vapor plumes

While there is a large body of research on the properties and detection of traditional military high explosives and propellant low explosives, there is a dearth of research on homemade explosive (HME) materials, though they are prevalent today. The safety of working with these materials in the laboratory is the greatest limiting factor preventing HME research. A vapor delivery tool, the Mixed Vapor Generation Device (MV-Gen), was designed to safely contain the individual solid or liquid components that often compose homemade explosives vapor plumes and deliver the mixed component vapors for instrumental sampling and analysis. Within the MV-Gen, each component is separated and only the vapors mix as they are carried through the device by flowing air. The resulting mixed vapor is representative of either mixed explosive material or bulk explosives. Component materials are held in up to four individual, removable vials with vapor concentrations controlled by vial orifice size, temperature, and diluent airflow. The total concentration can be adjusted by altering vial temperature via a thermal water jacket surrounding the entirety of the device, or by adjusting the flow rate of diluent air through the device. The MV-Gen was evaluated first with surrogate compounds, followed by two types of homemade explosives, to include a binary explosive mixture and a peroxide explosive. To evaluate the device, vapors were cold-trapped on an online sampling system and analyzed by gas chromatography/mass spectrometry. It was determined that the device yielded reproducible vapor concentrations of both single and mixed components, and the ratio of these vapors can be easily adjusted to mimic varying forms of homemade explosives.

Aliphatic Aldehyde Detection and Adsorption by Nonporous Adaptive Pillar[4]arene[1]quinone Crystals with Vapochromic Behavior.

The detection and adsorption of volatile low-molecular-weight aliphatic aldehydes is of significance, owing to their physical volatility, chemical toxicity, and widespread applications in chemical industrial processes. Here, nonporous adaptive pillar[4]arene[1]quinone (EtP4Q1) crystals with vapochromic behavior are used for the volatile aliphatic aldehyde uptake and sensing. When desolvated EtP4Q1 crystals (EtP4Q1α) are exposed to aliphatic aldehydes with different carbon chain lengths, they quantitatively adsorb vapors of these aldehydes, accompanied by different color changes. Crystal structure analyses show that the structure of EtP4Q1 transforms from EtP4Q1α into the corresponding new structures after the adsorption of these aldehydes, which leads to different color changes. The selectivity of EtP4Q1α crystals, which function as both sensors and adsorbents upon exposure to mixed aldehyde vapors, is also explored. Finally, it is demonstrated that EtP4Q1α crystals can be recycled many times without loss of performance.

Selectivity Behavior of a Robust Porous Organic Salt Based on the Pamoate Ion

The selectivity of a porous hydrogen-bonded framework, 1, toward various solvent mixtures has been investigated. Framework 1, which is the hydrate of 3,4-lutidinium pamoate, crystallizes as its THF solvate, 1·THF. Solvent exchange can take place either by exposing crystals of 1·THF to solvent vapors or by immersing the crystals in a solvent. Framework 1 shows preferential inclusion of particular solvents when exposed to mixed solvent vapors, or to mixed solvents in the liquid form. Analysis showed that solvents are included in the same ratios when exposed to mixed solvents in the liquid or vapor phase, despite the significant differences in mole ratios between the liquid and vapor phases due to the different vapor pressures of the solvents investigated. In some cases, when immersed in solvent mixtures containing acetonitrile or acetone, 1·THF recrystallizes as an acetonitrile or acetone solvate of 3,4-lutidinium pamoate. The crystal structures of these two new solvates are also reported.