Multicomponent Vapor Research Articles

Fractional condensation of sawdust pyrolysis vapors: Separation of complex components, enhancement of bio-oil properties, and life cycle assessment

This study investigates the fractional condensation of multicomponent vapors obtained from the pyrolysis of sawdust in a fluidized bed reactor at 500 °C, and the resulting pyrolytic vapors which were subjected to fractional condensation using a temperature-controlled system consisting of four condensers. The objective was to assess the effectiveness of this fractional condensation system in separating complex components and enhancing bio-oil properties. The characterization of the bio-oil included evaluating pH value, total acid number (TAN), heating value, and chemical compositions. The findings revealed that the last two condensers effectively collected most of small molecular chemicals such as acetic acid, ketones, esters, alcohols, aldehydes, and water. Notably, Benzenes (benzene, toluene, and ethylbenzene) and certain types of phenols (creosol and Phenol, 2,3-dimethyl-) tended to condense in SBO 1, as their temperatures were higher than their dew points. SBO 1 exhibited the highest calorific value of 29.42 MJ/kg, whereas SBO 2 displayed the lowest acidity (1.19 mol/L) and a higher calorific value (11.38 MJ/kg) compared to SBO 3 and SBO 4. Additionally, a life cycle assessment (LCA) demonstrated that the fractional condensation method possesses economic and environmental advantages. This approach offers a promising technique for effectively separating complex components in bio-oil derived from sawdust pyrolysis, leading to improved product properties and reduced environmental impact. Consequently, these findings contribute to the advancement of sustainable biomass conversion processes and underscore the potential for optimizing the production of valuable bio-based products.

The effect of relative humidity on multicomponent organic vapor adsorption on composite beds with micro-fibrous entrapped activated carbon

Composite bed involves an alternative technique in which a layer of micro-fibrous entrapped composite material is added at the downstream end of a conventional fixed bed to strengthen the mass transfer process. In this study, our purpose was to compare the ability of composite beds to remove volatile organic compounds (VOCs) and Freon refrigerants with conventional fixed beds and analyse the effect of relative humidity (RH) on multicomponent organic vapor adsorption on composite beds. This would be used to guide the design of composite beds and their application in air purification. A series of micro-fibrous entrapped activated carbons (MFECs) were prepared using the wet layer paper-making/sintering technologies. The 1,1,1,2-tetrafluoroethane (R134a) and C6H6 breakthrough curves and times on composite beds were systemically evaluated under dry and wet conditions. Results show that under dry condition, due to the enhanced mass transfer, the R134a and C6H6 breakthrough times on composite beds were longer than on fixed beds. Under wet conditions, due to the water vapor competitive adsorption and the difference in organic vapor boiling point, the composite bed prolonged the C6H6 breakthrough time but weakened the R134a breakthrough time. Multicomponent competitive adsorption process (R134a/C6H6) under wet conditions was revealed and divided into six stages including Co-adsorption, H2O and R134a breakthrough, R134a desorption, R134a and H2O adsorption equilibrium, C6H6 breakthrough, and dynamic adsorption equilibrium. These findings indicated that composite beds may improve the breakthrough time of low-concentration C6H6 and lengthen the service life of conventional fixed beds at any RH, thereby displaying potential for use as an application in air purification.

Swellable Array Strategy Based on Designed Flexible Double Hypercross-linked Polymers for Synergistic Adsorption of Toluene and Formaldehyde.

High-capacity adsorption and removal of complex volatile organic compounds (VOCs) from real-world environments is a tough challenge for researchers. Herein, a swellable array adsorption strategy was proposed to realize the synergistic adsorption of toluene and formaldehyde on the flexible double hypercross-linked polymers (FD-HCPs). FD-HCPs exhibited multiple adsorption sites awarded by a hydrophobic benzene ring/pyrrole ring and a hydrophilic hydroxyl structural unit. The array benzene ring, hydroxyl, and pyrrole N sites in FD-HCPs effectively captured toluene and formaldehyde molecules through π-π conjugation and electrostatic interaction and weakened their mutual competitive adsorption. Interestingly, the strong binding force of toluene molecules to the skeleton deformed the pore structure of FD-HCPs and generated new adsorption microenvironments for the other adsorbate. This behavior significantly improved the adsorption capacity of FD-HCPs for toluene and formaldehyde by 20% under multiple VOCs. Moreover, the pyrrole group in FD-HCPs greatly hindered H2O molecule diffusion in the pore, thus efficiently weakening the competitive adsorption of H2O toward VOCs. These fascinating properties enabled FD-HCPs to achieve synergistic adsorption for multicomponent VOC vapor under a highly humid environment and overcame single-species VOC adsorption properties on state-of-the-art porous adsorbents. This work provides the practical feasibility of synergistic adsorption to remove complex VOCs in real-world environments.

A methodology for propellant composition optimization in aerosol consumer products, considering economic, safety, and environmental objectives

In this work we present for the first time a methodology to simultaneously optimize the composition of aerosol propellant mixes for consumer products, considering economical, safety, and environmental objectives. Selection of the suitable components for the propellant mix follows a decomposition approach that takes into account product and package compatibility, the regulatory framework, and the type of propellant. An inherent safety approach is considered for the safety objective. The core of the mathematical model is the multicomponent vapor–liquid equilibrium using the Peng–Robinson–Stryjek–Vera cubic equation of state. The optimization problem is defined as a multi-objective mixed-integer nonlinear programming model solved using the ϵ-constraint method. The application of the methodology is demonstrated with a case study for an underarm deodorant formulation. One propellant mix is obtained from the Pareto front as the best compromise of the three objective functions. The rationale to choose a different solution, based on stakeholder’s preferences, is discussed.

How volatile components catalyze vapor nucleation.

Gas phase nucleation is a ubiquitous phenomenon in planetary atmospheres and technical processes, yet our understanding of it is far from complete. In particular, the enhancement of nucleation by the addition of a more volatile, weakly interacting gaseous species to a nucleating vapor has escaped molecular-level experimental investigation. Here, we use a specially designed experiment to directly measure the chemical composition and the concentration of nucleating clusters in various binary CO2-containing vapors. Our analysis suggests that CO2 essentially catalyzes nucleation of the low vapor pressure component through the formation of transient, hetero-molecular clusters and thus provides alternative pathways for nucleation to proceed more efficiently. This work opens up new avenues for the quantitative assessment of nucleation mechanisms involving transient species in multicomponent vapors.

A Creative “Spark” for High-Entropy Alloys

In this issue of Matter, Feng et al. make a breakthrough understanding of an aerosol system for manufacturing unprecedented alloys with excellent catalytic properties. This work will inspire improved 3D nanoprinting techniques for creating new matter forms for broad applications, including additive manufacturing, catalysts, and metallurgy.

A study of the Composition of Tellurium Vapor by the Static Method

The static method with the use of a zero-pressure gauge makes it possible to accurately measure the vapor pressure. The data on the temperature dependence of the unsaturated vapor pressure of the substance (in the absence of the condensed phase) in the static experiment allow determining the vapor’s composition. A multicomponent system consisting of molecules containing i number of atoms is considered. Mathematical methods are developed to study the molecular composition of a multicomponent vapor. In combination with the initial equations, a system of n linear equations with n unknowns is obtained. The system of equations is compatible and has a unique solution, since the determinant composed of the coefficients at the unknown partial pressures of the components is different from zero. The composition of tellurium vapor was studied experimentally by the static method. It is shown that tellurium vapor consists mainly of one-, two-, and four-atom molecules in equilibrium (Te2 = 2Te and Te4 = 2Te2). The processing of the experimental data made allows obtaining the equations of the temperature dependence of the constants and reveal the change in the average number of tellurium atoms in the gas phase in a broad range of pressures and temperatures.

Insights from a Thermodynamic Study and Its Implications on the Freeze-Drying of Pharmaceutical Solutions Containing Water and tert-Butyl Alcohol as a Cosolvent.

In the production of several anticancer drugs, tert-butyl alcohol (TBA) is present as a co-solvent in the aqueous drug solution. In order to ascertain if TBA should be removed beforehand or if it could be retained to facilitate the freeze-drying of the drug solution, it is important to acquire both qualitative and quantitative knowledge of the variations occurring with respect to time in heat and mass transfer during the freeze-drying process. In this work, a thermodynamic model employing the UNIFAC (Dortmund) method was developed to determine the values of the currently experimentally unavailable partial vapor pressures of the binary gas mixture of water and TBA in equilibrium with their frozen solid mixtures. The results agree satisfactorily with relevant experimental measurements and indicate that TBA vapor has constantly higher pressures than water vapor and also promotes the vapor pressure of water during sublimation. The responses of the partial pressures of water and TBA vapors are found, through the analysis of their partial and total differentials, to be increasingly more sensitive to temperature change at elevated temperatures and to compositional change when the mole fraction of water in a frozen binary mixture approaches zero. The increased vapor pressures due to TBA lead to higher total pressures at the moving interface separating the dried and frozen layers, resulting in larger total pressure gradients and convective mass transfer rates in the dried layer during primary drying. But the higher total pressures reduce the magnitude of the bulk diffusivity of the gas mixture, and combined with the smaller Knudsen diffusivity of TBA, the pressures could significantly affect the competing mass transfer mechanisms during freeze-drying. The approach presented in this work could provide a general thermodynamic modeling approach for predicting the vapor pressures of multicomponent vapor mixtures in equilibrium with their multicomponent solid frozen mixtures.LAY ABSTRACT: tert-Butyl alcohol (TBA) is present as a cosolvent in a number of anticancer drug solutions. Its presence is known to affect the freeze-drying process of the drug solutions. In order to determine a better operational policy with respect to the freeze-drying process, a thermodynamic approach was developed in this work to provide the needed data of water and TBA vapors that are currently experimentally unavailable. The results agree satisfactorily with experimental measurements. They indicate that TBA vapor has constantly higher pressures than water vapor, promoting faster sublimation and generating higher total pressures at the moving interface to enhance convective mass transfer during primary drying. However, the higher total pressures also reduce the magnitude of the bulk diffusivity of the gas mixture, and combined with the smaller Knudsen diffusivity of TBA, these pressures could significantly affect the competing mass transfer mechanisms during freeze-drying. The thermodynamic method and analysis developed in this work are useful in their own physicochemical importance and also provide a necessary component for a new class of freeze-drying mathematical models. Moreover, they could provide a general modeling approach for predicting the vapor pressures of multicomponent vapor mixtures in equilibrium with their frozen solid mixtures.

Multicomponent Vapor–Liquid Equilibrium Measurement and Modeling of Ethylene Glycol, Water, and Natural Gas Mixtures at 6 and 12.5 MPa

High pressure subsea natural gas dehydration (NGD) units using ethylene glycol (MEG) absorption have been proposed. To expand the experimental database and assist design qualification, new vapor–liquid equilibrium (VLE) experimental data have been measured for a 20-component glycol–water–natural gas mixture at T = (288–323) K, p = (6.0, 12.5) MPa, and wMEG,feed = (90, >99.8) %. MEG, H2O, CO2, N2, and alkane (methane to n- and i-pentane) phase distributions have been quantified. Experimental uncertainty ranges from ±2–42%, with the greatest uncertainty for the quantification of trace components. Experimental results are modeled using the Cubic-Plus-Association (CPA) equation of state. Overpredictions (∼9%) are observed for the water content of the vapor phase. CO2 is shown to have a large effect on yMEG, leading to modeling deviations in the order of 65%. A relatively accurate prediction of the natural gas partition coefficients was observed for major components C1–C3 and CO2, with modeling errors ranging from 5% for methane to 10% for CO2. More significant deviations were observed for trace components, with the largest deviation of 73% N2. The CPA model provides both satisfactory and conservative results suitable for use in NGD process designs. On the basis of this work, operation at subsea conditions would significantly improve dehydration capability.

Butanol Separation from Humid CO2-Containing Multicomponent Vapor Mixtures by Zeolitic Imidazolate Frameworks

Butanol is a promising renewable fuel and feedstock. A major challenge in fermentative butanol production is to find a cost-effective butanol separation process from dilute aqueous solutions, usually an acetone-butanol-ethanol (ABE) mixture. Nanoporous zeolitic imidazolate frameworks (ZIFs) have shown potential for alcohol separation from dilute solutions. However, little is known about butanol separation from multicomponent mixtures using ZIFs, including the effects of the humid acid gas (CO2) used to sparge the fermenter and generate the vapor product stream. We present a study of butanol separation by ZIF-8, ZIF-90, ZIF-71 and hybrid ZIF-8–90 and ZIF-8–71 adsorbents with binary butanol/water and multicomponent ABE feeds. To obtain reliable structure–property relations for ZIF adsorbents in realistic conditions, we combine multicomponent vapor breakthrough with structural, textural, and stability characterization techniques in humid CO2 environments. In the absence of CO2, more hydrophobic materials suc...

The spinodal of single- and multi-component fluids and its role in the development of modern equations of state

The spinodal represents the limit of thermodynamic stability of a homogeneous fluid. In this work, we present a robust methodology to obtain the spinodal of multicomponent fluids described even with the most sophisticated equations of state (EoS) available. We elaborate how information about the spinodal and its uncertainty can contribute both in the development of modern EoS and to estimate their uncertainty in the metastable regions. Inequality constraints are presented that can be exploited in the fitting of modern EoS of single-component fluids to avoid inadmissible pseudo-stable states between the vapor and liquid spinodals. We find that even cubic EoS violate some of these constraints.With the use of a selection of EoS representative of modern applications, we compare vapor and liquid spinodal curves, superheat and supersaturation limits from classic nucleation theory (CNT), and available experimental data for the superheat limit. Computations are performed with pure species found in natural gas, binary mixtures, as well as a multi-component natural gas mixture in order to demonstrate the scalability of the approach. We demonstrate that there are large inconsistencies in predicted spinodals from a wide range of EoS such as cubic EoS, extended corresponding state EoS, SAFT and multiparameter EoS. The overall standard deviation in the prediction of the spinodal temperatures were 1.4 K and 2.7 K for single- and multi-component liquid-spinodals and 6.3 K and 26.9 K for single- and multi-component vapor spinodals.The relationship between the measurable limit of superheat, or supersaturation, and the theoretical concept of the spinodal is discussed. While nucleation rates from CNT can deviate orders of magnitude from experiments, we find that the limit of superheat from experiments agree within 1.0 K and 2.4 K with predictions from CNT for single- and multi-component fluids respectively. We demonstrate that a large part of the metastable domain of the phase diagram is currently unavailable to experiments, in particular for metastable vapor. Novel techniques, experimental or with computational simulations, should be developed to characterize the thermodynamic properties in these regions, and to identify the thermodynamic states that define the spinodal.

The Stefan outflow in a multicomponent vapor–gas atmosphere around a droplet and its role for cloud expansion

A new comprehensive analysis of Stefan׳s flow caused by a free growing droplet in the vapor–gas atmosphere with several condensing components is presented. This analysis, based on the nonstationary heat and material balance and diffusion transport equations, shows the appearance of the Stefan inflow in the vicinity of the growing droplet and the Stefan outflow at large distances from the droplet as a consequence of nonisothermal condensation. For an ensemble of droplets in the atmospheric cloud, this outflow provides an increase of the total volume of the cloud, which can be treated as cloud thermal expansion and leads to the rise of the cloud as a whole due to increasing its buoyancy. We have formulated the self-similar solutions of the nonstationary diffusion and heat conduction equations for a growing multicomponent droplet and have derived analytical expressions for the nonstationary velocity profile of Stefan׳s flow and the expansion volume of the vapor–gas mixture around the growing droplet. To illustrate the approach, we computed these quantities in the case of droplet of stationary composition in air with several specific vapors (C2H5OH/H2O; H2SO4/H2O; H2O).

Equations for the evolution of a growing or evaporating free microdroplet under nonstationary conditions of diffusion and heat transfer in a multicomponent vapor–gas medium

A set of equations has been derived for the nonstationary composition, size, and temperature of a growing or evaporating multicomponent microdroplet of a nonideal solution under arbitrary initial conditions. Equations for local nonstationary diffusion molecular and heat fluxes in a mixture of a multicomponent vapor with a noncondensable carrier gas have been obtained within the framework of nonequilibrium thermodynamics with allowance for hydrodynamic flow of the medium. The derived closed set of equations takes into account the nonstationarity of the diffusion and heat transfer, effect of thermodiffusion and other cross effects in the multicomponent vapor–gas medium, the Stefan flow, and droplet boundary motion, as well as the nonideality of the solution in the droplet. The general approach has been illustrated by the consideration of the multicomponent medium at low concentrations of vapors taking into account its thermal expansion due to the Stefan flow in the case of a nonstationary diffusion regime of the nonisothermal condensation growth of a one-component droplet.

Estimation of multicomponent organic solvent vapor mixture composition with electroconducting polymer chemiresistors

An approach to quantitative analysis of multicomponent gaseous mixtures with an array of cross-selective sensors is proposed, and experimentally tested with the mixtures of four organic solvent vapors (acetone, chloroform, isopropanol and toluene) in atmospheric air and conducting polymer based chemiresistive sensors with three different sensitive coatings – polyaniline, polypyrrole and poly-3-methyltiophene doped with phosphotungstic and perchloric acid ions. The proposed method employs simplified semi-parametric model for prediction of the sensor responses, with emphasis on direct use of the information contained in the reference calibration data. Analysis algorithm is based on the matching between predicted and observed responses with additional regularization of the optimal prediction search procedure. Potential possibility of utilization of the presented approach for quantitative analysis of selected components, albeit with limited accuracy, is demonstrated, with the best case relative error of about 30% achieved for the studied sample data. The ways to further improvement of the analysis quality are discussed.

Modeling the Adsorption Kinetics of Activated Carbon for Oil Vapor Recovery and Applications

Oil Vapor recovery is a critical process in downstream chemical industries, in oil and gas industries and in environmental protection. For that purpose, highly-efficient absorbent materials for vapor recovery are in high demand and their associated adsorption kinetics is of great importance for their performance. As oil vapor consists of multiple components with different physical and chemical properties, modeling the overall adsorption kinetics of activated carbon for multi-component oil vapor is essentially valuable for industrial applications. In this work, we developed a comprehensive model of multi-component gas adsorption kinetics on activated carbon in a packed-bed reactor and numerically solved the model by the finite element method. The predictions from the model are all in the reasonable range indicating good validity of the model. Some dimensionless parameters are also derived to further investigate the prediction results.

Vapour–liquid equilibrium of carboxylic acid–alcohol binary systems: 2-Propanol + butyric acid, 2-butanol + butyric acid and 2-methyl-1-propanol + butyric acid

Isothermal vapour–liquid equilibrium (VLE) data were measured for alcohol–carboxylic acid systems using a dynamic recirculating apparatus operated isothermally. For super-atmospheric pressures, a stainless steel version of the apparatus was used with sight glasses in the Cottrell pump and liquid and condensate sampling chambers to observe flow patterns. Data are presented for 2-propanol+butyric acid, 2-butanol+butyric acid, and 2-methyl-1-propanol+butyric acid at 333.15K, 353.15K, and 373.15K. To account for vapour phase non-ideality the iterative procedure of Prausnitz et al. [J.M. Prausnitz, T.F. Anderson, E.A. Grens, C.A. Eckert, H. Seih, J.P. O’Connell, Multicomponent Vapor–Liquid and Liquid–Liquid Equilibria, Prentice Hall, Englewood Cliffs, NJ, 1980], based on the chemical theory and corresponding states correlations, was used to obtain true species concentrations, association constants (Kii), and from these liquid phase activity coefficients. The Lewis fugacity rule was used for the true species fugacity coefficient. For the low pressures and moderate temperatures of the study, only dimerization of the acid in the vapour phase was considered. Satisfactory modelling of the data was obtained with the NRTL equation and also, for the direct (EOS) method, with the cubic-based Soave–Redlich–Kwong equation of state and the Wong–Sandler mixing rules. The high non-ideality of the vapour phase for the mixtures studied was confirmed by the considerable departure of the vapour phase correction factors, Φi, from unity. The thermodynamic consistency of the data is shown by the area test and the more rigorous Van Ness point and direct tests.

Fractional Condensation of Multicomponent Vapors from Pyrolysis of Cotton Stalk

Bio-oil derived from the fast pyrolysis of biomass is a multicomponent mixture comprised of over 400 types of organics, which need to be separated for specific applications. Moisture contents and acids also have to be removed from the compounds for efficient energy consumption. In this study, unlike the conventional approaches of separating bio-oil after condensation, we developed a multicondenser system for separating bio-oil compounds in order to better utilize them in different applications. A biomass sample (cotton stalk) was pyrolyzed in a fluidized bed reactor operated at 400 and 600 °C. The pyrolysis vapors passed through four condensers arranged in sequence at 300 °C, 100 °C, 0 °C, and −20 °C, respectively. Each component on fractions was more efficiently separated based on their varied boiling points. Each fractional bio-oil (FBO) exhibits different chemical and physical properties. Over 90% of small molecular materials including acetic acid, ketones, aldehydes, and water, were gathered in the 0 ...

New Design Method for Fully Thermally Coupled Distillation Column Using Group and Approximate Methods

A new design method for determining the structure of a fully thermally coupled distillation column is proposed. The method involves approximate group method and the Fenske equation. To design the prefractionator, an approximate calculation procedure that relates compositions of multicomponent vapor and liquid streams is developed to formulate the expressions used to compute the number of stages. To investigate the usability and performance of this design method, different feed mixtures are tried. The results indicate that the method works well for a variety of process conditions; the results show that the structure design from group method leads to a process similar to a feasible actual process. The structure design results and operating conditions for the whole column system enable the examination of the optimal internal flows and their effects on the structure design equations. The results show that the proposed design method provides good initial values for rigorous simulation.

Heterogeneous nucleation in multi-component vapor on a partially wettable charged conducting particle. I. Formulation of general equations: Electrical surface and line excess quantities

Thermodynamics is applied to formulate general equations for internal energies and grand potential for a system consisting of a dielectric liquid nucleus of a new phase on a charged insoluble conducting sphere within a uniform macroscopic one- or multicomponent mother phase. The currently available model for ion-induced nucleation assumes complete spherical symmetry of the system, implying that the seed ion is immediately surrounded by the condensing liquid from all sides. We take a step further and treat more realistic geometries, where a cap-shaped liquid cluster forms on the surface of the seed particle. To take into account spontaneous polarization of surface layer molecules we introduce the electrical surface and line excess quantities.

Heterogeneous nucleation in multi-component vapor on a partially wettable charged conducting particle. II. The generalized Laplace, Gibbs-Kelvin, and Young equations and application to nucleation

Based on the results of a previous paper [M. Noppel, H. Vehkamäki, P. M. Winkler, M. Kulmala, and P. E. Wagner, J. Chem. Phys. 139, 134107 (2013)], we derive a thermodynamically consistent expression for reversible or minimal work needed to form a dielectric liquid nucleus of a new phase on a charged insoluble conducting sphere within a uniform macroscopic one- or multicomponent mother phase. The currently available model for ion-induced nucleation assumes complete spherical symmetry of the system, implying that the seed ion is immediately surrounded by the condensing liquid from all sides. We take a step further and treat more realistic geometries, where a cap-shaped liquid cluster forms on the surface of the seed particle. We derive the equilibrium conditions for such a cluster. The equalities of chemical potentials of each species between the nucleus and the vapor represent the conditions of chemical equilibrium. The generalized Young equation that relates contact angle with surface tensions, surface excess polarizations, and line tension, also containing the electrical contribution from triple line excess polarization, expresses the condition of thermodynamic equilibrium at three-phase contact line. The generalized Laplace equation gives the condition of mechanical equilibrium at vapor-liquid dividing surface: it relates generalized pressures in neighboring bulk phases at an interface with surface tension, excess surface polarization, and dielectric displacements in neighboring phases with two principal radii of surface curvature and curvatures of equipotential surfaces in neighboring phases at that point. We also re-express the generalized Laplace equation as a partial differential equation, which, along with electrostatic Laplace equations for bulk phases, determines the shape of a nucleus. We derive expressions that are suitable for calculations of the size and composition of a critical nucleus (generalized version of the classical Kelvin-Thomson equation).