Real Mixtures Research Articles

천연가스의 탄화수소 이슬점 측정방법 비교 연구

탄화수소 이슬점은 천연가스 응축형태를 특성화하는 가장 일반적이고 자주 이용되는 물성으로 가스 품질 사양의 중요한 항목이다. 탄화수소 이슬점은 미량의 고탄화수소 성분에도 매우 민감한 것으로 알려져 있어, 특히 천연가스를 공급하는 가스 회사 입장에서는 기존 합의된 가스 사양을 만족하는 것 뿐만 아니라, 발생된 탄화수소 응축물에 의해 운영설비 및 안전에 심각한 문제를 일으킬 수 있으므로 탄화수소 이슬점을 정확하게 구하는 절차를 확립하는 것이 중요하다. 본 연구에서는 실제 현장조건 하에서 탄화수소 이슬점을 측정하기 위해 냉각 거울 방식의 이슬점 측정기를 설치, 운영하였으며, 측정된 이슬점 온도는 가스분석기에 의해 분석된 조성 및 천연가스 산업계에서 인정된 상태방정식을 이용하여 계산된 이슬점 온도와 비교하였다. 시험 결과 탄화수소 이슬점 측정기는 매우 안정되게 이슬점을 측정하였으며, 이슬점 측정기를 검증하기 위한 시험 가스로는 순수 프로판 가스가 적정하였다. 제조 표준가스 및 실제가스의 측정결과를 가스분석기에 의한 간접 측정 결과와 비교시에도 적정한 범위 내에서 일치하는 것을 확인하였다. Hydrocarbon dew point(HCDP), a property which is the most generally used for describing natural gas condensation, is a very important parameter of natural gas quality specifications. HCDP is strongly influenced by the concentration of the heavier hydrocarbon components, especially <TEX>$C_6+$</TEX>, so, along with compliance with gas quality specifications, build up of procedures for obtaining accurate HCDP is essential for gas transmission company, because hydrocarbon condensation present may cause serious operational and safety problems. This study has been carried out in an attempt to measure HCDP accurately by the automatic hydrocarbon dew point meter under the actual field conditions. Measured HCDP also has been compared with calculated HCDP using the composition determined by gas chromatograph and industry accepted equation of state at multiple pressures, along with the cricondentherm. The test results are 1) the automatic hydrocarbon dew point meter was able to measure stable HCDP continuously 2) the automatic hydrocarbon dew point meter has been performed reference measurement by pure propane with a known dew point from literature, and 3) A meaningful differences was observed when comparing the automatic hydrocarbon dew point meter and gas chromatograph results for synthetic standard gas mixtures and real gas mixtures.

Thermodynamics of mixtures with strong negative deviations from Raoult’s law. XIII. Relative permittivities for (1-alkanol + cyclohexylamine) systems, and dielectric study of (1-alkanol + polar) compound (amine, amide or ether) mixtures

Relative permittivities, εr, at 1MHz have been measured for (1-alkanol+cyclohexylamine) systems at T=(293.15 to 303.15)K and atmospheric pressure. The excess permittivity values, εrE, Kirkwood’s correlation factors, gK, and the excess values of this magnitude, gKE, have been also determined for these solutions and, using measurements available in the literature, for mixtures containing a number of 1-alkanols and n-propylamine, n-butylamine, aniline, N-methylaniline, pyridine, di-n-ethylamine, N,N-dimethylformamide, N,N-dimethylacetamide, di-n-propylether, di-n-butylether, 2,5,8,11,14-pentaoxapentadecane, or propanal. At ϕ1 (volume fraction)=0.5, εrE values of cyclohexylamine solutions change in the sequence: 1-propanol>1-butanol>1-heptanol<1-decanol and the symmetry of the εrE curves becomes skewed to higher ϕ1 values when the alcohol size increases. This seems to be a rather general behavior as is also encountered for many of the systems investigated. It can be explained in terms of the weaker and lower self-association of longer 1-alkanols. The analysis of gK data shows that cyclohexylamine solutions including shorter alcohols are more structured. In addition, mixtures with this cyclic amine are more structured than those containing a linear amine or aniline. The εrE(ϕ1) and gKE(ϕ1) curves of (1-alkanol+amine) mixtures show similar patterns. Thus, negative εrE values can be ascribed to the real mixture is less structured than the ideal solution; positive εrE values are due to the system is more structured than the ideal solution. We have also determined the orientational polarization and the corresponding excess values, PmE. The PmE and gKE functions have the same sign That is, negative values of such magnitudes suggest that the loss of structure of the real mixture compared with that of the ideal solution can be ascribed, at least in part, to a weakening of the orientational polarization.

Novel methodologies for automatically and simultaneously determining BTEX components using FTIR spectra

This study introduced a patented novel methodological system for automatically analysis of Fourier Transform Infrared Spectrometer (FTIR) spectrum data located at ‘fingerprint’ region (wavenumber 670–800cm−1), to simultaneously determinate multiple petroleum hydrocarbons (PHs) in real mixture samples. This system includes: an object oriented baseline correction; Band decomposition (curve fitting) method with mathematical optimization; and Artificial Neural Network (ANN) for determination, which is suitable for the characteristics of this IR regions, where the spectra are normally with low signal to noise ratio and high density of peaks. BTEX components are potentially lethal carcinogens and contained in many petroleum products. As a case study, six BTEX components were determinate automatically and simultaneously in mixture vapor samples. The robustness of the BTEX determination was validated using real petroleum samples, and the prediction results were compared with gas chromatography–mass spectrometry (GC–MS).

Exergy Analysis of a Two-Pass Reverse Osmosis (RO) Desalination Unit with and without an Energy Recovery Turbine (ERT) and Pressure Exchanger (PX)

This paper presents an exergy analysis of an actual two-pass (RO) desalination system with the seawater solution treated as a real mixture and not an ideal mixture. The actual 127 ton/h two pass RO desalination plant was modeled using IPSEpro software and validated against operating data. The results show that using the (ERT) and (PX) reduced the total power consumption of the SWRO desalination by about 30% and 50% respectively, whereas, the specific power consumption for the SWRO per m3 water decreased from 7.2 kW/m3 to 5.0 kW/m3 with (ERT) and 3.6 kW/m3 with (PX). In addition, the exergy efficiency of the RO desalination improved by 49% with ERT and 77% with PX and exergy destruction was reduced by 40% for (ERT) and 53% for (PX). The results also showed that, when the (ERT) and (PX) were not in use, accounted for 42% of the total exergy destruction. Whereas, when (ERT) and (PX) are in use, the rejected seawater account maximum is 0.64%. Moreover, the (PX) involved the smallest area and highest minimum separation work.

Largely Cu-doped LaCo1−xCuxO3 perovskites for TWC: Toward new PGM-free catalysts

Doping of LaCoO3 with copper to add reduction functionality in addition to the known oxidation properties has been investigated, aiming at three-way catalysis (TWC) applications. Nanoscale perovskites with nominal composition LaCo1−xCuxO3, (x=0, 0.1, 0.3, and 0.5) have been synthesized by means of the citrate method. A stable perovskitic phase with rhombohedral geometry up to an unprecedented x=0.5 has been obtained and characterized by BET, X-ray diffraction (XRD), Temperature Programmed Reduction (TPR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The crystallite size decreases with increasing the copper amount and also the morphology differs; moreover the surface reactivity with respect to atmospheric moisture and carbon dioxide is more evident in the sample with x=0.5. Reactivity has been measured in simple NO+CO and CO+O2 model reactions, as well as with complex mixtures approaching automotive exhaust composition, at both stoichiometric and O2 limiting conditions. The catalysts have been characterized after reaction as well. The perovskite with the highest Cu amount, LaCo0.5Cu0.5O3, exhibits an interesting compromise of oxidation and NO reduction functionality at interesting, low temperatures with very short contact time (GHSV=1,000,000h−1). Still, activity for NO reduction in real mixtures requires substoichiometric O2.

Selective nickel-catalyzed conversion of model and lignin-derived phenolic compounds to cyclohexanone-based polymer building blocks.

Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Lignin is converted into novel polymer building blocks through four steps: catalytic hydroprocessing of softwood to form 4-alkylguaiacols, their conversion into 4-alkylcyclohexanols, followed by dehydrogenation to form cyclohexanones, and Baeyer-Villiger oxidation to give caprolactones. The formation of alkylated cyclohexanols is one of the most difficult steps in the series. A liquid-phase process in the presence of nickel on CeO2 or ZrO2 catalysts is demonstrated herein to give the highest cyclohexanol yields. The catalytic reaction with 4-alkylguaiacols follows two parallel pathways with comparable rates: 1) ring hydrogenation with the formation of the corresponding alkylated 2-methoxycyclohexanol, and 2) demethoxylation to form 4-alkylphenol. Although subsequent phenol to cyclohexanol conversion is fast, the rate is limited for the removal of the methoxy group from 2-methoxycyclohexanol. Overall, this last reaction is the rate-limiting step and requires a sufficient temperature (>250 °C) to overcome the energy barrier. Substrate reactivity (with respect to the type of alkyl chain) and details of the catalyst properties (nickel loading and nickel particle size) on the reaction rates are reported in detail for the Ni/CeO2 catalyst. The best Ni/CeO2 catalyst reaches 4-alkylcyclohexanol yields over 80 %, is even able to convert real softwood-derived guaiacol mixtures and can be reused in subsequent experiments. A proof of principle of the projected cascade conversion of lignocellulose feedstock entirely into caprolactone is demonstrated by using Cu/ZrO2 for the dehydrogenation step to produce the resultant cyclohexanones (≈80 %) and tin-containing beta zeolite to form 4-alkyl-ε-caprolactones in high yields, according to a Baeyer-Villiger-type oxidation with H2 O2 .

Repulsive core-soft models for binary aqueous mixtures

A model for aqueous mixtures, consisting of core-softened water together with a soft-core or core-softened solute, is shown to represent a minimal molecular model for hydrophilic aqueous mixtures. In spite of having purely repulsive interactions, this model is able to produce Kirkwood–Buff integrals very similar to that of the real hydrophilic aqueous mixtures. Monte Carlo simulations and integral equation study of this model are in better agreement between them when entropic effects are predominant. It is intriguing that the entropic effect of purely repulsive interactions capture better hydrophilic effects rather than the hydrophobic ones. The interplay between the concentration fluctuations and the intrinsic structural micro-heterogeneity of these systems help clarifying some of these issues.

Modeling ethanol–blended gasoline droplet evaporation using COSMO-RS theory and computation fluid dynamics

A new single droplet evaporation model for ethanol–blended gasoline is presented. The real liquid mixture model based on the quantum chemical ab initio description of non-ideality of liquid phase without need of any adjustable parameters. The multi-scale model applies the COSMO-RS theory (micro level) for the estimation of vapor–liquid equilibrium of non-ideal solutions and the Maxwell–Stefan diffusion and convection theory for the calculation of gas phase transport (macro level) characteristics of the components. Solvation mixture thermodynamics and computational fluid dynamics (CFD) simulation were used to perform the calculations for the quasi-equilibrium evaporation of compounds from curved liquid surface. Physical–chemical properties, which are difficult to measure experimentally the activity coefficients of the components, the liquid and vapor phase compositions, the cumulative and components evaporation fluxes among others were computed during the evaporation process. A new approach for calculating the temperature-depression of evaporating droplets is also reported. The model was validated against experimental evaporation data of multi-component alcohol–alkane mixtures. The validated model was used to predict the impact of ethanol on volatilities of droplets of ethanol–blended model gasoline. The estimated non-linear trend in vapor pressures of ethanol–blended model gasoline is consistent with the experimentally observed effects of ethanol addition on dry vapor pressure equivalent values of gasoline base stock samples.

Separation of Lactic Acid Produced by Hydrothermal Conversion of Glycerol Using Ion-Exchange Chromatography

Production of lactic acid by hydrothermal conversion of glycerol is an option to add value to the large amounts of glycerol that is being generated during the production of biodiesel. This work aimed to separate lactic acid by ion-exchange resins in a fixed-bed column. Adsorption isotherms were obtained from the breakthrough curves using different initial concentrations of lactic acid (60-302 g/l) and temperatures (30, 40 and 60 °C). Maximum adsorption capacities were estimated by the Langmuir model. Adsorption and desorption cycles for a binary and a real mixture were performed. The methodology proposed for the separation of lactic acid in a fixed-bed column presented high values of adsorptive capacity for both Amberlite IRA-96 and Amberlite IRA-67 resins at 30 °C. Lactic acid was more strongly adsorbed by Amberlite IRA-96 than the IRA-67 resin with maximum adsorption capacity of 544 and 341 g/l, respectively. Chromatographic experiments for the single-component solution (lactic acid), binary mixture (la...

A colourimetric sensor for the simultaneous determination of oxidative status and antioxidant activity on the same membrane: N,N-Dimethyl-p-phenylene diamine (DMPD) on Nafion

A colourimetric sensor capable of simultaneously measuring oxidative status (OS) in terms of the hazard produced by reactive oxygen species (ROS) and antioxidant activity (AOA) in regard to ROS-scavenging ability of antioxidant compounds was developed. The coloured cationic semi-quinone derivatives, caused by ROS oxidative degradation of N,N-dimethyl-p-phenylene diamine hydrochloride (DMPD) in pH 5.7 acetate-buffered medium, were formed in solution and immobilized on a perfluorosulfonate-based Nafion membrane. ROS, namely hydroxyl (OH) and superoxide (O2−) radicals, were produced by Fenton/UV and xanthine/xanthine oxidase methods, respectively. The pink-coloured, (+)-charged chromophore (referred to as DMPD-quinone or DMPDQ), resulting from the reaction between DMPD and ROS, could be completely retained on the solid membrane sensor by electrostatic interaction with the anionic sulfonate groups of Nafion. After equilibration, the Nafion membrane surface was homogeneously coloured enabling an absorbance measurement at 514nm, while the aqueous phase completely lacked colour. Antioxidants, when present, caused an absorbance decrease on the membrane due to their ROS scavenging action, giving rise to less DMPDQ production. The absorbance decrease on the sensor was linearly dependent on antioxidant concentration over a reasonable concentration range, enabling the simultaneous determination of OS and AOA-against ROS. The proposed antioxidant sensing method was tested in synthetic and real antioxidant mixtures, and validated against standard antioxidant capacity assays (i.e. ABTS and CUPRAC) for a variety of polyphenolic and antioxidant compounds. The dynamic linear ranges of antioxidants with the DMPD sensor in protection against hydroxyl and superoxide radicals generally varied within the micromolar to a few tens of micromolar concentration interval over one order-of-magnitude. Choosing three representative compounds in the high (epigallocatechin gallate), medium (quercetin) and low (p-coumaric acid) molar absorptivity range, the detection limits ranged within the concentration intervals of 0.2–0.9μM, 0.3–0.8μM, and 4–14μM, respectively, depending on the radical scavenged.

Composition dependent non-ideality in aqueous binary mixtures as a signature of avoided spinodal decomposition

We explore the potential energy landscape of structure breaking binary mixtures (SBBM) where two constituents dislike each other, yet remain macroscopically homogeneous at intermediate to high temperatures. Interestingly, we find that the origin of strong composition dependent non-ideal behaviour lies in its phase separated inherent structure. The inherent structure (IS) of SBBM exhibits bi-continuous phase as is usually formed during spinodal decomposition. We draw analogy of this correlation between non-ideality and phase separation in IS to explain observation of non-ideality in real aqueous mixtures of small amphiphilic solutes, containing both hydrophilic and hydrophobic groups. Although we have not been able to obtain IS of these liquids, we find that even at room temperature these liquids sustain formation of fluctuating, transient bi-continuous phase, with limited lifetime (τ≲20 ps). While in the model (A, B) binary mixture, the non-ideal composition dependence can be considered as a fluctuation from a phase separated state, a similar scenario is expected to be responsible for the unusually strong non-ideality in these aqueous binary mixtures.

Computational Method for Calculating the Effective Permittivity of Complex Mixtures

This work presents a computational method for the calculation of the effective complex permittivity of a heterogeneous material using its microscopic properties and structure. The new method to calculate the effective properties aims to guarantee that the electric energy stored and dissipated by the heterogeneous material is the same. The analysis of a bi-phase mixture with periodic cubic sample was tested to check the homogenization of the material. An iterative procedure that corrects the initial permittivity yields an electric field distribution of the effective material that is in good agreement with the electric field of the real mixture.

On the multi‐component modelling of human brain tissue to survey clinical interventions

AbstractSerious diseases within the brain's tissue often require a medical intervention, such as the treatment of brain tumours. The present contribution aims at predicting the expected impacts of a scheduled clinical procedure via numerical simulations based on a sophisticated constitutive model. The enormous complexity of the tissue's microscopic composition encourages the application of the Theory of Porous Media (TPM), providing a well‐suited way to model the brain's tissue aggregate in a compact manner on the macroscale. In particular, a multi‐component model is used which is strongly related to the drug‐delivery problem within the brain's tissue, cf. [2]. In this model, the solid skeleton is given by the tissue cells (with cell content) and the vascular walls. This solid skeleton is perfused by two mobile but basically separated pore‐liquid constituents, the blood and the overall interstitial fluid constituent. To provide the particular description of administered therapeutic agents within the overall interstitial fluid, this real mixture is treated as a chemical solution of two components. These are the liquid solvent and the dissolved therapeutic agent (drug). Numerical examples demonstrate the applicability of the derived model. In particular, infusions of therapeutics into the extra‐cellular space (ECS) are simulated under various conditions and complemented by an evaluation of the local numerical sensitivity to survey the influence of certain involved parameters. (© 2014 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Critical fluctuations of a confined binary mixture

Exploiting the mapping between a binary mixture and the Ising model we have analyzed the critical fluctuations by means of the density-matrix renormalization group technique. The calculations have been carried out for a two-dimensional Ising strip subject to equally strong surface fields. It was found that the critical Casimir force has significantly different behavior on opposite sides of the capillary condensation line, especially below the critical temperature. It can be concluded that in real binary mixtures t he most attractive force appears at temperatures near �� and at reservoir compositions slightly away from the critical composition.

Multidimensional capillary electrophoresis.

Multidimensional separation where two or more orthogonal displacement mechanisms are combined is a promising approach to increase peak capacity in CE. The combinations allow dramatic improvement of analytical performance since the total peak capacity is given by a product of the peak capacities of all methods. The initial reports were concentrated on the construction of effective connections between capillaries for 2D analysis. Today, 2D and 3D CE systems are now able to separate real complex biological or environmental mixtures with good repeatability, improved resolution with minimal loss of sample. This review will present the developments in the field of multidimensional CE during the last 15 years. The endeavors in this specific field were on the development of interfaces, interface-free techniques including integrated separations, microdevices, and on-line sample concentration techniques to improve detection sensitivity.

Influence of Normal Component Composition of Ruminal Fluid on Level of Biosensor Luminiscence Level

2 Abstract: During the study of differential biological toxicity of rumen fluid and its individual components the following reporter strains of E.coli fabA:: lux, E.coli ibpA:: lux, E.coli recA:: lux and E.coli cda:: lux were used. Measurement of luminescence was carried out with illuminometer in kinetic mode for 120 min. Bioluminescence level of bacterial strains was expressed in bioluminescent index (BLI). In the course of studies it was found that the real (native) luminal fluid and model mixture gave similar effects of bioluminescence suppression level in the beginning of the experiment with toxic effect not expressed. These data confirm the possibility of using the created model mixture to determine the influence of separate components of luminal fluid on bioluminescence of the recombinant strain E. coli. Components of model luminal fluid had not any expressed toxic effect on sensory luminescent strain E. coli; and the effect of bacterial bioluminescence suppressing in the initial stage of the experiment can be explained, in our opinion, by the influence of ammonia and acetic acid, which can be considered as a manifestation of moderate toxicity.

Perspective: The Asakura Oosawa model: a colloid prototype for bulk and interfacial phase behavior.

In many colloidal suspensions, the micrometer-sized particles behave like hard spheres, but when non-adsorbing polymers are added to the solution a depletion attraction (of entropic origin) is created. Since 60 years the Asakura-Oosawa model, which simply describes the polymers as ideal soft spheres, is an archetypical description for the statistical thermodynamics of such systems, accounting for many features of real colloid-polymer mixtures very well. While the fugacity of the polymers (which controls their concentration in the solution) plays a role like inverse temperature, the size ratio of polymer versus colloid radii acts as a control parameter to modify the phase diagram: when this ratio is large enough, a vapor-liquid like phase separation occurs at low enough colloid packing fractions, up to a triple point where a liquid-solid two-phase coexistence region takes over. For smaller size ratios, the critical point of the phase separation and the triple point merge, resulting in a single two-phase coexistence region between fluid and crystalline phases (of "inverted swan neck"-topology, with possibly a hidden metastable phase separation). Furthermore, liquid-crystalline ordering may be found if colloidal particles of non-spherical shape (e.g., rod like) are considered. Also interactions of the particles with solid surfaces should be tunable (e.g., walls coated by polymer brushes), and interfacial phenomena are particularly interesting experimentally, since fluctuations can be studied in the microscope on all length scales, down to the particle level. Due to its simplicity this model has become a workhorse for both analytical theory and computer simulation. Recently, generalizations addressing dynamic phenomena (phase separation, crystal nucleation, etc.) have become the focus of studies.

Finite Element Models for Asphalt Mixture Fatigue Behavior Study

This paper presents digital models of indirect tensile test and four point bending fatigue test for asphalt mixture at a microstructural level. Conventional images were converted into Finite Element (FE) models which consist of the information of material heterogeneity and microstructures of real asphalt mixtures. It was found that the material heterogeneity especially the volumetric properties can significantly affect the fatigue behavior which is quite different from the traditional findings based on the hypothesis of homogeneous material. The results show that the proposed method for FE model of fatigue test can be extended for other analyses like rutting or low temperature cracking.

Modeling the Phase Behavior of Essential Oils in Supercritical CO2 for the Design of a Countercurrent Separation Column

This work describes a generalized procedure for high pressure equilibrium calculations for terpene oils. A simple semiempirical model allows the prediction of the solubilities of essential oils at high pressure on the basis of the physicochemical properties of their compounds (molecular weight, boiling temperature, density, and solubility parameter). This easy model can be useful for the determination of the fractionation and for the preliminary scale-up and economic evaluation. The theoretical basis considers any essential oil composed of two types of components: oxygenated and nonoxygenated. Vapor–liquid equilibrium data of binary systems (terpenoids/CO2) are used to correlate the semiempirical model proposed. Validity of the prediction is checked by comparison with literature data concerning ternary systems (limonene + linalool + CO2) and real mixtures (lemon and orange oils + CO2). Finally, the simulation and optimization of a countercurrent column for the fractionation of terpenes from lemon oil are ...

Estimating the number of pure chemical components in a mixture by X-ray absorption spectroscopy.

Principal component analysis (PCA) is a multivariate data analysis approach commonly used in X-ray absorption spectroscopy to estimate the number of pure compounds in multicomponent mixtures. This approach seeks to describe a large number of multicomponent spectra as weighted sums of a smaller number of component spectra. These component spectra are in turn considered to be linear combinations of the spectra from the actual species present in the system from which the experimental spectra were taken. The dimension of the experimental dataset is given by the number of meaningful abstract components, as estimated by the cascade or variance of the eigenvalues (EVs), the factor indicator function (IND), or the F-test on reduced EVs. It is shown on synthetic and real spectral mixtures that the performance of the IND and F-test critically depends on the amount of noise in the data, and may result in considerable underestimation or overestimation of the number of components even for a signal-to-noise (s/n) ratio of the order of 80 (σ = 20) in a XANES dataset. For a given s/n ratio, the accuracy of the component recovery from a random mixture depends on the size of the dataset and number of components, which is not known in advance, and deteriorates for larger datasets because the analysis picks up more noise components. The scree plot of the EVs for the components yields one or two values close to the significant number of components, but the result can be ambiguous and its uncertainty is unknown. A new estimator, NSS-stat, which includes the experimental error to XANES data analysis, is introduced and tested. It is shown that NSS-stat produces superior results compared with the three traditional forms of PCA-based component-number estimation. A graphical user-friendly interface for the calculation of EVs, IND, F-test and NSS-stat from a XANES dataset has been developed under LabVIEW for Windows and is supplied in the supporting information. Its possible application to EXAFS data is discussed, and several XANES and EXAFS datasets are also included for download.