Real Mixtures Research Articles

Understanding CO2/CH4 Separation in Pristine and Defective 2D MOF CuBDC Nanosheets via Nonequilibrium Molecular Dynamics.

The separation of CO2/CH4 gas mixtures is a key challenge for the energy sector and is essential for the efficient upgrading of natural gas and biogas. A new emerging field, that of metal–organic framework nanosheets (MONs), has shown the potential to outperform conventional separation methods and bulk metal–organic frameworks (MOFs). In this work, we model the CO2/CH4 separation in both defect-free and defective 2D CuBDC nanosheets and compare their performance with the bulk CuBDC MOF and experimental data. We report the results of external force nonequilibrium molecular dynamics (EF-NEMD) for pure components and binary mixtures. The EF-NEMD simulations reveal a pore blocking separation mechanism, in which the CO2 molecules occupy adsorption sites and significantly restrict the diffusion of CH4. The MON structure achieves a better selectivity of CO2 over CH4 compared to the bulk CuBDC MOF which is due to the mass transfer resistance of the methane molecules on the surface of the nanosheet. Our results show that it is essential to consider the real mixture in these systems rather than relying solely on pure component data and ideal selectivity. Furthermore, the separation is shown to be sensitive to the presence of missing linker defects in the nanosheets. Only 10% of missing linkers result in nonselective nanosheets. Hence, the importance of a defect-free synthetic method for CuBDC nanosheets is underlined.

Robust Supervised Method for Nonlinear Spectral Unmixing Accounting for Endmember Variability

Due to the complex interaction of light with mixed materials, reflectance spectra are highly nonlinearly related to the pure material endmember spectra, making it hard to estimate the fractional abundances of the materials. Changing illumination conditions and cross-sensor situations cause spectral variability, further complicating the unmixing procedure. In this work, we propose a supervised approach to unmix mineral powder mixtures, containing endmember variability. First, the abundances are estimated by calculating the geodesic distances between the mixtures and the endmembers. It is argued and experimentally validated that the estimated geodesic abundances, although not correct, are invariant to external spectral variability. Then, a supervised approach is applied to learn a mapping from the obtained geodesic abundances to spectra that follow a linear model. To learn this mapping, groundtruth fractional abundances of a number of training samples are required. Although any nonlinear regression method can be used to learn the mapping, Gaussian process is found to be suitable when a limited number of training samples are available. The trained model is applicable to all manifolds that contain a similar nonlinear behavior as the trained manifold, e.g., when the same mixtures are measured by another sensor. Using the output spectra, a simple inversion of the linear model reveals the true abundances. Experiments are conducted on simulated and real mineral mixtures. In particular, we developed data sets of homogeneously mixed mineral powder mixtures, acquired by two different sensors, an Agrispec spectrometer and a snapscan shortwave infrared (SWIR) hyperspectral camera, under strictly controlled experimental settings. The proposed approach is compared to other supervised approaches and nonlinear mixture models.

Trois scènes de bal dans le roman français (« La Princesse de Clèves », « Madame Bovary », « Le Ravissement de Lol V Stein »)

"Three Ball Scenes in the French Novel (“La Princesse de Clèves”, “Madame Bovary”, “Le Ravissement de Lol V Stein”). This article aims to analyze – in a comparative manner – three ball scenes from novels belonging to leading authors of French literature (Madame de Lafayette, Gustave Flaubert and Marguerite Duras), highlighting a series of dramatic mechanisms used by novelists in the construction of such a diegetic plot. If La Princesse de Clèves describes a ball that takes place in the royal court, with all the typical scenes of the time (embodied in a real mixture of intrigue and gallantry specific to the living environment of the actors, which make the topos of the novel itself become a collective character), Madame Bovary describes, instead, a ball animated by the high society of the nineteenth century, with all the specifics of the realistic episteme (the ball becomes here an opportunity to evoke the painful contrast between different living environments, which the heroine cannot access and which causes her, consequently, to take refuge in an imaginary universe). Much closer to the spirit of contemporaneity, Le Ravissement de Lol V Stein, the famous “nouveau roman”, relies on an image of the harmful and destructive ball, paying particular attention to the psyche of the characters. These novels lean – starting from this narrative pretext of the ball – on some love stories built through specific strategies of the theatre, which is, in essence, the central object of our analysis. Keywords: ball scenes, French Novel, dramatic mechanisms, narrative pretext, love stories."

Micro-scale investigation of aging gradient within bitumen film around air-binder interface

The aging issue of bitumen is one of the most concerned topics for the bituminous pavement duration. Currently, the laboratory accelerates the aging by applying high temperature and pressure. However, an extremely thin state of bitumen in a real asphalt mixture could induce the interference of aging that happened at two interfaces, namely the air-bitumen interface and the bitumen-aggregate interface. Hence, it is of great importance to explore more deeply about what is happening on the air-bitumen interface. This study performed experimental research on the aging gradient of bitumen during the TFOT test, together with the molecular simulation. To that end, Thin Film Oven Tests (TFOTs) on bitumen with different aging durations (0, 1, 5, 10, 20 h) were conducted and further, the microscopic aging gradient along with the aging depths (11 layers in total) was investigated. The Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectroscopy (FTIR) tests were performed to characterize the aged bitumen samples. From the molecular perspective, this study adopted the molecular dynamic simulation of oxygen and bitumen. The results indicated that the aging of bitumen induced the increase of complex modulus and the generation of chemical functional groups. Experimental data demonstrated the microscopic aging gradient, and the effective depth of thermal oxidation could be within 1000 μm due to the limited oxygen diffusion. The results of molecular dynamics simulation showed consistent conclusions with the experimental results. This research revealed the complicated aging mechanism from the molecular scale and provided further research with fundamental findings.

Up north there: Discourse-pragmatic deixis in Northern Ontario

In this paper we analyze the discourse-pragmatic use of the adverbs there/here, e.g., “So, our grandsonthereis a real mixture”, in four small northern Ontario towns. 1200 examples contrasted by type of reference, ambiguous locative or non-locative, were coded for social and linguistic factors and analysed using statistical modelling. The results reveal that the strongest predictor of discourse-pragmatic use is date of birth: middle-aged speakers use it most in each town, but no other social factors (e.g. perceived gender, education, job type) are significant. Importantly, the higher the proportion of Francophone populations in the community, the greater the use of there but not here. We argue that alignment between Francophones and Anglophones is a likely explanation. More generally this study highlights the value of discourse-pragmatic features for understanding styles of interaction and underscores the research potential for comparing these phenomena across communities.

Calculation and Properties of the Inhomogeneity Function during the Phase Transformation of Multicomponent Systems

An equation is derived for calculating the inhomogeneity function in the equilibrium liquid–vapor phase transition processes. In the equations, there are no derivatives of the activity coefficients with respect to the degree of phase transformation. For calculations, data on the equilibrium phase compositions and on the heat of phase transformation are used. The change in the inhomogeneity function is studied depending on the relative volatility and the degree of phase transformation. Using the example of evaporation of a real azeotropic mixture, it is shown that neglecting the heats of mixing in the liquid phase leads to insignificant errors.

Aqueous phase reforming of lignin-rich hydrothermal liquefaction by-products: A study on catalyst deactivation

The water fraction derived from the hydrothermal liquefaction of a lignin-rich feedstock was subjected to aqueous phase reforming to produce hydrogen. Deactivation of the catalyst was observed, and it was ascribed to fouling phenomena caused by phenolic oligomers. Simple aromatics like guaiacol and phenol, as well as inorganics, were proved not to be the cause of the deactivation thanks to the use of a multi-component synthetic mixture. The influence of using activated carbon as a pretreatment was studied, leading to a strong improvement of the performance when it was carried out at high temperature. The extent of deactivation was assessed using aqueous phase reforming of glycolic acid as a model reaction test. The results were found to be correlated with the surface area of the catalyst. A thermal regeneration in inert conditions was evaluated as a mode of catalyst regeneration. While the textural properties were partially recovered, the performance of the catalyst only slightly improved. A spectroscopic analysis of the solids in the aqueous solution was carried out, highlighting the structural similarities between their nature and the lignin residue. The results obtained in this study helped to enlarge the knowledge on the aqueous phase reforming of real complex mixtures, looking at indicators of paramount importance for a possible industrial application such as the stability of the catalyst.

Analysis of the Fire Propagation in a Sublevel Coal Mine

A fire has been analyzed in a real underground coal mine, using a sublevel method, during an entire year. The study was focused on the collapsed area, reproducing a real mixture formed by coal, waste, and air gap. The analysis was done by means of an experimental analysis, a computational fuid dynamic model (CFD), and simulations using a mine ventilation software. Three scenarios were determined and studied regarding their influence on the evolution of the fire: (a) development of the fire without taking any action, (b) sealing off the affected areas, and (c) sealing and reducing the ventilation in the affected area and surrounding drifts. The study revealed the behavior of the fire in a real mine and the effectiveness of the main fire-fighting measures over time, verifying that none of the measures taken could eliminate the fire-induced in the collapsed area.

Calculation of portable properties of some real gas mixtures at high temperatures

A method for calculating the power parameters of a potential of the Lennard-Jones type for a number of individual gases, which can be products released during the ignition and combustion of a gas-vapor discharge with a liquid electrode, is presented. The information obtained makes it possible to calculate the viscosity and diffusion coefficients of individual gases and gas mixtures, which will make it possible to solve a range of problems when modeling processes in the processing technology of various materials (substances) by vapor-gas discharge plasma with a liquid electrode.

Naphthenic acid removal in model and real aviation kerosene mixture

Bovine bone activated charcoal (CAB) was evaluated for its ability to remove n- dodecanoic carboxylic acid (ACD) in model and real mixture of aviation kerosene through kinetic and adsorption equilibrium data. In the kinetic test, for both model and real mixture, equilibrium was reached in 180 min, and this result indicated relatively fast adsorption when compared to the use of other adsorbents presented in the literature, such as mesoporous sieves and modified perovskites. In the adsorption isotherm, it was found that the amount adsorbed in the equilibrium in model and real mixture was 600 and 780 mg g−1, respectively. The model with the best fit was that of Freundlich. CAB also proved to be more efficient at removing ACD, when compared to the polymer filtration system used by the fuel distribution company. Thus, CAB can become a viable, inexpensive option with the possibility of regeneration to be used as a filter material.

Separating Hydrocarbon Mixtures by Driving the Components in Opposite Directions: High Degree of Separation Factor and Energy Efficiency.

A radically different approach for separation of molecular mixtures is proposed. A judicious combination of levitation effect observed in zeolites with a counter intuitive Landauer blow torch effect provides driving forces for the two components of the mixture to move in opposite directions. Using nonequilibrium MonteCarlo simulations, we illustrate the efficacy of the method for separating real mixtures of both linear n-pentane and its branched isomer, neopentane, and linear n-hexane and its branched isomer, 2,2-dimethylbutane. The method yields several orders of magnitude improvement in separation factor and relative energy efficiency by using submicron zeolite column. The extremely high purity of the resulting single components makes the method best suited for green chemistry.

Trapping multiple dual mode liquid-liquid chromatography: Preparative separation of nootkatone from a natural product extract

Trapping multiple dual mode (trapping MDM) is a preparative liquid-liquid chromatography (LLC) technique well-suited to difficult separations of intermediately-eluting components from similarly structured impurities. In this demonstrative study, a design approach for high process throughput is applied for the trapping MDM separation of a target component, nootkatone (NK), initially comprising 16.7% of an industrial side stream mixture with over 90 impurities. This design approach, previously developed and validated using ternary mixtures of model solutes, is applied to a complex real mixture for the first time. The approach consists of five steps: (1) determination of the maximum starting mixture concentration for feed preparation; (2) determination of the maximum flow rate for maintenance of the pre-set stationary phase fraction; (3) determination of the partition coefficients of the target and main impurities; (4) selection of step durations and number of cycles using an established short-cut method; (5) execution of the trapping MDM separation. The target, NK, was obtained along with a co-eluting component at 78.7% purity and 84.6% yield, demonstrating the effectiveness of trapping MDM for the separation of intermediately-eluting natural product target components from complex starting mixtures.

APPLICATION OF THE BIOMASS PYROLISIS PRODUCTS AS A REBURNING FUEL FOR NITROGEN OXIDES REDUCTION: TESTING THE CHEMICAL KINETICS MECHANISM

The mechanisms of chemical kinetics of the Reburning process using pyrolysis gases as a reburn fuel are determined. It has been shown that CO, CO2, H2 have very little effect on the reduction of the nitrogen oxides under conditions characteristic for the coal combustion, and hydrocarbons play the major contribution to the reduction of the nitrogen oxides. The results of the test calculations showed that the process of the nitrogen oxides reduction by the biomass pyrolysis products can be calculated by a simplified mechanism of the chemical kinetics of the Reburning process by replacing hydrocarbons with one substance (with a close carbon/hydrogen ratio as in the real pyrolysis gas mixture), provided that the mass fraction of carbon is preserved, fed to the reduction of nitrogen oxides unchanged. This approach significantly reduces machine time and calculates the nitrogen oxides reducing efficiency by Reburning technology with an accuracy of 17%.

Impact of natural gas quality on engine performances during a voyage using a thermodynamic fuel system model

Liquefied Natural Gas (LNG) as a fuel is seen as a solution to curb harmful emissions in shipping and its quick uptake is now significant. As heat leaks into the LNG fuel tanks, composition of the vapor and liquid phase change. This process, known as ageing, alters the fuel properties and can impact negatively the main engine performance. In this paper, a dynamical model to assess the methane number at engine inlet from the bunkered composition is presented. The fuel system is made of a 40 ft container tank and two heat exchangers. The model considers the two-phase real mixture in the tank and solves explicitly the heat and mass conservation laws. Then a strategy is developed to avoid “off-spec” methane number at engine inlet. The approach is tested on two bunkered compositions, one from Libya and one from Australia. The simulations have been conducted for a concept LNG/wind electric ship using multiple removable 40 ft container LNG tanks. Results show that with the proposed mixing strategy, the methane number remains above its limit value at engine inlet, insuring optimal operating conditions of engines.

Spatial Variability of Electric Field Implied by Common Dielectric Effective Medium Models

Remote sensing measurements of Earth materials are always made at scales much larger than individual grains and cavities, yielding only upscaled effective properties. An “effective medium” is an idealized uniform material that has the same measured properties as the real mixture. A uniform electric field applied to the ideal effective medium remains uniform within the sample; however, the same electric field applied to the composite results in fine-scale spatial variations of field strength within the sample, which depend on the properties of the constituents, their volume fractions, and their microgeometries. We derived analytic expressions for the electric field strength heterogeneity implicit in commonly used dielectric effective medium models. Only two-phase, statistically isotropic, low-loss materials, e.g., ice, snow, minerals, and freshwater in the microwave UHF band are considered. The method applies to singly or biconnected phases. The results confirm the uniform field in the isolated phase of material lying on the Hashin–Shtrikman (HS) bounds; the continuous phase field variance increases with a decreasing volume fraction, approaching a well-defined limit as the fraction becomes vanishingly small. Expressions are found for field variance in higher-order composites of coated spheres, providing realizations of composites lying between the HS bounds, and illustrating field nonuniqueness when microstructure is unknown. The mean and variance of the field strength in popular effective medium models are also examined. Not only do the effective properties predicted by these models differ so do the electric field strength spatial variability, especially when the volume fraction of inclusions increases.

Estimation of PC-SAFT binary interaction coefficient by artificial neural network for multicomponent phase equilibrium calculations

Perturbed-Chain Statistical Associating Fluid Theory Equation of State (PC-SAFT EoS) requires cross interaction parameter for each binary pair in the mixture. For real mixtures, these parameters should be corrected by binary interaction coefficients (kij's). The values of kij's are tuned by an optimization method in order to minimize the deviation from equilibrium data. The Particle Swarm Optimization (PSO) algorithm is employed for optimization of kij's due to the continuous nature of kij and highly nonlinear nature of PC-SAFT EoS. Although kij can be adjusted using the mentioned algorithm, it is cumbersome and highly time-consuming because the optimization should be performed for each pair that exists in the multicomponent mixture. It has been shown that these optimal values can be obtained based on the basic characteristic properties of the participating molecules in each pair, this is particularly useful to avoid solving any optimization problem. Furthermore, Artificial Neural Networks (ANNs) as powerful function approximators have been used to predict binary interaction coefficients based on basic characteristic properties of molecules that exist in each pair. Two types of characteristic properties have been examined as inputs of the ANN's utilized to predict the optimum kij's. The first one contains PC-SAFT parameters (m, ε/k, σ) and molecular weight of each component; while the second category contains specific gravity, normal boiling point and molecular weight of each component.The best structure of ANN has been obtained by two approaches: 1) Genetic Algorithm (GA) and 2) a constructive approach. GA can find the structure with any possible connections between neurons whereas the constructive approach can only find the best structure for fully connected networks. The results show that the genetically designed ANN that uses the second set of inputs outperforms the others. This ANN is used to estimate kij's of PC−SAFT for a wide range of non-associating materials where the predicted kij's are in close agreement with those obtained by PSO with coefficient of determination R2 = (0.9921, 0.9631) for training and validation data, respectively. In addition to the evaluation of the ANN by validation data, its performance has been examined by using its estimated kij's in flash calculation of a synthesized multi-component mixture and bubble point calculation of a reservoir fluid. Comparing the results of equilibrium calculations with their experimental counterparts shows that they closely follow the measured data. Furthermore, its performance has been compared with other approaches of estimation of kij such as London theory and QSPR method and the results show that the proposed ANN outperforms the others.

Unraveling ingredients in complex mixtures by chromatographic spectrum recognition: Application to perfume deformulation

AbstractIn the past 40 years, progress in GC‐MS and GC‐FID has lent the modern perfume industry powerful tools for determining raw ingredients in fragrances, which is still often manual and based on molecular markers thus subjective and unreliable due to variability and chromatographic challenges. This article presents an alternative approach by introducing the concept of chromatographic spectrum. This approach was evaluated on a commercial database containing molecular composition of 4106 perfumery ingredients and on real and simulated mixtures. Five hundred and seven out of 565 database ingredients classes were differentiated by their chromatographic spectrum against 164 with distinctive markers. The 5 ingredients of a real Eau de Cologne mixture were identified, and their proportions estimated with less than 12% relative error for 4 of them. The usefulness of chromatographic spectra in a deformulation support algorithm is discussed based on the deformulation of 210 simulated mixtures of 5, 10, and 15 ingredients.

Characteristics of coconut protein separation process by means of membrane ultrafiltration

AbstractCross‐flow ultrafiltration has been reported as a promising technique to concentrate the coconut protein in the liquid by‐product called coconut skimmed effluent, which is produced from coconut oil wet process. However, the cake developed on the membrane surface always causes a measurable resistance, which extremely impedes the filtration efficiency. This study investigated the cross‐flow filtration performance under different operational conditions, which included membrane molecular weight cut‐off (10 and 30 kDa), transmembrane pressure (0.1, 0.2, and 0.3 MPa) and cross‐flow velocity (0.5, 1.0, and 1.5 l/min), and molecular electrostatic interaction by adjusting the feed suspension pH (2.0, 4.0, 6.3, 9.0). The results showed that there was no substantial difference in the filtration performance between 10 kDa and 30 kDa membrane because the number of molecules, in which the particle size was larger than 30 kDa, was high. Furthermore, the results confirmed that the permeate flux increased with the cross‐flow velocity but decreased with the transmembrane pressure due to the cake layer compressibility. For the suspension chemistry effects, although a thick cake layer was developed on the membrane when the feed suspension pH was very close to pI (pH 4.0), the permeate flux was surprisingly greater than the other pH conditions.Practical ApplicationThis research was carried out by focusing on the evaluation of the alternative method other than the traditional one, such as precipitation or centrifugation, for coconut protein concentration. The membrane ultrafiltration, which is widely used to improve the quality of many dairy products, has been applied to the coconut suspension and filtration performances including fouling behavior under various conditions have been investigated. The results obtained could provide extensive information for the operational optimization of the coconut liquor cross‐flow filtration process considering the hydrodynamic factors. Furthermore, since the experiment was conducted with a real polydispersed biopolymer mixture, its unique characteristics that depend on the change of pH would be able to extend the knowledge including the influence of the electrostatic interaction on the cake formation of such plant‐based protein–polysaccharide mixture.

ЗАКОНОМЕРНОСТИ ИЗМЕНЕНИЙ ПАРАМЕТРОВ ПРОЦЕССОВ ПЕРЕНОСА МНОГОКОМПОНЕНТНЫХ УГЛЕВОДОРОДНЫХ ГАЗОВЫХ СРЕД В УСЛОВИЯХ СЕПАРАЦИИ

A detailed study of the evolution of local and integral parameters of momentum, heat, and mass transfer processes in hydrocarbon gas mixtures under separation conditions at given temperature and pressure values in working media is carried out within the framework of the principles of equilibrium thermodynamics using the Aspen HYSYS software package, namely, the Peng-Robinson equation of state for real gas mixtures, the principles of statistical mechanics, the approaches of corresponding states, the Chapman-Enskog and the Golubev methods, and the theory of similarity and dimensional analysis. The limits of similarity method applicability in quantitative estimates and qualitative forecasts of the mechanisms and configurations of convective heat and mass transfer in oil treatment units are established. The paper also discusses results of the analog method application in separation process modeling for momentum, heat and mass transfer processes in the problems of oil and gas industry. The conclusions about the aspects of property changes in complex mixtures and about heat and mass transfer intensity during separation, which violate a triple analogy in non-isothermal homogeneous and heterogeneous media, are recommended to take into account when designing real equipment.

Benchmarking Acidic and Basic Catalysis for a Robust Production of Biofuel from Waste Cooking Oil

The production of biodiesel at the industrial level is mainly based on the use of basic catalysts. Otherwise, also acidic catalysis allowed high conversion and yields, as this method is not affected by the percentage of free fatty acids present in the starting sample. This work has been useful in assessing the possible catalytic pathways in the production of fatty acid methyl esters (FAMEs), starting from different cooking waste oil mixtures, exploring particularly acidic catalysis. It was possible to state that the optimal experimental conditions required concentrated sulfuric acid 20% w/w as a catalyst, a reaction time of twelve hours, a temperature of 85 °C and a molar ratio MeOH/oil of 6:1. The role of silica in the purification method was also explored. By evaluating the parameters, type of catalyst, temperature, reaction time and MeOH/oil molar ratios, it has been possible to develop a robust method for the production of biodiesel from real waste mixtures with conversions up to 99%.