Growth of a faujasite-type zeolite membrane and its application in the separation of saturated/unsaturated hydrocarbon mixtures

Faujasite type zeolite membranes were synthesized on porous ceramic alumina supports by using direct (in situ) and secondary (seeded) growth methods. In the secondary growth method a seed layer of ZSM-2 nanocrystals (prepared according to a report by Schoeman et al. J. Colloid Interface Sci. 1995, 170, 449–456) was deposited on the surface of the support before the hydrothermal growth. For both in situ and secondary growth, the mixture composition was 4.17 Na₂O:1.0 Al₂O₃:10 TEA (triethanol ammonium):1.87 SiO₂:460 H₂O. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron microprobe analysis (EPMA), indicate well intergrown 5–30 μm thick FAU films with Si/Al ∼1–1.5. The separation of saturated/unsaturated hydrocarbon mixtures is demonstrated over a range of temperatures (40–160°C). The mixtures examined (and the corresponding equimolar mixture separation factors) are benzene/cyclohexane (160), benzene/n-hexane (144), toluene/n-heptane (45), propylene/propane (6.2), and ethylene/methane (8.4). In all cases, the membranes are unsaturated hydrocarbon permselective. With equimolar feed mixtures (5 kPa/5 kPa benzene/cyclohexane) and in the temperature range 65–160°C, the membranes exhibit separation factor of 20–160 with the benzene flux in the range 10⁻⁴–10⁻³ mol m⁻² s⁻¹. Decreasing the total feed partial pressure (0.31/0.31 kPa benzene/cyclohexane) reduces both separation factor (12) and benzene flux. Similar trend is observed when the benzene/cyclohexane ratio in the feed mixture (0.5/9.5 kPa benzene/cyclohexane) is reduced. A sorption diffusion model based on the Stefan–Maxwell formulation has also been employed to show that the benzene/cyclohexane separation can mainly be attributed to differences of their adsorption properties.     

The connection between the specific refraction,the dispersion and the structure of saturated hydrocarbon mixtures

The method of determining the number of rings in saturated hydrocarbon mixtures with sufficient accuracy from the specific refraction and the dispersion was indicated. With this method the molecular weight of the mixture need not be known.     

Liquid-liquid equilibria for the acetonitrile + methanol + saturated hydrocarbon and acetonitrile + 1-butanol + saturated hydrocarbon systems

Tie-line results at 25°C and atmospheric pressure are presented for {(acetonitrile + methanol) + cyclohexane, or + n-hexane, or + n-heptane or + n-octane} and for {(acetonitrile + 1-butanol) + cyclohexane, or + n-hexane or + n-heptane}. Vapor-liquid equilibria for acetonitrile + methanol at 25° C are reported. The UNIQUAC associated-solution model is used to correlate binary vapor-liquid equilibria and mutual solubilities for the 13 systems constituting the ternary systems and to predict the ternary liquid-liquid equilibria by using binary parameters alone.     

Development of a push-pull microdialysis sampling technique for the quantitative determination of proteins

Summary An on-line push-pull sampling technique has been developed for continuous analysis of proteins of molecular weight from 5.7 to 67 kDa. The characteristics of the system include gradient elution with a total cycle time of 21 min, membrane stability, unattended automatic operation, and adjustment of the sampling mode and extraction fraction (the ratio of the concentration of analyte in the dialysate to that in the sample) by varying the effective dialysis length. The push and pull flow rates were adjusted in a manner which enabled three different modes of operation. When push-pull microdialysis was compared with conventional microdialysis sampling, significantly higher extraction fractions were obtained for all five model proteins studied. The technique has been applied to the quantification of proteins in cell samples. On-line fractionation enabled complementary MS identification of the proteins present.     

Comparison of comprehensive two-dimensional gas chromatography and gas chromatography--mass spectrometry for the characterization of complex hydrocarbon mixtures

In this paper, we compare the current separation power of comprehensive two-dimensional gas chromatography (GCxGC) with the potential separation power of GC-mass spectrometry (GC-MS) systems. Using simulated data, we may envisage a GC-MS contour plot, that can be compared with a GCxGC chromatogram. Real examples are used to demonstrate the current potential of the two techniques in the field of hydrocarbon analysis. As a separation technique for complex hydrocarbon mixtures, GCxGC is currently about as powerful as GC-MS is potentially powerful. GC-MS has not reached its potential separation power in this area, because a universal, soft ionization method does not exist. The greatest advantage of GCxGC is, however, its potential for quantitative analysis. Because flame-ionisation detection can be used, quantitative analysis by GCxGC is much more robust, reliable and reproducible.     

Liquid-liquid equilibria for ternary acetonitrile-ethanol-saturated hydrocarbon and acetonitrile-1-propanol-saturated hydrocarbon mixtures

Isothermal vapour-liquid equilibrium data for acetonitrile-1-propanol at 45° C were measured by use of a recirculating still. The liquid-liquid equilibria of (acetonitrile-etha-nol)-(n-hexane or n-heptane or n-octane) and those of (acetonitrile-1-propanol)-(cyclohexane or n-hexane or n-heptane) were obtained from measurements of tie-lines. The experimental results were compared with those calculated from the UNIQUAC associated-solution model.     

Broadband WET: a novel technique for quantitative characterization of minor components in foods

NMR analysis of foods frequently suffers from a problem of dynamic range, which limits the detection of minor components due to the huge signals of water and major components such as sugars. In the present study, we propose a new method named as ‘broadband WET’. This pulse scheme was applied to persimmon fruit juice for saturating the resonances of water and sugars, which covered a broad bandwidth. In comparison with the conventional solvent suppression methods such as WET and DPFGSE‐WATERGATE, it was shown that broadband WET provided highly selective suppression of resonances covering an extensive bandwidth and quantitative signals of minor components without distortion. The proposed method is suitable to detect quantitative signals of the minor components with a high sensitivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of quantitative artificial neural network analysis to 2D NMR spectra of hydrocarbon mixtures

Understanding relationships between the structure and composition of molecular mixtures and their chemical properties is a main industrial aim. One central field of research is oil chemistry where the key question is how the molecular characteristics of composite hydrocarbon mixtures can be associated with the macroscopic properties of the oil products. Apparently these relationships are complex and often nonlinear and therefore call for advanced spectroscopic techniques. An informative and an increasingly used approach is two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy. In the case of composite hydrocarbons the application of 2D NMR methodologies in a quantitative manner pose many technical difficulties, and, in any case, the resulting spectra contain many overlapping resonances that challenge the analytical work. Here, we present a general methodology, based on quantitative artificial neural network (ANN) analysis, to resolve overlapping information in 2D NMR spectra and to simultaneously assess the relative importance of multiple spectral variables on the sample properties. The results in a set of 2D NMR spectra of oil samples illustrate, first, that use of ANN analysis for quantitative purposes is feasible also in 2D and, second, that this methodology offers an intrinsic opportunity to assess the complex and nonlinear relationships between the molecular composition and sample properties. The presented ANN methodology is not limited to the analysis of NMR spectra but can also be applied in a manner similar to other (multidimensional) spectroscopic data.     

Corresponding-states correlation for the saturated liquid density of metals and metal mixtures

A corresponding-states correlation for the prediction of the orthobaric liquid density of molten metals has been developed. The correlation is the extension of the recently developed correlation by Iglesias-Silva and Hall, which needs the values of the critical and triple point constants as well as an adjustable parameter. The critical constants are scarce for almost all metals. Our corresponding-states correlation uses the normal boiling and melting point constants plus an adjustable parameter. While the present correlation is simpler in form than the correlation by Iglesias-Silva and Hall, all of its input data are more readily available for almost all metals. In this work, we have applied the present correlation to molten alkali metals, mercury, bismuth, tin, and lead. From about 150 data points for pure liquid metals the average absolute deviation and the maximum deviation are 0.29 and 1.06%, respectively. Also, we have extended the correlation to mixtures of any number of components. The predicted results for the liquid densities of K–Cs and K–Na mixtures over the whole range of concentrations and that of a ternary molten eutectic of K–Na–Cs at temperatures ranging from melting point up to several hundred degrees above the normal boiling point are in excellent agreement with experimental data. From 247 data points examined for molten alloys, the average absolute deviation and the maximum deviation are 0.59 and 1.91%, respectively.     

Separation of helium and hydrocarbon mixtures by a two-membrane column

The permeabilities to pure gases can be directly used in the calculation of mixed gas permeation through a rubbery membrane (silicone rubber), but the permeabilities of cellulose acetate membranes to mixed gases are considerably affected by the presence of hydrocarbons. The efficiency of separation increases with decreasing pressure ratio and reaches a maximum when the pressure ratio becomes zero. The enrichment of the less permeable gas can be easily achieved in a stripper. Combining two strippers made out of two different membranes, highly concentrated products (99%) are continuously obtained at both ends of the column. As a result, the overall separation factors are greatly increased.     

Oxidation of hydrocarbon mixtures over a complex vanadium catalyst

Vapor-phase oxidation of hydrocarbon mixtures over vanadium oxide (promoted by potassium sulfate)-silica catalyst has been studied. It is shown that the inhibition of the rates of formation of individual products depends on the ability of the added hydrocarbons to similar specific interaction with the catalyst.

---

. , , .

     

Use of gas-liquid chromatography for the analysis of certain hydrocarbon mixtures

Summary Gas-liquid chromatography was applied to the analysis of mixtures of some unsaturated hydrocarbons and dienes. An instrument for gas-liquid chromatography was developed.     

Prediction of viscosities of hydrocarbon mixtures

A new model for prediction of the viscosities of hydrocarbons including oil and gas mixtures is presented. The model is based on the principle of corresponding states with methane and decane as reference components. The viscosity of a given component or mixture is determined from the reduced viscosities of the reference components using the molecular weight as an interpolation parameter.

The model has been used for prediction of viscosities of both pure components and mixtures over large pressure ranges and for reduced temperatures above 0.476. The results are in good agreement with the experimental data. The new model compares favorably with earlier published methods, which use only one reference component.

Finally, the model has been tested on data for 6 oil mixtures from the North Sea. The mean deviation based on 34 experimental points was 6.4 %.     

Development of the split-Hopkinson pressure bar technique for viscous fluid characterization

The split Hopkinson pressure bar (SHPB) technique has been employed to evaluate the dynamic squeeze flow behavior of viscous Newtonian fluids. In this paper, the conditions under which classic Hopkinson bar data analysis is applicable for fluid specimens are discussed in detail. Requirements include the development of a parabolic flow profile and associated pressure distribution across the specimen. The times required for these processes to occur are calculated and compared with the experimental timescale in order to establish a specimen design criterion for valid SHPB testing. To evaluate this design criterion, an isothermal squeeze flow model describing the behavior of a cylindrical fluid specimen which includes inertial forces is used to predict the experimental results for a model Newtonian fluid. Good agreement between the theory and the experiment is obtained for thin specimens (1.0 mm) across a wide range of shear strain rates (over 10⁵ s⁻¹). As a result of this study, the conditions under which valid SHPB experimental results may be obtained for a Newtonian fluid specimen are identified.     

Biodegradation of chlorinated aliphatic hydrocarbon mixtures in a single-pass packed-bed reactor

Applied Biochemistry and Biotechnology - Aliphatic chlorinated compounds, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), are major contaminants of ground water. A single-pass...     

Multiple-injection technique for isolating a target protein from multicomponent mixtures

An integrated chromatographic process comprising ion exchange (IEC) and hydrophobic interaction chromatography (HIC) for isolating a target protein form multicomponent mixtures has been analyzed. The model mixture contained immunoglobulin G that was the key product of the separation process, cytochrome C and ovalbumin. The adsorption characteristics and the mass transport kinetics of the model proteins have been determined along with their dependencies on the operating variables such as pH, temperature and the salt concentration for IEC as well as HIC media. Limitations of the process efficiency resulting from kinetic effects, solubility constraints and the necessity of the mobile phase exchange between chromatographic steps have been discussed. To improve the performance of the integrated process the multiple-injection technique has been suggested. This technique consisted in loading feed mixtures dissolved in a good solvent onto the column by several small-volume injections under conditions of strong protein adsorption. It allowed diminishing interactions between the sample-solvent and protein and elimination of undesired effects such as band splitting and band broadening. For the process design and optimization a dynamic model has been used accounting for thermodynamics and kinetics of the process. The optimization results indicated superiority of the multiple-injection technique over standard isocratic injections in terms of the process yield and productivity.     

混合物定性定量分析的分枝定界算法

已知被测体系可能存在的物种范围, 但其确含何种物质及相应浓度必须经分析方可确定, 实为分析化学实践中常见的一类分析体系。基于分枝定界原理, 本文提出一种直接对其进行定性定量解析的光谱多元分析算法, 可显著减少计算量,却无失去真实信息的风险。对实际紫外可见及荧光混合物光谱进行解析, 均获满意结果。     

Application of adsorptive percolation to the analysis of hydrocarbon mixtures

A survey of the application of chromatograpinc analysis to mixtures of hydrocarbons has been given. An empirical constant called “transport factor” has been introduced. It is defined as the ratio of the weight of adsorbent contained in a certain column to the volume of developer necessary to transport the front of the adsorption band of a certain substance from the top of the column to its lower end. The transport factors on silicagel of five hydrocarbons in combination with several developers have been determined. A separation of a mixture of five hydrocarbons has been carried out using a series of three developers.The experimental “chromatogram” and the chromatogram calculated with the aid of the transport factors are in close agreement. In this way the transport factor may even serve as a means of identification.