The estimation of kinematic viscosity of petroleum crude oils and fractions with a neural net

This paper illustrates how a neural net, a three-layered perceptron, can be trained to estimate viscosities for undefined crude oils and fractions. Three Saudi-Arabian crude oils were employed to illustrate the use of the neural net to approximate the relation in a very simple manner with no need for a priori knowledge of the system. This empirical correlation was accurate to 98.74% if tested on experimental data not used during training, which is a fivefold improvement on average results obtained by two recently-proposed equations to estimate the viscosity of hydrocarbons. Although the neural net equation seems to be less transparent than former correlations, a method called backward analysis is proposed to analyze the weight matrix of the neural net in order to gain valuable insight into the viscosity system.     

An accurate empirical correlation for predicting natural gas viscosity

Natural gas viscosity is an important parameter in many gas and petroleum engineering calculations.This study presents a new empirical model for quickly calculating the natural gas viscosity.The model was derived from 4089 experimental viscosity data with varieties ranging from 0.01 to 21,and 1 to 3 of pseudo reduced pressure and temperature,respectively.The accuracy of this new empirical correlation has been compared with commonly used empirical models,including Lee et al.,Heidaryan et al.,Carr et al.,and Adel Elsharkawy correlations.The comparison indicates that this new empirical model can predict viscosity of natural gas with average absolute relative deviation percentage AARD (%) of 2.173.     

Chromatographic methods for petroleum fractions analysis

The state-of-the-art problem of the analysis of various petroleum fractions by the methods of high performance liquid and capillary gas chromatography, IR-spectroscopy, and mass-spectrometry has been considered. The core principle of high performance liquid chromatography as the principal method for petroleum fractions’ separation has been described. Some methods for the chemical modification of domestic silica have been presented. Methods for aromatic hydrocarbons in benzine, kerosene, and diesel petroleum fractions by the chromatography method have been described.     

Pyrolysis of petroleum fractions

Dynamic kinetic analyses were performed on different Brazilian petroleum fractions by thermogravimetry. The data were treated by a multiple heating rate methodology. The apparent activation energies for the light and middle fractions within the range of 62–74 kJ mol⁻¹ and for heavy distillation residues were within the range of 80–100 kJ mol⁻¹ at lower conversions and 100–240 kJ mol⁻¹ at higher conversions. The kinetic study can be a criterion for tells apart the main phenomena involved in the thermal behavior of the refinery feedstock.     

Nature of the kinematic shear viscosity of water

Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume $ \tilde \upsilon Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume , and the average number of hydrogen bonds per one molecule n _H (t = T/T _c, =υ/υ_c, T _c and υ_c are critical values of temperature and reduced volume) are analyzed in detail on a liquid-vapor coexistence curve. It is shown that at T < T _H (T _H ≈ 310 K is the characteristic temperature of water) the formation of the kinematic shear viscosity is induced by activation. At T > T _H, the shear viscosity of water is the sum of two contributions. One of them is of the same nature as in simple liquids, and another is caused by effects of hydrogen bonds. The temperature dependence of ν in this temperature region has nothing in common with exponential formulas of activation theory. The explicit form of the functional dependence of the kinematic shear viscosity on t, , and n _H is found and substantiated. It is shown that the value and temperature dependence of n _H resulting in the experimental values of the kinematic shear viscosity of water agree well with the values corresponding to density and evaporation heat data. __________ Translated From Zhurnal Strukturnoi Khimii, Vol. 49, No. 6, pp. 1092–1100, November–December, 2008. Original Russian Text Copyright ? 2008 by N. P. Malomuzh and A. V. Oleinik     

An internally consistent correlation for predicting the critical properties and molecular weights of petroleum and coal-tar liquids

Twu, C.H., 1984. An internally consistent correlation for predicting the critical properties and molecular weights of petroleum and coal-tar liquids. Fluid Phase Equilibria, 16: 137–150.The objective of this work was to use normal boiling points and specific gravities to develop simple but reliable and accurate methods for predicting the critical properties and molecular weights of petroleum and coal-tar liquids. The normal boiling points of the systems investigated range up to 1778 R and the specific gravities up to 1.436. This virtually covers the entire range of practical interest. The predictions of critical properties based on the above data show significant improvement over published correlations.     

Simplified determination of the normal paraffin content of petroleum fractions

Summary A greatly simplified method for the determination of the total normal paraffin content in petroleum fractions is described where the use of open-tubular columns and up-to-date data handling contribute to the criterion of separation before quantitation.     

Multivariate near infrared spectroscopy models for predicting the iodine value, CFPP, kinematic viscosity at 40 degrees C and density at 15 degrees C of biodiesel

Biodiesel is one of the main alternatives to fossil diesel. It is a non-toxic renewable resource, which leads to lower emissions of polluting gases. In fact, European governments are targeting the incorporation of 20% of biofuels in the fossil fuels until 2020.Chemically, biodiesel is a mixture of fatty acid methyl esters, derived from vegetable oils or animal fats, which is usually produced by a transesterification reaction, where the oils or fats react with an alcohol, in the presence of a catalyst. The European Standard (EN 14214) establishes 25 parameters that have to be analysed to certify biodiesel quality and the analytical methods that should be used to determine those properties.This work reports the use of near infrared (NIR) spectroscopy to determine some important biodiesel properties: the iodine value, the cold filter plugging point, the kinematic viscosity at 40 °C and the density at 15 °C. Principal component analysis was used to perform a qualitative analysis of the spectra and partial least squares regression to develop the calibration models between analytical and spectral data. The results support that NIR spectroscopy, in combination with multivariate calibration, is a promising technique applied to biodiesel quality control, in both laboratory and industrial-scale samples.     

石油中间馏分中异构烷烃的分子识别

以石油加氢异构中间馏分及直馏柴油为研究对象,采用气相色谱/质谱联用技术对异构烷烃的分子形态进行了研究。实验表明各碳数异构烷烃组分在毛细管气相色谱柱上表现出明显的按取代基个数簇分离的现象。对异构烷烃的异构程度进行了表征,得到不同取代基个数的异构烷烃的保留指数(RI)定性表;同时根据化合物的质谱断裂规律,参考文献数据并结合碳数及沸点规律,对73种甲基取代的异构烷烃及10种生物标记的化合物单体进行了结构定性,并计算了保留指数。为在分子水平上认识航空煤油及柴油等石油中间馏分中的异构烷烃提供了基础。定性结果表明:在研究的加氢异构中间馏分中,异构烷烃主要由单取代基和二取代基的异构烷烃组成;而在直馏柴油中,单取代基异构烷烃和类异戊二烯类生物标记化合物丰度较高。     

Improvements in the selection of real components forming a substitute mixture for petroleum fractions

Complex mixtures, particularly petroleum fractions, usually need to be suitably modeled before providing the simulation and other types of chemical engineering calculations. The most convenient way is to describe the original mixture by a substitute mixture. The formerly published approach based on the employment of substitute mixtures of real components can be improved in order to get a closer match between the behavior of the original and substitute mixtures. In the first phase of the algorithm, a new concept of a band around the characterization curves brings wider possibilities for the selection of real components into the substitute mixture. The second phase, which is used to determine the composition of the substitute mixture, can be also improved by considering the global or bulk properties of the original mixture if available. Typically, some of the properties e.g. liquid density, molecular mass and PNA (Paraffinic/Naphthenic/Aromatic carbon) analysis can be measured and used to improve the adjustment of the composition. The improved algorithm is illustrated by an example.     

Shear viscosity of liquid copper at experimentally accessible shear rates: application of the transient-time correlation function formalism

We report on nonequilibrium molecular dynamics (NEMD) simulations results on the shear viscosity of liquid copper, modeled by a many-body embedded-atoms model potential. Because conventional NEMD methods are restricted to very high shear rates (at least of the order of 10(10) s(-1), that is several orders of magnitude larger than those accessible by experiment), previous work only provided access to the response of the fluid in the shear-thinning regime. Using the transient-time correlation function formalism, we show how NEMD simulations can be extended to study the rheological properties of liquid copper subjected to low, experimentally accessible, shear rates. Our results provide a full picture of the rheology of the system, in the Newtonian regime as well as in the shear-thinning regime.     

An equation-of-state-based viscosity model for non-ideal liquid mixtures

A viscosity model based on the Eyring’s theory and a cubic equation of state (Peng–Robinson–Stryjek–Vera) has been applied to the correlation and prediction of experimental liquid viscosities of binary mixtures containing polar fluids within a wide range of temperature, pressure and composition (encompassing low-pressure and compressed liquid conditions). Highly non-idealities of the binary mixtures considered in this study were conveniently handled via the application of the Wong–Sandler approach for the mixing rules used in the cubic equation of state. The results obtained were highly satisfactory for various non-ideal binary mixtures over the whole composition range at a low pressure. The predictive capabilities of the present approach were also verified in the representation of liquid viscosities at elevated pressures preserving the same model parameters previously obtained at low pressure.     

Influence of petroleum fractions on the process of methane hydrate self-preservation

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Separation of different types of monoaromatic hydrocarbons in petroleum fractions by preparative high performance liquid chromatography on silica gel

Summary The character of preparative HPLC separation of monoaromatic hydrocarbons in light and middle petroleum fractions (containing C₁₀–C₁₇ hydrocarbons) has been studied, together with the dependence of the separation efficiency both on hydrocarbon molecular mass and the width of the distillation range of the analyzed petroleum cuts. Preparative HPLC may be advantageously used as a pre-concentration technique for detailed analyses of complex mixtures of petroleum monoaromatic hydrocarbons, owing to the fact that there are specific criteria holding for the separation of various structural types of monoaromatic hydrocarbons (the number of substituents on the aromatic ring, molecular mass, and the hydrocarbon type: benzenes-indanes).

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Trennung verschiedener Typen monoaromatischer Kohlenwasserstoffe aus Erdölfraktionen durch präparative HPLC an Silicagel

Zusammenfassung Die präparative HPLC-Trennung monoaromatischer Kohlenwasserstoffe (C₁₀–C₁₇) aus leichten und mittleren Erdölfraktionen wurde untersucht und die Abhängigkeit des Trennungseffektes von der Molekularmasse der Kohlenwasserstoffe und der Breite des Destillationsbereichs wurde geprüft. Die präparative HPLC kann vorteilhaft für die Vorkonzentrierung bei der Analyse komplexer Gemische monoaromatischer Erdölkohlenwasserstoffe eingesetzt werden, da spezifische Kriterien für die Trennung der verschiedenen Strukturtypen gelten (Anzahl der Substituenten am aromatischen Ring, Molekularmasse, KW-Typ: Benzole-Indane).

     

Chromatographic characterization of high‐boiling petroleum fractions

Detailed investigation of solvent‐separated fractions of petroleum vacuum residues is necessary for understanding the separation mechanism using different solvents and to prepare better feedstocks for secondary conversion processes. The efficiency of different solvents to remove polars and insolubles from vacuum residues (of two Indian crude oils) has been studied. The solvents used were n‐heptane, n‐hexane, and n‐pentane (non‐polar) and ethyl acetate (polar). Soluble fractions were characterized for hydrocarbon group type analysis using high performance liquid chromatography (HPLC), average molecular weights using size exclusion chromatography (SEC), and boiling point distribution using high temperature gas chromatography (HTGC). Method development for HPLC analysis involved the study of parameters such as columns, solvent polarity, detectors, model compounds study, calibration, flow, and solvent gradient programming. The study demonstrated that ultimate soluble fractions have the least content of polar structures of the kind which can cause problems, during cracking and are least prone to cracking. The HPLC, SEC, and simulated distillation (SIMDIS) methods developed and standardized are simple, accurate, and suitable for the rapid assay needed for quick compositional surveys.     

Characterization of basic properties for pure substances and petroleum fractions by neural network

A set of conventional feedforward multilayer neural networks have been proposed to predict basic properties (e.g., critical temperature (T_c), critical pressure (P_c), critical volume (V_c), acentric factor (ω) and molecular weight (MW)) of pure compounds and petroleum fractions based on their normal boiling point (T_b) and liquid density at 293 K. The accuracy of the method is evaluated by its application for basic property estimation of various components not used in the development of the method. Furthermore, the performance of the method is compared against the performance of the other alternatives reported as the most accurate and general methods for basic property prediction. Results of this comparison show that the proposed method outperforms the other alternatives using the same parameters, both in accuracy and generality. Furthermore, the accuracy of the proposed method is almost similar to the accuracy of the only general method despite the fact that the number of parameters required for the proposed method is less than the other alternative.     

Hydrocarbon group type analysis of petroleum heavy fractions using the TLC-FID technique

Hydrocarbon group type analysis is important in all conversion processes and in preparation of feed for these conversion processes so as to learn the selectivity of the different type of catalysts for product yield and quality. The use of the Mark 5 Iatroscan detector and the method reported here allowed for a rapid and quantitative hydrocarbon group type analysis of petroleum residues without prior separation of asphaltenes. SARA type analyses of petroleum residues have been performed by a three stage development using n-hexane, toluene and DCM (95%):MeOH (5%). The standard deviation and coefficient of variation in repeated measurements by this method were as low as 0.65 wt% or less and 3.5 wt% or less, respectively. The time required for analysis of 10 samples could be as short as 90 min.     

Hydrocarbon group type analysis of petroleum heavy fractions using the TLC-FID technique

Hydrocarbon group type analysis is important in all conversion processes and in preparation of feed for these conversion processes so as to learn the selectivity of the different type of catalysts for product yield and quality. The use of the Mark 5 Iatroscan detector and the method reported here allowed for a rapid and quantitative hydrocarbon group type analysis of petroleum residues without prior separation of asphaltenes. SARA type analyses of petroleum residues have been performed by a three stage development using n-hexane, toluene and DCM (95%):MeOH (5%). The standard deviation and coefficient of variation in repeated measurements by this method were as low as 0.65 wt% or less and 3.5 wt% or less, respectively. The time required for analysis of 10 samples could be as short as 90 min. Received: 20 May 1997 / Revised: 12 August 1997 / Accepted: 16 August 1997