Characterizing Petroleum Fractions

Petroleum streams, from crude oil to products such as gasoline, kerosene, diesel 

It is impractical to analyze such mixtures and represent them compositionaUy on the 

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Using Infrared Spectrometry to Characterize Petroleum Fractions according to the Nature of the Carbon Atoms... 

The liquid dynamic viscosities at 100°F and 210°F are used to characterize petroleum fractions, notably the heavy fractions. 

The simple distillation curve is the temperature as a function of the per cent distilled in a simple or Rayleigh type of distillation. This type of distillation is approximated by the laboratory A.S.T.M. distillation which is widely used to characterize petroleum fractions. The A.S.T.M. procedure gives some reflux and rectification, and the results are not exactly equal to the simple batch distillation, although the difference is not large. The temperature normally measured is the condensation temperature of the vapor flowing from the still to the condenser. Curve A of Fig. 11-1 is typical for the simple distillation of a complex mixture. The temperature at any point is the averaged result of a large number of components and includes all the effects of nonideality in the solutions. Thus in most cases it is impossible to relate such a curve to the volatility of the individual components involved. As a result, such simple distillation curves are not of much direct value for the solution of rectification problems. 

Distillation data and specific gravity are the most common properties used as inputs into empirical correlations to characterize petroleum fractions. This characterization is achieved by means of correlations that are useful for determining molecular weight, critical properties, etc. They can also be utilized for distinguishing reaction products as pseudocomponents or lumps (naphtha, middle distillates, etc.) of some typical refinery processes such as hydrocracking, catalytic cracking, etc. (Ancheyta et al., 2005b). To have accurate and reliable representations of distillation data for further interpolation, a strict analysis of other approaches apart from the traditional interpolation techniques is mandatory. 

To extend the applicability of the characterization factor to the complex mixtures of hydrocarbons found in petroleum fractions, it was necessary to introduce the concept of a mean average boiling point temperature to a petroleum cut. This is calculated from the distillation curves, either ASTM or TBP. The volume average boiling point (VABP) is derived from the cut point temperatures for 10, 20, 50, 80 or 90% for the sample in question. In the above formula, VABP replaces the boiling point for the pure component. 

Characterization of Crude Oils and Petroleum Fractions Based on Structural Analysis... 

Chapter 3. CHARACTERIZATION OF CRUDE OlLS AND PETROLEUM FRACTIONS... 

Characterization of a Petroleum Fraction by Carbon Atom Distribution... 

Characterization of Petroleum Fractions Based on Chemical Reactions... 

The current calculation methods are based on the hypothesis that each mixture whose properties are sought can be characterized by a set of pure components and petroleum fractions of a narrow boiling point range and by a composition expressed in mass fractions. 

Characterization of Mixtures of Pure Hydrocarbons and Petroleum Fractions (Petroleum Cuts)... 

Although the viscosity index is useful for characterizing petroleum oils, other viscosity—temperature parameters are employed periodically. Viscosity temperature coefficients (VTCs) give the fractional drop in viscosity as temperature increases from 40 to 100°C and is useful in characterizing behavior of siHcones and some other synthetics. With petroleum base stocks, VTC tends to remain constant as increasing amounts of VI improvers are added. Constant B in equation 9, the slope of the line on the ASTM viscosity—temperature chart, also describes viscosity variation with temperature. 

Step 4 deals with physical and chemical properties of compounds and mixtures. Accurate physical and chemical properties ate essential to achieve accurate simulation results. Most simulators have a method of maintaining tables of these properties as well as computet routines for calculations for the properties by different methods. At times these features of simulators make them suitable or not suitable for a particular problem. The various simulators differ ia the number of compounds ia the data base number of methods for estimating unknown properties petroleum fractions characterized electrolyte properties handled biochemical materials present abiUty to handle polymers and other complex materials and the soflds, metals, and alloys handled. 

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