ASTME

This is the ASTM D 2892 test method and corresponds to a laboratory technique defined for a distillation column having 15 to 18 theoretical plates and operating with a 5 1 reflux ratio. The test is commonly known as the TBP for True Boiling Point. 

Corresponding to ASTM D 86 (NF M 07-002), this method applies to gasolines, kerosenes, heating oils, and similar petroleum products. 

As stated above for the TBP distillation, petroleum cannot be heated above 340°C without its molecules starting to crack. Because of this, analytical distillation of heavy fractions is done according to the ASTM D 1160 method for petroleum materials that can be partially or completely vaporized at a maximum temperature of 400°C at pressures from 50 to 1 mm of mercury (6.55 to 0.133 kPa). 

Two ASTM methods described below are based on this technique ... 

D 2887, applies to products and petroleum fractions whose final boiling points are equal to or below 538°C (1000°F), and have boiling points above 38°C (100°F). The results obtained are equivalent to those obtained from the TBP distillation, ASTM D 2892. 

These are called high temperature induction furnace methods which differ only as to the kind of furnace used and employ the same ASTM procedure. The sample is heated to over 1300°C in an oxygen stream and transformed to SO2 which is analyzed with an infra-red detector. 

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. 

Refractive index this is one of the most precise measurements that can be carried out on a petroleum cut. The ASTM method D 1218 indicates a reproducibility of 0.00006, which is exceptional. 

As a consequence, other than its use in the ndM method, the refractive index is very often used in process operations because it can indicate smaii differences in product quality that would be missed by other measurements. The only restriction is that the color of the sample should be less than 5 on the ASTM D 1500 scale. 

This analysis, abbreviated as FIA for Fluorescent Indicator Adsorption, is standardized as ASTM D 1319 and AFNOR M 07-024. It is limited to fractions whose final boiling points are lower than 315°C, i.e., applicable to gasolines and kerosenes. We mention it here because it is still the generally accepted method for the determination of olefins. 

This method follows the ASTM D 1159 and D 2710 procedures and the AFNOR M 07-017 standard. It exploits the capacity of the double olefinic bond to attach two bromine atoms by the addition reaction. Expressed as grams of fixed bromine per hundred grams of sample, the bromine number, BrN, enables the calculation of olefinic hydrocarbons to be made if the average molecular weight of a sufficiently narrow cut is known. 

The temperatures 100°F and 210°F (37.8°C, 98.9°C) have been selected because they were initially used in the ASTM procedure for calculating the viscosity index of petroleum cuts (ASTM D 2270). 

As seen in Chapter 2, mixtures of hydrocarbons and petroleum fractions are analyzed in the laboratory using precise standards published by ASTM (American Society for Testing and Materials) and incorporated for the most part into international (ISO), European (EN) and national (NF) collections. We wiil recall below the methods utilizing a classification by boiling point ... 

Transformation of ASTM D 86 results into an atmospheric TBP, equation [4.19],... 

Transformation of ASTM D 1160 results into a TBP at 10 mmHg, equation [4.22]. 

Simulated Distillation for Petroleum Cuts (ASTM D Z887)... 

The API has recommended the use of a method to convert the D 2887 results into those of an ASTM D 86, developed by Riazi using the following... 

T = temperature result from the ASTM D 2887 test a, b,c = are conversion coefficients (refer to Table 4.7)... 

Table 4.7a Coefficients for converting a D 2887 curve into an ASTM D 86 curve [Equation 4.23] (Riazi s method). Factor F for the example 0.7774. ...

At atmospheric pressure, hydrocarbon viscosities can be estimated by two methods the ASTM method and that of Mehrotra (1990). 

ASTM proposes representing the kinematic viscosity of hydrocarbons by a straight line on graph paper, called viscometric, for which the scales are such that ... 

The Mehrotra and ASTM methods apply with acceptable accuracy only for viscosities between 1 and 1000 mPa s. The average error is about 20%. The largest spreads are obtained at low and very high viscosities. 

It is difficult to judge the accuracy of these methods because data are scarce. Table 4.9 compares the values obtained by different weighting methods with experimental values for a mixture of n-hexane-n-hexadecane at 25°C. The ASTM method shows results very close to those obtained experimentally. 

The exact calculation of the index is given in the ASTM D 2270 standard. The kinematic viscosity at 40°C (f/) of an oil whose viscosity index (V7) is being calculated is compared with those of two reference oils for which the viscosity indices are 0 and 100 respectively, and which have at 100°C the same kinematic viscosity as that of the oil being examined )... 

Tbe ASTM D 323 standard describes a method for determining the vapor pressure employing two chambers, A and B the volume of chamber A is four times that of chamber B. 

The flash curve at atmospheric pressure can be estimated using the results of the ASTM D 86 distillation by a correlation proposed by the API. For the same volume fraction distilled one has the following relation ... 

---