BOILING POINT DISTRIBUTION OF CRUDE OILS BY HIGH TEMPERATURE GAS CHROMATOGRAPHY: D7169
EXPLANATION
The determination of boiling point distribution of crude oils and vacuum residues, as well as other petroleum fractions provides important information for refinery operations as to the potential mass percent yield of products. This can aid in establishing operational conditions in the refinery. The amount of residue (or sample recovery) is determined using an external standard. The knowledge of such amount of residue produced is important in determining the economics of the refining process.
This test method extends the applicability of simulated distillation to samples that do not elute completely from the chromatographic system. This test method is used to determine the boiling point distribution through a temperature of 720° C which corresponds to the elution of n-C100. The method is used for analysis of crude oils and atmospheric and vacuum residues using capillary columns with thin films which result in the incomplete separation of C4 - C8 in the presence of large amounts of carbon disulfide, and thus yields an unreliable boiling point distribution corresponding to this elution interval. Additionally, quenching of the response of the detector employed to hydrocarbons eluting during carbon disulfide elution, results in unreliable quantitative analysis of the boiling distribution in the C4 - C8 region. Since the detector does not quantitatively measure the carbon disulfide, its subtraction from the sample using a solvent-only injection and corrections to this region via quenching factors, results in an approximate determination of the net chromatographic area. A separate high resolution gas chromatographic analysis of the light end portion of the sample may be necessary in order to obtain a more accurate description of the boiling point curve in the interval in question.
This method is not applicable to the analysis of materials containing a heterogenous component such as polyesters and polyolefins.
TEST SUMMARY
This gas chromatographic method utilizes an inlet and a capillary column, both of which are subject to a temperature program. A flame ionization detector is used as a transducer that converts mass to an electrical signal. A data acquisition system operating in the slice mode and chromatography software is used to accumulate the electronic signal. A retention time calibration mixture is used to develop a retention time versus boiling point curve. A solution of the Reference Oil 5010, which fully elutes from the column under the test conditions, and whose boiling point distribution has been characterized by Test Method D6352, is used to determine the detector response factor. Solvent injections are made, and the resulting signal is subtracted from both the response factor standard and the sample chromatogram.
Finally, the sample solution is injected, and with the use of the response factor, the amount of sample recovered is calculated. After converting the retention times of the sample slices to temperature, the boiling point distribution can be calculated up to the recovered amount.
TEST PRECISION
A preliminary repeatability of the test method was determined employing a limited round robin. The data are given in the following Tables 6 and 7. The reproducibility of the method is not available at present.
No information on bias is available because there is no accepted reference material for such analysis.
