Hydrocarbon Composition of Fractions of Typical Crude Oil
Abstract Generated abstract
This study characterizes the hydrocarbon composition of fractions from a representative crude oil mixture from the Nizhnevartovsk region. Group composition was determined by the aniline-point method and liquid chromatography, structural-group composition by the n-d-M method, and the light gasoline fraction by gas-liquid chromatography on a capillary column. The gasoline cut to 200 degrees C was found to be low in aromatics and rich in paraffinic hydrocarbons, while heavier fractions showed increasing aromatic content and decreasing paraffin-naphthene content. The results indicate that the gasoline distillates may be suitable feedstock for pyrolysis and catalytic reforming, and that kerosene and gas-oil fractions may be suitable for diesel fuel production.
Full Text
HYDROCARBON COMPOSITION OF FRACTIONS OF A REPRESENTATIVE CRUDE OIL
N. M. Smolyaninova, A. I. Levashova, V. A. Kuznetsova,
O. E. Abramova, L. I. Popova
(Presented by the scientific-methodological seminar of the organic departments)
The characterization of the representative crude oil, which is a mixture of oils from fields of the Nizhnevartovsk region, is given above (see the present collection).
To determine the group hydrocarbon composition, the aniline-point method and liquid chromatography were used. The structural-group composition was calculated by the \(n-d-M\) method. The results are presented in Tables 1—3.
Table 1
Group hydrocarbon composition of fractions of the representative crude oil
| Temperature limits of fraction collection, °C | Yield on crude oil, % | Aromatic hydrocarbons, wt % | Naphthenic hydrocarbons, wt % | Paraffinic hydrocarbons, total, wt % | Paraffinic hydrocarbons of n-structure, wt % |
|---|---|---|---|---|---|
| b.p.—60 | 2.0 | 0 | 0 | 100 | 44 |
| 60—95 | 3.8 | 2 | 42 | 56 | 29 |
| 95—122 | 4.5 | 7 | 40 | 53 | 26 |
| 122—150 | 4.7 | 14 | 31 | 55 | 25 |
| 150—200 | 9.3 | 26 | 23 | 51 | 19 |
| b.p.—200 | 24.3 | 14 | 29 | 57 | 26 |
| 200—250 | 12.2 | 26 | 31 | 43 | — |
| 250—300 | 11.8 | 30 | 27 | 43 | — |
| 300—350 | 13.0 | 34 | 15 | 51 | — |
Table 2
Group hydrocarbon composition of 50-degree fractions boiling from 200 to 450°C
| Temperature limits of fraction collection, °C | Yield on crude oil, % | Methane-naphthenic hydrocarbons, % | Aromatic hydrocarbons, 1st group, % | Aromatic hydrocarbons, 2nd group, % | Aromatic hydrocarbons, 3rd group, % | Aromatic hydrocarbons, 4th group, % | Aromatic hydrocarbons, sum, % | Intermediate fractions and resins, % |
|---|---|---|---|---|---|---|---|---|
| 200—250 | 9.2 | 73 | 20 | 2 | 5 | — | 27 | — |
| 250—300 | 9.7 | 70 | 20 | 3 | 7 | — | 30 | — |
| 300—350 | 9.5 | 66 | 18 | 4 | 12 | — | 34 | — |
| 350—400 | 11.2 | 53 | 17 | 8 | 17 | 2 | 43 | 2 |
| 400—450 | 9.4 | 48 | 16 | 10 | 16 | 6 | 48 | 4 |
Table 3
Structural-group composition of 50-degree fractions by the \(n—d—M\) method
| Distillation temperature, °C | \(C_A\) | \(C_H\) | \(C_{\text{ring}}\) | \(C_P\) | \(K_A\) | \(K_H\) | \(K_O\) |
|---|---|---|---|---|---|---|---|
| 200—250 | 18 | 39 | 57 | 43 | 0,32 | 0,72 | 1,04 |
| 250—300 | 19 | 31 | 50 | 50 | 0,46 | 0,76 | 1,26 |
| 300—350 | 20 | 25 | 45 | 55 | 0,53 | 0,91 | 1,44 |
| 350—400 | 23 | 20 | 43 | 57 | 0,81 | 0,92 | 1,73 |
| 400—450 | 24 | 24 | 48 | 52 | 1,01 | 1,33 | 2,34 |
As is evident from these data, the gasoline cut (initial boiling point—200°C) of the type crude oil is distinguished by a low content of aromatic hydrocarbons (14%) and a high content of paraffinic hydrocarbons (57%), among which representatives of iso-structure predominate; the amount of cyclanes is 29%.
On passing to heavier fractions, a considerable increase in the content of aromatics is observed (from 27% in the 200–250°C cut to 48% in the 400–450°C fraction), together with a corresponding decrease in the paraffin–naphthene portion (from 73 to 48%). Among the various groups of aromatic hydrocarbons, the 1st group (benzene derivatives) predominates. With increasing temperature limits of fraction withdrawal, the amount of cyclanes decreases. The data on structural-group composition (Table 3) are in agreement with the results of group analysis.
Table 4 gives the individual composition of the gasoline fraction boiling up to 122°C. The analysis was carried out by gas–liquid chromatography using a capillary column. Squalane was used as the stationary phase.
The data of Table 4 show that the gasoline studied contains a large amount of alkanes—72,99%, including 40,90% of normal structure. The content of naphthenic hydrocarbons is 25,52%; among them five-membered representatives predominate (14,59%).
Table 4
Individual hydrocarbon composition of the broad fraction
(initial boiling point—122°C) of the type crude oil
| Component | Hydrocarbon content, wt. % in the fraction | Hydrocarbon content, wt. % in the crude oil |
|---|---|---|
| 1 | 2 | 3 |
| Ethane | 0,10 | 0,012 |
| Propane | 2,71 | 0,323 |
| iso-Butane | 3,14 | 0,374 |
| n-Butane | 8,32 | 0,991 |
| iso-Pentane | 5,96 | 0,718 |
| n-Pentane | 9,10 | 1,083 |
| 2,2-Dimethylpentane | 0,03 | 0,004 |
| 2,3-Dimethylbutane | 0,16 | 0,019 |
| 2-Methylpentane | 4,75 | 0,565 |
| Cyclopentane | 0,91 | 0,108 |
| 3-Methylpentane | 2,71 | 0,322 |
| n-Hexane | 8,06 | 0,959 |
| Methylcyclopentane | 6,18 | 0,732 |
| 2,4-Dimethylpentane | 0,40 | 0,048 |
| Benzene | 0,18 | 0,021 |
| Cyclohexane | 2,86 | 0,340 |
| 2-Methylhexane | 2,86 | 0,340 |
| 2,3-Dimethylpentane | 0,88 | 0,105 |
| 3-Methylhexane | 4,16 | 0,495 |
| 1,3-Dimethylcyclopentane (cis) | 1,08 | 0,128 |
Continuation of Table 4
| 1 | 2 | 3 |
|---|---|---|
| 1,3-Dimethylcyclopentane (trans) | 1,03 | 0,123 |
| 1,2-Dimethylcyclopentane (trans) | 2,26 | 0,269 |
| n-Heptane | 10,32 | 1,228 |
| 1,2-Dimethylcyclopentane (cis) | 0,14 | 0,017 |
| 1,1,3-Trimethylcyclopentane | 0,12 | 0,014 |
| 2,5-Dimethylhexane | 1,45 | 0,173 |
| 2,4-Dimethylhexane | 0,66 | 0,078 |
| Methylcyclohexane | 6,78 | 0,808 |
| Ethylcyclopentane | 1,92 | 0,229 |
| 1,2,4-Trimethylcyclopentane (cis, trans, cis) | 0,21 | 0,025 |
| 3,3-Dimethylhexane | 0,34 | 0,040 |
| 1,2,3-Trimethylcyclopentane (cis, trans, cis) | 0,58 | 0,069 |
| 2-Methylheptane | 2,40 | 0,285 |
| 2,3,4-Trimethylpentane | 0,09 | 0,011 |
| 2,3-Dimethylhexane + 2-methyl-3-ethylpentane | 0,14 | 0,017 |
| 4-Methylheptane | 0,77 | 0,092 |
| 3-Methylheptane | 0,71 | 0,084 |
| Toluene | 1,31 | 0,156 |
| 3,4-Dimethylhexane | 0,24 | 0,029 |
| 1,2,4-Trimethylcyclopentane (cis, cis, trans) + 1,2,3-trimethylcyclopentane (cis, cis, trans) | 0,01 | 0,001 |
| 1,2,4-Trimethylcyclopentane (cis, cis, cis) | 0,03 | 0,004 |
| 1,4-Dimethylcyclohexane (trans) | 0,30 | 0,036 |
| 1,3-Dimethylcyclohexane (cis) | 0,30 | 0,036 |
| 1-Methyl-2-ethylcyclopentane (trans) | 0,08 | 0,009 |
| 1,1-Dimethylcyclohexane | 0,67 | 0,080 |
| 1-Methyl-1-ethylcyclopentane | 0,02 | 0,002 |
| n-Octane | 2,29 | 0,273 |
| 2,4,4-Trimethylhexane + 1,4-dimethylhexane (cis) | 0,02 | 0,002 |
| 1,3-Dimethylcyclohexane (trans) | 0,01 | 0,001 |
| 1,3-Dimethylhexane | 0,01 | 0,001 |
| iso-Propylcyclopentane | 0,02 | 0,002 |
| 2,6-Dimethylheptane | 0,04 | 0,005 |
| n-Propylcyclopentane | 0,06 | 0,007 |
| Ethylcyclohexane | 0,12 | 0,014 |
| Total: | 100,00 | 11,900 |
| Paraffinic hydrocarbons | 72,99 | 8,689 |
| including: n-structure | 40,90 | 4,869 |
| iso-structure | 32,09 | 3,820 |
| Naphthenic hydrocarbons | 25,52 | 3,034 |
| including: five-membered | 14,59 | 1,732 |
| six-membered | 10,93 | 1,302 |
| Aromatic hydrocarbons | 1,49 | 0,177 |
The significant discrepancy in the amount of aromatic hydrocarbons determined by the aniline-point method and by GLC attracts attention; this, apparently, is a consequence of the error that occurs when using a flame-ionization detector to determine a small number of components at their low concentrations in a complex mixture.
It should be noted that the gasoline contains substantial amounts of methylcyclopentane (6.18%) and methylcyclohexane (6.78%).
Thus, the data on the hydrocarbon composition of fractions of the representative crude oil make it possible to conclude that the gasoline distillates are good feedstock for pyrolysis and catalytic reforming, and the kerosene–gas-oil fractions are suitable for obtaining diesel fuels.