Study of Neutral Oils from Peat Tar
Abstract Generated abstract
This study examines light neutral oils isolated from peat tars produced by thermal decomposition at 600, 700, and 800°C, including tars from pure peat and peat, iron ore fuel-smelting briquettes. The oils were separated by steam distillation, acid-base treatment, solvent extraction, and, for selected samples, fractional distillation, then analyzed by gas-liquid chromatography using retention times, additions, and internal normalization. The results show that the oils are complex mixtures dominated by aromatic compounds, especially alkyl-substituted benzenes, with notable amounts of xylenes, indene, methylindenes, tetralin, and naphthalene. Pyrolysis temperature affected component proportions, such as decreasing indene and increasing naphthalene at higher temperature, while addition of iron ore had little effect on the principal components of the light neutral oil fraction.
Full Text
STUDY OF NEUTRAL OILS OF PEAT TAR
K. K. Stramkovskaya, L. A. Ponomareva
(Presented by the scientific seminar of the Faculty of Chemical Technology)
A detailed study of the material composition of tars from the thermal decomposition of solid fuels and of the oils isolated from them will make it possible to determine the most rational ways of using these products.
In the present work, light neutral oils of tars from the thermal decomposition of peat at temperatures of 600, 700, and 800°C were investigated. The tars were obtained both from pure peat and from fuel-smelting materials (TPM), consisting of briquettes made of peat and iron ore. The characteristics of the initial fuel and the conditions for obtaining the tar are described in one of the articles in the present collection [1].
To isolate the neutral light oils, the tar was distilled with steam. The distillate obtained was treated with 5% alkali to neutralize acidic substances; then the light oils were extracted from the neutralized distillate with sulfur ether. The ether extract was treated with 10% sulfuric acid to remove bases, dried over calcined sodium sulfate, and the ether was distilled off.
The yield of neutral oils, calculated on an anhydrous-tar basis, is given in Table 1.
Table 1
Yield of neutral oils volatile with steam, % on anhydrous tar
| Fuel | For the pyrolysis regime | For the pyrolysis regime | For the pyrolysis regime |
|---|---|---|---|
| 600°C | 700°C | 800°C | |
| Vasyugan upland peat | 12.6 | 8.2 | 10.3 |
| Tagan lowland peat | 16.3 | — | — |
| Fuel-smelting materials from Tagan peat and iron ore (TPM) | 11.3 | — | — |
The neutral oils thus isolated from Vasyugan peat, without additional distillation, were studied by gas–liquid chromatography on a KhL-4 chromatograph with a thermal-conductivity detector.
The oils from the tar of Tagan peat and TTM were additionally distilled, and the fraction boiling up to 200°C was subjected to chromatographic analysis; its yield was 26.2–26.8% of the neutral substances volatile with steam.
Apiezon L, deposited on INZ-600 brick (0.25–0.5), was used as the stationary phase in the analysis; hydrogen served as the carrier gas, passed through the column at a rate of 200 ml/min. The operating temperature of the column was 155°C.
The results of the analysis of the neutral oils, given in Tables 2 and 3, indicate their very complex composition.
Table 2
Composition of neutral oils volatile with steam from the tar of thermal decomposition of Vasyugan peat
| No. | Component name | Content, % at 600°C | Content, % at 700°C | Content, % at 800°C |
|---|---|---|---|---|
| 1 | Benzene | 1.32 | 1.49 | 2.39 |
| 2 | Octane | 1.25 | 0.79 | 0.40 |
| 3 | Toluene | 3.80 | 5.27 | 3.03 |
| 4 | Ethylbenzene | 2.60 | 2.98 | 2.61 |
| 5 | p + m-xylene | 4.21 | 5.07 | 4.22 |
| 6 | o-xylene | 8.91 | 8.00 | 12.60 |
| 7 | n-propylbenzene | 8.12 | 5.95 | 4.36 |
| 8 | Mesitylene | 3.12 | 2.70 | 2.86 |
| 9 | Pseudocumene | 6.28 | 10.50 | 9.66 |
| 10 | 1,2,3-trimethylbenzene | 3.86 | 2.68 | 9.00 |
| 11 | Indene | 27.30 | 15.60 | 16.90 |
| 12 | 1-Methylindene | 8.65 | 9.80 | 4.36 |
| 13 | 5-Methylindene | 2.03 | 2.48 | 1.98 |
| 14 | Tetralin | 3.90 | 7.15 | 4.75 |
| 15 | Naphthalene | 6.56 | 14.30 | 17.00 |
| 16 | Unidentified portion | 8.09 | 5.24 | 3.88 |
| Total: | 100 | 100 | 100 |
The chromatograms obtained contained 19–22 peaks. Qualitative identification was carried out by the method of additions and according to the retention times of individual components known from the literature. Quantitative calculation was performed by the internal-normalization method.
The predominant content in these oils (up to 80%) consists of compounds of aromatic character, mainly alkyl-substituted benzenes.
As can be seen from the table, the neutral oils of all tars obtained at 600, 700, and 800°C have the same qualitative composition, but quanti-
the quantitative content of individual components changes with changes in the pyrolysis conditions and the nature of the starting material.
Table 3
Composition of neutral oils boiling up to 200°C
| No. | Name of components | Content, % by weight of oil from tar: peat | Content, % by weight of oil from tar: TPM |
|---|---|---|---|
| 1 | benzene | 1.00 | 1.00 |
| 2 | toluene | 2.22 | 2.62 |
| 3 | octane | 0.49 | 0.84 |
| 4 | ethylbenzene | 7.20 | 7.19 |
| 5 | m- + p-xylene | 7.25 | 6.70 |
| 6 | o-xylene | 7.15 | 7.26 |
| 7 | iso-propylbenzene | 4.70 | 5.56 |
| 8 | n-propylbenzene | 4.21 | 3.79 |
| 9 | pseudocumene | 5.15 | 6.05 |
| 10 | mesitylene | 4.67 | 5.05 |
| 11 | 1,2,3-trimethylbenzene | 12.65 | 7.04 |
| 12 | indane | 8.51 | 9.87 |
| 13 | indene | 7.90 | 6.74 |
| 14 | 1-methylindene | 1.01 | 2.67 |
| 15 | 5-methylindene | 3.17 | 7.41 |
| 16 | 3-methylindene | 6.68 | 2.78 |
| 17 | naphthalene | 3.92 | 2.67 |
| 18 | unidentified fraction | 12.38 | 14.75 |
| Total: | 100 | 100 |
In the oils studied, the amount of low-boiling aromatic hydrocarbons—benzene and toluene—is small. During pyrolysis of Vasyugan peat, the benzene content in the oil of the 600-degree regime is 1.3% and increases to 2.4% at a temperature of 800°C. The toluene content increases from 3.8% to 5.27% as the pyrolysis temperature is raised from 600 to 700°C. With a further increase in temperature to 800°C, the content of this product in the neutral oils distilling with steam again decreases to 3.0%.
In these oils, as the analytical data show, there is a large amount of xylenes—a raw material of great value for organic synthesis.
In the oils of the 600-degree regime, the predominant component (27.3%) is indene. However, at a pyrolysis temperature of 800°, its content falls to 17%, with a simultaneous increase in the concentration of naphthalene in this oil also to 17%.
As for the influence of iron ore on the composition of the light neutral oils, the data in Table 3 show that, in terms of the principal components, the tar oils obtained from peat and with the addition of ore differ hardly at all.
Conclusions
-
The possibility of quantitative analysis of a complex mixture of neutral oils from tars of the thermal decomposition of peat by gas-liquid chromatography has been demonstrated, and the conditions for this analysis have been determined.
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The composition of the light neutral oils from tars of the thermal decomposition of peat, obtained at pyrolysis temperatures of 600, 700, and 800°C, has been determined.
LITERATURE
- K. K. Stramkovskaya, A. T. Rubanov, Yu. L. [[unclear: surname]]. Study of peat tar. This collection, p. 123.