Study of Phenols in the Resin from Thermal Decomposition of Peat

K. K. Stramkovskaya, L. F. Karpova, G. I. Kravtsova

(Presented by the scientific seminar of the Chemical Technology Faculty)

When fuel-fluxing materials based on peat are used in a chemical-metallurgical process, a considerable amount of resin will be obtained along with the metal and gas. To develop a rational technology for using this resin, it is necessary to study it thoroughly.

One of the valuable components of the resins from the thermal decomposition of peat are phenols. However, the existing chemical methods and the method of precise rectification do not make it possible to identify the individual components present in this mixture with sufficient reliability.

The purpose of the present work was to develop a procedure for isolating light phenols from the resin that would be suitable for identification by gas-liquid chromatography, and also to select conditions for their chromatographic separation.

The resin was obtained in a laboratory unit consisting of a reactor, which was a stainless-steel tube 60 mm in diameter and 900 mm long, and condensation apparatus—a cooler and a receiver for resin and water. The reactor was heated by two tubular furnaces, one of which was located over the part of the reactor into which the peat was placed, i.e., over the coking chamber, while the other was installed over the part of the tube that served as the pyrolysis chamber.

The resin was obtained at coking temperatures and at pyrolysis temperatures of the vapor-gas products of 600, 700, and 800°C. Upper peat from the Vasyugan bog (sample 7), whose characteristics are presented in Table 1, was subjected to thermal decomposition.

As a result of pyrolysis, resin was obtained with the following yields:

For all resin samples, the group composition was determined by the method of G. L. Stadnikov [1] and is presented in Table 2.

Phenols were isolated from the resin by the usual method: by treatment with 5% caustic soda, and then the volatile light phenols were distilled from the crude phenols obtained by steam distillation. These latter were separated from the water by extraction with ether. The content of the indicated phenols, as can be seen from

Table 5, increases significantly with an increase in the temperature of the thermal decomposition of peat.

With an increase in the temperature of the pyrolysis process from 600° to 800°C, the amount of volatile phenols in the resin increased from 3.4% to 5.1%.

Table 1

Technical and elemental composition of peat

Table 2

Group composition of resins from the thermal decomposition of peat

The phenols isolated in this way were analyzed by gas–liquid chromatography on a KhL-4 chromatograph with a thermal-conductivity detector. Apiezon \(L\) on an INZ-600 support (0.3–0.5 mm fraction) was used as the stationary phase; hydrogen served as the carrier gas. During the analysis the temperature was maintained at 161°C, and the carrier-gas flow rate at the column outlet was set at 150 ml per minute.

The chromatograms obtained were characterized by six peaks. The retention times calculated relative to phenol are given in Table 3.

These data indicate good agreement between the retention times of the phenols of peat resin and those for the phenols of an artificial mixture, the chromatogram of which we recorded under the same conditions on Apiezon L, as well as with literature data [2].

The first peak on the chromatogram corresponded to sulfur ether; the following ones—to phenol and o-cresol; the pair and metacresols, under the accepted chromatographic conditions, emerged as a single peak. Then the next two peaks corresponded to 2,4- and 2,3-xylenols [2]. However, in the present case it may be assumed that, along with 2,3-xylenol, p- and m-ethylphenols, which have close boiling temperatures, may emerge as one peak, while together with 2,4-xylenol there also emerges 2,5-xylenol, which boils at the same temperature.

The calculation of the quantitative composition from the chromatograms was carried out by the method of internal normalization [3].

Table 3

Retention times of components relative to phenol on Apiezon L

The results of analyses of phenols of peat resins distilling with steam are presented in Table 4.

Table 4

Composition of phenols of peat resin distilling with steam

The found yields of these phenols based on anhydrous resin and on the combustible mass of peat are given in Table 5.

Table 5

Yield of phenols from peat resin

According to A. Dirichs and V. Kubichko [4], and also A. V. Gofman [5], in the coking of coals the yield, in % relative to the coal (on average), is: phenol 0.012, cresols 0.024, xylenols 0.006. The total amount of these products is 0.04%.

The results we obtained make it possible to suppose that, in the pyrolysis of peat, 20 times more phenol will be obtained per ton of combustible mass than is obtained from a ton of coal in coke production.

Conclusions

1. The conditions have been found for the chromatographic separation of phenols volatile with water vapor from the resin of the thermal decomposition of peat.

2. It has been shown that, in the resin from peat pyrolysis at temperatures of 600–700°C, there is 20 times more phenol than in the resin from the coking of bituminous coal.

Literature

1. G. L. Stadnikov. Analysis and Investigation of Coals. Publishing House of the Academy of Sciences of the USSR, 1936.

2. V. Kuzi. Analysis of a mixture of phenols with boiling temperature 180–270°C obtained from bituminous coal. Gas Chromatography, 1961. Gostopmekhizdat, pp. 101–106. 1963.

3. M. Shinglyar. Gas Chromatography in Practice. Khimiya Publishing House, 1964.

4. A. Dirichs, R. Kubichko. Phenols and bases from coals. Gostoptekhizdat, 1958.

5. A. V. Gofman. Applied Chemistry of Solid Fuel. Metallurgizdat, 1963.