STUDY OF THE TAR FROM THE THERMAL DECOMPOSITION OF PEAT-ORE MATERIALS

G. I. Kravtsova, K. K. Stramkovskaya, S. I. Smolyaninov,
L. V. Terekhova, V. P. Bashorina

(Presented by the scientific-methodological seminar of the CTF)

The integrated metal-energy-chemical utilization of peat will make it possible to obtain, along with metal and gas, a large quantity of tar.

We studied an experimental tar obtained during the thermal decomposition of peat in the course of experimental smelting in a large laboratory shaft furnace on a charge containing peat-ore briquettes (with a carbon-to-iron ratio of 1.82) in an amount of 65% by weight and 35% hard-coal coke. Along with the experimental tar, tar from the semicoking of peat was studied. The semicoking of peat was carried out in a laboratory installation with heating at 5°C per minute to a final temperature of 550°C.

The characteristics of the tars studied are given in Table 1.

Table 1

Characteristics of tars

Analyzing the results obtained, we note significant differences among the compared resins in physicochemical characteristics and in fractional and group compositions. These data indicate the heavier character of the experimental resin.

The neutral oils isolated from the resins were subjected to detailed study by adsorption chromatography with the use of IR and UV spectroscopy.

Adsorption separation was carried out on ASK silica gel with a particle size of 160 mesh in a column 2.8 m high and 35 mm in diameter. The substances were eluted with petroleum ether, mixtures of petroleum ether with benzene in various ratios (90 : 10; 80 : 20; 50 : 50), benzene, mixtures of benzene with alcohol (95 : 5; 80 : 20; 50 : 50), ethyl alcohol, and acetone. According to the refractive index, the fractions obtained were combined into groups. The results of the studies are presented in Table 2.

The data given show that the neutral oils include: 1) methane-naphthene hydrocarbons—17.3% for the peat semicoking resin and 9.05% for the experimental resin;

2) aromatic hydrocarbons—37.30% and 28.70%, respectively;

3) oxygen-containing compounds—30.60% for the peat semicoking resin and 45.70% for the experimental resin.

For all groups isolated by adsorption chromatography, IR and UV spectra were recorded.

Infrared spectra were recorded on a double-beam spectrophotometer IR-10 directly for the initial substances and their solutions. With the aid of the catalog of molecular spectra [1] and other literature sources [2, 3], their qualitative interpretation was carried out, and for some functional groups their quantitative content was calculated on the basis of the Bouguer–Beer–Lambert law. Some data from these studies are given in Table 3. The work carried out in this direction

Table 3

Some data on the IR spectra of the groups studied

made it possible to establish that the paraffin-naphthene hydrocarbons are represented mainly by paraffins and olefins of normal structure with a maximum chain length \((—\mathrm{CH}_2—)=20—25\) for the peat semicoking resin and \((—\mathrm{CH}_2—)=30—31\) for the experimental resin.

The aromatic compounds of the resins studied are alkylated aromatics with a length of substituent groups \((—\mathrm{CH}_2—)=6—12\).

Table 2

Characteristics of the products of chromatographic separation of the neutral part of resins

Oxygen-containing compounds are also represented by alkylated aromatics, but the carbonyl group predominates as the substituent.

UV spectra were obtained on an SP-700 spectrophotometer. Molecular extinction coefficients were calculated for the spectra recorded. The characteristics of the ultraviolet spectra are given in Table 4.

A combined analysis of the data on physicochemical indices, homologous formulas (Table 2), and IR and UV spectra (Tables 3, 4) makes it possible to conclude that the first group of aromatic representatives

Table 4

Characteristics of the ultraviolet spectra of the groups studied

is composed of alkylated mononuclear aromatics, the second—mainly bicyclic aromatic hydrocarbons; in the subsequent groups tri- and polycyclic compounds predominate. Oxygen-containing compounds are condensed structures with the presence of a carbonyl group (aldehyde and ketone).

Conclusions

1. A study was carried out of the experimental tar obtained in the process of blast-furnace smelting on peat-ore materials, and of peat semicoking tar.

2. It was shown that the experimental tar is heavier than peat semicoking tar.

3. By the method of adsorption chromatography in combination with IR and UV spectroscopy, a detailed study was made of the neutral oils isolated from the tars.

4. It was shown that the neutral oils include paraffin-naphthenic hydrocarbons, aromatic and oxygen-containing compounds, the latter constituting a significant portion.

1. It has been established that the paraffin–naphthenic hydrocarbons are represented mainly by paraffins and olefins with a maximum chain length \((-\mathrm{CH}_2-)=20\text{–}24\) for the semicoking tar and \((-\mathrm{CH}_2-)=30\text{–}31\) for the experimental tar; the aromatic hydrocarbons are represented by alkylated mononuclear, bicyclic, and polycyclic aromatics; and the oxygen-containing compounds are condensed structures containing a carbonyl group.

References

1. Documentation of Molecular Spectroscopy, Butterworth, Verlag Chemie.
2. K. Nakanishi. Infrared Spectra and the Structure of Organic Compounds. Mir Publishing House, Moscow, 1965.
3. A. Duncan, V. Gordy, Norman, Jones, F. Matson, K. Sandorfy, V. West. Application of Spectroscopy in Chemistry. Foreign Literature Publishing House, Moscow, 1959.