CORRELATION BETWEEN THE SPECIFIC GRAVITY, COKING PROPERTIES OF CRUDE OILS, AND THEIR MOLECULAR WEIGHT

G. G. Blagopoluchnaya, A. F. Fedorov

(Presented by the scientific-methodological seminar of the organic departments of the Chemical-Technology Faculty)

Determination of the principal characteristics of crude oils is, in most cases, associated with great difficulties. In our opinion, for estimating certain characteristics that are difficult to determine, one may use analytical expressions obtained on the basis of statistical studies of the interrelations among a number of parameters.

In the present work an attempt is made to analyze the closeness of relationships and to find analytical expressions for these relationships between the specific gravity \((\rho_4^{20})\), coking property \((K)\), and molecular weight \((M)\) of crude oils. As initial data we used the results of studies of crude oils reported in [1, 2] and obtained in the Problem Laboratory for the Integrated Utilization of Peat of the Tomsk Polytechnic Institute. A selection of the results used is given in the table.

The measurement results were tested for normality of the distribution law by the \(\chi^2\) goodness-of-fit criterion.

The presence and closeness of relationships between the parameters were established from the values of the pair-correlation coefficients

\[ R_{\rho,M}=0.86 \quad \text{and} \quad R_{K,M}=0.73. \]

Their values indicate the presence of relationships between the parameters. The significance of the coefficients was determined by Student’s criterion [3] for a probability threshold of 0.95. The condition \(t_{\text{calc}} > t_{\text{tab}}\) is satisfied; the coefficients are significant.

The coefficients of the regression equations were determined by the method of multiple correlation analysis on the MIR computer [4].

The regression equations may be represented in the form

\[ M=-1169+1661\,\rho_4^{20}; \tag{1} \]

\[ M=-293+1352\,\rho_4^{20}+5.3\,K. \tag{2} \]

Testing by Fisher’s criterion [3] showed that equations (1) and (2), with a confidence probability of 0.95, correspond to the data considered and may be used to estimate molecular weight from specific gravity and coking property.

REFERENCES

1. New Crude Oils of the Eastern Regions of the USSR. Edited by S. N. Pavlova, Z. V. Driatskaya. Moscow, Khimiya, 1967.
2. Crude Oils of the Eastern Regions of the USSR. Moscow, Gostoptekhizdat, 1962.
3. N. A. Plokhinskii. Biometrics. Moscow, Moscow State University Press, 1970.
4. V. A. Silich, M. M. Shershnina. Program for constructing a linear multiple regression. In: Cybernetics and Higher Educational Institutions, issue 4. Tomsk, Tomsk State University Press, 1971.

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