A study of the high frequency discharge in methane



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The problem of the utilization of natural gas is one which has commanded considerable attention because of the enormous supply of this material, its very low value in its natural form and the attendant commercial possibilities of any economic method which might be evolved for its use. Of the methods which had been employed in decomposing methane, only two, decomposition by heat and decomposition by electric discharges, have industrial significance because by these methods alone could energy be supplied in large quantities. Of these two, the use of electric discharges seemed most feasible because carbon formation was not so marked and because, since the conditions could be more readily controlled, the type of product could be more readily varied. It appeared from the work of previous investigators that, in order to obtain a product of a definite kind, it was necessary to impose extreme conditions upon the discharge. Those of pressure and, more particularly, of temperature, had been used. That of extremely high frequency seemed to suggest possibilities since it had been shown that, in a much more simple reaction, the decomposition of carbon dioxide, the frequency had a definite effect upon the type of reaction taking place. This work is a study of the effects of a high frequency discharge in the range of 6 to 15 x 10⁶ cycles per second in the pressure range of 2 to 60 mm. In addition to these factors the effects of changing such variables as time of contact, current density, and temperature were determined. The general procedures employed were to maintain as many variables constant as could be maintained constant while one of them was being changed, or to change one of them under different conditions and compare the results. In order to assist in the interpretation of the data obtained with methane, and in order to secure additional information on the reactions of hydrocarbons in the high frequency discharge, ethylene, acetylene and mixtures of these gases with hydrogen were subjected to the discharge. The results of this study are to be found in Mr. Draeger's dissertation. It might be well to say a few words about the experimental difficulties encountered in carrying out this investigation. Methane decomposed to form, as gaseous products, principally ethane, ethylene, acetylene and hydrogen. These, in turn, reacted to form secondary products and finally these secondary products decomposed. The liquid or solid polymer formed also reacted under the influence of the discharge. The measurement of physical phenomena was again frought with complications. The power consumed in the discharge could not be measured. Hence the current flowing through the discharge was taken as the fundamental variable. But the current as measured was not the true current flowing through the discharge because of leakage through the polymer and carbon formed on the walls of the discharge tube. The low pressures at which this work was conducted made necessary the use of small amounts of material, and hence, since a large amount of data had to be taken, a system of micro gas analysis had to be devised. The use of micro gas analysis itself imposed limitations on the constituents which could be determined