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1786. KLEMPT, W., AND BRODKORB, F. [Methane-Steam Equilibrium and Its Control.] Ber. Gesell. Kohlentech., vol. 3, 1930, pp. 220-229; British Chem. Abs., 1931, B, p. 325.
Theoretically, at high temperatures the reaction between CH4 and steam takes place according to the equation (1) CH4+H2O=CO+3H2-48.9 kcal., while at lower temperatures it takes the form (2) CH4+2H2O=CO2+4H2-38.5 kcal. The equilibrium constants for these two reactions have been determined only for a few temperatures, but it is possible to calculate their values from those obtained in the reactions CH4=C+2H2; C+CO2=2CO; and CO+H2O=CO2+H2, which are known over the range 450°-1,200°. The constants K’p=pCH4·pH2O/pCO·pH2 and K”p=pCH4·pH2O2/pCO2·pH24 are tabulated over the same range, but it is emphasized that the values of K’p is limited to lower temperatures. Calculation of the equilibrium condition shows that at 500° the cracked gas contains CH4, 33.3%; H2O, 33.3%; CO, 8.33%; and H2, 25.0%; while at 940° the composition is CH4, 0.505%; H2O, 0.505%; CO, 24.8%; and H2, 74.1%; when reaction (1) takes place. A similar table is given in connection with equation (2). Since in practice an excess of steam would be used, calculations have been made to find the effect of 2-fold and 6-fold excess of steam on the equilibrium when pure CH4 is used. The influence is considered of the other constituents on the equilibrium amount of CH4 present in a gas of the following composition: 10% (CO+CO2), 30% (CH4+CnHm) 50% H2, 10% N2. Temperature-composition graphs are given for both reactions (1) and (2) with this mixture. At about 820° the CH4 decomposes to give at equilibrium a gas containing equal proportions of CO and CO2.