THE FORMATION OF METHANE FROM HYDROGEN AND CARBON AT HIGH TEMPERATURES AND PRESSURES

Abstract

The rate of methane production from hydrogen and carbon (spectroscopically pure electrode material) in a fixed bed was investigated at temperatures between 1000 and 1250°C and hydrogen pressures of 10 to 100 atm. At lower temperatures the reaction rate of graphitic carbon is unimportant, while at higher temperatures the methane production becomes uninteresting because of the very low equilibrium concentration of methane. From the temperature dependence of reaction rate the activation energy was determined to be 85.5 kcal. The order of reaction with respect to hydrogen came out between 1.0 and 1.1. Obviously the hydrogenation of —CH2—CH2— groups at the graphite lattice combined with a splitting of the —CH2—CH2— bond is the rate-determining step of the whole process. The results with different gas flow rates led to the conclusion that the reverse reaction, i.e. the decomposition of methane, runs proportionally to the methane concentration and inversely proportionally to the hydrogen concentration. A comparison between the rate of methane production and the rate of carbon-carbon dioxide reaction shows that both increase in the same way with temperature, i.e. have the same energy of activation, but under comparable conditions the gasification of carbon with carbon dioxide runs about 230 times faster than the formation of methane.