2434. NEUMANN, B., AND JACOB, K. [Equilibrium in Formation of Methane From Carbon Monoxide and Hydrogen, or From Carbon Dioxide and Hydrogen.] Ztschr. Elektrochem., vol. 30, 1924, pp. 557-576; Brennstoff-Chem., vol. 6, 1925, p. 197; Chem. Abs., vol. 19, 1925, p. 1083.
Correlated survey of equilibrium conditions for the formation of CH4 by the reactions (1) CO+3H2=CH4+H2O and (2) CO2+4H2=CH4+2H2O over the temperature range 300°-1,050°. The experimental determinations of the equilibrium were made by the dynamic method, highly purified gas mixtures being passed over a Ni catalyst. The catalyst was made by igniting Ni(NO3)2 that had been deposited on MgO granules. The supported NiO thus formed was reduced at about 280° by H2. All experiments were at atmospheric pressure. The velocity of gas flow was in all cases 5 cm.3 per min. In experiments on reaction (1) the catalyst was 6.6 gm. Ni deposited on 45 gm. MgO. Reduction of CO to CH4 began at 170°, was complete at 288°, and remained so up to 303°. Above 303° the CH4 yield decreased regularly, until at 1,052° it had become zero. At temperatures above 389° the methanation reaction (1) is complicated by the secondary reactions 2CO=CO2+C, CO+H2O=CO2+H2 and CO2+4H2=CH4+2H2O. In the temperature region 450°-780° all 4 reactions go on together. Above 780° the secondary reactions subside. In experiments on reaction (2) the same amount of catalyst was used. Reduction of CO2 to CH4 began slightly over 180° and reached a maximum at 328°, corresponding to a CH4 yield of 95.3%. The CH4 yield decreased above 328° and reached zero at 1,020°. Above 540° the reaction (2) is complicated by many secondary reactions. Among them are C+CO2=2CO, CO2+H2=CO+H2O, CO2+Ni=NiO+CO. In experiments on reaction (3) CH4+H2O=CO+3H3 the catalyst was 1.6 gm. Ni deposited on 45 gm. MgO. The gas mixture was 43% CH4 and 57% steam. No reaction was observed below 330°. From 330°-1,034° the amount of CH4 undergoing reaction increased regularly. In the region 300°-860° the reaction is complicated by secondary reactions, as in the reverse reaction (1). Above 860° the reaction proceeds exclusively in accordance with the equilibrium reaction (3). Experiments on reaction (4) CH4+2H2O=CO2+4H2 from 320°-1,040° show plainly that, in spite of the presence of excess steam, the principal reaction is that corresponding to reaction (3). The observed values for the equilibrium constants P COXP3H2/P CH4XP H2O in the temperature region 860°-1,052°, agreed fairly well with those calculated by combination of the equilibrium constants for the 3 reactions C+CO2=2CO, C+2H2=CH4 and CO2+H2=CO+H2O. The experimental results show somewhat better agreement with those calculated by means of “chemical constants” (Nernst). Agreement between the observed values for the equilibrium constants of reaction (2), P CO2XP4 H2/P CH4XP2 H2O, and those calculated by combining the equilibrium constants of the 3 reactions C+CO2=2CO, C+2H2=CH4 and 2(CO2+H2=CO+H2O) was very poor.