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.