Reduction of alkali metal carbonate to methane with water in the presence of Raney alloy

In the presence of Raney alloy, the direct reaction of alkali or alkali-earth metal carbonates with water resulted in reduction of the carbonates to give methane in high selectivity at a temperature near the critical point of water (similar to 380 degrees C). Raney Ni showed an efficient activity to promote the methanation. On the contrary, Raney Fe did not cause the methanation, but the addition of catalytic amount of a carbon-supported ruthenium (Ru/C) to the Raney Fe brought about a highly selective reduction of the carbonates to methane. The reaction was also controlled by the reaction temperatures, i.e,, the selectivity and yield of methane increased with increasing temperature suppressing the formation of metal formate. One characteristic in the present reaction is a rapid formation of a considerable amount of metal formate at an initial stage. It is proposed that the formation of methane from metal carbonate occurs via the formation of metal formate and its subsequent hydrogenation by nascent hydrogen which is produced from water by action of Raney alloy. The apparent activation energy for the methanation of Na,CO, on Raney Fe-Ru/C mixed catalyst was estimated to be 14 kcal mol-(-1). (C) 1999 Elsevier Science B.V. All rights reserved.