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-ear th metal carbonates with water resulted in reduction of the carbonates to g ive 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 metha nation, but the addition of catalytic amount of a carbon-supported rutheniu m (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 tem peratures, i.e,, the selectivity and yield of methane increased with increa sing temperature suppressing the formation of metal formate. One characteri stic 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 wat er by action of Raney alloy. The apparent activation energy for the methana tion 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.