A mechanism of sodium-catalyzed carbon dioxide gasification of carbon investigation by pulse and TPD techniques

Sodium-catalyzed CO 2 gasification was investigated with pulse and TPD techniques using 13 CO 2 . Several reaction paths (elemental reactions) were considered in both oxidation of sodium on carbon surface and reduction of oxidized sodium species in the oxygen transfer mechanisms as follows: M x O y +CO 2 ⇄M x O y+1 +CO (1), and M x O y+1 +C f →M x O y +CO (2). In the catalyst oxidation step (eq 1), two reaction paths are proposed to proceed as follows: (a) formation of dispersed sodium-CO 2 complex interacting strongly with carbon and its decomposition to form sodium oxide, (b) oxidation of sodium in the sodium cluster, where transformation of cluster-CO 2 complex to cluster oxide-CO complex occurs. Two reaction paths proceed in the catalyst reduction step (eq 2) as follows: (c) fast oxidation of carbon by «active oxidant» and (d) slow gasification by metal cluster oxide through the following two steps: Na n O+ 12 C f →[ 12 C f -O-Na n ] (3), and [ 12 C f -O-Na n ]→ 12 CO+Na n (4)