Hydrocondensation of carbon dioxide over an iron-alumina catalyst: A three-step model

Abstract

The hydrogenation of CO 2 has been studied at atmospheric pressure from 200 to 275°C on a Fe/Al 2CO 3 catalyst and compared with CO hydrogenation. The catalytic results can be described by a three-step model: (I) fast loss of activity; (II) reactivation; and (III) final deactivation. The selectivity towards CH 4 is very high at the beginning of step (I). The characterization of the catalyst during the reaction was effected by means of IR and Mössbauer spectroscopies and magnetic measurements. The results show that only methane can be formed directly from CO 2, while homologous hydrocarbons are formed from CO, itself derived from CO 2. Two reaction paths for CO 2 → CO were shown to exist. Finally, it seems that the formate species, detected by IR during the reaction, plays an important role both in the regeneration of the catalytic activity and in CO formation by the reverse water-gas shift reaction.