Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

Cobalt hydrotalcite-derived catalysts, doped with potassium, are active materials for the ethanol steam reforming reaction. Potassium addition reduces the acid sites number and strength. It acts as a promoter of the ethanol steam reforming (ESR); ethanol conversion is higher at lower temperature, as the amount of potassium at the surface of the catalyst increases. The catalysts are stable for long-term experiments (300 h) under high loads of ethanol and bioethanol (0.036 gEtOH min−1, H2O:CH3CH2OH = 4:1 molar). Moreover, they generate a low amount of carbon (0.0067 gC gcatalyst−1 h−1). The catalysts after reaction contain almost exclusively high spin Co2+ in cobalt oxide (or in (Co,Mg)O); only traces of metallic cobalt are identified by magnetometry, <0.1 wt.% Co0, suggesting that oxidized cobalt is an active species in ESR.

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► K is a promoter of Co/Mg/Al hydrotalcite-derived catalysts for ethanol reforming.
► Little carbon is generated under practical conditions using commercial bioethanol.
► Co spinel particles transforms into CoO strongly interacting with MgO.
► No metallic cobalt is detected after reaction.