Formation and Evolution of Carbonate Species in Na-Doped Al₂O₃and V₂O₅-Al₂O₃

Investigation of the behaviour of a Pd/γ-Al2O3 catalyst during methane combustion reaction using in situ DRIFT spectroscopy

“…Finally, the peak at 1440 cm À1 can be representative of bicarbonates or carbonates species. Based on these considerations, peaks observed at 1650 and 1440 cm À1 below 300 8C, when CO 2 is Free carbonates [78] Complementary bands out of this frame are not reported. present in the gaseous feed, will be ascribed to CO 2 adsorbed on alumina, most probably as hydrogenocarbonates.…”

“…The assignment of the peak at 1460 cm À1 is as difficult as that of the band at 1590 cm À1 . However, based on literature data (Table 1), it can tentatively be ascribed to free carbonates ions on the alumina surface or to m-CO 3 2À species [60,[65][66][67][68][69]71,74,[76][77][78], without excluding the potential formation of hydrogenocarbonates [64,67] or surface methoxy groups [73]. The peak at 1460 cm À1 will therefore tentatively be assigned to carbonates species, likely in the monodentate conformation.…”

“…In the same region, another band may also appear below 200 8C, even in absence of CO 2 , at 1640 cm À1 . This signal can be assigned to bending vibration d(HOH) of water adsorbed on surface and OH-groups of alumina [58,59,62,78,80,82]. Finally, the peak at 1440 cm À1 can be representative of bicarbonates or carbonates species.…”