Manufacturing AAl2O4 (A=Cu, Co, Ni, Zn) Spinel Catalysts for Toluene Combustion: Elucidating the A‐site Replacement Effect on the Reactivity

Abstract To decode the A‐site substitution effect on the reactivity of Al‐based spinel complex oxides, a series of AAl 2 O 4 (A=Cu, Co, Ni, Zn) compounds were manufactured and tested by toluene combustion. It was confirmed that a pure spinel crystalline phase has been successfully synthesized for all the catalysts. The toluene and CO oxidation activity are sequenced as CuAl 2 O 4 >CoAl 2 O 4 >NiAl 2 O 4 >ZnAl 2 O 4 . As discovered, both active surface O 2 − and acid sites are the two critical factors to determine the reactivity, which can adsorb and activate the reactants effectively to form active intermediates, possibly following a Mars‐van‐Krevelen pathway. The activity improves positively with the amount increasing of these two kinds of active sites, thus showing an evident A‐site replacement effect. CuAl 2 O 4 owns the biggest numbers of these two kinds of active sites, thereby exhibiting the optimal catalytic activity. Moreover, it also shows good stability in a dry feed, and considerable ability to resist water vapor and sulfur poisoning. In‐situ DRIFTS results have indicated that benzyl, benzoate, benzaldehyde and benzoquinone might be the major reaction intermediates.