Applied Catalysis A: General, Vol.399, No.1-2, 93-99, 2011
On the acid-base properties of Zn-Mg-Al mixed oxides
The influence of Zn2+ cation substitution in Mg-Al mixed oxides is explored in the Zn2+ concentration range from 20 to 60 mol%. The mixed oxides are derived by calcination of layered double hydroxide precursors. Structural analyses by XRD and Al-27 MAS NMR show that Al3+, Mg2+ and Zn2+ cations are well dispersed among the oxide phases. The acid site concentration increases with increasing zinc content, while the concentration of basic sites decreases compared to Zn2+ free mixed oxides. Acetone is the primary reaction product of propan-2-ol elimination with all zinc containing oxides. This suggests that the high activity for dehydrogenation of propan-2-ol is related to the pronounced hydride abstraction ability of Zn2+ cations and not to an enhanced strength or concentration of basic sites. (C) 2011 Elsevier B.V. All rights reserved.
Keywords:Zn-Mg-Al mixed metal oxides;XRD;Al-27 MAS NMR;Propan-2-ol elimination reactions;Hydride transfer