An FT-IR study of the adsorption of isopropanol on calcined layered double hydroxides containing isopolymolybdate

The acid–base and red–ox properties of amorphous magnesium and zinc molybdates obtained through calcination at 400 °C of Mg2Al- and Zn2Al-heptamolybdate layered double hydroxides, which had been prepared by anionic exchange from the corresponding nitrate-hydrotalcite precursors, have been studied. Lewis-type acid and basic sites have been detected in both systems, in addition to Brönsted-type acid sites in magnesium molybdate; however, as studied by FT-IR spectroscopy, none of them is strong enough to yield propene through isopropanol decomposition. The higher reducibility of Mo6+ cations in zinc-containing samples than the magnesium containing ones makes them more selective for acetone production. Moreover, a small amount of products formed on basic sites through acetone aldol reaction have been identified at high reaction temperatures.