Application of calcined Mg–Al hydrotalcites for Michael additions: an investigation of catalytic activity and acid–base properties

• DOI: 10.1016/j.jcat.2005.06.004
• Publication Date: 2005-07-18T09:49:46Z
• Authors: H PRESCOTT; Z LI; E KEMNITZ; A TRUNSCHKE; J DEUTSCH; H LIESKE; A AUROUX
• Keywords: [CHIM.CATA] Chemical Sciences/Catalysis; [CHIM.CATA]Chemical Sciences/Catalysis; 01 natural sciences; 0104 chemical sciences

Mg-Al hydrotalcite catalysts with different Mg/Al molar ratios (0.6, 1.4, 2.2, 3.0) were calcined and tested in liq.-phase Michael addns. at room temp. The catalysts and pure oxides (MgO and Al2O3) were characterized by XRD, XPS, N2 adsorption expts., 27Al MAS NMR, and TG-DTA. The acid-base properties of the samples were investigated by (a) FTIR spectroscopy after pyridine and CO2 adsorption and (b) microcalorimetry with CO2 and benzoic acid. Both acid sites (Lewis) and base sites (Lewis and Bronsted) are present on the surface of calcined hydrotalcites. The calcined hydrotalcites (CHT) catalyzed the Michael addns. of CH-acid compds. to Me vinyl ketone to give high product yields with 100% selectivity; the Al-rich sample exhibited the highest activity.