Addition of metal cations to magnesium oxide catalyst for the aldol condensation of acetone

Abstract

Addition of metal cations to magnesium oxide changes the catalytic activity and selectivity for the aldol condensation of acetone. Na +, K +, Rb +, Cs +, Al 3+, Mn 4+, Fe 3+, Co 2+, Ni 2+, Cu 2+, Zn 2+ and Zr 4+ were examined and Na +, Zr 4+ and Zn 2+ effectively increased the catalytic activity. The amounts of the metal cation influenced the activity; for Na +, Cr 3+ and Zr 4+, maximum activities were observed with 0.5–1 wt.-% of metal cation. Addition of suitable amounts of water increased both the activities and the selectivities. The basic strengths of MgO catalysts containing Zr 4+ and Cr 3+ were measured by temperature-programmed desorption of carbon dioxide. Basic sites were strengthened by the addition of the metal ions. In particular, magnesium oxide containing 0.5 wt.-% of Zr 4+ showed the strongest basic sites. The effects of metal cation addition on 1,3-butadiene hydrogenation and 1-butene isomerization were compared with those on the aldol condensation of acetone, and differences in the active sites for these reactions are discussed. Finally, the location of Na +, Cr 3+ and Zr 4+ were examined by X-ray photoelectron spectroscopy.