Synthesis of Solid Base Catalyst of BaO–Al2O3 Binary Oxide by Solid-liquid Interface Reaction of Hydrated Barium Hydroxide with Aluminum Alkoxide

Solid base BaO–Al2O3 catalyst was synthesized using the solid-liquid interface reaction of Ba(OH)2 · H2O in the solid phase with Al(OCH(CH3)2)3 dissolved in ethyl acetate. Water of crystallization in the barium hydroxide, Ba(OH)2 · H2O was consumed by hydrolysis of Al(OCH(CH3)2)3 into Al2O3 and isopropanols. BaO–Al2O3 catalyst synthesized by solid-liquid interface reaction of Ba(OH)2 · H2O with equal mols of Al(OCH(CH3)2)3 and heat-treated at 673 K showed the highest activity among the prepared catalysts for the retro-aldol reaction of diacetone alcohol. Active BaO–Al2O3 catalysts with various contents of BaO were obtained by heating at appropriate temperatures just below those of Ba5Al2O8 and BaAl2O4 crystallization. X-ray diffraction analysis detected no BaO phase in this solid base catalyst. Barium oxide highly dispersed in amorphous Al2O3 was prepared by the solid-liquid interface reaction. The interface reaction of metal hydroxide in the solid phase with alkoxide in the liquid phase is useful to form well-dispersed mixed metal oxides.