Synthesis of a,b-unsaturated ketones over MgO-based catalysts

VERÓNICA K. DÍEZ; CARLOS R. APESTEGUÍA; JUANA I. DI COSIMO

Baltimore, Maryland, USA

Congreso; 11th. International Congress on Catalysis; 1996

Valuable a,b-unsaturated organic compounds such as ketones, aldehydes or nitriles of application in the solvent, fragrance, pharmaceutical or plastic industries, are synthesized by aldol condensation reactions. The oligomerization of acetone over base catalysts to yield a,b-unsaturated carbonyl compounds is a typical example of this kind of reactions. The function of the base is to abstract the proton in a position to the carbonyl group (Ha) giving rise to a carbanion which reacts with a second acetone molecule to produce diacetone alcohol. When the reaction is carried out in the vapor phase at relatively high temperature, the diacetone alcohol rapidly dehydrates to mesityl oxide.  Further self- or cross-condensation reactions involving mesityl oxide and acetone lead to formation of heavier a,b-unsaturated ketones such as isophorone. In   this work, we have studied the vapor-phase self-condensation of acetone at  573 K over MgO-based catalysts promoted with alkali or alkaline earth metals.  The objective was to establish the effect of the promoter on the catalyst activity and selectivity toward a,b-unsaturated ketones.