There is growing interest to use lactic acid in the production of biodegradable plastics and solvents. A clean process has been developed for oxidation of propanal to lactic acid using heterogeneous catalysts. The process involves five steps. The first step is the acetalization of propanal with alcohol over zeolite, followed in step two by the conversion of the acetal to vinyl ether. In step three, the vinyl ether is oxidized to the hydroxyl acetal using hydrogen peroxide or organic peroxide over Ti-molecular sieves. Hydrolysis of the hydroxyl acetals over zeolite (step four) resulted in two products: hydroxypropanal as a major product and hydroxyacetone. In step five the hydroxypropanal is oxidized to lactic acid with air using Pt/ C. The overall yield is above 80% to lactic acid. Only hydroxyacetone was formed as a by-product, which is a high value chemical. (C) 2006 Elsevier B.V. All rights reserved.