Synthesis of lactic acid from dihydroxyacetone: use of alkaline-earth metal hydroxides

By-products from bio-based processes show great potential as renewable feedstock sources. In this context, upgrading the biodiesel by-product glycerol is highly promising. This paper focuses on the production of lactic acid from dihydroxyacetone, which is a primary oxidation product of glycerol, under mild reaction conditions (ambient pressure and temperatures below 90 degrees C) with alkaline-earth metal hydroxides. Whereas both Ca(OH)(2) and Ba(OH)(2) effectively catalysed the formation of lactic acid in the liquid phase, lactic acid was not formed with Mg(OH)(2) at 25 degrees C. The final yield was higher with Ca(OH)(2) (59%) than with Ba(OH)(2) (50%). With Ca(OH)(2), increasing reaction temperatures resulted in higher reaction rates. At 85 degrees C, however, competing side and degradation reactions were dominating, limiting the yield of lactic acid to 36%. We demonstrated that the method can be directly applied to dihydroxyacetone in fermentation broths. This research opens up a new synthesis route for lactic acid from dihydroxyacetone and glycerol, respectively.