Biologically synthesized crude calcium lactate as a substrate for propylene glycol production

Abstract

Lactic acid (LA) can be obtained easily through fermentation of saccharides, and is an extremely useful building block for the synthesis of valuable chemicals, including propylene glycol (PG). Catalysis is one of the key elements in this platform approach. The present study focuses on PG synthesis via catalytic hydrogenation of lactate ions. In the conventional biological method, separation and downstream processing of pure LA account for up to 50% of production costs. Therefore, we propose using a less pure solution of lactate ions as a feedstock. To this end, we have developed a new method for the treatment of post-fermentation broth containing calcium lactate, obtained from sugar beet pulp. Activated carbon was used for the purification of the post-fermentation broth, which was acidified to pH 2–3. Hydrogenation of LA into PG was performed over supported metallic catalysts, based mainly on ruthenium, under mild conditions. The yield of PG was satisfactory and the PG water solution obtained could be used in concentrated form as a component in antifreeze.