Influence of salts on the dehydration of several biomass-derived polyols in sub- and supercritical water

We investigated the dehydration of several biomass-derived polyols in sub- and supercritical water, in particular m-erythritol, 1,2-propanediol and 1,3-propandiol. The resulting main products were 1,4-anhydroerythritol and propionaldehyde. ditives tested for their catalytic performance were among others zinc, nickel, copper, magnesium and sodium sulfate as well as sulfuric acid. A positive catalytic effect of bivalent transition metal salts was found. l educt and ZnSO4 concentration variations were carried out in order to determine the reaction orders. Further, activation energies and activation volumes were measured for zinc catalysed dehydrations of the above-mentioned polyols. y, a possible explanation for the reaction enhancing or inhibiting effect of different salts is given and discussed.