Catalytic hydrogenation of arabinonic acid and arabinonolactones

Aqueous solutions of arabinonic acid in equilibrium with the corresponding γ-lactone and δ-lactone were hydrogenated to arabitol in a batch reactor in the presence of an active-carbon-supported, ruthenium catalyst. Total conversion was achieved at 100 °C under 10 MPa H2 pressure. Depending upon the impurities present in solutions, the selectivities to arabitol were in the range 93.6–97.9% and the initial reaction rates in the range 73–460 mmol h−1gRu−1. Introduction of small amounts of sodium anthraquinone-2-sulfonate in pure solution decreased the reaction rate, but increased the selectivity from 93.6% to 97.9%. The presence of these molecules, which remain adsorbed on the catalyst surface even after successive recycling of catalyst, decreased markedly the rate of dehydroxylation reactions leading to unwanted deoxy-products. The promoter molecules probably act as modifier of the metal surface because of their basic and/or oxido-reduction properties.