The catalytic hydrogenation of aqueous solutions of 3-hydroxypropanal (3-HPA) to 1,3-propanediol (1,3-PDO) was conducted at 40-60 degreesC and 40 bar hydrogen with heterogeneous ruthenium catalysts in a trickle-bed reactor. Catalysts were optimized to obtain stable activity and selectivity as a function of time on stream. Catalyst deactivation was attributed to the deposit of heavy organic impurities on the catalyst surface blocking the reactant access to the active ruthenium particles. The pore structure of the catalyst had a significant influence on the catalytic results. The most stable catalysts were supported on low surface area macroporous titania (rutile, ca. I m(2) g(-1)), whereas mesoporous TiO2, and particularly microporous SiO2 supports deactivated because of surface blockage by organic impurities. (C) 2003 Elsevier Science B.V. All rights reserved.