Synthesis of 1,3-Propanediol by Cross Aldol Reaction and Hydrogenation of Formaldehyde with Acetaldehyde

3-Hydroxypropanal (3-HPA) is formed by the cross-aldol reaction of formaldehyde (HCHO) with acetaldehyde (CH3CHO), which further converts to 1,3-propanediol (1,3-PDO). Mg/SiO2 and X-5Mg/SiO2 (X = Mn, Fe, Co, Ni) catalysts were prepared using the sol–gel method and characterized with XRD, BET, TEM, and NH3- and CO2-TPD methods. The 5Mg/SiO2 showed higher activity in terms of the yield and selectivity due to its suitable basic and acidic density. The addition of Mn to the 5Mg/SiO2 catalyst caused dispelling of weak basic sites but maintained strong basic sites, and the high CH3CHO conversion was maintained. The increase of weak acidic sites contributed to the increase of 3-HPA selectivity for the 1Mn-5Mg/SiO2 catalyst. The cross-aldol reaction of HCHO with CH3CHO to produce 3-HPA more easily proceeded than the self-aldol reaction of CH3CHO according to the reaction kinetic analysis. Furthermore, Raney nickel was successfully applied to the hydrogenation process of 3-HPA to 1,3-PDO with over 90% HPA conversion and 1,3-PDO selectivity.