Development of an acid-base synergistic catalytic system for acrolein hydration: Experimental and theoretical studies

1,3-Propanediol (1,3-PDO) as an important chemical intermediate can be used in the synthesis of polyesters, plasticizers, and surfactants. Catalytic hydration of acrolein to 3-hydroxypropionaldehyde (3-HPA) is a key step for the industrial production of 1,3-PDO from renewable glycerol. However, conventional acid catalytic hydration reactions have the issue of low 3-HPA yield resulting from the trade-off effect between acrolein conversion and 3-HPA selectivity, which is mainly due to the formation of unstable intermediates in the reaction pathway and the high reaction energy barriers. Here, we developed a synergistically catalytic system consisting of proton-donating carboxyl groups as the Brønsted acid sites and amino groups as the Lewis base sites, which was employed in acrolein hydration reaction. Compared with the acid catalytic process, the acrolein conversion significantly increased from 11.9 % to 89.3 % under the acid-base synergistic catalysis, with the 3-HPA selectivity increased from 95.5 % to 97.1 %. Density functional theory (DFT) calculations indicate that the reaction intermediates can be stabilized via the robust C N covalent bonds. Moreover, the energy barrier of the acrolein hydration reaction is reduced from 58.2 to 46.2 kcal/mol, which contributes to the increase in the 3-HPA yield.