Balanced acid–base <scp>MgO</scp> –Y ₂ O ₃ catalysts enable selective acetaldehyde condensation to 3‐hydroxybutanal

Abstract BACKGROUND 3‐Hydroxybutanal (3‐HBA) is an important chemical product with a wide range of applications. This study investigated the liquid‐phase condensation of acetaldehyde to produce 3‐HBA over MgO‐based catalysts, such as MgO–Y 2 O 3 , MgO–La 2 O 3 , and MgO–Al 2 O 3 . The influence of the Mg/Y ratio on the catalyst performance was thoroughly investigated, and the effects of the reaction conditions on the formation of 3‐HBA were also studied. Furthermore, the relationship between the catalyst properties and the catalytic activity was investigated. RESULTS The MgO–Y 2 O 3 catalyst showed a high catalytic performance for the production of 3‐HBA, and the optimal Mg/Y molar ratio was 1:1. The MgO–Y 2 O 3 catalyst with a molar ratio of 1:1 exhibited both weak acidic and weak basic properties, and its acid and base amounts were lower than those of MgO. Reaction temperature significantly affected the reaction, and increasing the temperature was detrimental to the formation of 3‐HBA. In the reaction conducted using the MgO–Y 2 O 3 catalyst at 45 °C for 2.5 h, the conversion of acetaldehyde achieved was 52.5% with a 3‐HBA selectivity of 82.4%. CONCLUSION The MgO–Y 2 O 3 catalyst with appropriate acid–base properties effectively promotes the formation of 3‐HBA. An insufficient or excessive number of acidic or basic active sites is detrimental to 3‐HBA yield. It is proposed that the acidic sites activate the CO bond via an electron‐withdrawing effect, while the basic sites facilitate α ‐H elimination to generate a delocalized reactive intermediate. This intermediate subsequently undergoes nucleophilic addition to form 3‐HBA. © 2026 Society of Chemical Industry (SCI).