关键词: 正丁醛, 催化剂, 羟醛缩合, 合成, 辛烯醛, 多相反应

Abstract: Aldol self-condensation of n-butyraldehyde to 2-ethyl-2-hexenal is one of the important processes for industrial production of 2-ethyl hexanol. Firstly, the catalytic performance of H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀ and H₃PMo₁₂O₄₀ was evaluated and the results showed that H₄SiW₁₂O₄₀ presented the best catalytic activity. Secondly, supported H₄SiW₁₂O₄₀ catalysts were prepared with the impregnation method and the influence of the kind of support and preparation process parameters on catalyst performance was investigated. The suitable preparation conditions were determined as follows: taking SiO₂ as support, loading of H₄SiW₁₂O₄₀= 50% (mass), calcination temperature of 150℃ and calcination time of 2 h. The effect of reaction conditions on the catalyst performance of H₄SiW₁₂O₄₀/SiO₂ was also studied and the suitable reaction conditions was determined as follows: mass ratio of catalyst to n-butyraldehyde 0.15, reaction temperature of 120℃ and reaction time of 6 h. Under the above conditions, the conversion of n-butyraldehyde and the selectivity to 2-ethyl-2-hexenal were 90.4% and 89.2%, respectively. However, the reusability of H₄SiW₁₂O₄₀/SiO₂ catalyst was poor. Analysis of ICP-AES and XRD demonstrated that the loss of active species H₄SiW₁₂O₄₀ was the main reason. In order to decrease the loss of H₄SiW₁₂O₄₀, H₄SiW₁₂O₄₀/SiO₂ catalyst was prepared with the sol-gel method using [emim]BF₄ ionic liquid as template. The activity test result showed that the reusability of the prepared catalyst was improved to some extent.

Key words: n-butyraldehyde, catalyst, aldol condensation, synthesis, 2-ethyl-2-hexenal, multiphase reaction