关键词: 正丁醛, La-Al₂O₃催化剂, 催化, 羟醛缩合, 多相反应, 合成, 辛烯醛

Abstract:

2-Ethylhexanol is a kind of important plasticizer alcohols. n-Butanal self-condensation to 2-ethyl-2-hexenal is one of the important processes for industrial production of 2-ethylhexanol. In order to overcome the shortcomings such as equipment corrosion, environmental pollution and high production cost in the present industrial n-butanal self-condensation reaction using alkali aqueous catalyst, the La-modified γ-Al₂O₃ catalyst (La-Al₂O₃) was adopted to catalyze n-butanal self-condensation reaction. Firstly, the influence of different preparation methods and conditions on the La-Al₂O₃ catalytic activity was studied. The results showed that the catalytic activity of La-Al₂O₃ prepared by colloidal chemical method and calcined at 700℃ for 4 h was better. The existing acidic centers and basic centers matching with each other were the key to present better catalytic activity. The influence of reaction conditions on n-butanal self-condensation reaction was studied using the La-Al₂O₃ catalyst. The suitable reaction conditions were obtained as follows: mass ratio of catalyst to n-butanal 0.15:1, reaction temperature of 180℃ and reaction time of 8 h. Under the above conditions, the conversion of n-butanal was 90.6% and the selectivity of 2-ethyl-2-hexenal was 91.7%. La-Al₂O₃ could be reused for 4 recycles without losing its activity significantly. In addition, the by-products existing in the reaction system were identified by GC-MS analysis and then a possible reaction network for n-butanal self-condensation to 2-ethyl-2-hexenal catalyzed by La-Al₂O₃ was established.

Key words: n-butanal, La-Al₂O₃ catalyst, catalysis, aldol self-condensation, multiphase reaction, synthesis, 2-ethyl-2-hexenal