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本文以纳米TiO2为催化剂,UV-LED(=365 nm)为紫外光源,在自制的恒温石英玻璃光催化反应器中成功实现了芳香醛的非均相光催化缩醛反应.以乙醇等作为溶剂和反应物,快速高效和高选择性地合成了苯甲醛二乙基缩醛(BDA).在光强为0.6 mw/cm2,苯甲醛初始浓度为0.05 mol/L,催化剂TiO2(P25)用量为5.0 g/L,反应时间为15 min的条件下,苯甲醛二乙缩醛的产率可达99.86%.研究表明,氧气的存在是顺利发生光催化缩醛反应的重要条件.反应液pH值、醇溶剂种类及苯环对位取代基等因素都会对光催化缩醛反应速率和产率产生影响.pH值及醇溶剂的pKa越小,缩醛反应速率越快.苯环上对位取代基会抑制缩醛反应的进行,其中供电子取代基相对吸电子取代基更有利于缩醛反应进行.结合实验,提出了光催化缩醛反应的机理.
In this paper, the heterogeneous photocatalytic acetal reaction of aromatic aldehydes has been successfully achieved in a home-made, constant-temperature quartz glass photocatalytic reactor using nano-TiO2 as the catalyst and UV-LED (= 365 nm) as the UV light source. And benzaldehyde diethyl acetal (BDA) were synthesized quickly and efficiently with high selectivity.When the light intensity was 0.6 mw / cm2, the initial concentration of benzaldehyde was 0.05 mol / L and the amount of TiO2 (P25) was 5.0 g / L, the reaction time was 15 min, the yield of benzaldehyde diethyl acetal reached 99.86% .The results showed that the presence of oxygen is an important condition for smooth photocatalytic acetal reaction.The pH of the reaction solution , Alcohol solvent type and benzene ring para-position substituents and other factors will have an impact on the photocatalytic acetal reaction rate and yield .pH value and alcohol solvent pKa smaller acetal reaction rate faster para-position substitution Based on the experimental results, the mechanism of photocatalytic acetal reaction was proposed.