正丁醛自缩合合成2-乙基-2-己烯醛(辛烯醛)是2-乙基己醇(辛醇)工业生产中实现碳链增长的关键步骤.采用溶胶-凝胶法制备了TiO2催化剂,使用NH3-TPD、CO2-TPD、BET和XRD等手段对TiO2催化剂酸碱性、织构性质和晶相进行了表征,发现锐钛矿型TiO2催化剂的表面酸位和碱位数量明显高于金红石型TiO2.活性评价结果表明,锐钛矿晶型TiO2催化性能优于金红石晶型TiO2.以TiO2凝胶在空气气氛下,于400℃ 焙烧1 h制备的锐钛矿TiO2为催化剂,正丁醛自缩合反应适宜的反应条件为:TiO2用量为15.0%(wt),反应温度180℃,反应时间8 h.在此条件下,正丁醛的转化率可达91.1%,辛烯醛的收率和选择性分别为81.6%和89.6%.TiO2重复使用7次,催化活性无明显下降.采用GC-MS对反应液进行定性分析,确定了反应副产物,探讨了锐钛矿型和金红石型TiO2催化性能存在差异的原因,并且构建了锐钛矿型TiO2催化正丁醛自缩合的反应网络.%n-Butanal self-condensation to synthesize 2-ethyl-2-hexenal is one of the key reactions to achieve carbon-carbon bond extension in industrial production of 2-ethylhexanol. TiO2 catalysts were prepared by sol-gel methods and characterized by CO2-TPD, NH3-TPD, BET and XRD. The results indicate that the numbers of acid sites and base sites on the surface of anatase TiO2 are significantly higher than that of rutile TiO2. Activity evaluation results show that the catalytic performance of anatase TiO2 is superior to that of rutile TiO2. Anatase TiO2 catalysts prepared by calcination of TiO2 gel at 400 for 1℃ h in air were used, and suitable n-butanal self-condensation reaction conditions were obtained as follows: catalyst weight percentage = 15.0%, reaction temperature = 180 and reaction time℃ = 8 h. n-Butanal conversion, 2-ethyl-2-hexenal yield and selectivity are 91.1%, 81.6% and 89.6%, respectively. TiO2 can be reused for seven times without significant loss of catalytic activity. The by-products existing in the reaction system catalyzed by anatase TiO2 and rutile TiO2 are identified by GC-MS, and the difference in the catalytic performance between anatase TiO2 and rutile TiO2 is explained. In addition, a possible reaction network for n-butanal self-condensation to 2-ethyl-2-hexenal catalyzed by anatase TiO2 is established.
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