期刊
JOURNAL OF CATALYSIS
卷 200, 期 2, 页码 352-359出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1006/jcat.2001.3208
关键词
citronellal; cyclisation; isopulegol; dual acid sites-Lewis and Bronsted; zirconium hydroxide; phosphated zirconia
The cyclisation of citronellal to isopulegol is an important step in the synthesis of menthol. Several zirconia-based catalysts were evaluated for this reaction. Zirconium hydroxides and phosphated zirconia had very good activity and selectivity. Ammonia TPD and pyridine IR studies indicate the presence of strong Lewis together with weak Bronsted acid sites. Other strong acids like sulfated zirconia, Amberlyst, and Nafion were very active but the selectivity toward isopulegol was poor. They catalysed side reactions such as dehydration, cracking, and etherification of isopulegol. Silica, with only weak Lewis acidity, showed very low activity. The presence of both Lewis and Bronsted sites is therefore essential for the reaction. A reaction mechanism is proposed where the citronellal molecule binds to a zirconium Lewis acid site via the aldehyde oxygen and the jr-electrons of the double bond so that the right configuration is attained for cyclisation. Subsequent protonation of the aldehyde via a neighbouring Bronsted acid site initiates the cyclisation to isopulegol. (C) 2001 Academic Press.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据