离子液体介质中用Cu/ZrO2-SiO2催化香茅醛加氢合成薄荷醇

制备了Cu/ZrO2-SiO2双载体催化剂, 并在离子液体介质中研究了香茅醛催化加氢合成薄荷醇的反应. 研究结果表明, 离子液体中的阳离子与香茅醛分子中的羰基形成氢键, 使香茅醛更容易异构化为胡异薄荷醇, 提高了催化剂的选择性; 特别是可调节酸度的bmim]AlmCln]离子液体, 有效地提供了香茅醛的异构化所需要的路易斯酸条件, 在竞争性加氢中促进了香茅醛向生成薄荷醇的方向转化. 在0.8 MPa, 90 ℃, 2 h的条件下, 香茅醛一锅反应生成薄荷醇的转化率为100%, 对薄荷醇的选择性为91.3%, 而且, 催化剂和离子液体可回收和重复使用.

Synthesis of Menthols via Selective Hydrogenation of Citronellal Catalyzed by Cu/ZrO2-SiO2 in Ionic Liquid

The simple and efficient catalyst of Cu/ZrO2-SiO2 was prepared and chemoselective hydrogenation of citronellal was performed over this catalyst in room temperature bmim]Al2Cl7] ionic liquids as the clean solvent and assisted-catalysts.The isomerization of citronellal under very mild hydrogenation conditions can be favor toward isopulegols that was hydrogenated to further menthols in Lewis acid ionic liquids.Citronellal can be converted,100% of conversion and 91.3% of selectivity based on menthols were obtained in one-pot process by competitive hydrogenation.The products distribution was found to depend strongly on hydrogen bond formed between carbonyl group of citronellal molecule and cation of ionic liquids.This reaction process was discussed especially and its evolution was also suggested to use in the future.The catalysts and ionic liquids can readily be recovered and reused.