Esterification of Acetic Acid with n-Butanol Catalyzed by Metallocenes

Efficient esterification of acetic acid with n-butanol has been achieved using metallocenes as the catalyst, and the ester can be produced with a high yield. The effect of several factors such as reaction time, molar ratio of catalyst/alcohol, and different metallocenes on the yield has been investigated. The results of homogeneous catalytic reaction show that Cp2Fe, Cp2TiCl2, Cp2ZrCl2, and [o-MeOC6H4C(Et)(2)Cp](2)ZrCl2 are effective catalysts for aliphatic acid esterification at a very low catalyst/alcohol molar ratio. When Cp2TiCl2 was used as the catalyst at a molar ratio of Ti/n-butanol equal to 0.049%, 90% yield was gained after 30 min. Silica gel (400 mesh) was used as the support to load metallocenes. The supported Cp2ZrCl2 catalyst exhibits high activity as that of Cp2ZrCl2 under optimum experimental conditions (calcination temperature = 400 degrees C, calcination time = 4.0 h, the molar ratio of Zr/butanol = 0.487%, reaction time = 45 min) with the ester yield of 90.6%. The use of supported metallocenes as the catalysts results in a cleaner process for esterification without wastewater produced. Moreover, the catalyst is easy to recycle.