Niobic Acid as an Efficient Catalyst for Vapor Phase Esterification of Ethyl Alcohol With Acetic Acid

The niobic acids calcined at moderate temperatures of 120–300 °C showed high catalytic activities (52–75% conv. in 1 h) and selectivities (100%) for the esterification at reaction temperatures of 120–160 °C. No catalyst deactivation was observed even after the use for 60 h. The niobic acid catalysts were more effective than cation exchange resin, SiO2–Al2O3, HZSM-5, and solid super acids such as ZrO2–SO42−, TiO2–SO42−, and Fe2O3–SO42−.