Aluminum Fluoride Modified Beta Zeolite as Highly Selective Catalyst for the Esterification of sec-Butanol with Acetic Acid

This article describes a simple but effective method to dealuminate and realuminate H-Beta zeolite as a catalyst for removing organic acids from bio-oils via their esterification reactions with alcohols. A series of modified Beta zeolites were prepared by mechanically mixing an oxalic acid leached Beta zeolite with different amounts of solid-phase aluminum fluoride (AlF3) and calcinating the resulting mixtures. The structure, texture property, and acidity of the oxalic acid leached Beta zeolite can be finely adjusted by simply changing the amount of AlF3 used. Dealumination and realumination could simultaneously take place via the interaction of Beta zeolite with AlF3 when the content of AlF3 was between 1.5 and 3.0 wt %. Only dealumination happened when the content of AlF3 was lower than 1.0 wt % or higher than 4.0 wt %. The catalytic activities for esterification reaction of sec-butanol and acetic acid showed that the modified Beta zeolite with a suitable amount of AlF3 exhibited much higher selectivity than the oxalic acid leached H-Beta zeolite.