Esterification of Acrylic Acid with Different Alcohols Catalyzed by Zirconia Supported Tungstophosphoric Acid

The liquid phase esterification of acrylic acid with different alcohols (butanol, iso-butanol, or hexanol) was investigated in a batch reactor with zirconia supported tungstophosphoric acid (TPA) as heterogeneous catalyst. The prepared catalysts with different TPA loadings (20, 25, and 30 wt %) and calcination temperatures (550, 650, and 750 degrees C) were characterized by nitrogen adsorption studies, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques. In addition, acidity measurements were performed by potentiometric titration with n-butylamine. The activitiy of catalysts strongly dependent on the acidic characteristic of the catalysts. The most active catalyst, 25 wt % TPA, calcined at 650 degrees C, gave more than 33%, 31%, and 27% conversions of acrylic acid for butyl, iso-butyl, and hexyl acrylate synthesis, respectively.