CONVERSION OF GLYCEROL TO ACRYLIC ACID OVER POLYOXOMETALATE CATALYSTS

Abstract

This work was carried out to convert glycerol to acrylic acid in liquid phase over supported polyoxometalate (POM) catalysts. The investigated parameters were H2O2 concentration (2.74-6.85 mol/L), reaction temperatures (70-90 oC), POM types (PW, PMo, SiW), support types (Al2O3, SiO2, HZSM-5) and the catalyst to glycerol ratio (2-8 wt%). It was found that the SiW/HZSM-5 catalyst can enhance the conversion of glycerol of around 85.54% at H2O2 concentration of 2.74 mol/L, temperature of 90 oC, the catalyst to glycerol of 4 wt.%. The doping of vanadium (V) at 6 wt.% on the surface of SiW/HZSM-5 (V6-SiW/HZSM-5) catalyst can promote the conversion of glycerol up to 99.67% and provide the yield of glycolic acid, formic acid, acetic acid, acrolein, acrylic acid and propionic acid of 19.45%, 12.03%, 23.62%, 0.25%, 36.23% and 7.06%, respectively. The rate of glycerol conversion was fit with a pseudo-first order reaction with respect to glycerol concentration, with the activation energy of 26.63 kJ/mol. The Eley-Rideal model, assuming a reaction between adsorbed oxygen molecule, obtained from H2O2 dissociation, and glycerol molecule provided the best fit with the experimental results.