Selective synthesis of furfuryl acetate over solid acid catalysts and active site exploration using density functional theory†
Furfuryl acetate is obtained from the esterification of biomass derivative furfuryl alcohol which has potential applications as a biofuel additive, fragrance, and flavoring agent. For acid catalyzed reactions such as esterification, the integration of experimental outcomes with DFT studies to develop a method to derive a general correlation between active site energetics with catalytic activity is needed. Herein, various catalysts such as zeolites, mesoporous materials, ion-exchanged macro reticular resin, and silicoalumino phosphates with diverse physicochemical properties such as porosity, strength and amount of acidity, topology, and material stability were investigated for this transformation. The catalysts were characterized by PXRD, FTIR spectroscopy, ICP-OES, N2 sorption study, NH3-TPD, and SEM measurements to correlate the physicochemical properties with catalytic performance. Sulfated zirconia was the best performing catalyst which exhibited the highest furfuryl acetate yield of 95% at a low catalyst loading and reactant mole ratio with good recyclability. The excellent catalytic activity of the three top-performing catalysts (sulfated zirconia, SAPO-11 and Al-SBA-15) was explained using adsorption energies of various species on the catalyst by density functional theory (DFT) studies. Importantly, a new method of correlation was developed with respect to the hydrogen removal energy of the catalysts obtained from DFT which correlated well with the catalytic performance of distinctly different solid catalysts.