Theoretical insights into furfural reduction to furfuryl alcohol via the catalytic hydrogen transfer reaction catalyzed by cations exchanged zirconium-containing zeolites

Abstract

The density functional theory has been employed to study the reduction of furfural to furfuryl alcohol via the catalytic transfer hydrogenation (CTH) reaction over cations exchanged zirconium (Zr) containing zeolites. From the calculations results, the reaction proceeds through the following three steps: (i) the dissociation of the hydroxyl (OH) group of i-propanol to form i-propoxide, (ii) the hydrogen transfer from i-propoxide to furfural and (iii) the formation of furfuryl alcohol. The Li-Zr-BEA zeolite shows higher catalytic activity than Li-Sn-BEA due to its lower activation free energy (25.8 vs 20.8 kcal/mol). The effect of cations (Li, Na and K) which are exchanged on Zr-BEA is also considered. Based on the activation energy of rate determining step and turn over frequencies (TOFs), the catalytic activity rises when the group period of an exchanged metal decreases. The finding shows that the exchange of cations in Zr-zeolite surface is a simple process to make a tunable catalyst for the catalytic transfer hydrogenation reaction. The effects of different zeolite frameworks (BEA, ZSM-5 and FAU) are also studied. The relative catalytic activity of Li-Zr-BEA and Li-Zr-ZSM-5 zeolite is found to be almost similar and higher than that of Li-Zr-FAU zeolite.