Dehydration of Tetrahydrofurfuryl Alcohol Into Dihydropyran on γ-Al2O3 Catalyst: Reaction Monitoring by In Situ DRIFT Spectroscopy

In this study, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to analyze the surface reactivity during the dehydration of tetrahydrofurfuryl alcohol (THFA) to 3,4-dihydro-2H-pyran (DHP). The dehydration reaction of THFA is carried out in the gas phase at 648 K using activated γ-Al₂O₃ as catalyst. Under these conditions, a yield of 84% DHP is obtained in a fixed-bed reactor and the catalyst shows no signs of deactivation after 70 h. The information obtained with DRIFT in situ spectroscopy depends on the reaction conditions, with the concentration of THFA in the gas phase being a critical variable. The temperature and time on stream have also been studied. This technique has allowed to identify DHP, the product of interest, two products with carbonyl group (C = O) formed in the surface of the catalyst during the reaction, and also the formation of carboxylates from the reaction of surface species with the oxygens of the oxide catalyst. This is of considerable significance, as an understanding of the molecular processes occurring at the surface during the reaction would permit the rational design of catalysts to enhance their catalytic properties. Therefore, in situ DRIFT spectroscopy is a valuable tool for studying active catalysts in the THFA dehydration reaction.