. Herein,
the deposition of the xylose-derived solid residues on the spent
ZrO2 catalysts may change the surface properties and introduce a
higher amount or stronger Brønsted acid sites than the fresh ZrO2,
thus promoting the dehydration reaction.As shown in theATR-FTIR
spectra (Fig. 5), the spent ZrO2 catalyst obviously shows the signal
of adsorbed species: (1) the broad peak at around 3400 cm−1 is