Investigation of the WO3/ZrO2 surface acidic properties for the aqueous hydrolysis of cellobiose

A series of WO x/ZrO 2 with various tungsten oxide loadings (1-20) wt.% was prepared by co-precipitation. The catalysts were characterized by XRD, BET, XPS, Raman spectroscopy, TPR, ammonia adsorption microcalorimetry and pyridine FT-IR spectroscopy. XRD and Raman results showed that the ZrO 2 support is predominantly present in the monoclinic phase when the WO 3 loading was less than 5 wt.% and predominantly in the tetragonal phase above 10 wt.%. No formation of bulk WO 3 was detected for the catalysts calcined at 700 °C, which is also the case for the highest loaded samples. TPR results revealed that isolated WO 3 species are easier to reduce than amorphous WO x. The ammonia adsorption microcalorimetric study evidenced acid sites with adsorption heats in the range 90 < Q diff < 130 kJ.mol -1, in amounts which increase with increasing WO 3 loading until reaching the monolayer. Concerning the acid site nature, a progressive increase of the amount of Brønsted sites with the WO 3 loading was observed. The catalytic reaction of cellobiose disaccharide hydrolysis showed a better catalytic performance on the highest WO 3 loaded catalysts, associated to the presence of Zr-stabilized WO x clusters and a strong protonic acidity.