TEM measurements indicated that Pd particles diameter observed was in the range 2.5–10 nm. No significant variation of TOF and selectivity values with the metal particle size was observed in this range. Moreover, the activity and the selectivity towards reaction products were found to be strongly dependent on the acid–base characteristics of the support.
The acid systems have been found more active and selective to isomerisation and hydrogenolysis products than the basic ones. No hydrogenolysis reaction was observed on basic supports. Among the examined catalysts, Pd/TiO2 resulted the most selective to 2-hydroxytetrahydrofuran. A maximum yield to this compound of about 74%was, in fact, obtained at 0.01 MPa of H2 pressure.