Role of tungsten in the aqueous phase hydrodeoxygenation of ethylene glycol on tungstated zirconia supported palladium

Abstract

The focus of the present work was specifically on the elucidation of the role played by tungsten on the catalytic activity and selectivity of tungstated zirconia supported palladium (Pd-mWZ) for the aqueous phase hydrodeoxygenation (APHDO) of ethylene glycol (EG). Zirconia supported palladium (Pd-mZ) was used as reference. The catalysts were prepared via incipient wet impregnation and characterized using X-ray diffraction (XRD), temperature-programmed reduction (TPR), CO pulse chemisorption, CO-DRIFTS, ammonia temperature-programmed desorption (NH3-TPD) and pyridine adsorption. The presence of W results in larger Pd particles on supported Pd catalysts, i.e., 0.9 and 6.1nm Pd particles are for Pd-mZ and Pd-mWZ, respectively. The catalytic activity measurements show that the overall intrinsic activity of Pd particles on mWZ is 1.9 times higher than on mZ. APHDO process appears to be highly favored on Pd-mWZ whereas Pd-mZ exhibits a higher selectivity for reforming. This difference in terms of selectivity seems to be related to the high concentration of Brønsted acid sites and electron-deficient Pd species present on Pd-mWZ.