Effects of co loadings on NaCo/ZnO catalysts for ethanol steam reforming: XAFS studies

Abstract

This study focused on the elucidation of the Co phase in NaCo/ZnO catalysts with different Co loadings for ethanol steam reforming. The catalysts were applied for ethanol steam reforming with a feed of 20 wt% ethanol in water at 773 K. The characterizations of catalysts were made by temperature programmed reduction (TPR), X-ray absorption near-edge spectroscopy (XANES) and X-ray diffraction (XRD). The TPR and XANES analysis indicated that a Co loading less than 1 wt% led to the formation of a Co-ZnO composite while Co loadings of 10 wt% gave rise to the formation of Co metal after reduction. The XRD analysis of the oxidic precursors revealed that the ZnO phase was dominant without any Co oxidic phase for the Co loaded samples below 1 wt% due to the formation of Co-ZnO composite, but with evident contribution of Co3O4 being found for the 10 wt% NaCo/ZnO sample. The activity test of the catalysts in ethanol steam reforming showed that the catalysts with Co loadings more than 10 wt% exhibited good and stable activity with an ethanol conversion of 90%. These results demonstrate that the Co metal phase is active for the ethanol steam reforming and viable with Co loadings of 10 wt%.