Promoter effect of alkalis on CuO/CeO2/carbon nanotubes systems for the PROx reaction

Abstract

The effect of alkali promotion (Li, Na, K and Cs) on the CO preferential oxidation (CO PROX) reaction has beenstudied over Cu-CeO2 catalyst supported on carbon nanotubes (CNT). The catalysts were prepared with 2.5 wt.%Cu and 20 wt.% CeO2 loadings, and alkali/Cu atomic ratios of 0.68. The catalytic performance and thecharacterization by powder X-ray diffraction (XRD), TEM-STEM, H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) has been presented. TEM and XRD analyses showed that theaddition of alkali reduces the size of ceria crystallites. It was found that in general the incorporation of alkalifavored the conversion of CO at low temperatures, being more pronounced for the K-doped catalyst. Thecharacterization showed that the addition of K favored the Cu-CeO2 interaction, the activity of the catalyst wasenhanced and the opposite was observed for Cs-doped sample. The characterization results reveal that theobserved increase in the Cu+ species proportion and in lattice oxygen are related to the better catalyticperformance.