Poisoning effect of chlorine anions in the catalytic activity of CuO/CeO2/UiO-66 for CO-PROX reaction and strategy for catalyst activation

Abstract

UiO-66 was synthesized using ZrOCl₂·8H₂O as metal precursor, and CuO/CeO₂/UiO-66 catalysts were prepared and tested for preferential CO oxidation in H_2-rich streams (CO-PROX reaction), a reaction of practical significance in hydrogen purification for fuel cells. The study highlights the detrimental effect of residual chlorine anions from UiO-66 synthesis and DMF washing on the catalytic performance of CuO/CeO₂/UiO-66. An activation strategy involving rigorous water washing and thermal treatment at 160 °C under CO-PROX conditions was developed. Both steps were deemed necessary, as employing only one proved insufficient to reduce chlorine levels to non-poisoning thresholds. This activation procedure does compromise UiO-66 crystallinity and porosity, but it is justified by achieving a fully functional catalyst. TEM images confirm the uniform dispersion of the CuO/CeO₂ active phase on the UiO-66 matrix post-activation and after catalytic testing. A 16-h CO-PROX test at 160 °C with the CuO/CeO₂/UiO-66 catalyst, once activated, demonstrated stable performance throughout the extended long-term experiment. This research provides valuable insights into optimizing CuO/CeO₂/UiO-66 catalysts for CO-PROX application.