Selective CO removal in a H 2-rich stream over supported Ru catalysts for the polymer electrolyte membrane fuel cell (PEMFC)

Abstract

We prepared various Ru catalysts supported on different supports such as yttria-stabilized zirconia (YSZ), ZrO 2, TiO 2, SiO 2 and γ-Al 2O 3 with a wet impregnation method. We applied them to the selective CO removal in a hydrogen-rich stream via the preferential CO oxidation (PROX) and the selective CO methanation simultaneously. Among them, Ru/YSZ showed the highest CO conversion especially at low temperatures. Several measurements: the N 2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), the CO chemisorptions, the temperature-programmed oxidation (TPO), the temperature-programmed reduction (TPR), the temperature-programmed desorption (TPD) of CO 2 with mass spectroscopy and the transmission electron microscopy (TEM), were conducted to characterize the catalysts. No linear correlation can be found between the amount of CO chemisorbed at 300 K and the PROX activity. On the other hand, the facile activation of O 2 appeared to be closely related to the high PROX activity, judging by the TPO experiment. In addition, the strong adsorption of CO 2 suppressed the low-temperature PROX activity. Ru/YSZ can be easily oxidized and also reduced at low temperatures. It is found that Ru/YSZ uptakes only small amounts of CO 2, which can be desorbed at low temperatures. Ru/YSZ can reduce the high inlet CO concentration to be less than 10 ppm even in the presence of H 2O and CO 2.