Low Pt Loading High Catalytic Performance of PtFeNi/Carbon Nanotubes Catalysts for CO Preferential Oxidation in Excess Hydrogen I: Promotion Effects of Fe and/or Ni

Abstract

The commercial carbon nanotubes (CNTs-o) and purified carbon nanotubes (CNTs-p) have been utilized to prepare Pt(FeNi)/CNTs catalysts for CO preferential oxidation (PROX) in H-2 rich stream. The 3 wt%Pt0.41 %Fe 0.35 %Ni/CNTs-p catalyst after activation at 500 A degrees C in H-2 can almost completely remove CO at 6 A degrees C in feed gas containing 1 % CO, 0.5 % O-2 (volume ratio) and H-2 balance. CNTs-o supported 3 wt% Pt can also remove CO almost completely at room temperature, after activation at 500 A degrees C in the feed gas. And this catalyst can keep high activity, high selectivity and high stability for PROX of CO at room temperature. These catalysts are the most effective catalysts for PROX of CO with much lower Pt loading until so far. H-TPR, XRD, HRTEM and reaction results indicate that the Fe and/or Ni precursors have been reduced to metallic state after activation in H-2 which can be oxidized to coordinatively unsaturated FeOx and/or NiOx active species after exposure to feed gas. XPS data point out that over oxidation of Fe and Pt species will deactivate the catalysts seriously. The high catalytic performance is mainly due to the promotion effects of in situ formed coordinatively unsaturated FeOx and/or NiOx species and the unique properties of CNTs.