Fe-Modified CuNi Alloy Catalyst as a Nonprecious Metal Catalyst for Three-Way Catalysis

Abstract

In this study, we explored the feasibility of using base metal catalysts for three-way catalysis. The catalysts contain up to three base metals that were chosen to replace or reduce use of platinum group metals (Rh, Pd, and Pt). The aim was to develop catalysts with high activities at low temperatures having robustness against oxygen concentration fluctuations. Various base metal catalysts supported on alumina [10 wt % X/Al2O3 (X = Fe, Co, Ni, or Cu), 10 wt % CuY/Al2O3 (Y = Mn, Fe, Co, or Ni; Cu/Y = 1:1 in atomic ratio), and 10 wt % CuNi–5 wt % Z/Al2O3 (Z = Mn, Fe, or Co; Cu/Ni = 1:1 in atomic ratio)] were tested by temperature-programmed reaction in NO–CO–C3H6–O2 flow and under fluctuating oxygen concentration conditions. We found that the rate of reduction of NO over the 10 wt % CuNi–5 wt % Fe/Al2O3 catalyst in the low-temperature region was comparable to that of 1 wt % Pt/Al2O3, and this catalyst was also tolerant to oxidative conditions to some extent. Ex situ characterization of the catalysts before and after the three-way catalytic reaction was carried out via powder X-ray diffraction, X-ray absorption spectroscopy, scanning transmission electron microscopy with an energy-dispersive X-ray spectrometer, and in situ diffuse reflectance infrared Fourier transform measurements and revealed that the presence of Fe species resulted in the significantly improved oxidation of C3H6 and, thus, an increased rate of reduction of NO.

Platinum Group Metals: A Review of Resources, Production and Usage with a Focus on Catalysts

“…The activity of single crystals in the presence of some of these promoters is presented in Figure 7c. It can be seen that the reactivity of surfaces Fe(100) and Fe (110), containing Al x O y and pre-treated in 20 Torr of H 2 O, increases to that of Fe (111) in the presence of Al x O y [185]. These results highlight the complexity of surface structures in heterogeneous catalysis and point to the potential complexity of finding substitutes which will have good structures for dinitrogen dissociation.…”

“…The C 7 site is the most active for nitrogen dissociation. (b) Energy diagram for different surface states on Fe (111). The α'→ β transition is from dinitrogen to atomic nitrogen.…”

“…It seems unlikely, at least in the near future, that PGMs will be replaced by other catalyst systems in many of the examples discussed above. However, in the case of auto catalysts research is being undertaken using other transition metals [111,112]. Asakura et al [111] summarised the approaches for PGM alternatives as being (1) metal oxides supported on zeolites, spinels, or perovskites, (2) single atom or atomically dispersed metal sites as active centres, or (3) alloyed metal nanoparticles.…”

“…However, in the case of auto catalysts research is being undertaken using other transition metals [111,112]. Asakura et al [111] summarised the approaches for PGM alternatives as being (1) metal oxides supported on zeolites, spinels, or perovskites, (2) single atom or atomically dispersed metal sites as active centres, or (3) alloyed metal nanoparticles. A number of groups have examined highly dispersed Cu on a range of supports (combining paths 1 and 2) which show some good activity for NO reduction, but not at a low enough temperature [112].…”

“…Far more work has been done on binary, ternary, and quaternary mixture of 3d transition metals. For example, Asakura et al [111] have examined ternary alloys incorporating Fe into binary alloys of Cu-Ni and found that they can perform the oxidation and reduction requirements in laboratory conditions. Hirakawa et al [112] have examined nanoparticles comprising 3d transition metal quaternary mixtures of Fe, Ni, and Co, with Cu.…”