Boosting RuO₂ Surface Reactivity by Cu Active Sites over Ru/Cu-SSZ-13 for Simultaneous Catalytic Oxidation of CO and NH₃

Abstract

Catalytic removal of CO from industrial flue gases has been an increasing concern. One attempt is utilizing the tail part of an SCR unit to oxidize abundant CO and trace “slip NH3” synergistically. Herein, Ru/Cu-SSZ-13 was developed to conduct the oxidation of CO and the selective catalytic oxidation of NH3 (NH3-SCO) simultaneously and showed 10 times higher reaction rates than Ru/SSZ-13 on both oxidations. The RuO2 (110) surface was highly active for CO oxidation and NH3 dehydrogenation but would turn insensitive due to the accumulation of adsorbed NO species (NOcus), which derived from the peroxidation during NH3 dehydrogenation. With the assistance of Cu-SSZ-13, generated NOcus could be consumed in an internal SCR route conducted by the activated Cu2+/Cu+ redox cycle, which made NOcus available for the NH3 preferential oxidation rather than the blocked reactive surface. Also, it promoted NH3 transformation on the Cu-SSZ-13 side and boosted the regeneration of Ru-active sites from occupation by NOcus to enable simultaneous CO oxidation. Therefore, the reactivity of RuO2 was boosted after minimizing the interference between the transformation paths of CO and NH3. Furthermore, due to the high NH3-SCO sensitivity of Ru/Cu-SSZ-13, the trace “slip NH3” can be preferentially removed from CO-rich flue gas.

Tunable Redox Cycle and Enhanced π-Complexation in Acetylene Hydrochlorination over RuCu Catalysts

“…Generally, the desorption temperature of TPD profiles reflects the adsorbed species' binding strength on the catalyst surface, and the peak area correlates with the amount of adsorbed species. 12,38,42 For the C 2 H 2 -TPD, the desorption temperatures were almost the same for the four catalysts (approx. 300 °C), indicating that the different valence states of Cu had little effect on the bonding strength between the catalyst and C 2 H 2 , instead of enhancing the adsorption capacity for C 2 H 2 (Table S5).…”

“…The distinct peaks in the range of 300−450 °C for RuCu/ AC can be attributed to the reduction of Cu(II) → Cu(I) → Cu(0). 42 As presented in the inset in Figure 2c, with the addition of Cu, the temperature of the reduction bands of Ru (from 100 to 103, 105, and 108 °C) increased slightly, demonstrating that the reduction of the Ru species on the RuCu/AC catalysts was more difficult in comparison with that of the Ru species on the Ru/AC catalyst. Compared with Cu(II) and Cu(0), Cu(I) increased the reduction temperature of the Ru species to the greatest extent, indicating that Cu(I) has an inhibitory effect on Ru reduction.…”

“…Hydrogen temperature-programed-reduction (H 2 -TPR) experiments were carried out to investigate the effect of Cu valence changes on the reducibility of the Ru species (Figure c). The distinct peaks in the range of 300–450 °C for RuCu/AC can be attributed to the reduction of Cu­(II) → Cu­(I) → Cu(0) . As presented in the inset in Figure c, with the addition of Cu, the temperature of the reduction bands of Ru (from 100 to 103, 105, and 108 °C) increased slightly, demonstrating that the reduction of the Ru species on the RuCu/AC catalysts was more difficult in comparison with that of the Ru species on the Ru/AC catalyst.…”

“…Three peaks were observed at 931.4, 933.1, and 934.6 eV (Figure d), corresponding to Cu(0), Cu­(I), and Cu­(II) . The peaks centered at 461.1, 463.9, and 465.7 eV are assigned to Ru(0), Ru­(III), and Ru­(IV) (Figure e), respectively. ,, Note that the conversion efficiency of Cu­(II) to Cu­(I) could not reach 100% after regulating the Cu valence state. The RuCu­(I)/AC catalyst still contained a small amount of Cu­(II), which had little effect on the results.…”

Review of the application of Cu-containing SSZ-13 in NH3-SCR-DeNOx and NH3-SCO

“…115 On the other hand, the enhanced activity of bifunctional catalysts was reported, with single examples given as mixed, dual-layer and hybrid layer designs composed of Pt/Al 2 O 3 and Cu-SSZ-13, 196–198 or Ru/Cu-SSZ-13. 199 Similar to Cu-containing SSZ-13 applied in NH 3 -SCR-DeNO x , also the catalysts applied in NH 3 -SCO lost their activity after poisoning, e.g. , with P 96,105 (Fig.…”