Highly selective catalytic reduction of NO by H{sub 2} over Au{sup 0} and Au(I) impregnated in NaY zeolite catalysts
- Hokkaido Univ., Sapporo (Japan)
The NO-H{sub 2} reaction has been studied over Au{sup 0}/NaY and Au(I)/NaY catalysts, which were prepared by the mechanical mixing of AuCl{sub 3} with NaY zeolite and by the monolayer dispersion of Au(I) species into NaY zeolite, respectively. The precursor samples were reduced in flowing hydrogen at 423 K. The NO-H{sub 2} reaction over these catalysts took place at relatively low temperatures under isothermal conditions from 373 to 673 K. The Au(I)/NaY catalysts were more active toward the above reaction compared with the Au{sup 0}/NaY catalysts. The NO selectivity was pointed to the N{sub 2} and N{sub 2}O formation, with the former catalysts being more selective to N{sub 2}. In situ FT-IR study of the NO-H{sub 2} reaction compared with the Au{sup 0}/NaY catalysts. The NO selectivity was pointed to the N{sub 2} and N{sub 2}O formation, with the former catalysts being more selective to N{sub 2}. In situ FT-IR study of the NO-H{sub 2} reaction on the gold catalysts demonstrated that NH{sub 3} was detected in the adsorbed NH{sub 4}{sup +} form at 1440 cm{sup -1}, along with N{sub 2}O at 2240 (2220) cm{sup -1} and H{sub 2}O at 1645 cm{sup -1}. Two characteristic bands due to the vibrations of N-O bond is adsorbed NO were identified. The bands at 1880 cm{sup -1} in the spectra of Au{sup 0}/NaY were assigned to Au{sup n+}-NO (n{approx}0) complexes, and the corresponding bands at 1910 cm{sup -1} in the spectra of Au(I)/NaY were assigned to Au{sup n+} NO (n=1) complexes in cages of zeolite. It was proposed that N{sub 2}O and NH{sub 3} formed simultaneously at low to moderate temperatures (<500 K) by the addition of N atom to NO and H atoms, respectively. The presence of adsorbed N atoms was confirmed by the coadsorption of NO/CO/H{sub 2} mixture onto Au(I)NaY at 423 K, where a band at 2280 cm{sup -1} ascribed to isocyanate [NCO] intermediate was developed intensively with time. This band did not deliver when mixture of NO/CO was admitted alone to the IR cell.
- OSTI ID:
- 494268
- Journal Information:
- Journal of Catalysis, Vol. 162, Issue 2; Other Information: PBD: 1 Sep 1996
- Country of Publication:
- United States
- Language:
- English
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