Journal
APPLIED CATALYSIS B-ENVIRONMENTAL
Volume 101, Issue 3-4, Pages 598-605Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.apcatb.2010.10.034
Keywords
Hollandite-type manganese oxides; Selective catalytic reduction of NO; Ammonia; Semitunnel structured external surface; Active surface lattice oxygen
Funding
- Natural Science Foundation of China [20977018, 21077026]
- Natural Science Foundation of Shanghai [09ZR1402500]
- Foundation of Ministry of Education, China [20090071120005]
- Fudan's Undergraduate Research Opportunities Program
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Hollandite-type manganese oxides with K+ or H+ cations in the tunnels (K-Hol or H-Hol) were successfully synthesized and investigated in low-temperature selective catalytic reduction of NO by NH3. The results of the catalytic tests revealed that both K-Hol and H-Hol with almost same catalytic activities had much higher reaction rates than beta-MnO2 under the same conditions, and even at a high gas hourly space velocity of 160,000 h(-1), K-Hol obtained more than 90% conversions of NO in a wide temperature window of 100-300 degrees C. The high resolution transmission electron microscopy observations showed that both K-Hol and beta-MnO2 were tetragonal prism-shaped nanorods with same exposed {110} planes, and the atoms in the {110) planes of K-Hol arranged to form semitunnel structures, while the {110) planes of beta-MnO2 were relatively smooth surfaces. The temperature-programmed reduction by H-2 and thermal gravimetric analyses indicated that active surface lattice oxygen atoms of K-Hol were around 1.6% with respect to total lattice oxygen atoms. The transition reactions of NH3 demonstrated that K-Hol with special semitunnel structured surface and active surface lattice oxygen showed much stronger ability to efficiently adsorb and activate NH3 molecules than beta-MnO2. Hence, both efficient semitunnel structured external surfaces and high active surface lattice oxygen atoms predominantly accounted for the high catalytic activities. (C) 2010 Elsevier B.V. All rights reserved.
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