Abstract
(n)MnOx–(1−n)CeO2 binary oxides have been studied for the sorptive NO removal and subsequent reduction of NOx sorbed to N2 at low temperatures (≤150 °C). The solid solution with a fluorite-type structure was found to be effective for oxidative NO adsorption, which yielded nitrate (NO− 3) and/or nitrite (NO− 2) species on the surface depending on temperature, O2 concentration in the gas feed, and composition of the binary oxide (n). A surface reaction model was derived on the basis of XPS, TPD, and DRIFTS analyses. Redox of Mn accompanied by simultaneous oxygen equilibration between the surface and the gas phase promoted the oxidative NO adsorption. The reactivity of the adsorbed NOx toward H2 was examined for MnOx–CeO2 impregnated with Pd, which is known as a nonselective catalyst toward NO–H2 reaction in the presence of excess oxygen. The Pd/MnOx–CeO2 catalyst after saturated by the NO uptake could be regenerated by micropulse injections of H2 at 150 °C. Evidence was presented to show that the role of Pd is to generate reactive hydrogen atoms, which spillover onto the MnOx–CeO2 surface and reduce nitrite/nitrate adsorbing thereon. Because of the lower reducibility of nitrate and the competitive H2–O2 combustion, H2–NO reaction was suppressed to a certain extent in the presence of O2. Nevertheless, Pd/MnOx–CeO2 attained 65% NO-conversion in a steady stream of 0.08% NO, 2% H2, and 6% O2 in He at as low as 150 °C, compared to ca. 30% conversion for Pd/γ–Al2O3 at the same temperature. The combination of NOx-sorbing materials and H2-activation catalysts is expected to pave the way to development of novel NOx-sorbing catalysts for selective deNOx at very low temperatures.
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References
M. Machida, in Catalysis, Vol. 15 (The Royal Society of Chemistry, Cambridge, 2000) ch. 3.
H. Arai and M. Machida, Catal. Today 22 (1994) 97.
K. Tabata, H. Fukui, S. Kohiki, N. Mizuno and M. Misono, Chem. Lett. (1988) 799.
M. Machida, K. Yasuoka, K. Eguchi and H. Arai, J. Chem. Soc. Chem. Commun. 1165 (1990).
K. Eguchi, M. Watabe, S. Ogata and H. Arai, Bull. Chem. Soc. Jpn. 68 (1995) 1739.
K. Eguchi, M. Watabe, M. Machida and H. Arai, Catal. Today 27 (1996) 297.
S. Hodjati, P. Bernhardt, C. Petit, V. Pitchon and A. Kiennemann, Appl. Catal. B: Environ. 19 (1998) 209.
S. Hodjati, P. Bernhardt, C. Petit, V. Pitchon and A. Kiennemann, Appl. Catal. B: Environ. 26 (2000) 5.
M. Machida, S. Ogata, K. Yasuoka, K. Eguchi and H. Arai, Proc. Int. Cong. Catal., eds., L. Guczi, F. Solymosi and P. Tetenyi, (Elsevier: Amsterdam, 1993) p. 2645.
M. Machida, H. Murakami, K. Eguchi and H. Arai, J. Chem. Soc. Chem. Commun. (1995) 485.
M. Machida, H. Murakami and T. Kijima, J. Mater. Chem. 4 (1994) 1621.
M. Machida, H. Murakami, T. Kitsubayashi and T. Kijima, Chem. Mater. 8 (1996) 197.
M. Machida, H. Murakami, T. Kitsubayashi and T. Kijima, Chem. Mater. 9 (1997) 135.
M. Machida, H. Murakami, T. Kitsubayashi and T. Kijima, Appl. Catal. B: Environ. 17 (1996) 195.
M. Machida, D. Kurogi and T. Kijima, Chem. Mater. 12 (2000) 3158.
M. Machida, D. Kurogi and T. Kijima, Chem. Mater. 12 (2000) 3165.
M. Machida, A. Yoshii and T. Kijima, Int. J. Inorg. Mater. 2 (2000) 413.
F.G. Galasso, Structure and Properties of Inorganic Solids, (Pergamon, Oxford, 1970), p. 115.
M.F. Luo, X.X. Yuan and Z.M. Zheng, Appl. Catal. A: General. 175 (1998) 121.
CRC Handbook of Chemistry and Physics, 72nd Edn.; ed., D.R. Lide, (CRC Press, Boston, 1991).
Y. Hirao, C. Yokoyama and M. Misono, J. Chem. Soc. Chem. Commun. (1996) 597.
A. Ueda and M. Haruta, Appl. Catal. B: Environ. 18 (1998) 115.
K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 4th ed. (Wiley, New York, 1986).
J.W. London and A.T. Bell, J. Catal. 31 (1973) 32.
C.H. Rochester and S.A. Tppham, J. Chem. Soc. Faraday Trans. 75 (1979) 872.
G. Busca and V. Lorenzelli, J. Catal. 72 (1981) 303.
M.J.D. Low and R.T. Yang, J. Catal. 34 (1974) 479.
M. Machida, D. Kurogi and T. Kijima, J. Mater. Chem. 4 (2001) 1621.
N. Miyoshi, S. Matsumoto, K. Katoh, T. Tanaka, J. Harada, N. Takahashi, K. Yokota, M. Sugiura and K. Kasahara, SEA Paper (1995) 950809.
K.Y. Lee, M. Misono and K. Watanabe, Appl. Catal. B: Environ. 13 (1997) 241.
M. Machida, D. Kurogi and T. Kijima, Stud. Surf. Sci. Catal. 138 (2001) 267.
K. Yokota, M. Fukui and T. Tanaka, Appl. Surf. Sci. 121/122 (1997) 273.
B. Frank, G. Emig and A. Renken, Appl. Catal. B: Environ. 19 (1998) 45.
R. Burch and M.D. Coleman, Appl. Catal. B: Environ. 23 (1999) 115.
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Machida, M. NOx-Sorbing Metal Oxides, MnOx–CeO2. Oxidative NO Adsorption and NOx–H2 Reaction. Catalysis Surveys from Asia 5, 91–102 (2002). https://doi.org/10.1023/A:1015160919161
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DOI: https://doi.org/10.1023/A:1015160919161