TY - JOUR
T1 - Effect of reductants in N2O reduction over Fe-MFI catalysts
AU - Nobukawa, Takeshi
AU - Yoshida, Masanori
AU - Okumura, Kazu
AU - Tomishige, Keiichi
AU - Kunimori, Kimio
N1 - Funding Information:
A part of this research was supported by the Research Institute of Innovative Technology for the Earth (RITE) and a Center of Excellence Grant-in-aid for the 21st Century COE Program for Frontiers from the Ministry of Education, Culture, Sports, Science and Technology. This work was performed under the approval of the Photon Factory Advisory Committee (Proposal No. 2003G255). The authors are grateful to the Chemical Analysis Center, University of Tsukuba, for ICP analysis of Fe-MFI catalysts.
PY - 2005/1/25
Y1 - 2005/1/25
N2 - We investigated the effect of reductants over ion-exchanged Fe-MFI catalysts (Fe-MFI) based on the catalytic performance in N2O reduction in the presence and absence of an oxygen atmosphere. In the case of N2O reduction with hydrocarbons (CH4, C2H 6, and C3H6) in the presence of excess oxygen, the order of N2O contribution was as follows: CH4 > C2H6 > C3H6. This indicates that CH4 is a more efficient reductant than C2H6 and C3H6. The TOFs of N2O decomposition and the N2O reduction by various reductants (H2, CO, CH 4) in the absence of oxygen increased with increasing Fe/Al ratio (Fe/Al≥0.15), wheras the TOFs were lower and constant in the range of Fe/Al≤0.10. Temperature-programmed reduction with hydrogen (H 2-TPR) showed that the catalysts with a higher Fe/Al ratio were reduced more easily than those with a lower Fe/Al ratio. Temperature-programmed desorption of O2 (O2-TPD) showed that oxygen was desorbed at lower temperatures over the catalysts with a higher Fe/Al ratio. As the result of extended X-ray absorption fine structure (EXAFS) analysis, only mononuclear Fe species were observed over Fe(0.10)-MFI after treatment with N2O or O2. On the other hand, binuclear Fe species and mononuclear Fe species were observed over Fe(0.40)-MFI after treatment with N2O or H2. More reducible Fe species, which gave lower-temperature O2 desorption, can be due to Fe binuclear species. Since the N2O reduction with reductants proceeds via a redox mechanism, the reducible binuclear Fe species can exhibit higher activity. Furthermore, CH4 can be oxidized by N2O more easily than can H2 and CO, although it is generally known that the reactivity of methane is very low.
AB - We investigated the effect of reductants over ion-exchanged Fe-MFI catalysts (Fe-MFI) based on the catalytic performance in N2O reduction in the presence and absence of an oxygen atmosphere. In the case of N2O reduction with hydrocarbons (CH4, C2H 6, and C3H6) in the presence of excess oxygen, the order of N2O contribution was as follows: CH4 > C2H6 > C3H6. This indicates that CH4 is a more efficient reductant than C2H6 and C3H6. The TOFs of N2O decomposition and the N2O reduction by various reductants (H2, CO, CH 4) in the absence of oxygen increased with increasing Fe/Al ratio (Fe/Al≥0.15), wheras the TOFs were lower and constant in the range of Fe/Al≤0.10. Temperature-programmed reduction with hydrogen (H 2-TPR) showed that the catalysts with a higher Fe/Al ratio were reduced more easily than those with a lower Fe/Al ratio. Temperature-programmed desorption of O2 (O2-TPD) showed that oxygen was desorbed at lower temperatures over the catalysts with a higher Fe/Al ratio. As the result of extended X-ray absorption fine structure (EXAFS) analysis, only mononuclear Fe species were observed over Fe(0.10)-MFI after treatment with N2O or O2. On the other hand, binuclear Fe species and mononuclear Fe species were observed over Fe(0.40)-MFI after treatment with N2O or H2. More reducible Fe species, which gave lower-temperature O2 desorption, can be due to Fe binuclear species. Since the N2O reduction with reductants proceeds via a redox mechanism, the reducible binuclear Fe species can exhibit higher activity. Furthermore, CH4 can be oxidized by N2O more easily than can H2 and CO, although it is generally known that the reactivity of methane is very low.
KW - EXAFS
KW - Fe binuclear
KW - Fe-MFI
KW - NO reduction
KW - Reductant
KW - Turnover frequency
KW - Wet ion-exchange
UR - http://www.scopus.com/inward/record.url?scp=13444293204&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=13444293204&partnerID=8YFLogxK
U2 - 10.1016/j.jcat.2004.11.009
DO - 10.1016/j.jcat.2004.11.009
M3 - Article
AN - SCOPUS:13444293204
VL - 229
SP - 374
EP - 388
JO - Journal of Catalysis
JF - Journal of Catalysis
SN - 0021-9517
IS - 2
ER -