Selective reduction of NO{sub x} by methane on Co-ferrierites

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1994.1356· OSTI ID:47982

Li, Yuejin; Armor, J N ^[1]

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1. Air Products and Chemicals, Inc., Allentown, PA (United States)

Cobalt-exchanged ferrierite zeolite catalysts were found to be very active (about twice the activity compared to Co-ZSM-5) for the selective reduction of NO{sub x} with CH{sub 4}. The presence of oxygen (gaseous O{sub 2} or O atoms via N{sub 2}O decomposition) greatly enhanced the NO{sub x} conversion to N{sub 2}. In the absence of O{sub 2}, NO{sub 2} can be effectively reduced with CH{sub 4}, but its conversion decreased with increasing temperature at T > 500{degrees}C with a formation of small amount of O{sub 2}. Temperature programmed desorption measurement show that the presence of O{sub 2} alters the NO adsorption/desorption on Co-ferrierite, yielding an additional, high-temperature NO desorption peak. Partial pressure dependencies were measured as a function of reaction temperature under both dry and wet conditions. In the absence of added H{sub 2}O vapor, the empirical reaction order with respect to NO (0.2 to 0.4) increased with increasing temperature with no change in the reaction order for CH{sub 4} (0.7). Addition of H{sub 2}O vapor (2%) significantly increased the empirical reaction orders with respect to both NO (0.7) and CH{sub 4} (0.8-0.9). Under wet conditions, the reaction orders are higher at lower temperatures. The added H{sub 2}O vapor also substantially raised the apparent activation energies for both NO reduction and CH{sub 4} combustion. The turnover frequencies for both reactions increased with increasing Co{sup 2+} level, demonstrating the heterogeneity of the Co{sup 2+} sites. The differences in activity and selectivity and in the distribution of active sites between Co-ferrierite and Co-ZSM-5 may be related to the different channel systems of these two zeolites. 26 refs., 11 figs., 5 tabs.

• OSTI ID: 47982
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 150; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
40 CHEMISTRY
ACTIVATION ENERGY
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
COBALT OXIDES
COMBUSTION
METHANE
NITROGEN OXIDES
SELECTIVE CATALYTIC REDUCTION
ZEOLITES