Selective catalytic reduction of NO with CH4 over cobalt-exchanged cage-based, small-pore zeolites with different framework structures

Selective catalytic reduction of NO with CH4 (CH4-SCR) has been studied over divalent cobalt ions exchanged into four cage-based, small-pore zeolites with different framework topologies, i.e., Co-CHA, Co-RTH, Co-UFI, and Co-LTA with similar Si/Al and Co/Al ratios (10-11 and 0.44 - 0.49, respectively). The catalytic results obtained are compared with those of Co-ferrierite, one of the most active catalysts for this reaction. While the CH4-SCR activity of all zeolite-supported cobalt catalysts decreases under wet conditions, the activity of Co-CHA is least affected by water vapor, thereby outperforming Co-ferrierite. More interestingly, a decrease in Si/Al ratio of its support from 10 to 6 gave a NO conversion to N-2 of 90 % at 773 K under wet conditions. The overall characterization results of this study demonstrate that both the framework topology and composition of zeolite supports are critical factors determining the intrazeolitic Co2+ ion locations and thus their CH4-SCR activity.