NOx storage during H2 assisted selective catalytic reduction of NOx reaction over a Ag/Al2O3 catalyst

The effect of temperature and transient addition of H2 on the NOx–SCR reaction was investigated over a 2-wt.% Ag/Al2O3 catalyst using isotopically labelled 15NO. The addition and removal of hydrogen had a marked effect on the nitrogen balance at temperatures ranging from 245 to 400 °C. At a low temperature (245 °C), the addition of hydrogen resulted in the storage of NOx, whereas, the reverse was true at 400 °C, where NOx was stored upon removal of hydrogen from the feed. The transient NOx storage effect could be harnessed to allow continuous high NOx conversion with intermittent hydrogen addition. In particular, an average NOx conversion of 79% could be achieved during transient experiments in which H2 was switched in and out of the feed in 6-s intervals at 300 °C.