The CO adsorption and subsequent reaction with preadsorbed NOx on Pd and K cosupported Mg-Al mixed oxides (Pd-K/MgAlO, 1/8/100 w/w) were investigated using in situ FTIR spectroscopy. During CO adsorption, a peculiar and well-defined IR band at 2160 cm-1 was observed. Several elaborately designed experiments such as the competitive adsorption of CO and CO2 demonstrated that the 2160 cm-1 band was exclusively assigned to a carbonyl species on K sites due to the CO spillover from Pd to K, which results from a strong Pd-K interaction based on temperature-programmed reduction with H2 experiments. Importantly, the spillover of CO is found to be involved in the reduction of preadsorbed NOx from temperature-programmed surface reactions with CO. Thus, all adsorbed NO x can be reduced by CO before desorption. Like the process of "pumping" CO by Pd from the atmosphere to "irrigate the field" of the nitrates/nitrites, the adsorbed NOx at not only K sites adjacent to Pd but also at the remote K sites can be reduced into N 2 and N2O effectively.
ASJC Scopus subject areas
- Environmental Chemistry