Non-Noble Metal-Loading for Catalysis

Non-noble metals such as Ni, Co, Mo, W, Fe, Ag and Cu have been added to zeolites for use in catalysis. In addition to CO, nitric oxide (NO) has been shown to be a good adsorbate for probing the electronic environment of these metals. When NO chemisorbs on these metals, it can form mononitrosyl (M-NO) and dinitrosyl species (ON-M-NO). The monontrosyl species has a single absorption band and the dinitrosyl species has two bands due to asymmetric and symmetric vibrational modes of the (ON-M-NO) moiety. Again, there have been many studies reported in the literature on the use of NO and/or CO adsorption on non-noble metals supported on zeolites and they are too numerous to list here. Several examples have been selected and summarized to provide the reader with the type of information that can be provided by this method. 

The adsorption of NO and CO has been used to characterize the properhes of Co in Co-exchanged zeoHtes [148-151]. NO is a selective probe for Co and CO is selective for Co species. Datka and coworkers used the combination of CO and NO adsorption IR to quantitahvely determine the concentration of Co as an oxide and the Co present as in exchange positions, oxide-like clusters, and cobalt oxide in a series of Co-exchanged ZSM-5 and ferrierite (PER) zeolites [151]. They established conditions under which the CO and NO would react selectively with the various types of sites and estabhshed absorphon coefficients for the quanhtative calculations. Differences in the distributions of the various forms of Co species were found to be dependent on both the structure and framework Si/Al of the zeolite. 

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