Noble metal-loading for catalysis

Kubelkova and coworkers studied the interaction of CO with platinum in a NaX zeolite [141]. They decomposed PtlNHj I]] on the zeolite under various conditions and observed distinct CO vibrational spectra for PtO-CO, Pt -CO, Pti -CO and [Pt(CO)2] complexes after CO adsorption at room temperature. Subsequent reduction with hydrogen resulted in characteristic particle size distributions with distinct CO vibrational frequencies depending on whether the clusters (-1.2 nm) were inside the supercages or outside the cages (-4.0nm). 

Sachtler and coworkers showed evidence of CO adsorption on monoatomic Pt with a CO vibrational frequency at 2123cm Hn H-MOR zeolite [142]. This band is shifted to significantly higher frequencies than the -2070 cm band that is typically observed for CO on multiatomic clusters. They proposed that these electron- 

The effect of crystallite size and shape of K-L zeolite on the dispersion of Pt was examined by a variety of techniques by Resasco and coworkers [143], They obtained multiple overlapping CO bands on these samples and were able to assign them to Pt clusters located inside the zeoHte pores ( 2050cm ), near the pore mouth (2050-2075 cm ) and outside the pores ( 2075 cm ). They were able to correlate high -octane aromatization activity with the K-L zeolite samples with short channels where most of the Pt is inside the pores. 

Bischoff and coworkers showed that there is a clear parhcle size dependent shift of the linearly absorbed CO stretching vibrational frequency on Pt supported in a zeolite [144]. They observed shift from 2055 cm for CO chemisorbed on 1-2 nm particles to 2070 cm for CO on 4—5nm particles. They correlated the frequency shift with the occurrence of higher indexed crystal planes for the smaller particles. 

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