FT-IR Spectroscopic Studies of Catalysts

The role of FTIR speetroscopy in catalytic studies is briefly discussed and some typical examples are shown. IR spectra of weakly bound hydrogen on PtjSi02 reveal surface heterogeneity; The hydrogen concentration on the surface is described by a Temkin isotherm. Adsorption of unsaturated C6 ring compounds on hydrogen poor PtjSi02 is essentially a self'-hydrogenation process resulting in the formation of cyclohexane and carbon deposit on the metal surface. Chemisorption of n-hexane and benzene on hydrogen-rlch NijSi02 surface gives identical spectra under similar conditions. The same phenomenon is established for n-butane and benzene after chemisorption on the hydrogen-poor surface. The infrared and Raman spectra of C.H6 on NijSi02 suggested a symmetry Iowering somewhere between C6v and C3v because of the nonplanarity of C6H6and the site symmetry of the surface.