Rhodium catalysts Isotherms

Figure 2. Hydrogen adsorption and desorption Isotherms for rhodium catalysts. Solid lines denote total adsorption and dashed lines denote reversible adsorption. The meaning of symbols Is as follows ...

Fig. 4 Energy distribution function, (p(e t) (cmol/kJ/mol/), against the dimensionless product of the lateral interaction energy (P) and the local isotherm (0)P0, for carbon monoxide adsorption over a bimetalhc Pto.25-Rho.75 silica supported catalyst, at 698 K. Source From Gas chromatographic kinetic study of carbon monoxide oxidation over platinum-rhodium catalysts, in J. Chromatogr.

The catalyst surface areas were determined using the BET equation from the nitrogen isotherms at 77 K. The rhodium particle was characterized by X-ray diffraction (XRD, Rigaku,... 

If, however, conditions are chosen appropriately, rates are a linear fraction of amounts of hydrogen chemisorbed thus with platinum and rhodium on ceria, alumina and their mixtures, such a linear plot has been used as a means of estimating dispersion from activity measurement, this being a more sensitive and simple procedure than determining an adsorption isotherm. Thus after reduction at 1273 K, the dispersion of a platinum catalyst was estimated to be 3%. 

The slopes of the isotherms for the various substances are approximately identical in the central part and close to the slope of the hydrogen adsorption isotherm. On iridium the methanol adsorption isotherms are satisfedby the Freundlich equation, where the power in the equation of the isotherm is close to that in the isotherm for hydrogen adsorption on iridium. The adsorption isotherms for methanol and hydrogen on rhodium are the same in nature. These results lead to the conclusion that the dependence of 0 andc is determined not by the nature of the adsorbed substance but by the nature and character of inhomogeneity in the catalyst surface. 

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