Activation energy Carbon monoxide Desorption

Potentiometric techniques have been used to study autonomous reaction rate oscillations over catalysts and carbon monoxide oxidation on platinum has received a considerable amount of attention43,48,58 Possible explanations for reaction rate oscillations over platinum for carbon monoxide oxidation include, (i) strong dependence of activation energy or heat of adsorption on coverage, (ii) surface temperature oscillations, (iii) shift between multiple steady states due to adsorption or desorption of inert species, (iv) periodic oxidation or reduction of the surface. The work of Sales, Turner and Maple has indicated that the most... 

Carbon dioxide and hydrogen also interact with the formation of surface formate. This was documented for ZnO by the IR investigation of Ueno et al. (117) and, less directly, by coadsorption-thermal decomposition study (84). Surface complex was formed from C02 with H2 at temperatures above 180°C, which decomposed at 300°C with the evolution of carbon monoxide and hydrogen at the ratio CO Hs 1 1. When carbon dioxide and hydrogen were adsorbed separately, the C02 and H2 desorption temperatures were different, indicating conclusively that a surface complex was formed from C02 and H2. A complex with the same decomposition temperature was obtained upon adsorption of formaldehyde and methanol. Based upon the observed stoichiometry of decomposition products and upon earlier reported IR spectra of C02 + H2 coadsorbates, this complex was identified as surface formate. Table XVI compares the thermal decomposition peak temperatures and activation energies, product composition, and surface... 

Table 2 Activation energies (kJ moP ) corresponding to the adsorption, Eai. desorption, E -i, and disproportionation reaetion, 2, of carbon monoxide over silica-supported Pt, Rh, and Pto.5o-Rho.5o alloy catalysts...

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