Adsorption heterogeneous

Another study examined the NH3 and CO2 adsorption heats on several zirconia catalysts, differing in their preparation procedure and/or in the addition of dopants [46]. The differential heats of NH3 and CO2 adsorption show a wide range of variability, displaying either a plateau of constant heat or a continuous decrease indicative of adsorption heterogeneity [12]. The ratio between the number of the basic and acidic sites, Ub/ua, was calculated for each catalyst from the microcalorimetry results, by dividing the amount of adsorbed CO2 by the amount of adsorbed NH3. These catalysts were used to produce alk-l-ene from 4-methylpentan-2-ol. Alk-1-ene selectivity was found to first increase with the b/Wa ratio, reach a maximum and then decrease, whereas ketone formation continuously increased, being negligible for low Ub/ua values. 

A principally different method is based on thermal desorption. In it the temperature of an adsorbent-adsorbate sample is steadily raised and the desorption rate of the adsorbate is measured. The resulting graph is interpreted in the parameters of the adsorption heterogeneity of the surface. The method seems promising for problems of our interest, though to the best of our knowledge, it has not yet been used to study systems like ours. 

Zeolites, which are a well-known class of molecular sieves and have been proposed in the past for several industrial applications (ion exchange, adsorption, heterogeneous catalysis), are also investigated, but their storage capacity remains not satisfactory also at 77 K [135]. 

The adsorption/heterogeneous impedance ZadMet) is given according to Pilla [1970] ... 

Processes in fuel-cell systems typically involve complex multi-step reactions that can proceed along several parallel reaction pathways, for example, adsorption, heterogeneous reactions at interfaces, and bulk and surface transport. In the case of advanced electrodes, neither of these reaction steps dominates the overall cell characteristics. The extent to which the various steps contribute to cell performance is governed by their complex dependence on each other and also on the particular... 

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