Transient SSITKA measurements

Although SSITKA measurements can be useful in studying reaction induction and deactivation, SSITKA transients (which may last from a few seconds to minutes depending on the catal3 t, reaction, and temperature) should be used where the rate of reaction during the collection of the transient data varies by only ca. 5%. Otherwise, interpretation may be more difficult. 

The greater activity of Pd for methanol decomposition reaction was also found by using the steady state isotopic transient kinetic analysis (SSITKA) method over noble metal (Pt, Pd, Rh)/ceria catalysts. Their activity increased in the order Rh < Pt < Pd, while the by-products were (i) methane, carbon dioxide, water, methyl formate and formaldehyde in most cases and (ii) ethylene and propylene, formed only over Rh/Ce02, at 553 K. SSITKA measurements indicated that two parallel pools exist for the formation of CO (via formation and decomposition of formaldehyde and methyl formate). The difference in the activity order of noble metal/ceria catalysts seems to correlate with the surface coverage of active carbon containing species, which followed the same order. The latter implies that a part of these species is formed on the ceria surface or/and metal-ceria interface. ... 

The effect of water on the Fischer-Tropsch synthesis over alumina-supported cobalt catalysts has been studied using isotopic transient kinetic methods (SSITKA) in combination with steady-state measurements. Water has been introduced to the catalytic system as a pretreatment procedure as well as under reaction conditions. The SSITKA results showed a decrease in the number of active surface sites, but no change in the specific site activity. 

Other useful information that can be extracted from SSITKA data using advanced mathematical analysis includes the reactivity distribution, f(k). On a heterogeneous catalyst surface, the active sites exhibit a non-uniform reactivity which can be characterised by a reactivity distribution function f(k), where k represents a measure of site activity. The determination of f(k) from the isotopic transient of P requires a numerical deconvolution technique. 

---