15 research outputs found
Eluciating reaction mechanisms based on transient thin-zone temporal analysis of products (TAP) data: the Y-procedure approach
Activation of Vanadium Phosphorus Oxide Catalysts for Alkane Oxidation. The Influence of the Oxidation State on Catalyst Selectivity
New method for studying the pyrolysis of VPE/CVD precursors under vacuum conditions. Application to trimethylantimony and tetramethyltin
New method for studying the pyrolysis of VPE/CVD precursors under vacuum conditions. Application to trimethylantimony and tetramethyltin. [Erratum to document cited in CA116(6):44934a]
The Y-procedure methodology for the interpretation of transient kinetic data: analysis of irreversible adsorption
Shadowing effect in catalyst activity : experimental observation
The influence of the spatial distribution of catalyst particles in a fixed bed reactor on the observed reaction rates has historically been of central interest in catalysis and chemical physics. Results from both fields suggest that the apparent catalyst activity is determined by the distance between active particles and transport phenomena, although a universal understanding of their combined influence remains incomplete. In this study, pulse experiments under contrasting transport regimes show that a given amount of catalyst particles exhibits higher activity with increasing degrees of separation. This is attributed to a shadowing effect induced by the competition between closely neighboring active particles, which limits their combined apparent activity. Experimental results also suggest the dependence of this effect on mass transport phenomena within the reactor space
Momentary Equilibrium in Transient Kinetics and Its Application for Estimating the Concentration of Catalytic Sites
We
describe the novel concept of momentary equilibrium (ME), a special
event during a pulse-response transient experiment in which the non-steady-state
rates of adsorption and desorption of a probe molecule are instantaneously
balanced. In the absence of other reactions, any system with reversible
adsorption will always pass through ME during a pulse-response experiment
with effusion. We also suggest a new method for measuring the concentration
of adsorption sites on heterogeneous catalysts and the corresponding
equilibrium constant by observing momentary equilibrium in thin-zone
temporal analysis of products (TZTAP) pulse-response experiments with
modulated pulse intensity. The suggested method employs reversible
adsorption of probe molecules, contrary to traditional methods of
counting adsorption sites which utilize irreversible reactions