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4063649 
Journal Article 
Light-off curve of catalytic reaction and kinetics 
Duprat, F 
2002 
Yes 
Chemical Engineering Science
ISSN: 0009-2509 
Elsevier 
57 
6 
901-911 
WOS:000175028300001 
The light-off curve is the conversion-temperature plot of a catalytic reaction; it is usually used in catalyst development. The possibility to deduce kinetic information such as the apparent reaction order or mass transfer limitation from the shape of the curve is examined here. The light-off plots obtained by numerical simulation with several different rate equations are compared between themselves and with experimental curves. This is illustrated with the oxidation of carbon monoxide and methane on noble metal catalysts with different degree of mass transfer resistance. The comparison is complemented with the Arrhenius plots, i.e. the logarithm of the apparent rate constant versus the reverse of temperature.



From the shape of the curves, the three following situations can be discriminated: first-order kinetics, negative first-order kinetics in the absence or in the presence of external mass transfer limitation. The range of diffusional limitation is well defined for negative-order reaction. However, the mass transfer resistance is difficult to evidence for first-order reaction. It is observed that the Lanamuir-Hinshelwood reaction kinetic model is not convenient to represent the effect of strong external transport limitation on a reaction in the regime of reactant inhibition (negative apparent reaction order). (C) 2002 Published by Elsevier Science Ltd. 
reaction engineering; catalyst; kinetics; mass transfer; light-off plot