Reaction kinetics and reactor modelling in the design of catalytic reactors for automotive exhaust gas abatement

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>The tightening environmental legislation and technological development in automotive engineering form a challenge in reactor design of catalytic reactors for automotive exhaust gas abatement. The catalytic reactor is the heart of the exhaust aftertreatment processes, but it can be seen also just as one subsidiary part of vehicles.</p><p>The aim of this work is to reveal applicable kinetic models to predict behaviour of the particular catalysts and to establish guidelines for modelling procedures and experimentation facilitating catalytic reactor design, especially in the field of automotive exhaust gas abatement. </p><p>The studies in this thesis include catalyst kinetics with synthetic exhaust gas composition in stoichiometric and net oxidative conditions, DRIFT measurements, and the warm-up of three-way catalysts in real conditions.</p><p>Knowledge on surface concentrations facilitates kinetic model construction and discrimination. For example, identification of even semi-quantitative surface concentrations may lead to a successful falsification of incorrect kinetic model candidates. Especially, that is clearly seen in cases where models predict the same kind of gas phase behaviour but different kinds of surface concentration profiles. </p><p>The transient kinetic experiments could give a hint on predominant reaction mechanism, support quantifying of the adsorption capacity and reveal the impact of surface phenomena on reactor dynamics. </p><p>The level of model complexity should be adapted depending on the purpose of the model. For example, it is mostly convenient for reactor design purposes to perceive only one type of active sites even in a case of mechanical mixture of different catalytic materials; whereas the optimisation of catalyst content demands the management of every prominent site type separately. Or, when a catalytic material has been selected, the stationary kinetic model is, in most cases, adequate for the catalytic converter design and structural optimization for warm-up conditions. </p></div>