β Scribed by Tapio Salmi
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Cieneralized mathematical models for coupled heterogeneous catalytic reactions consisting of elementary steps are presented. Arbitrary reaction schemes and several types of active sites are accounted for. Two ideal reactor models, a gradientless reactor with a continuously stirred gas phase and a plug flow-type fixed,bed reactor are considered. Transient simulations of six model reactions are carried out. Typical model reactmns are: Eley-Rideal mechanism, Langmuir-Hinshelwood mechanism, monomolecular decomposition and catalyst poisoning. The simulations are performed with an interactive computer program package. The responses of the reaction products give most information about plausible reaction mechanisms. The product responses are monotonously increasing or they pass through a maximum (an overshoot response), depending on the values of the kinetic constants of the elementary steps. Monotonously increasing responses are obtained mostly when the surface reaction and/or product desorption steps are slow. A very slow, S-formed response indicates a slow desorption step with stable surface intermediates.
An overshoot response can be obtained if the adsorption step is slow; a slow surface reaction can, however, also cause an overshoot response. The shape of the step response is determined not only by the kinetic parameters but also by the concentration levels in the gas phase and the initial state of the catalyst. The same types of step responses can be observed in both reactor types. the characteristic shape of the response is better preserved in the fixed bed reactor.
π SIMILAR VOLUMES
Transient model for packed bed non-catalytic reactors, which avoids many of the simplifying assumptions of the earlier models, has been developed. The model includes the effects of inter-and intra-pellet transfer resistances and the additional effects of axial dispersion in the bulk fluid. The solut
and time. A theoretical analysis yields that simplier control strategies, e.g. feedforward control, can be applied for without any loss of quality in the kinetic parameters provided that the catalyst deactivation is only of minor significance. A comparison of the kinetic parameters for the catalytic