Strategies and methods for the investigation of chemical reaction
kinetics
Chemical Engineering Science, 54 (11):
1639-1647 (1999/6 1999)TY - JOUR.Abstract
The qualitative theory of differential equations has been used to
analyze strategies and methods for kinetic investigations. For the
investigation of chemical reaction kinetics one needs not necessarily
the mechanism of the reactions, but must develop a mathematical function
(e.g. hyperbolic or power laws) which, based on experimental results,
can present or interpret the experimental data at best in the range
of experiments. With this function the design and analysis of a chemical
reactor operating at steady state can be carried on; errors in simulation
should be the same as with the so called mechanistic kinetics. Compared
with experimental data obtained from a polythermal or an adiabatic
reactor, isothermal experimental data are at the least sensitive
to wrong models. Kinetics and transport parameters in reactor model
determined separately from laboratory data under isothermal conditions
can be used together only with caution to simulate another type of
reactors because the Lipschitz constants for different reactor models
are different (e.g. a polythermal or an adiabatic reactor model has
a larger Lipschitz constant than an isothermal reactor model) and
epsiv (errors due to the limited accuracy of instruments and the
use of an ideal reactor model as well as the errors lumped in parameters)
from an isothermal reactor model may be enlarged. Furthermore, the
number of system equations for a polythermal or an adiabatic reactor
model is increased by one (enthalpy balance) compared to that of
an isothermal reactor system. The simulation results of a polythermal
or an adiabatic reactor will therefore be much more sensitive to
the kinetic model derived from an isothermal reactor and might deviate
from real systems. It is recommended therefore that some polythermal
or adiabatic experiments should be performed for the investigation
of kinetic models and process scale-up. These conclusions are theoretically
supported and illustrated with an example. To simulate the dynamic
behavior of reactors and to develop or discriminate catalysts, mechanistically
based kinetics should be more useful.