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 epsilon (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.