Page 195 - Principles of Catalyst Development

CATALVST CHARACTERIZATION 183
the temperature. Catalyst A is better than B because it gives identical
conversion at lower temperatures. This is the most dangerous of all practical
methods. Catalyst C may not reach the specified conversion within limits
of the apparatus. It is tempting to extrapolate as shown. This could be
misleading, since kinetics may change at higher tempt:ratures. Also, if
compensation effects exist, curves for A and B cross, and opposite con-
clusions result depending on the conversion level used. Although useful for
limited temperature ranges, this method has no kinetic :,ignificance. It is
often used to follow deactivation in pilot plants.

7.6. SOME FINAL THOUGHTS

We have seen that a large number of techniques exist to characterize
catalyst properties and measure activities. Not all of these will be useful in
a given application. The experimenter must be discriminating and select
the tests that yield the most information with accuracy, speed, and economy.
To do this, it is necessary to know precisely the objective,: of the investiga-
tion, the capabilities and limitations of each technique, and the expected
value of the results.