Page 189 - Principles of Catalyst Development

CATALYST CHARACTERIZATION 177
co

Mass Flow
Controllers
Solenoid
Shut-off
Valves
Check Valv·u

Intake Manil'old
& Mixing Chamber

To Analysis (Strearn 1)

Mass Flow
Controllers
Solenoid
Shut-off
Valves
Check Valvl!s

To Preheater
Figure 7.32. Equipment for the control of multiple reaCl:Ors.

In the differential mode, conversion is maintained at low values of less
than 5%, while initial concentrations are varied over as wide a range as
possible. Under these conditions

(7.25)
rate = XA ( ~) CAO

and postulated rate equations are checked directly. Complex rate equations
adapt welI to this procedure, but low conversions require good analytical
precision.
Precautions must be taken to ensure that external or pore diffusion
resistance is not significant. This may be done either by calculation, as
discussed in Chapter 1, or with experimentation in whi<:h conversion is
checked against linear velocity and particle size. It is also wise in making