Page 37 - Principles of Catalyst Development
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STRUCTURE OF CATALYSTS
What They Contain
2.1. CATALYST ENGINEERING
The ability to engineer desired functions into particles is perhaps the ultimate
achievement of the catalyst designer. In many cases, direct and obvious
procedures are sufficient; in others, more subtle and innovative measures
are called for. Although catalyst designs tend to evolve slowly as process
experience accumulates, anticipating future problems will decrease develop-
ment time.
In this chapter, we examine the architecture or structure of the catalyst;
what it contains and why.
2.2. THE BALANCED PARTICLE-A COMPROMISE
Correct formulation of the catalyst is a compromise between good fluid
flow, activity, and stability. The relative importance of these factors depends
upon the reaction, reactor design, process conditions, and economics. In
Fig. 2.1, these are represented as three sides of a triangle to emphasize
mutual dependence and interaction.
Good flow distribution and low pressure drop are achieved through
proper selection of the shape and size of the particle, (34) mechanical strength
during manufacture. (35) These are questions of formulation-making the
particle-and must be matched to demands of the process for which the
catalyst is intended. Generally, the greater the severity of process conditions
(e.g., heavier feedstocks, higher temperatures and pressures, larger space
velocities) the greater these demands become. For example, the preferred
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