(82b) Scaling Fixed-Bed Catalyzed Processes

The heart of a chemical process is its reactor.  The fixed-bed reactor is a popular reactor for a process using a solid catalyst.  The reasons for that popularity are

• ease of separating catalyst from reactant and solvent;
• ease of catalyst loading;
• ease of catalyst regeneration or recharging;
• ease of identifying catalyst location (the catalyst is in the reactor --- or should be).

Traditionally, space velocity has been used to scale fixed-bed reactors.  Unfortunately, space velocity leads to disparate flow regimes with regard to laboratory, pilot plant, and commercial plant reactors.  Thus, the rate constants measured for each reactor scale reflects a different mass transfer controlling rate.  Many commercial fixed-bed reactors are pore diffusion rate limited while, for the same solid catalyst, the laboratory reactors may be stagnant film diffusion rate limited.

This paper advocates using flow regime as the scaling parameter for fixed-bed catalyzed processes rather than space velocity.  The model and mathematics necessary for this advocacy are discussed.