The Scale-Up Conundrum

FIGURE 2.1 Typical concentration profiles for a gas-liquid reaction. (Reproduced with permission from Doraiswamy and Sharma (1984). John WUey Sons Inc.) 

The process development starts at the laboratory level. For catalytic reactions, the first step obviously involves screening of various catalysts. Data on selectivity, activity, and life of the catalyst are acquired at this stage, typically approximately on gram level. Commercially available completely automated high-throughput screening 

In the absence of reasonable pilot-scale data, process designers tend to be conservative and substantial factors of safety are provided. At this stage, the dangers of overdesign need to be emphasized. As an example, consider a continuous flow 

A high scale-up factor in Table 2.1 reflects the ease in scahng up of the reactor. It can be seen that heterogeneons/mnltiphase reactors have substantially smaller scale-up factors than those for homogeneous systems. This is due to the complex nature of scale-dependent diffnsional processes (Section 2.4). 

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