Hi Robert:
There are three principle catalyst structures: honeycomb, plate, and corrugated. Honeycomb-shaped catalysts are common in metal oxide and zeolite catalysts. A holed-honeycomb form provides a high level of surface area so active sites can maximize the reduction reaction.
Chemkin has a honeycomb monolith reactor model that will allow you to enter the structural properties of your catalyst- see below:



Hope this helps,
Best Regards,
Judy