ABSTRACT
Catalytic reactions are frequently conducted under conditions in which only the outer periphery of the catalyst particle functions actively. This means that the interior (frequently any portion below the outer 1000 angstroms) is catalytically of little or no value. It also is true that the site of catalytic action, which is in the lower reaches of the pores, is frequently where the objectionable by-products form and unwanted side reactions take place. As a consequence, it may be highly desirable that a relatively impervious core be coated with a thin layer (a few micrometers thick) of the catalytic material. There are also highly porous, low surface area fused supports in which the pores are quite large and can themselves be coated and because of their size will permit easy egress and ingress of the catalytic reactants.
