Selective Catalytic Reactions at the External Surface of Zeolite Crystals

The arrangement of the pore openings serves as a template for the positions of the branchings in the isomerization of n‐alkanes—this is the explanation proposed by Martens et al. (Angew. Chem. Int. Ed. Engl. 1995, 34, 2528) to rationalize their results in the isomerization of n‐heptadecane on the zeolite ZSM‐22. This reaction would thereby be the first example of key–lock catalysis on the external surface of a zeolite.