Catalytic Test Reactions Information on Pore Geometry

5 Catalytic Test Reactions Information on Pore Geometry 

The initial reaction used by Mobil (the results of which are quoted in most of their patents of new materials) is the competitive cracking of an equimolar mixture of n-hexane and 3-methylpentane under standard conditions. In the 

The hydroisomerisation of -decane is one such test reaction where a modified constraint index Cl is defined as the ratio of the formation of 2-methylnonane to that of 5-methylnonane. Cl is found to increase over the range 1-10 as the pore size decreases from large to medium pore (for Y, Cl is ca. 1, whereas for ZSM-5, Cl is ca. 10). However, like Cl, it gives relatively little differentiation between large-pore zeolites, and explanation for the origin of the Cl values remains ambiguous. 

This index is found to be very sensitive to changes in pore size. For example, for zeolites Y and Beta, SI is around 20, but for ZSM-5 it is around 2. 

Combinations of these test reactions, and others like them, can therefore be used to indicate the likely pore geometry of a new microporous solid aeid and suggest its probable performance in reactions where shape seleetivity plays a controlling role. 

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