Which phenomenon causes decreased catalytic activity in zeolites with high aluminum content used in catalytic cracking?

💡 Explanation

When zeolites have high aluminum content, the isomorphic substitution of Si with Al creates charge imbalance, promoting formation of extra-framework aluminum species (EFAL) during reaction because EFAL lowers the catalytic activity. Therefore, EFAL formation decreases activity rather than dealumination, coking, or hydrophobicity changes, which have distinct conditions.

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