Q.Describe some features of catalysis by zeolites.

Step 1. Zeolites are microporous, crystalline, hydrated aluminosilicates built from a three-dimensional framework of silicon and aluminium tetrahedra — there are roughly 50 known natural zeolites and about 150 synthetic ones.

Step 2. Because silicon is tetravalent (+4) but the aluminium that substitutes for some silicon atoms is only trivalent (+3), the overall zeolite lattice carries an extra negative charge, which must be balanced by extra-framework cations such as $\text{H}^+$ or $\text{Na}^+$ sitting within the pores.

Step 3. Zeolites carrying $\text{H}^+$ (protons) act as solid ACID catalysts and are extensively used in the petrochemical industry, most importantly for cracking heavy hydrocarbon fractions down into more valuable lighter products such as gasoline and diesel. Zeolites carrying $\text{Na}^+$ instead act as BASIC catalysts. …

Describe zeolites' structure (aluminosilicate framework, charge-balancing cations), their acid/basic catalytic character, and their …

Omitting shape selectivity, which is the single most distinctive and most commonly examined feature of zeolite catalysis, i …