Isomerization of cis-2-butene and trans-2-butene catalyzed by acid- and ion-exchanged smectite-type clays

Two commercial acid-activated montmorillonites (F24 and F124) were exchanged with different cations (Al3+, Cr3+, Fe3+, and Ni2+). The catalytic activity of the acid- and the ion-exchanged clays was measured using the isomerization of cis- and trans-2-butene at 300 °C to yield the corresponding isomers. The order of activity for the acid- and the different cation-exchanged forms was: acid clays >Al3+≈Ni2+>Cr3+>Fe3+, which slightly correlated with the acidity values determined by cyclohexylamine desorption and the d001 spacing obtained from integral series of reflections. The maximum conversion for the isomerization of cis-2-butene was ≈75% for F24 and F124, while the maximum conversion for the isomerization of trans-2-butene was ≈53% for F24 and F124. Cracking produced propylene and methane and their amounts increased with the acidity.