n-Butane isomerization over Cs-salts of H3PW12O40: a mechanistic study by 1C MAS NMR Original Research Article

Reaction mechanism of skeletal isomerization of n-butane over Cs2.5H0.5PW12O40 catalyst was studied using 13C MAS NMR. The reaction proceeds mainly via a monomolecular mechanism at 80 °C. The contribution of the bimolecular mechanism becomes more significant as the reaction temperature is increased to 150 °C. Hydrogen suppresses the bimolecular mechanism, in particular on Pt-promoted Cs2.5H0.5PW12O40 catalyst. The latter catalyst is highly selective to isobutane in the presence of H2 even at 220 °C. The kinetics of the monomolecular isomerization reaction and the reaction schemes of 13C scrambling and n-butane isomerization are discussed.