Abstract
Skeletal isomerization of n-heptane to clean gasoline can be catalyzed by solid acids such as zeolites, sulfated zirconia, heteropoly compounds, and WO3/ZrO2 and their Pt or Pd-modified catalysts (bifunctional catalysts). The catalytic properties of these catalysts for isomerizations of n-butane and n-pentane are generally reviewed. The activation steps of alkane and factors influencing the activity and selectivity are discussed. Our study on the reaction mechanism for the isomerization of n-butane using 13C-n-butane is interpreted. The bimolecular mechanism is the main contributor on solid acid catalysts (sulfated zirconia and Cs2.5H0.5PW12O40). In contrast, the monomolecular mechanism is predominant over the bifunctional catalysts in the presence of H2. The reaction pathways of n-heptane isomerization are presented and the characteristics of this reaction are discussed. Recent reports and our data for the isomerization of n-heptane are summarized and discussed. Pt-Cs2.5H0.5PW12O40/SiO2 and Pd-H4SiW12O40/SiO2 are comparable to Pt-H-β in selectivity to branched heptanes and the latter heteropoly catalyst has superior activity.
