n-pentane isomerization and disproportionation catalyzed by promoted and unpromoted sulfated zirconia

Isomerization and disproportionation of n-pentane were catalyzed by sulfated zirconia, Fe- and Mn-promoted sulfated zirconia, and Pt-, Fe-, and Mn-promoted sulfated zirconia in a flow reactor at temperatures of −25 to 50°C and n-pentane partial pressures of 0.005–0.01 atm. Incorporation of the Fe and Mn promoters increased the activity of the sulfated zirconia by two orders of magnitude at 50°C; addition of Pt to the latter catalyst increased the activity only slightly. The primary reactions, disproportionation (to give butanes and hexanes) and isomerization, occurred in parallel; secondary disproportionation reactions gave heptanes, propane, butanes, and pentanes. The data are consistent with acid-base catalysis and carbenium ion intermediates, and the isomerization is inferred to proceed both by unimolecular and bimolecular mechanisms. H2 in the feed stream and Pt in the catalyst both led to reductions in the rate of catalyst deactivation.