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 Row reactor at temperatures of -25 to 50 degrees 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 degrees 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. H-2 in the feed stream and Pt in the catalyst both led to reductions in the rate of catalyst deactivation.