Pentane isomerization and disproportionation catalyzed by sulfated zirconia promoted with iron and manganese

Fe- and Mn-promoted sulfated zirconia was used to catalyze the conversion of n-pentane in a flow reactor at temperatures in the range of -25 to 40 degrees C and n-pentane partial pressures in the range of 0.005 to 0.01 atm. The rates of reaction increased with time on stream during an induction period and then decreased rapidly. The predominant reaction at -25 degrees C and short times on stream was isomerization to give isopentane; no dibranched products were observed. The selectivity for isomerization decreased and that for disproportionation increased with increasing temperature, with disproportionation becoming predominant at 40 degrees C; the principal product was then isobutane. The product distribution data are consistent with acid-base catalysis and carbocation intermediates. However, there appears to be more to the reaction mechanism than acid-base chemistry, and the roles of the iron and manganese promoters are not yet explained.