HYDROISOMERIZATION OF N-HEXANE ON PT SO42--ZRO2 - EFFECT OF TOTAL ANDHYDROGEN PARTIAL-PRESSURE/

The effect of both total pressure and hydrogen partial pressure during the n-hexane isomerization on Pt/SO42--ZrO2 at 200 degrees C and 4 h( -1) weight hourly space velocity was studied. Total pressure was varie d between 1.0 and 10.0 kg cm(-2); different hydrogen partial pressures were obtained by dilution with nitrogen keeping the total pressure at 6 kg cm(-2). The n-hexane isomerization activity increases when incre asing either total pressure or hydrogen partial pressure. Methylpentan es are the C-6 isomers formed in major proportion and the 2-methylpant ane/3-methylpentane ratio practically reaches the equilibrium value in most of cases. Isomerization is always accompanied by hydrocracking. Hydrogenolysis products were not observed, the main cracking products being propane, isobutane and isopentane; then, the cracking product di stribution cannot be interpreted by considering an intramolecular rear rangement of carbocation intermediates. A slight deactivation takes pl ace with time-on-stream. The lifetime of surface intermediates is long er in the absence of hydrogen or at a low hydrogen partial pressure; i t allows oligomerization and cracking to prevail at short times and po lymerization and coke formation at long times.