PT SO42--ZRO2 - CHARACTERIZATION AND INFLUENCE OF PRETREATMENTS ON N-HEXANE ISOMERIZATION/

The n-hexane isomerization on Pt/SO42-ZrO2 was studied at 473 K and 6 bar. The catalyst was prepared by adding platinum to zirconium hydroxi de by the incipient wetness technique followed by dipping in 0.5 M sul furic acid solution. Before reaction, the material was calcined and re duced under different conditions. While reduction is unnecessary, the calcination step is very important because it changes the catalytic ac tivity level, The large increase in activity occurs by calcining at 77 3 K when the material begins to show crystalline structure in X-ray di ffraction patterns. The catalytic activity reaches the highest values for calcination between 803 ana 878 K, the selectivity to isomers bein g almost constant. The crystalline structure is not sufficient to gene rate an active material, and the catalytic activity is not proportiona l to the sulfur content and/or the total acidity, A minimum sulfur loa ding and sulfur species generated by calcination are necessary.