MODIFICATION OF SO42--ZRO2 AND PT SO42--ZRO2 PROPERTIES DURING N-HEXANE ISOMERIZATION/

The modification of the textural properties and crystalline structure of SO42--ZrO2 and Pt/SO42--ZrO2 during n-hexane reaction at 473 K and 6 kg cm(-2) has been studied in the presence of either hydrogen or nit rogen. Sulfur content before and after reaction and the amount of coke at the end of the reaction were measured. The coke deposited on the c atalysts blocks the pores of small size and decreases the surface area of the used catalysts. After regeneration, surface area is not comple tely restored. The loss of sulfur during reaction, probably associated to the reaction medium, also produces a decrease in surface area by t he collapse of the smallest pores which generates larger ones. The tra nsformation of tetragonal to monoclinic crystalline structure of zirco nia begins to occur when sulfur content drops below a critical value.