1-HEXENE ISOMERIZATION ON A PT GAMMA-AL2O3 CATALYST - THE DRAMATIC EFFECTS OF FEED PEROXIDES ON CATALYST ACTIVITY/

During 1-hexene (P-c = 31.7 bar; T-c = 231 degrees C) isomerization on a Pt/gamma-Al2O3 reforming catalyst, the formation of hexene oligomer s in the bulk fluid causes catalyst deactivation with time. Organic pe roxides present in the 1-hexene feed stock are responsible for the for mation of these oligomers. With 130 ppm peroxides in the feed, the cat alyst undergoes total deactivation in about 10 hours at subcritical co nditions (281 degrees C, 1 bar and 135 g hexene/h/g cat.). The deactiv ation rate is reduced at supercritical operating conditions due to the ability of supercritical reaction media to solubilize and extract the se oligomers from the catalyst surface. When the feed peroxides are vi rtually eliminated prior to introduction into the reactor (by pretreat ment with activated alumina and by simultaneous deoxygenation of the f eed), nearly constant isomerization activity is observed with about 45 % hexene conversion to isomers at subcritical conditions, and about 65 % conversion at supercritical conditions (281 degrees C, 70 bar). Duri ng an extended 42 hour run at supercritical conditions, catalyst activ ity was nearly constant with neither measurable coke laydown nor surfa ce area/pore volume losses in the spent catalyst.