Kinetics on a supported catalyst at supercritical, nondeactivating conditions

Intrinsic kinetic parameters are reported for the Pt/gamma-Al2O3 catalyzed geometric isomerization of 1-hexene (P-c = 29.7 bar; T-c = 231 degrees C) u nder conditions of steady catalyst activity. Deaerating the hexene feed, pr etreating it in a bed of activated alumina to reduce the peroxide impuritie s to 2 ppm or less, and passivating the reactor surface (by silicosteel coa ting) reduce the formation of hexene oligomers (coke precursors) by about a n order of magnitude. This, in conjunction with operation at supercritical conditions (235-304 degrees C, 35-70 bar), results in steady isomerization activity with no measurable coke laydown. Arrhenius plots of rate constants , estimated from the steady isomerization rates, yield an intrinsic activat ion energy of roughly 109 kJ/mol. This value is up to twofold greater than those reported for similar reaction systems, but on a deactivating catalyst s. Our results confirm that optimum conditions that maximize catalyst activ ity and effectiveness factor exist in the near-critical region-with catalys t activity and effectiveness factor.