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) under conditions of steady catalyst activity. Deaerating the hexene feed, pretreating it in a bed of activated alumina to reduce the peroxide impurities to 2 ppm or less, and passivating the reactor surface (by silicosteel coating) reduce the formation of hexene oligomers (coke precursors) by about an 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 activation energy of roughly 109 kJ/mol. This value is up to twofold greater than those reported for similar reaction systems, but on a deactivating catalysts. Our results confirm that optimum conditions that maximize catalyst activity and effectiveness factor exist in the near-critical region-with catalyst activity and effectiveness factor.