Low temperature hydrocracking of n-heptane over Ni-supported catalysts:: study of global kinetics

Two kinetic models were applied to n-heptane hydrocracking on a Ni-Re/ZSM-5 catalyst over a wide range of operating experimental conditions (temperature = 433-493 K, and pressure = 760 mm Hg). In the first model, the hydrogen is adsorbed on the catalyst surface without dissociation, while the second model assumes hydrogen dissociation. Both models assume that the adsorption follows Langmuir isotherm. The molecular hydrogen associated with an active site is most likely involved in the C-C bond rupture, which is concluded to be the rate controlling step in this work. The extracted intrinsic kinetics were estimated via the derivation of the reactor model. The apparent activation energy for n-heptane cracking is found to be 83 kJ/mol. Both models describe well the n-heptane consumption rate. The simulation results revealed that the hydrogen adsorption constant is smaller than the n-heptane adsorption constant. (C) 2001 Elsevier Science B.V. All rights reserved.