Hydrogasification of coke in heptane reforming over Pt-Re/Al2O3

We reported previously that coke can indiscriminately deposit on the metal, acid, and already-coked sites on a Pt-Re/Al2O3 reforming catalyst. Here we show that the thus-deposited coke, when still in a freshly formed state, can be indiscriminately gasified by hydrogen at temperatures as low as 477 degreesC. Once the freshly formed coke transforms into a more refractory form, it cannot be gasified by hydrogen. The kinetics of coke hydrogasification is first order with respect to both the concentration of the freshly formed coke and hydrogen partial pressure, with an apparent activation energy of 9.2 kcal/mol. A random coke deposition model offers a theoretical basis for correlating the decoking data.