A Single-Event MicroKinetic model for the cobalt catalyzed Fischer-Tropsch Synthesis

The Single-Event MicroKinetic methodology has been successfully extended from Fe to Co catalyzed Fischer-Tropsch Synthesis. A total of 82 experiments were performed in a plug flow reactor with a H-2 to CO molar inlet ratio between 3 and 10, a temperature range from 483 to 503 K, CO inlet partial pressures from 3.7 to 16.7 kPa and space time varying between 7.2 and 36.3 (kg(cat) s) mol(-1). Via regression, statistically significant and physicochemically meaningful estimates were obtained for the activation energies in the model and the H, C and O atomic chemisorption enthalpies as required for the UBI-QEP method. A reaction path analysis allowed relating the observed deviations from the Anderson-Schulz-Flory distribution, i.e., a high methane and low ethene selectivity, to the symmetry numbers and a higher chemisorption enthalpy of the metal methyl species compared to the other metal alkyl species. Simulations at industrially relevant conditions show that, as a catalyst descriptor, the H atomic chemisorption enthalpy crucially determines both the CO conversion and the C5+ selectivity. The higher FTS activity of Co compared to Fe is explained via the higher oxygen atomic chemisorption enthalpy on the latter compared to the former. (C) 2016 Elsevier B.V. All rights reserved.