Voronov, Alexey; Tsakoumis, Nikolaos E.; Hammer, Nina; van Beek, Wouter; Emerich, Hermann; Roenning, Magnus

Catalysis Today (2014), 229, 23-33 CODEN: CATTEA; ISSN: 0920-5861. English.

A rhenium-promoted Co/Al2O3 catalyst and a sample containing Re/Al2O3 were studied using XAS measured at both rhenium LIII (10,535 eV) and K (71,676 eV) edges. Results obtained from both sets of expts. are consistent and demonstrate that the higher penetration power of the X-rays at the Re K edge is a viable option that gives less stringent requirements in the choice of reactor material and x-ray window material. The in situ cell used at the high-energy Re K edge is conveniently of the same dimensions and material as a typical lab-scale fixed-bed reactor. Catalyst performance from such measurements can be directly compared to the results from conventional fixed-bed catalytic expts. High energy X-rays are thus an attractive option for in situ studies of catalysis at demanding conditions. Both sets of expts. (Re K and LIII edges) indicate that Re is atomically distributed inside the bulk Co particles. The results indicate a local distortion of the Co environment in intimate contact with the Re atoms, which may contribute to the observed increase in catalytic activity for the Re promoted catalysts. A minor fraction of Re (approx. 15%) remains in an oxidic state after a typical reduction procedure for Co-based Fischer-Tropsch synthesis catalysts.