In situ studies on a working catalyst: Direct evidence for an important deactivation route in the Fischer Tropsch synthesis followed by AP-XPS

BORONDICS F.; JIANG P.; RODRIGUEZ C. E.; PACH E.; GIOVANETTI L.; BLUHM H.; SALMERON M.

Bariloche

Workshop; Segundo Workshop de Usuarios Argentinos de Técnicas de Luz Sincrotrón; 2013

Instituto Balseiro ? Centro Atómico Bariloche

Heterogeneous catalysis is a particularly important field for the industry as catalysts are heavily used in a broad range of applications. Naturally, process optimization is crucial for lowering costs and increasing reaction yields, thus a very strong link exists between industry and fundamental research in the field. To minimize the factors that can introduce artifacts in the research models it is important to consider the catalyst reactants-product system in an integrated manner, and reproduce working conditions as close as possible to the actual industrial catalytic reaction environment. To date numerous studies have been reported on FT catalysts trying to optimize the conditions for production of hydrocarbons, alcohols and other organic products by investigating the reaction mechanism. Optical methods such as infrared and Raman spectroscopy or methods that are based on hard x-rays are ideal because of high penetration power and thus the possibility of in situ experiments. However, soft x-ray investigations always rely on secondary evidences, because of the need for ultra high vacuum. Thus, the reliability of data is often less reliable than that of provided by in situ experiments. Thus, in situ methods should be favored in catalysis research. In this article we report on the behavior of a polycrystalline Cobalt surface under Fischer-Tropsch (FT) conditions followed by ambient pressure X - Ray photoelectron spectroscopy (AP-XPS). Our findings reinforce some reports that have been published previously based on data obtained from ex situ experiments and confirm the conclusions drawn from infrared spectroscopy studies on working catalysts. Furthermore, comparing the low and high photon energy measurements it is clear that the thin surface layer of graphitic and amorphous carbon can be easily overlooked in studies done with regular laboratory based XPS instruments since even at a photon energy as low as 1000eV the Co2p region shows metallic state of the surface.