An in‐situ laboratory‐based X‐ray Absorption Near Edge Structure (XANES) Spectroscopy set‐up is presented, which allows performing long‐term experiments on a solid catalyst at relevant reaction conditions of temperature and pressure. Complementary to research performed at synchrotron radiation facilities the approach is showcased for a Co/TiO2 Fischer‐Tropsch Synthesis (FTS) catalyst. Supported cobalt metal nanoparticles next to a (very small) fraction of cobalt(II) titanate, which is an inactive phase for FTS, were detected, with no signs of re‐oxidation of the supported cobalt metal nanoparticles during FTS at 523 K, 5 bar and 200 h, indicating that cobalt metal is maintained as the main active phase during FTS.

The cobalt K‐edge X‐ray absorption near‐edge structure of a cobalt carbide compound, synthetized under in‐situ conditions, has been determined by using laboratory‐based and synchrotron‐based X‐ray absorption spectroscopy. We have carburized pure cobalt metal in‐situ, avoiding all adverse effects of metal‐support interactions as well as any degradation of the cobalt carbide formed. A non‐negative matrix factorization was applied to determine the features of the spectrum of cobalt carbide, highly needed to identify this phase in an unambiguous manner in cobalt‐based Fischer‐Tropsch catalysts.

A state-of-the-art operando spectroscopic technique is applied to Co/TiO catalysts, which account for nearly half of the world's transportation fuels produced by Fischer-Tropsch catalysis. This allows determination of, at a spatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra- and interparticular heterogeneities previously believed not to occur in particles under 200 μm. These heterogeneities are strongly dependent on changes in H /CO ratio, but also on changes thereby induced on the Co and Ti valence states. We have captured the genesis of an active FTS particle over its propagation to steady-state operation, in which microgradients lead to the gradual saturation of the Co/TiO catalyst surface with long chain hydrocarbons (i.e., organic film formation).

We present in-situ experiments to study the possible formation of cobalt carbides during Fischer-Tropsch synthesis (FTS) in a Co/TiO2 catalyst at relevant conditions of pressure and temperature.The experiments were performed using a combination of X-ray Raman scattering (XRS) spectroscopy and X-ray diffraction (XRD). Two different experiments were performed: (1) a Fischer-Tropsch Synthesis (FTS) reaction of a ~ 14 wt.% Co/TiO2 catalyst at 523 K and 5 bar under H2-lean conditions (i.e., a H2:CO ratio of 0.5) and ( 2) carburization of pure cobalt (as reference experiment). In both experiments, the Co L3-edge XRS spectra reveal a change in the oxidation state of the cobalt nanoparticles, which we assign to the formation of cobalt carbide (Co2C). The C K-edge XRS spectra were used to quantify the formation of different carbon species in both experiments.

Astate-of-the-art operando spectroscopic technique is applied to Co/TiO 2 catalysts,which account for nearly half of the worldst ransportation fuels produced by Fischer-Tropsch catalysis.This allows determination of,ataspatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra-and interparticular heterogeneities previously believed not to occur in particles under 200 mm. These heterogeneities are strongly dependent on changes in H 2 /CO ratio,but also on changes therebyi nduced on the Co and Ti valence states.W e have captured the genesis of an active FTS particle over its propagation to steady-state operation, in which microgradients lead to the gradual saturation of the Co/TiO 2 catalyst surface with long chain hydrocarbons (i.e., organic film formation).Heterogeneous catalytic reactions such as the Fischer-Tr opsch synthesis (FTS) of long-chain hydrocarbons are dynamic and complex, often comprised of inorganic (catalyst) and organic parts (reactants and products). Conventional and widely applied spectroscopic techniques often focus on either the organic part (e.g., vibrational spectroscopy) or on the inorganic part (e.g., X-ray spectroscopic techniques). The combination of both inorganic and organic information shows great promise to answer long-standing questions about complex catalytic reactions.T he FTS propagates through ac omplex surface polymerization process of adsorbed C 1 reaction intermediates derived from synthesis gas (a mixture of CO and H 2 ). [1][2][3][4][5][6][7] Cobalt-based FTS catalysts are an integral part of this gas-to-liquid (GTL) process because of their high wax selectivity and relatively high stability. [8,9] Theactivation and deactivation of these cobalt nanoparticles supported on an inorganic oxide,such as Al 2 O 3 or TiO 2 ,isbelieved to occur through am ultitude of mechanisms,h owever consensus in literature is often still lacking. While the literature is imbued with proposed deactivation mechanisms, [5,10,11] the equally interesting catalyst activation period is often overlooked. [12,13] During the day(s)-long activation or induction period (which is highly dependent on reaction conditions and the catalyst), FTS catalyst particles are believed to be gradually saturated by afilm of long-chain hydrocarbons,followed by pore filling through which further reactants must diffuse. [12,14,15] The complexity of the FTS process is also captured in the myriad of proposed deactivation mechanisms,w hich are generally related to the conversion of the active phase, considered as metallic cobalt, into an inert phase.F or example,cobalt reoxidation or carburization, [16,17] the formation of support oxide-cobalt species occurring through strong metal-support interactions (SMSI), [8,18,19] the loss of active cobalt surface area arising from crystalline growth (i.e., metal sintering), [11,[20][21][22] and finally fouling for example by hydrocarbon deposition in the form of various carbon species formed at the cob...