Catalysts for the Fischer-Tropsch synthesis (FTS) have been studied at conditions close to what is commonly used in the industrial process using a wide range of in situ techniques (XAS, XRD, ASAXS, FT-IR, Raman). The combination of techniques allows for probing both electronic and structural perturbations in the catalysts leading to changes in activity. We discuss characterization of the FTS catalysts during activation, reaction and initial deactivation. We have used a set-up for combined in situ XAS/XRD/Raman catalyst characterization able to operate at 20 bar pressure and high temperatures while simultaneously monitoring the catalyst activity. X-ray absorption spectroscopy (XAS) is a powerful technique to probe local structure, electronic transitions and chemical evolution of catalytic systems. The collection of this information, contained in different parts of the spectrum, can be extracted by different kinds of data treatment. The in situ set-up has been used for modulation enhanced XAS where the catalysts are being exposed to periodic changes in reaction environment. Such in situ experiments generate a large amount of data which require new strategies for data analysis. Thus, multivariate curve resolution (MCR) has been applied to large data sets from in situ X-ray absorption spectroscopy experiments. The results show that the information extracted from MCR goes well beyond the information from conventional XAS experiments. The information obtained from in situ XRD and Raman is complimentary to XAS. A rapid 2D CMOS detector allows for XRD acquisition on the same time-scale as for XAS (5-10 sec). Additional measurements using in situ ASAXS and FT-IR on the same catalysts at similar conditions provides comprehensive information on the state of catalysts during Fischer-Tropsch synthesis. The combination of these techniques allows all involved catalyst phases to be monitored at the different stages of the process.

Fischer-Tropsch synthesis catalysts: Strategies to enhance the sensitivity of in situ characterization techniques

251st National Meeting (2016)

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