545758 MOF-Mediated Synthesis of Highly Active Fe- and Co-Based FTS Catalysts

Tuesday, June 4, 2019: 11:51 AM
Texas Ballroom EF (Grand Hyatt San Antonio)
Freek Kapteijn1, Giusy Petty1, Christian van der Sande1, Patricia S Garcia Guerrero1, Lide Oar-Arteta1, Tim A. Wezendonk1, Xiaohui Sun1 and Jorge Gascon2, (1)Catalysis Engineering, Department of Chemical Engineering, Delft University of Technology, Delft, Netherlands, (2)KAUST Catalysis Center, Advanced Catalytic Materials, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia

Metal Organic Frameworks are well-defined crystalline porous hybrid structures with an excellent distribution of inorganic and organic building blocks. Many examples contain elements that are active in catalysis, including Fe and Co, well-known high and low temperature Fischer-Tropsch synthesis (FTS) catalysts, respectively.

Subjecting these specific MOFs to a thermal treatment in inert atmosphere, called MOF-mediated synthesis (MOFMS), causes decomposition, pyrolysis, reduction and particle growth phenomena resulting in a composite of nanosized oxidic or metallic particles covered by graphenic shells. The metal loadings may reach up to 60 wt.% [1]. Depending on the inorganic element the thermal decomposition, followed by in-situ XRD and TGA, can be described by a single- or a two-step solid conversion process, well captured by the Avrami-Erofeev nucleation models with as most relevant parameters heating rate and final temperature.

Fe-MOF precursors yield nanoparticles of Fe-suboxide encapsulated by a porous carbon shell. When exposed to the reducing FTS environment Fe-carbide is formed. Temperature and gas composition can be used to form the Hägg and/or epsilon carbide.

The Fe-loading (36–46 wt%) and nanoparticle size (3.6–6.8 nm) of the obtained Fe@C catalysts are directly related to the elementary composition and porosity of the initial MOFs. Furthermore, the carbonization leads to similar surface areas for the C matrix (SBETbetween 570 and 670 m2g-1), whereas the pore width distribution is completely different for the various MOFs. Comparison of different Fe-MOF precursors shows that the high temperature FTS activity is proportional to the external particle surface. Promotion with alkali elements boosts the activity and increases the olefin/paraffin selectivity considerably. The catalytic performance @ 340 oC, stable >600 h, results in iron time yields (FTY) in the range of 1.9–4.6·10-4molCOgFe-1s-1. In combination with the high Fe-loading these materials represent extreme highly active catalysts on a mass or volume basis [2-5].

This material, however, is not easy to pelletize, and these pellets disintegrate quickly. A procedure based on phase-inversion of a slurry of the MOF precursor and a selected polymer, followed by pyrolysis results in robust catalyst particles. Interestingly, the nitrogen stemming from the polymer already exerts a promotion influence on the selectivity of the catalyst.

A similar approach using a Co-MOF precursor (ZIF-67), yielded metallic Co nanoparticles covered with an impermeable graphene coating. This was nearly inactive for low temperature FTS. Adaptation of the synthesis procedure towards an oxidative treatment after impregnation with a silicon precursor and pyrolysis, yielded an extremely active LT-FTS catalyst consisting of highly loaded cobalt nanocomposites (~ 50 wt.% Co, ~12 nm Co), with cobalt oxide reducibility in the order of 80% and a good particle dispersion, that exhibit high activity, C5+selectivity and stability in Fischer–Tropsch synthesis [6]. The structure of this material resembles that envisaged as optimal for this process, while the activity is about 30% of the maximum reachable for a pure Co catalyst of the optimal particle size [7].


  1. Oar-Arteta, T. Wezendonk, X. H. Sun, F. Kapteijn, J. Gascon, Materials Chemistry Frontiers 2017,1, 1709-1745.
  2. P. Santos, T.A. Wezendonk, et al., Nat. Commun. 6:6451, doi:10.1038/ncomms7451 (2015).
  3. A. Wezendonk, X. H. Sun, A. I. Dugulan, A. J. F. van Hoof, E. J. M. Hensen, F. Kapteijn, J. Gascon, Journal of Catalysis 2018, 362, 106-117.
  4. A. Wezendonk, Q. S. E. Warringa, V. P. Santos, A. Chojecki, M. Ruitenbeek, G. Meima, M. Makkee, F. Kapteijn, J. Gascon, Faraday Discussions 2017, 197, 225-242.
  5. A. Wezendonk, V. P. Santos, M. A. Nasalevich, Q. S. E. Warringa, A. I. Dugulan, A. Chojecki, A. C. J. Koeken, M. Ruitenbeek, G. Meima, H.-U. Islam, G. Sankar, M. Makkee, F. Kapteijn, J. Gascon, ACS Catalysis 2016, 6, 3236-3247.
  6. Sun, A. I. O. Suarez, M. Meijerink, T. van Deelen, S. Ould-Chikh, J. Zecevic, K. P. de Jong, F. Kapteijn, J. Gascon, Nat Commun 2017, 8:1680, doi:10.1038/s41467-017-01910-9
  7. Guttel, T. Turek, Energy Technology 2016, 4, 44-54.

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