Nitrogen‐ and Oxygen‐Functionalized Multiwalled Carbon Nanotubes Used as Support in Iron‐Catalyzed, High‐Temperature Fischer–Tropsch Synthesis

Schulte, H.; Graf, Barbara; Xia, Wei; Mühler, Martin

doi:10.1002/cctc.201100275

Cited by 130 publications

(108 citation statements)

References 35 publications

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“…The initial catalytic activities, expressed as iron time yield (FTY; mol of CO converted to hydrocarbons per gram of Fe per second), and apparent turnover frequencies (TOF) of Fe@C samples are summarized in Table 4. Furthermore, relevant data from literature for other Fe-catalysts, containing different Fe loadings and supported on carbon nano-fibres 11 ('X-Fe/CNF', X: Fe loading) and oxidized carbon nano-tubes 36 ('20-Fe/O-CNT'), are included in the Table 4. The catalysts prepared by the MOFMS route display much higher FTY in comparison with X-Fe/CNT.…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts

et al. 2015

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Depletion of crude oil resources and environmental concerns have driven a worldwide research on alternative processes for the production of commodity chemicals. Fischer-Tropsch synthesis is a process for flexible production of key chemicals from synthesis gas originating from non-petroleum-based sources. Although the use of iron-based catalysts would be preferred over the widely used cobalt, manufacturing methods that prevent their fast deactivation because of sintering, carbon deposition and phase changes have proven challenging. Here we present a strategy to produce highly dispersed iron carbides embedded in a matrix of porous carbon. Very high iron loadings (440 wt %) are achieved while maintaining an optimal dispersion of the active iron carbide phase when a metal organic framework is used as catalyst precursor. The unique iron spatial confinement and the absence of large iron particles in the obtained solids minimize catalyst deactivation, resulting in high active and stable operation.

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Section: Synthesis and Characterizationmentioning

confidence: 99%

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts

et al. 2015

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“…To put into perspective, the productivity of lower olefins as chemicals precursors is maximized with the best KFe@C catalysts, obtaining 50-90% of olefins in the C 2 -C 5 range with CO 2 -free selectivity over 53% without showing deactivation after 80 h. As discussed, deactivation was only observed for Nfunctionalized Fe@C catalysts, although this apparent relationship seems somewhat counterintuitive. For example, in studies on Fe/CNT for use as FTS catalysts, N-functionalization is often used to enhance the anchoring of Fe particles in the CNTs, thus increasing their activity and stability [46][47] . Furthermore, the increased addition of N groups to the support often decreases the CH 4 selectivity in FTS over these N-doped carbons 48 .…”

Section: Catalytic Testingmentioning

confidence: 99%

Structural and elemental influence from various MOFs on the performance of Fe@C catalysts for Fischer–Tropsch synthesis

et al. 2017

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The structure and elementary composition of various commercial Fe-based MOFs used as precursors for Fischer–Tropsch synthesis (FTS) catalysts have a large influence on the high-temperature FTS activity and selectivity of the resulting Fe on carbon composites. The selected Fe-MOF topologies (MIL-68, MIL-88A, MIL-100, MIL-101, MIL-127, and Fe-BTC) differ from each other in terms of porosity, surface area, Fe and heteroatom content, crystal density and thermal stability. They are re-engineered towards FTS catalysts by means of simple pyrolysis at 500 °C under a N2 atmosphere and afterwards characterized in terms of porosity, crystallite phase, bulk and surface Fe content, Fe nanoparticle size and oxidation state. We discovered that the Fe loading (36–46 wt%) and nanoparticle size (3.6–6.8 nm) of the obtained 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 (SBET between 570 and 670 m2 g−1), whereas the pore width distribution is completely different for the various MOFs. The high catalytic performance (FTY in the range of 1.9–4.6 × 10−4 molCO gFe−1 s−1) of the resulting materials could be correlated to the Fe particle size and corresponding surface area, and only minor deactivation was found for the N-containing catalysts. Elemental analysis of the catalysts containing deliberately added promoters and inherent impurities from the commercial MOFs revealed the subtle interplay between Fe particle size and complex catalyst composition in order to obtain high activity and stability next to a low CH4 selectivity.

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“…1−3 A catalyst for the selective production of C 2 − C 4 olefins from synthesis gas that has been previously reported consists of iron nanoparticles dispersed on an inert support material. 1,2 The Fischer−Tropsch reaction is recognized as a structuresensitive reaction 4,5 which means that the catalytic performance is strongly related to the particle size of the metal or active phase. The effect of metal particle size has been extensively studied for cobalt 6−10 and ruthenium.…”

Section: ■ Introductionmentioning

confidence: 99%

Iron Particle Size Effects for Direct Production of Lower Olefins from Synthesis Gas

et al. 2012

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ABSTRACT:The Fischer−Tropsch synthesis of lower olefins (FTO) is an alternative process for the production of key chemical building blocks from non-petroleum-based sources such as natural gas, coal, or biomass. The influence of the iron carbide particle size of promoted and unpromoted carbon nanofiber supported catalysts on the conversion of synthesis gas has been investigated at 340−350°C, H 2 /CO = 1, and pressures of 1 and 20 bar. The surface-specific activity (apparent TOF) based on the initial activity of unpromoted catalysts at 1 bar increased 6−8-fold when the average iron carbide size decreased from 7 to 2 nm, while methane and lower olefins selectivity were not affected. The same decrease in particle size for catalysts promoted by Na plus S resulted at 20 bar in a 2-fold increase of the apparent TOF based on initial activity which was mainly caused by a higher yield of methane for the smallest particles. Presumably, methane formation takes place at highly active low coordination sites residing at corners and edges, which are more abundant on small iron carbide particles. Lower olefins are produced at promoted (stepped) terrace sites that are available and active, quite independent of size. These results demonstrate that the iron carbide particle size plays a crucial role in the design of active and selective FTO catalysts.

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Nitrogen‐ and Oxygen‐Functionalized Multiwalled Carbon Nanotubes Used as Support in Iron‐Catalyzed, High‐Temperature Fischer–Tropsch Synthesis

Cited by 130 publications

References 35 publications

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts

Structural and elemental influence from various MOFs on the performance of Fe@C catalysts for Fischer–Tropsch synthesis

Iron Particle Size Effects for Direct Production of Lower Olefins from Synthesis Gas

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