Hydrocarbon synthesis from CO$z.sbnd;H2 on supported iron: Effect of particle size and interstitials

Relationship between Iron Carbide Phases (ε-Fe2C, Fe7C3, and χ-Fe5C2) and Catalytic Performances of Fe/SiO2 Fischer–Tropsch Catalysts

“…It is also reported that the size can influence the iron phase structures and selectivity. , For example, Raupp et al considered that larger particles tended to form χ-Fe 5 C 2 , whereas smaller ones formed a less stable ε′-carbide. McDonald et al concluded that ε′-Fe 2.2 C was easier to form in small particles than χ-Fe 5 C 2 , and small particles exhibited lower H 2 adsorption uptake. Wezendonk et al found that the carbide phase evolved in a sequence of ε-Fe 2.2 C → χ-Fe 5 C 2 → θ-Fe 3 C with the particle size increasing from 2.5 to 28.4 nm when the calcination temperature increased from 400 to 900 °C during pyrolysis of Fe-BTC.…”

“…This is in agreement with previous works. 53,71,72 McDonald et al 71 found that the fraction of C 2+ increased with increasing content of ε′-carbides. Pour et al 72 suggested that the order of Fe−C bond strength is ε′carbides < χ-carbides, and the surface carbons on the ε′carbides are more easily hydrogenated to form hydrocarbons.…”

Active and Selective Bifunctional Catalyst for Gasoline Production through a Slurry-Phase Fischer−Tropsch Synthesis

“…This also suggested that MCM-22 zeolites have a higher external surface area. A larger surface area of support promotes well dispersion of active metal species loaded, which may affect the formation of light hydrocarbon products . It was also suggested that the small crystal zeolite support enhances the extent of secondary acid-catalyzed reactions …”

Hard X‐ray Nanotomography of Catalytic Solids at Work

“…Recently, detailed physicochemical studies [26] have shown that the surface areas of Fe 3 O 4 and FeC x control the conversion rates, irrespective of the residual iron oxides, and those catalysts with high yields towards olefins have better reduction and carburization properties. Boudart and co-workers [27] already found a relationship between the iron particle size and its selectivity, indicating that large iron particles were more active for methane production showing lower selectivity for C 2+ . It is very likely that FeC x is formed as soon as Fe 3 O 4 is in contact with syngas, but in our experiments the FeC x crystallites could be too small to be readily detected by TXM, although already visible in the bulk XRD measurements.…”

“…With increasing time on stream the FeC x crystallites become bigger and/or increase in their amount, which goes hand in hand with an increasing selectivity towards methane as well as a decreasing CO conversion. Boudart and co-workers [27] already found a relationship between the iron particle size and its selectivity, indicating that large iron particles were more active for methane production showing lower selectivity for C 2+ . Our TXM and catalytic performance data confirm these observations by Boudart and co-workers, which were based on CO titration experiments of pretreated Fe-based FTO catalysts.…”