Iron/manganese oxide catalysts for fischer-tropsch synthesis

A Mössbauer study of In–Fe2O3/HZSM-5 catalysts for the selective catalytic reduction of NO by methane

“…From the comparison of this behavior with the results of Topsøe et al, 26 Lund et al 21 and Gao et al 27 in their studies on magnetite-supported lead, silica-supported magnetite and titania-supported magnetite, it is suggested that the iron cations in octahedral sites in the first reduction stage of the In-Fe 2 O 3 /HZSM-5(I) catalyst were substituted by indium cations, resulting in the decrease in S. After the sample was treated at 630 C, the spectrum showed a doublet with parameters typical of high-spin Fe 2+ in tetrahedral vacancies, 16,28,29 a typical sextuplet of a-Fe and a singlet which possibly resulted from the small particles of metallic iron. 30,31 Since pure wustite is thermodynamically unstable at room temperature, 22,32 and the interaction between indium oxide and iron oxide was weak in the In-Fe 2 O 3 /HZSM-5(I) catalyst, the existence of stable ferric cations was apparently caused by the interaction between the iron oxide and the HZSM-5 support. From Table 3 it can be seen that, at the end of the TPR process, 51.5% Fe 0 was found, implying that 48.5% Fe 2+ could not be reduced due to the strong interaction between Fe 2+ and the HZSM-5 support.…”

CO Hydrogenation to Light Alkenes Over Mn/Fe Catalysts Prepared by Coprecipitation and Sol-gel Methods

“…The morphology of the samples with high manganese contents were different from those of the samples with low Mn contents, which has been identified by TEM. For instance, it can be seen from the TEM image in figure 3 (right) that there are some long and narrow cubic crystals in sample CP-4, which were attributed to cubic Mn 2 O 3 [20] or cubic (Mn, Fe) 2 O 3 [18]. Figure 3 (left) shows the TEM result of sample CP-2, in which no cubic crystal can be found.…”

“…For the pure iron samples of CP-0 and SG-0, the three hydrogen consumption peaks of I (represents the first initial reduction peak), M (represents the second peak in the medium temperature range) and H (the last peak in the region of high temperature) could be considered as the reduction from Fe 2 O 3 to Fe 3 O 4 [21,22], from Fe 3 O 4 to FeO and from FeO to Fe [20], respectively. In the case of small manganese amount (below 4 mol.%) added by means of coprecipitation, the whole H 2 -TPR profiles shift to the low temperature field.…”

Stabilization of iron by manganese promoters in uniform bimetallic FeMn Fischer–Tropsch model catalysts prepared from colloidal nanoparticles

“…Mn is widely used as the promoter of choice for iron FTS catalysts, particularly when used for producing lower olefins. [10][11][12] It has also been reported that manganese acts not only as a chemical promoter to alter the chemisorption of the reactants on the catalyst but also as a structural promoter to enhance dispersion of active iron and to stabilise the catalyst during the FTS process. [13][14][15] Stabilising the catalysts in their active state for a longer time is often an important challenge and understanding how structural promoters enhance catalyst stability is of great importance.…”