Iron/Zirconia catalyst

F-T Catalysts The patent literature is replete with recipes for the production of F-T catalysts, with most formulations being based on iron, cobalt, or ruthenium, typically with the addition of some pro-moter(s). Nickel is sometimes listed as a F-T catalyst, but nickel has too much hydrogenation activity and produces mainly methane. In practice, because of the cost of ruthenium, commercial plants use either cobalt-based or iron-based catalysts. Cobalt is usually deposited on a refractory oxide support, such as alumina, silica, titania, or zirconia. Iron is typically not supported and may be prepared by precipitation. 

X. Carrier, P. Lukinskas, S. Kuba, L. Stievano, F. E. Wagner, M. Che, and H. Knozinger, The State of the Iron Promoter in Tungstated Zirconia Catalysts, Chem. Phys. Chem. 5, 1191-1199 (2004). 

For illustration, we may consider the preparation of a palladium/zirconia catalyst highly active for the oxidation of CO [4.47,71], the preparation of a copper/zirconia catalyst for the hydrogenation of C02 [4.23], and the preparation of iron/zirconia for ammonia synthesis [4.44]. 

Most feeds contain some olefin as an impurity moreover many sulfated zirconia catalysts contain traces of iron or other transition metal ions that are able to dehydrogenate hutane. In the presence of such sites, the olefin concentration is limited by thermodynamics, i.e a high pressure of H2 leads to a low olefin concentration. That aspect of the reaction mechanism has been proven in independent experiments. The isomerization rate over sulfated zirconia was dramatically lowered by H2. This effect is most pronounced when a small amount of platinum is deposited on the catalyst, so that thermodynamic equilibrium between butane, hydrogen and butene was established. In this way it was found that the isomerization reaction has a reaction order of +1.3 in -butane, hut -1.2 in hydrogen [40, 41]. The byproducts, propane and pentane, are additional evidence that a Cg intermediate is formed in this process. As expected, this kinetics is typical for butane isomerization only in contrast pentane isomerization is mainly a monomolecular process, because for this molecule the protonated cyclopropane ring can be opened without forming a primary carbenium ion [42]. 

Some conclusions can be drawn about the interaction of the iron-on-zirconia catalysts. In catalysts containing only iron, it is observed that while the first onset of reduction is equal in all samples, complete reduction is retarded in the catalysts prepared using the Engelhard support and with EDTA. Addition of potassium shifts the onset temperature of the initial reduction to temperatures about 100°C higher than in catalysts without potassium. This effect has been observed before [3]. 

XPS was used to determine the iron oxidation state and the dispersion of the applied iron phase of the iron-on-zirconia catalysts. As expected, iron was found to be in the trivalent state. Dispersion calculations (performed as published elsewhere [17]) indicated that no significant difference in dispersion was obtained when using either different precursors, or different supports, and whether or not applying a thermal pre-treatment. The iron oxide particle sizes calculated according to the procedure of Kuipers et a/. [18] range from 100 to 150A, which is smaller than found with XRD. This can be explained, however, when taking the specific sensitivities of XPS and XRD into account. 

Butene conversion of iron-on-zirconia catalysts ex citrate ( ), ex EDTA ( ) and on Engelhard support ( )... 

It was possible to prepare titania or zirconia-supported iron-potassium catalysts displaying a macroscopically as well as microscopically homogeneous distribution. The characterization results, however showed an important difference between the two oxidic supports ... 

An interesting variation on sulfated metal oxide type catalysts was presented by Sun et al. (198), who impregnated a dealuminated zeolite BEA with titanium and iron salts and subsequently sulfated the material. The samples exhibited a better time-on-stream behavior in the isobutane/1-butene alkylation (the reaction temperature was not given) than H-BEA and a mixture of sulfated zirconia and H-BEA. The product distribution was also better for the sulfated metal oxide-impregnated BEA samples. These results were explained by the higher concentration of strong Brpnsted acid sites of the composite materials than in H-BEA. 

Although the decomposition of ozone to dioxygen is a thermodynamically favoured process,126 it is thermally stable up to 523 K and catalysts are needed to decompose it at ambient temperature in ventilation systems, in the presence of water vapour and at high space velocity. A limited number of catalysts have been evaluated and active components are mainly metals such as platinum, palladium and rhodium, and metal oxides including those of manganese, cobalt, copper, iron, nickel and silver. Supports that have been used include 7-alumina, silica, zirconia, titania and activated carbon.125,170... 

S. Ruba, B. C. Gates, P. Vijayanand, R. R. Grasselli, and H. Rnozinger, An active and selective alkane isomerization catalyst iron - and platinum - promoted tungstated zirconia, J. Chem. Soc. Chem. Commun. 321-322 (2001). 

Figure 4.21 shows the XPS core level spectra of the Fe 2p and Zr 3d electrons measured for the stable active catalyst. The outer surface is covered with iron oxide (in hematite-like forms) and zirconia exists as non-stoichio-metric Zr02-x. In the iron 2p spectrum, a contribution of metallic iron is visible indicating that the surface oxide film is thin within the information depth of XPS (ca. 2.5 nm). It has been suggested that the surface oxide stabilizes the iron... 

This new single-step synthesis unites the simplicity of preparation and lower production costs, with the outstanding properties of the final catalysts. By the single-step procedure proposed here, deposition of dispersed nanoparticles of noble metals on ceramic supports with customised textural properties and shape was achieved. Noble metals including platinum, palladium, rhodium, ruthenium, iridium, etc. and metal oxides including copper, iron, nickel, chromimn, cerium oxides, etc on sepiolite or its mixtures with alumina, titania, zirconia or other refractory oxides have been also studied. 

Ferric chloride Ferric chloride hexahydrate precipitant silver salts, photographic plates Ammonium bromide precision engineering, high-temp. Polyphenylene ether precursor, iron catalysts Iron pentacarbonyl precursor, iron oxides Iron pentacarbonyl precursor, iron chemically pure Iron pentacarbonyl precursor, penicillin G Phenylacetic acid precursor, zirconia Ammonium zirconium carbonate pre-emergence/postemergence, crops Pendimethalin... 

Mundschau et al. [122] presented a catalytic membrane reformer for diesel fuel, which was composed of yttria-stabilized zirconia for distributed air introduction into fuel feed reaching into the catalytic fixed bed. The latter contained either iron or cobalt perovskite catalysts (Lao sSro sCoOs. or Lao.5Sro.5Fe03 a). However, the catalyst produced significant amounts of methane impairing the hydrogen yield. 

It was possible to prepare catalysts showing a good interaction of the active components with the support, with a uniform distribution over the support pellets. This interaction proved detrimental with ti-tania-supported catalysts, which deactivate rapidly due to the formation of mixed compounds of iron and/or potassium with the support. Zirconia-supported catalysts, however, proved to be very stable in the dehydrogenation reaction, which was attributed to the formation of a finely divided supported phase. 

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