Iron oxide supports

Two or more soHd catalyst components can be mixed to produce a composite that functions as a supported catalyst. The ingredients may be mixed as wet or dry powders and pressed into tablets, roUed into spheres, or pelletized, and then activated. The promoted potassium ferrite catalysts used to dehydrogenate ethylbenzene in the manufacture of styrene or to dehydrogenate butanes in the manufacture of butenes are examples of catalysts manufactured by pelletization and calcination of physically mixed soHd components. In this case a potassium salt, iron oxide, and other ingredients are mixed, extmded, and calcined to produce the iron oxide-supported potassium ferrite catalyst. 

The electron interaction between nanosized gold particles and iron oxide support is only one factor which determines the properties of the gold/oxide system. For instance, in the Au/FeO,c/Si02/Si(l 0 0) model sample the depth profile (after successive Ar ion bombardment at a... 

Kozlova, A.P. Sugiyama, S. Kozlov, A.I. Asa-kura, K. Iwasawa.Y. (1998) Iron oxide supported gold catalysts derived from gold phosphor complex Au(PPh3) (NO3) State and structure of the support. J. Catalysis 176 426-438... 

In contrast with these observations, it has been found that manganese and iron oxide supported on magnesium oxide catalyze cracking reactions via a free-radical mechanism and ensure enhanced ethylene and ethane production.64... 

Apparent Activation Energies of S02 Oxidation over Iron Oxide Supported by Silver and... 

Ir4(CO)i2 and Ir6(CO)i6, supported metal nanoclusters, 68-69 Ir4 in zeolite NaX supported metal nanoclusters, 69 theoretical investigation, 70 Iron oxide support, preparation of gold particles on, 6-7... 

Herzing AA, Kiely CJ, Carley AF, Landon P, Hutchings GJ. Identification of active gold nanoclusters on iron oxide supports for CO oxidation. Science. 2008 321 1331-5. 

Lewandowski M, Sun YN, Qin ZH, Shaikhutdinov S, Freund HJ. Promotional effect of metal encapsulation on reactivity of iron oxide supported Pt catalysts. Appl Catal A. 2011 391 407-10. 

Tanaka S, Nakagawa K, Kanezaki E, Katoh M, Murai K-1, Moriga T, Nakabayashi 1, Sugiyama S, Kidoguchi Y, Miwa K (2005) Catalytic activity of iron oxides supported on gamma-Al Oj for methane oxidation. J Jpn Pet Inst 48 223... 

Examples of supports modifying the properties of transition metal oxides have also appeared in the literature. Recent work points to iron oxide phases as important species in Fischer-Tropsch synthesis (3 ). Iron oxide supported on SiO2 (4 ) and TiO ( ) resist reduction under conditions in which bulk iron oxide easily reduces. Thus supported iron oxide catalysts are potentially interesting Fischer-Tropsch catalysts. The extensive studies on ethylene polymerization catalysts suggests that chromium (VI) species exist on a SiOp surface at temperatures above which bulk chromic anhydride (CrOg) decomposes ( ). 

As discussed above, low catalytic activities of iron oxide supported on Si02, AI2O3, and Ti02 (compared to Fe30 ) were observed at all iron loadings investigated in this study, and this suggests that the 3 4 particles on the support were also covered by a surface phase. 

CFCs were decomposed to HCl, HF, and CO2 at 150 °C to 350 °C by the reaction of H2O over amorphous alloy catalysts consisting of at least one element selected from the group of Ni and Co, at least one element selected from the group Nb, Ta, Ti, and Zr, and at least one element selected from the group Ru, Rh, Pd, Ir, and Pt. The alloys were activated by immersion in HF [105]. CFCs are decomposed by the reaction of water vapor at temperatures above 300 °C in the presence of iron oxide supported on activated carbon [106]. They are also decomposed by steam in... 

A catalyst formed from iron vanadate and iron oxide supported on asbestos fibers has been proposed for the oxidation of toluene in vapor phase.104... 

A new catalyst for the selective oxidation of hydrogen sulfide in Claus tail gas to elemental sulfur has been developed. The catalyst consists of highly dispersed iron oxide supported on a silica carrier. During operation the activity of this catalyst decreases due to transformation of iron(III) oxide into a less active component. X-ray diffraction, wet chemical qualitative analysts and Mossbauer spectroscopy reveal the component comprises iron(II) sulfate. Although the transformation of inon(III) oxide into iron(IQ sulfate causes deactivation, the increase in selectivity results in high sulfur yields (up to 94%). 

Fio. 28. Magnetic moment (O) and chemical oxidation state for iron oxide supported... 

Gif systems were originally designed to mimic non-heme enzymatic oxidation of alkanes. All of them involve a pyridine-acetic acid (or other carboxylic add) solution of the hydrocarbon being oxidized, an iron-based catalyst, and an electron source. However, Gif systems have a ploblem in the separation of catalyst because the homogeneous catalytic systems are employed. Thus, we have modified the GiflV system by using heterogeneous catalysts, iron oxide supported on silica, and then the results are reported in this paper. 

A. N. Basinska, F. Domka, Influence of iron influence of iron oxide support preparation method on the properties of Ru/Fe203 catalysts for water gas shift reaction. React. Kinet. Catal. Lett. 67 (1999) 111-116. 

In 2011, Woo and collaborators prepared ORR catalysts from the pyrolysis at 700, 800, and 900 °C of a mixture of iron oxide supported on Vulcan and dicyandiamide (C2H4N4 a dimer of cyanamide) [111]. TEM of the catalysts revealed that at 700 °C metal particles were encapsulated with a carbon layer, while they were mostly in carbon tubes at 900 °C. The total N content was 2.2,3.5, and 6.6 at.% for the catalysts heat treated at 700,800, and 900 °C, respectively. This N content was broken down as 54 % pyridinic and 0 % graphitic nitrogen atoms at 700 °C, while it was 61.4 % pyridinic and 10.7 % graphitic at 900 C. The Fe content was also measured in these catalysts and also for the catalyst iron... 

A large amount of Mossbauer work has been devoted to in situ surface characterization of iron catalyst. These experiments were carried out, however, using small particles of iron oxide supported on inert carriers. These materials represent a different class of catalysts to the industrial ammonia synthesis catalyst. The Mossbauer studies which has helped to evaluate the concept of structure sensitivity in ammonia synthesis will therefore not be discussed here. 

Much attention has been devoted in recent litraatuie to the phenomenon of interaction between oxides (refs. 1-3). The supported oxides in the form of three-dimensional crystallites whose properties are similar to bulk crystals, do not interact strongly with the support. However, when the oxide is dispersed in monolayer on the oxidic supports, the interacdon between them becomes strong and the properties of such monolayer of the oxide differ from those of bulk oxide. Growth of three dimensional crystallites occurs only after a substantial fraction of the surface is covered by the monolayer and this is often the case for the oxides of Cr, Mo, W, V, Re and Ni. Extensive studies have been devoted to these systems. For other systems, however, the slate of dispersion is complicated, depending on the nature of the support, the preparative method and the conditions used in such process. In this paper, we tried to prepare well-dispersed iron oxide supported on various supports by different methods and investigate the physico-chemical properties of these iron oxides. 

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