Iron, catalysts for preparation

Iodostannates(IV), formation of, by tin (IV) iodide, 4 121 Iron, catalysts for preparation of sodium amide, 2 133... 

Three series of Au nanoparticles on oxidic iron catalysts were prepared by coprecipitation, characterized by Au Mossbauer spectroscopy, and tested for their catalytic activity in the room-temperature oxidation of CO. Evidence was found that the most active catalyst comprises a combination of a noncrys-taUine and possibly hydrated gold oxyhydroxide, AUOOH XH2O, and poorly crystalhzed ferrihydrate, FeH0g-4H20 [421]. This work represents the first study to positively identify gold oxyhydroxide as an active phase for CO oxidation. Later, it was confirmed that the activity in CO2 production is related with the presence of-OH species on the support [422]. 

Catalyst composition also depends on the type of reactor used. Fixed-bed iron catalysts are prepared by precipitation and have a high surface area. A silica support is commonly used with added alumina to prevent sintering. Catalysts for fluidized-bed application must be more attrition-resistant. Iron catalysts produced by fusion best satisfy this requirement. The resulting catalyst has a low specific surface area, requiring higher operating temperature. Copper, another additive used in the preparation of precipitated iron catalysts, does not affect product selectivity, but enhances the reducibility of iron. Lower reduction temperature is beneficial in that it causes less sintering. 

Two series of iron catalysts were synthesized one with varying amounts of copper and one with varying amounts of potassium. The catalysts and their BET surface areas are shown in Table 1. The microscope showed the Cu/Fe series of catalysts to have very large particles (80 nm), which, since the potassium and copper iron catalysts were prepared by different chemists, probably accounts for, in part, the significant differences in surface area between the two batches of catalyst. 

Orientation is, therefore, quite important for catalytic praxis. It may well be assumed that empirically found preferred methods for preparing active catalysts are often those methods leading to the most active orientation. Westrik and Zwietering 18) proved that the iron catalyst for anunonia synthesis, prepared by a careful slow reduction of magnetite is well oriented in the [111] direction. 

Two iron FTS catalysts with an atomic ratio of K Fe=10 100 and Be Fe=1.44 100 were prepared and utilized in this study. Precipitated iron catalysts were prepared using Fe(N03)3 9H20 tetraethyl orthosilicate, Cu(N03)2 3H20, and K2CO3 or Be(N03)2 was used as the promoter precursor. Details of the preparation procedure was given elsewhere (5). In this study, the potassium promoted iron catalysts were pretreated with CO at 270°C and 1.2 MPa for 24 hours. The CO flowed through a catalyst slurry in 300 ml of Ethylflow oil... 

Ray et al. [93] treated organically modified MMT (OMMT) with a MAO solution after vacuum-drying at 100°C. The resulting MAO-treated clay was subsequently used for ethylene polymerization in the presence of 2,6-bis [l-(2,6-diisopropylphenylimino)ethyl]pyridine iron(ll) dichloride with additional MAO in a glass reactor. In addition, they compared the methods of nanocomposite preparation and observed that the nanocomposite produced by catalyst supported on MAO-pretreated OMMT was more efficiently exfoliated than the nanocomposite produced when only a mixture of catalyst and clay was used. This result led them to conclude that at least some of the active centers resided within the clay galleries. Similarly, Guo et al. [100] in a separate studies successfully used pyridine diimine-based iron(ll) catalysts for preparation of exfoliated PE/clay nanocomposites. 

Nitrates. Iron(II) nitrate hexahydrate [14013-86-6], Fe(N03)2 6H20, is a green crystalline material prepared by dissolving iron in cold nitric acid that has a specific gravity of less than 1.034 g/cm. Use of denser, more concentrated acid leads to oxidation to iron(III). An alternative method of preparation is the reaction of iron(II) sulfate and barium or lead nitrate. The compound is very soluble in water. Crystallisation at temperatures below — 12°C affords an nonahydrate. Iron(II) nitrate is a useful reagent for the synthesis of other iron-containing compounds and is used as a catalyst for reduction reactions. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Reactions of acetylene and iron carbonyls can yield benzene derivatives, quinones, cyclopentadienes, and a variety of heterocycHc compounds. The cyclization reaction is useful for preparing substituted benzenes. The reaction of / fZ-butylacetylene in the presence of Co2(CO)g as the catalyst yields l,2,4-tri-/ f2 butylbenzene (142). The reaction of Fe(CO) and diphenylacetylene yields no less than seven different species. A cyclobutadiene derivative [31811 -56-0] is the most important (143—145). 

A platinum-iron on silica gel catalyst was prepared by impregnating silica gel (BDH, for chromatographic adsorption) with an aqueous solution of chloroplatinic acid (analytical grade) and sodium hydroxide (analytical grade). The dry product was then impregnated by a ferrous sulfate solution (C.P. grade) and the water was removed in a rotating evaporator. The prepared catalyst contained 1% Pt, 0.7% Fe, and 2% NaOH (by... 

Formaldehyde, produced by dehydrogenation of methanol, is used almost exclusively in die syndiesis of phenolic resins (Fig. 7.2). Iron oxide, molybdenum oxide, or silver catalysts are typically used for preparing formaldehyde. Air is a safe source of oxygen for this oxidation process. 

Iron impregnated on activated carbon was used as catalyst for the direct synthesis of phenol from benzene. The effect of Sn addition to the catalyst was studied. The prepared catalysts were characterized by BET, SEM and XRD analysis. The catalyst 5.0Fe/AC showed good activity in the conversion of benzene and addition of Sn seemed to improve the selectivity of phenol in the reaction. 

Catalysts were prepared with 0.5, 1.0, 2.0 and 5.0 wt% of iron loaded on activated carbon. Benzene hydroxylation with hydrogen peroxide as oxidant was carried out. The conversion of benzene, selectivity and yield of phenol for these catalysts are shown in Fig. 4. As the weight of loaded metal increased the benzene conversion increased by about 33% but the selectivity to phenol decreased. The yield of phenol that was obtained with S.OFe/AC was about 16%. 

C-C and C-E (E = heteroatom) bond formations are valuable reactions in organic synthesis, thus these reactions have been achieved to date by considerable efforts of a large number of chemists using a precious-metal catalysts (e.g., Ru, Rh, and Pd). Recently, the apphcation range of iron catalysts as an alternative for rare and expensive transition-metal catalysts has been rapidly expanded (for recent selected examples, see [12-20, 90-103]). In these reactions, a Fe-H species might act as a reactive key intermediate but also represent a deactivated species, which is prepared by p-H elimination. 

Dodolet JP, Cote R, Faubert G, Denes G, Guay D, Bertrand P (1998) Iron catalysts prepared by high-temperature pyrolysis of tetraphenylporphyrins adsorbed on carbon black for oxygen reduction in polymer electrolyte fuel cells. Electrochim Acta 43 341-353... 

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