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Iron catalysts reactions

If the synthesis is carried out on iron catalysts reaction is most easily followed by conversion of water... [Pg.960]

In the early 1920s Badische Arulin- und Soda-Fabrik aimounced the specific catalytic conversion of carbon monoxide and hydrogen at 20—30 MPa (200—300 atm) and 300—400°C to methanol (12,13), a process subsequendy widely industrialized. At the same time Fischer and Tropsch aimounced the Synth in e process (14,15), in which an iron catalyst effects the reaction of carbon monoxide and hydrogen to produce a mixture of alcohols, aldehydes (qv), ketones (qv), and fatty acids at atmospheric pressure. [Pg.79]

The uv—hydrogen peroxide system has advantages over the iron—hydrogen peroxide (Fenton s reagent) procedures, eg, the reaction is not limited to an acid pH range and the iron catalyst and resulting sludges are eliminated. However, the system to date is not effective for dye wastewaters because of absorption of uv by colored effluent. [Pg.383]

Remaining trace quantities of CO (which would poison the iron catalyst during ammonia synthesis) are converted back to CH4 by passing the damp gas from the scmbbers over a Ni methanation catalyst at 325° CO -t- 3H2, CRt -t- H2O. This reaction is the reverse of that occurring in the primary steam reformer. The synthesis gas now emerging has the approximate composition H2 74.3%, N2 24.7%, CH4 0.8%, Ar 0.3%, CO 1 -2ppm. It is compressed in three stages from 25 atm to 200 atm and then passed over a promoted iron catalyst at 380-450°C ... [Pg.421]

The ability of iron(III) chloride genuinely to catalyze Friedel-Crafts acylation reactions has also been recognized by Holderich and co-workers [97]. By immobilizing the ionic liquid [BMIM]Cl/FeCl3 on a solid support, Holderich was able to acetylate mesitylene, anisole, and m-xylene with acetyl chloride in excellent yield. The performance of the iron-based ionic liquid was then compared with that of the corresponding chlorostannate(II) and chloroaluminate(III) ionic liquids. The results are given in Scheme 5.1-67 and Table 5.1-5. As can be seen, the iron catalyst gave superior results to the aluminium- or tin-based catalysts. The reactions were also carried out in the gas phase at between 200 and 300 °C. The acetylation reac-... [Pg.207]

The cyclodimerization of 1,3-butadiene was carried out in [BMIM][BF4] and [BMIM][PF(3] with an in situ iron catalyst system. The catalyst was prepared by reduction of [Fe2(NO)4Cl2] with metallic zinc in the ionic liquid. At 50 °C, the reaction proceeded in [BMIM][BF4] to give full conversion of 1,3-butadiene, and 4-vinyl-cyclohexene was formed with 100 % selectivity. The observed catalytic activity corresponded to a turnover frequency of at least 1440 h (Scheme 5.2-24). [Pg.251]

Fischer Tropsch synthesis is catalyzed by a variety of transition metals such as iron, nickel, and cobalt. Iron is the preferred catalyst due to its higher activity and lower cost. Nickel produces large amounts of methane, while cobalt has a lower reaction rate and lower selectivity than iron. By comparing cobalt and iron catalysts, it was found that cobalt promotes more middle-distillate products. In FTS, cobalt produces... [Pg.124]

Hydrogen cyanide reactions catalysts, 6,296 Hydrogen ligands, 2, 689-711 Hydrogenolysis platinum hydride complexes synthesis, 5, 359 Hydrogen peroxide catalytic oxidation, 6, 332, 334 hydrocarbon oxidation iron catalysts, 6, 379 reduction... [Pg.141]

A heterogeneous catalyst is a catalyst present in a phase different from that of the reactants. The most common heterogeneous catalysts are finely divided or porous solids used in gas-phase or liquid-phase reactions. They are finely divided or porous so that they will provide a large surface area for the elementary reactions that provide the catalytic pathway. One example is the iron catalyst used in the... [Pg.686]

The reactant is adsorbed on the catalyst s surface. As a reactant molecule attaches to the surface of the catalyst, its bonds are weakened and the reaction can proceed more quickly because the bonds are more easily broken (Fig. 13.36). One important step in the reaction mechanism of the Haber process for the synthesis of ammonia is the adsorption of N2 molecules on the iron catalyst and the weakening of the strong N=N triple bond. [Pg.687]

Until recently, iron-catalyzed hydrogenation reactions of alkenes and alkynes required high pressure of hydrogen (250-300 atm) and high temperature (around 200°C) [21-23], which were unacceptable for industrial processes [24, 25]. In addition, these reactions showed low or no chemoselectivity presumably due to the harsh reaction conditions. Therefore, modifications of the iron catalysts were desired. [Pg.30]

Hydrogenation of substrates having a polar multiple C-heteroatom bond such as ketones or aldehydes has attracted significant attention because the alcohols obtained by this hydrogenation are important building blocks. Usually ruthenium, rhodium, and iridium catalysts are used in these reactions [32-36]. Nowadays, it is expected that an iron catalyst is becoming an alternative material to these precious-metal catalysts. [Pg.35]

The comparison of a bis(imino)pyridine iron complex and a pyridine bis (oxazoline) iron complex in hydrosilylation reactions is shown in Scheme 24 [73]. Both iron complexes showed efficient activity at 23°C and low to modest enantioselectivites. However, the steric hindered acetophenone derivatives such as 2, 4, 6 -trimethylacetophenone and 4 -ferf-butyl-2, 6 -dimethylacetophenone reacted sluggishly. The yields and enantioselectivities increased slightly when a combination of iron catalyst and B(CeF5)3 as an additive was used. [Pg.49]

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. [Pg.52]

A mechanistic proposal, which is based on the mthenium-catalyzed dehydration reaction reported by Nagashima and coworkers [146], is shown in Scheme 44. Reaction of a primary amine with hydrosilane in the presence of the iron catalyst affords the bis(silyl)amine a and 2 equiv. of H2. Subsequently, the isomerization of a gives the A,0-bis(silyl)imidate b and then elimination of the disiloxane from b produces the corresponding nitrile. Although the disiloxane and its monohydrolysis product were observed by and Si NMR spectroscopy and by GC-Mass-analysis, intermediates a and b were not detected. [Pg.59]

In addition, also nonheme iron catalysts containing BPMEN 1 and TPA 2 as ligands are known to activate hydrogen peroxide for the epoxidation of olefins (Scheme 1) [20-26]. More recently, especially Que and coworkers were able to improve the catalyst productivity to nearly quantitative conversion of the alkene by using an acetonitrile/acetic acid solution [27-29]. The carboxylic acid is required to increase the efficiency of the reaction and the epoxide/diol product ratio. The competitive dihydroxylation reaction suggested the participation of different active species in these oxidations (Scheme 2). [Pg.85]

An XPS Investigation of iron Fischer-Tropsch catalysts before and after exposure to realistic reaction conditions is reported. The iron catalyst used in the study was a moderate surface area (15M /g) iron powder with and without 0.6 wt.% K2CO3. Upon reduction, surface oxide on the fresh catalyst is converted to metallic iron and the K2CO3 promoter decomposes into a potassium-oxygen surface complex. Under reaction conditions, the iron catalyst is converted to iron carbide and surface carbon deposition occurs. The nature of this carbon deposit is highly dependent on reaction conditions and the presence of surface alkali. [Pg.124]

Invented in 1909 by Fritz Haber (1868-1934), the Haber-Bosch process requires very high pressure (250 atmospheres) and a temperature of approximately 932°F (500°C). The reaction also requires a porous iron catalyst. [Pg.70]

The basis of the demonstration can be based on already published data on the surface reaction between NOz and adsorbed organic compounds. Yokoyama and Misono have shown that the rates of N02 reduction over zeolite or silica are proportional to the concentration of adsorbed propene [29], whereas Il ichev et al. have demonstrated that N02 reacts with pre-adsorbed ethylene and propylene on H-ZSM-5 and Cu-ZSL-5 to form nitro-compounds [30], Chen et al [2-4] have observed the same nitrogen-containing deposits on MFI-supported iron catalysts. The question on the pairing of nitrogen atoms is not considered here. [Pg.161]

The first reported work on the kinetics of hydrogenolysis reactions of simple hydrocarbons appears to be that of Taylor and associates at Princeton (2-4, 14, 15), primarily on the hydrogenolysis of ethane to methane. The studies were conducted on nickel, cobalt, and iron catalysts. More recently, extensive studies on ethane hydrogenolysis kinetics have been conducted on all the group VIII metals and on certain other metals as well (16,28-83). [Pg.94]

It has been suggested [21,22] that the presence of Cu and K increases the rates and extent of Fe304 carburization during reaction and the FTS rates, by providing multiple nucleation sites that lead to the ultimate formation of smaller carbide crystallites with higher active surface area. In the present investigation, Cu- and K-promoted iron catalysts performed better than the unpromoted catalysts in terms of (1) a lower CH4 selectivity, (2) higher C5+ and alkene product selectivi-ties, and (3) an enhanced isomerization rate of 1-alkene. [Pg.144]

Miller, D.G., and Moskovits, M. 1988. A study of the effects of potassium addition to supported iron catalysts in the Fischer-Tropsch reaction. J. Phys. Chem. 92 6081-85. [Pg.146]


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See also in sourсe #XX -- [ Pg.1477 , Pg.1478 ]




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