Iron catalytic reaction

Ethylamines. Mono-, di-, and triethylamines, produced by catalytic reaction of ethanol with ammonia (330), are a significant outlet for ethanol. The vapor-phase continuous process takes place at 1.38 MPa (13.6 atm) and 150—220°C over a nickel catalyst supported on alumina, siUca, or sihca—alumina. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethylamine product can be controlled by recycling the unwanted products. Other catalysts used include phosphoric acid and derivatives, copper and iron chlorides, sulfates, and oxides in the presence of acids or alkaline salts (331). Piperidine can be ethylated with ethanol in the presence of Raney nickel catalyst at 200°C and 10.3 MPa (102 atm), to give W-ethylpiperidine [766-09-6] (332). 

The decomposition of NO is a very slow catalytic reaction. Amirazmi, Benson, and Boudart recently studied the kinetics over platinum and over oxides of copper, cobalt, nickel, iron and zirconium from 450 to 900°C. They found that the kinetics is first order in NO with concentrations from 1.5 to 15%, and that oxygen has a strong inhibiting effect. Even at these temperatures, the kinetics is about a factor of 1000 too low for automotive usage (97). 

Hydride species were also formed in the dehydrogenative coupling of hydrosilanes with DMF [45]. The catalytic system is applicable to tertiary silanes, which are known to be difficult to be converted into disiloxanes (Fig. 17). The catalytic reaction pathway involves the intermediacy of a hydrido(disilyl)iron complex... 

Until now examples for catalytic reactions involving ferrates with iron in the oxidation state of -l-3 are very rare. One example is the hexacyanoferrate 8-catalyzed oxidation of trimethoxybenzenes 7 to dimethoxy-p-benzoquinones 9/10 by means of hydrogen peroxide which was published by Matsumoto and Kobayashi in 1985 [2]. Using hexacyanoferrate 8 product 9 was favored while other catalysts like Fe(acac)3 or Fe2(S04)3 favored product 10 (Scheme 2). The oxidation is supposed to proceed via the corresponding phenols which are formed by the attack of OH radicals generated in the Fe/H202 system. 

The role of the iron-sulphur system of xanthine oxidase in the catalytic reaction is somewhat problematical. Nevertheless, it is clear, both from rapid freezing EPR (53) and from stopped-flow measurements monitored optically at 450 nm (58, 63) (where both iron and flavin are measured), that iron is reduced and oxidized at catalytically significant rates. Perhaps the best interpretation is that it functions as a store for reducing equivalents within the enzyme when this is acting as an oxidase, though it may well represent the main site of electron egress in dehydrogenase reactions (52). 

Variation of the content of impurities in the different CNT preparations [21] offers additional challenges in the accurate and consistent assessment of CNT toxicity. As-produced CNTs generally contain high amounts of catalytic metal particles, such as iron and nickel, used as precursors in their synthesis. The cytotoxicity of high concentrations of these metals is well known [35, 36], mainly due to oxidative stress and induction of inflammatory processes generated by catalytic reactions at the metal particle surface [37]. Another very important contaminant is amorphous carbon, which exhibits comparable biological effects to carbon black or relevant ambient air particles. 

A stoichiometric amount of promoter, at least, is required for the reaction to proceed, leading to an environmentally hostile process with gaseous effluents and mineral wastes. With some metal salts, however, an increase in reaction temperature sets them free from their complex with the ketone, and a true catalytic reaction becomes possible [73] this is observed for iron(III) chloride [74] and some metal tri-flates [72, 75], including their use under the action of MW heating [76]. 

What can all these studies suggest to the inorganic chemist interested in the controlled and fAcile catalytic oxidation of hydrocarbons Groves and coworkers have already shown that iron porphyrins in the presence of iodosylbenzene and peracids can be used for such catalytic reactions (37, 38). However, the cost of the oxidants makes such reaction uneconomical at this time. 

Metal complexes, especially involving transition metals, are known for their role as catalysts in a broad variety of chemical processes including isomerization, oxidization, hydrogenation, and polymerization. Such catalytic reactions play an important role not only in many industrial processes, such as petroleum and polymer industries, but also in many biological systems, e.g., a variety of selective oxidation catalysts with heme (1) and nonheme (2) iron centers. The transition metals in these systems usually constitute a fundamental part of the catalyst, due to their... 

The enhanced chemiluminescence associated with the autoxidation of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) in the presence of trace amounts of iron(II) is being used extensively for selective determination of Fe(II) under natural conditions (149-152). The specificity of the reaction is that iron(II) induces chemiluminescence with 02, but not with H202, which was utilized as an oxidizing agent in the determination of other trace metals. The oxidation of luminol by 02 is often referred to as an iron(II)-catalyzed process but it is not a catalytic reaction in reality because iron(II) is not involved in a redox cycle, rather it is oxidized to iron(III). In other words, the lower oxidation state metal ion should be regarded as a co-substrate in this system. Nevertheless, the reaction deserves attention because it is one of the few cases where a metal ion significantly affects the autoxidation kinetics of a substrate without actually forming a complex with it. 

The product is exclusively carbon monoxide, and good turnover numbers are found in preparative-scale electrolysis. Analysis of the reaction orders in CO2 and AH suggests the mechanism depicted in Scheme 4.6. After generation of the iron(O) complex, the first step in the catalytic reaction is the formation of an adduct with one molecule of CO2. Only one form of the resulting complex is shown in the scheme. Other forms may result from the attack of CO2 on the porphyrin, since all the electronic density is not necessarily concentrated on the iron atom [an iron(I) anion radical and an iron(II) di-anion mesomeric forms may mix to some extent with the form shown in the scheme, in which all the electronic density is located on iron]. Addition of a weak Bronsted acid stabilizes the iron(II) carbene-like structure of the adduct, which then produces the carbon monoxide complex after elimination of a water molecule. The formation of carbon monoxide, which is the only electrolysis product, also appears in the cyclic voltammogram. The anodic peak 2a, corresponding to the reoxidation of iron(II) into iron(III) is indeed shifted toward a more negative value, 2a, as it is when CO is added to the solution. 

As to catalytic reactions in homogeneous media, Moritz Traube found in his studies of the oxidation of hydrogen iodide by hydrogen peroxide in aqueous solution, that the catalyst ferrous sulfate is activated by copper sulfate (5). As to the magnitude of such effects, Price stated in 1898 (6) that the simultaneous action of iron and of copper compounds on the reaction between persulfate and hydrogen iodide causes an unexpected acceleration of the reaction, which is more than twice as great as the acceleration calculated as an additive effect of the two single catalysts. However, effects were also observed of the opposite kind,... 

Ferrisilicate zeolites wherein iron ions replace silicon in the lattice framework have potential as catalyst in various conversion processes. During the past decade ferrisilicate analogs of sodallte, MFI, M, MTT, EUO, MTW, FAU, BETA, MOR and LTL have been synthesised and characterised by various physicochemical techniques as well as catalytic reactions. After a review of the general synthesis procedures a list of criteria is presented to confirm the location of Fe in the zeolite framework. Examples are provided to illustrate the utility of the various characterisation techniques. 

In a recent work we were able to show that an electronic effect was detected between Bi2Mo30i2 and a mixed iron and cobalt molybdate with an enhancement of the electrical conductivity of the cobalt molybdate with the substitution of the cobaltous ions by the ferrous ions (7). However this effect alone cannot explain the synergy effect and we have investigated the influence of both the de ee of subtitution of the cobalt with the iron cations in the cobalt molybdate and the ratio of the two phases (for a given substituted cobalt molybdate) on the catalytic propert cs of the mixture.We have tried to characterize by XPS and EDX-STEM the catalysts before and after the catalytic reaction in order to detect a possible transformation of the solid. The results obtained are presented and discussed in this study. 

Since a polymorphic transition (a/p) of the mixed iron and cobalt molybdate occurs in the temperature range of the catalytic reaction (10,13,14), and since the high temperature form (p) can metastably be maintained at low temperature,... 

XPS has been used to characterize the three mixtures containing respectively 7,25, and 50 weight % of Bi2Mo30i2 (Table II samples J,K and L). These samples have been characterized before and after catalytic reaction (table III). Bi, Mo, Fe, Co and O have been analyzed. The Mo/0 ratio remains equal to 0.25 for all the samples, before and after catalysis which confirms that no new phase was formed since the molybdates suspected to have formed, have a much lower Mo/0 ratio (0.17 for Bi2Mo06 and Bi3FeMo20i2). Concerning the Bi/(Fe+Co) ratio, it can first be observed that before catalysis this ratio was always lower than that calculated from chemical analysis. This can be explained by the difference between the particles size of the bismuth molybdate and the iron and cobalt molybdates which is in a ratio of more than 30 as calculated from differences in surface area values, 0.3 and 9 to 22 m. g Secondly the Bi/(Fe+Co) ratio increased systematically after catalysis which could be explained by the decrease in size of the bismuth molybdate particles or by the covering of the iron and cobalt molybdate particles by the bismuth molybdate or by both effects. 

On the other hand, electrical conduction via mixed-valence states is essential for iron oxides used in electrochemical cells or for the mediation of catalytic reactions at iron oxides used as heterogeneous catalysts. 

All three AAH enzymes require iron in order to be catalytically active (2,17-19), and a vast amount of information has accumulated on the direct and extensive involvement of the metal in the catalytic reaction (5). A solid proof for a vacant position on Fe for coordination of dioxygen was obtained by Kemsley et al. (42) using circular dichroism and magnetic circular dichroism spectroscopy and suggested a direct involvement of the metal in the catalytic reaction. 

Dinuclear iron centres occur in several proteins. They either bind or activate dioxygen or they are hydrolases. Ribonucleotide reductase (RR) of the so-called class I type contains one such centre in the R2 protein in combination with a tyrosyl radical, both being essential for enzymatic activity which takes place in the R1 protein subunit. The diiron centre activates dioxygen to generate the tyrosyl radicals which in turn initiate the catalytic reaction in the R1 subunit. The interplay between the tyrosyl free radical in R2 and the formation of deoxyribonucleotides in R1 which also is proposed to involve a protein backbone radical is a topic of lively interest at present but is outside the scope of this review. Only a few recent references dealing with this aspect are mentioned without any further discussion.158 159 1 1,161... 

---