Activation of Fe

At die slag-matte interface, the activity of FeO can be 0.3 as a maximum before Si02 saturation sets in. The activity of FeS can be assumed to vary over die activity range aFeS = 0.5-10 during the process, and so the oxygen... 

To simplify the catalytic system further, Kodadek and Woo investigated the activity of [Fe(F2o-TPP)Cl] for alkene cyclopropanation with EDA in the absence of cobaltocene. These workers proposed that electron-deficient porphyrin would render the Fe(III) porphyrin more easily reduced by EDA. Indeed, [Fe(F2o-TPP)Cl] efficiently catalyzes alkene cyclopropanation with EDA with high catalyst turnover... 

In figure 8 the activity of the catalyst before and after the addition of 13.5 kPa water is indicated for the three catalysts. After 10 h the activity of Fe-ZSM-5 had declined by a factor of three and was still declining. Only the Co-ZSM-5 turned out to be quite stable, although it suffers the strongest from the inhibition. 

Yu, J., Xiang, Q., and Zhou, M. (2009) Preparation, characterization and visible-light-driven photocatalytic activity of Fe-doped titania nanorods and first-principles study for electronic structures. Applied Catalysis B Environmental,... 

The ent-fes-fep gene cluster is necessary for the synthesis of enterobactin and transport of the iron loaded siderophore. The fes gene product was shown to be necessary for utilization of the siderophore-bound iron inside the cell. The protein has an esterase activity which cleaves the ester bonds of the cyclic 2,3-dihydroxybenzoylserine ester in enterobactin. However, the esterase activity of Fes does not seem to be important for iron mobilization since Fes is also necessary for the utilization of iron from enterobactin analogues which do not have ester bonds (Heidinger et ah, 1983). No reductase activity has been found in Fes (Brickman and McIntosh, 1992) or in any other protein encoded in the ent-fes-fep gene cluster. 

The increasing volume of chemical production, insufficient capacity and high price of olefins stimulate the rising trend in the innovation of current processes. High attention has been devoted to the direct ammoxidation of propane to acrylonitrile. A number of mixed oxide catalysts were investigated in propane ammoxidation [1]. However, up to now no catalytic system achieved reaction parameters suitable for commercial application. Nowadays the attention in the field of activation and conversion of paraffins is turned to catalytic systems where atomically dispersed metal ions are responsible for the activity of the catalysts. Ones of appropriate candidates are Fe-zeolites. Very recently, an activity of Fe-silicalite in the ammoxidation of propane was reported [2, 3]. This catalytic system exhibited relatively low yield (maximally 10% for propane to acrylonitrile). Despite the low performance, Fe-silicalites are one of the few zeolitic systems, which reveal some catalytic activity in propane ammoxidation, and therefore, we believe that it has a potential to be improved. Up to this day, investigation of Fe-silicalite and Fe-MFI catalysts in the propane ammoxidation were only reported in the literature. In this study, we compare the catalytic activity of Fe-silicalite and Fe-MTW zeolites in direct ammoxidation of propane to acrylonitrile. 

Table 1 Catalytic activity of Fe-zeolites in propane ammoxidation at 540 °C...

The rate constants k and ku for la calculated from the data in Fig. 14 of ca. 3.5 x 103 and 1.5 x 104M 1s 1 (pH 11, 25°C), respectively, illustrate a very high activity of Fe-TAML activators particularly in terms of k. For example, Oakes and Gratton reported the value of 0.08M s1 for the oxidation of Orange II by p-sulfonated perbenzoic acid under the same conditions (57). 

Fig. 16. Retardation of the catalase activity of Fe-TAML activators by the dye Safranine O as an electron donor. Conditions [H202] 2.65 x 10-3 M [lk] 1.18 x 10 6M pH 10, 25°C. Inset shows that the rate of 02 evolution is inversely proportional to [Safranine O]. From Ref. (53).

The higher coordinating ability and Lewis acidity of Zn(H) ion in addition to the low pK of the metal-bound water molecule and the appearance of this metal ion in native phosphatases inspired a number of research groups to develop Zn(II)-containing dinuclear artificial phosphatases. In contrast, very few model compounds have been published to mimic the activity of Fe(III) ion in dinuclear centers of phosphatase enzymes. Cu(II) or lanthanide ions are not relevant to natural systems but their chemical properties in certain cases allow extraordinarily high acceleration of phosphate-ester hydrolysis [as much as 108 for copper(II) or 1013 for lanthanide(III) ions]. 

Although the isomerization of allylic alcohols can be catalyzed by Fe(CO)s under thermal conditions, this reaction suffers from slow reaction rates, low yields, and high reaction temperature. To overcome these problems, photochemical activation of Fe(CO)s was investigated. By employing photochemical activation conditions, the isomerization of a wide variety of allylic alcohols proceeded in good to excellent yields using 1-10 mol% of Fe(CO)s in pentane (Scheme 9).32... 

Many copper(II) complexes, including Cu(DIPS)2 (DIPS = diisopro-pylsalicylate), Cu(salicylate)2, and Cu(Gly-His-Lys), are also active in superoxide dismutation (437, 438), but their use in vivo is limited by dissociation of Cu(II) and binding to natural ligands such as albumin (439). In contrast, the activity of Fe-93 is not affected by albumin (439, 440). 

Figure 11.43 Space-filling models of the ligands C32 (high activity of Fe(ll) complex) and A32 (low activity of Fe(ll) complex). Structure of the metal ligand complex under polymerization conditions.

The catalytic activity of Fe was tested in an electrolysis of 1.5 liters of an oxygen saturated solution of 50 mM Na2S04 + 0.1 mM RB5 + 1 mM Fe at pH 2. It was performed in a divided flow cell, working at an averaged current of 0.150 Amperes and AEceii = 2.0V. Figure 7 reports the spectra recorded at various stages in the electrolysis. 

From eq. (9.6) the activity of Fe " in equilibrium with the solid phase can be calculated as a function of pH this relationship is linear and has a slope of-3. 

The differences effected in activity by the central atom with all the ligands studied can hardly be explained solely by the occupation scheme of the d level (Fig. 30) as calculated for the porphyrins. The influence of the 5th ligand is not taken into account in the above discussion. In addition, there is no information as to which of the two requirements for interaction with oxygen (empty d orbitals, or filled dxz and dyz orbitals) has the greater influence. For example, the requirement would be best fulfilled in the case of Fe(II) followed by Fe(III) if the Az2 orbital were raised so far as to be no longer occupied. Where the orbitals lie close together, an occupation such as that shown in Fig. 30 will occur and the activity of Fe(II) should then be less than that of (II). 

The catalytic activity of Fe carbides, molybdenum oxynitride and oxycarbide has been evaluated for coal liquefaction and heteroatom removal of model compounds related to coal. Preliminary results show that the LP nanoparticles are active catalysts for coal liquefaction. In fact, they are more active for heteroatom removal than a molybdenum promoted sulfated hematite, even though surface characterization indicates that as introduced into the reactor they exhibit surface oxidation. 

Brunner s group investigated the influence of thermal or photoinduced activation of Fe(Cp) (CO) complexes in the hydrosilylation of acetophenone (4b) with diphenylsilane, forming quantitatively the silylated l-phenylethanol59 (Scheme 4.26) [56,57]. Brunner... 

The activities of Fe— and Mn—SODs are decreased above pH 8.5, consistent with the involvement of an ionizable group of the protein with a pKa value between 9 and 10 in the catalytic cycle.77 The most likely residue appears to be Tyr-34, which is only 5 A apart from the Mn.51 A possible route of O2 to the Mn site in T. thermophilus Mn-SOD50 runs across the helix 1 between the Lys-29 and Tyr-34, and the O2 binds to the Mn3+ tram to Asp-163 with octahedral coordination (Figs. 10.7 and 10.8). The route to the metal is lined by aromatic and histidine residues including His-26, His-30, Tyr-34, His-81, Phe-84, Trp-165 and His-167. 

With increase in ionic strength, the activities of Fe- and Mn—SODs that bear a net negative charge at neutral pH are decreased, suggesting that they also have a cluster of positive charges around the active site.80 Acetylation of the lysine residues of Fe- and... 

The Fe-SOD activity remaining after the treatment with H2O2 is different from that of the native enzyme, with respect to several criteria including heat stability and inhibition by azide. Thus, the H202-resistant activity of Fe-SOD represents an activity of the H2O2-modified Fe-SOD. 

Figure 33. Catalytic activity of Fe-Cu bimetallic particles supported on alumina (squares), activated carbon (triangles) and carbon nanolibers (dots). The inset shows the activity of the metal particles on nanofibers in the decomposition of ethylene into solid carbon (squares), ethane (triangles) and methane (dots).

The effect of weight percent iron on the catalytic activity of Fe/ZSM-5 and Fe/13X catalysts was investigated by comparison of the catalytic data obtained for 7.0% Fe/ZSM-5 with that for 15.0%... 

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