Iron as catalyst

Bromination of 43 (R = H) also gave a tetrabromo product initially, but base treatment induced elimination with the formation of the 4,7-dibromo derivative (70RCR923), as well as about 20% of the 4,6- and a trace of the 4,5-isomers (70JHC629). With iron as catalyst, one molar proportion ofbromineinameltof43(R = H) resulted in almost exclusive formation of... 

Iron as catalyst for FT synthesis does not exhibit the dynamic characteristics observed with cobalt26 (Figure 9.14, left). 

Fig. 9. Changes in catalytic effect on loss of ferromagnetism at the reaction CO + H2—> CH4 + H20 with cast iron as catalyst. Reaction mixture 1 part CO, 3 parts Eb gas velocity 3.17 cm.Vmin. temperature increase curve 1—1.15, curve 2—0.9 curve 3—0.8°/min. The early increase of the H2 content is caused by the subsidiary reaction CO + H2 = H2Oiiq + C. The decreasing percentages above the Curie temperature correspond to the formation of CH4.

In nature, ammonia is produced by the action of nitrogen-fixing bacteria on atmospheric N2 under very mild conditions (room temperature and 0.8 atm N2 pressure). These bacteria contain nitrogenases, iron- and molybdenum-containing enzymes that catalyze the formation of NH3. Industrially, NH3 is synthesized from its elements by the Haber-Bosch process, which typically uses finely divided iron as catalyst ... 

Oxidation can also lead to an increase in viscosity and the formation of sludge that can restrict oil paths, thus impairing circulation of the oil and interfering with the function of governors and oil relays. Correctly formulated turbine oils have excellent resistance to oxidation and will function satisfactorily for long periods without changing the system charge. Oxidation stabiUty can be assessed by various tests (ASTM D-943, IP 114, IP 157) that use copper as well as iron as catalysts in the presence of water to simulate metals present in service conditions. 

LIQUID PHASE FISCHER-TROPSCH SYNTHESIS USING ULTRAFINE PARTICLES OF IRON AS CATALYST... 

The mechanism represented by Eqs. (V.2)-(V.3) has been suggested first by Doehlemann 30), and subsequently by Kul kova and Temkin (31). Doehlemann 30) confirmed this mechanism semiquantitatively for iron as catalyst. Temkin and his associates 31, 32) showed that the observed dependence of the rate on the partial pressures of reactants and products for FegOi and other metal oxides as catalysts is in accord with the above mechanism, which is also supported by the results of measurements of the exchange reaction... 

We have studied the synthesis of fatty acids by the closed Fischer-Tropsch process, using various carbonates as promoters and meteoritic iron as catalyst. The conditions used were D2/CO mole ratio = 1 1, temperature == 400°C, and time = 24-48 hr. Sodium, calcium, magnesium, potassium, and rubidium carbonates were tested as promoters but only potassium carbonate and rubidium carbonate produced fatty acids. These compounds are normal saturated fatty adds ranging from C5 to Cis, showing a unimodal Gaussian distribution without predominance of odd over even carbon-numbered aliphatic chains. The yields in general exceed the yields of aliphatic hydrocarbons obtained under the same conditions. The fatty acids may be derived from aldehydes and alcohols produced under the influence of the promoter and subsequently oxidized to the acids. 

Figure 9.3 Proposed degradation reaction of phenol-formaldehyde resin with copper and iron as catalysts. Reproduced with permission from M. Kristkova, P. Filip, Z. Weiss and R. Peter, Polymer Degradation and Stability, 2004, 84, 49. ...

The strong o- and m-substitution suggests a free radical mechanism. At low temperatures and with traces of iron as catalyst, sulfones are formed as side products. 

Hydroperoxides (ROOH) can be decomposed by enzymes called peroxidases. Most of peroxidases are dependent on iron as catalyst, but a few of them use manganese. A very interesting peroxidase, called glutathione peroxidase, uses selenium as its catalytic element. Selenium is one of the most toxic elements, but a very small quantity of it is required by almost all organisms. It is used for glutathione peroxide as well as a few other enzymes. This enzyme is much more efficient in destroying certain types of hydroperoxides than the other more common iron-dependent peroxidases. 

Three studies investigated the synergistic flame retardant performance of combined organoclay-MWNT/EVA [poly(ethylene-co-vinyl acetate)] nanocomposites prepared by melt blending. The MWNTs were prepared by catalytic decomposition of acetylene with cobalt and iron as catalysts supported on alumina. The synthesized MWNTs were used directly as a crude sample, and purified MWNTs were also made by boiling concentrated sodium hydroxide water solution and removing mainly alumina in concentrated hydrochloric acid... 

High pressure hydrothermal conversion of Spirulina was studied with iron as catalyst (Matsui et al., 1997). It showed that the bio-oil yield increased linearly from 54.4 to 63.7 wt. % with increasing amount of Fe(CO)5-S from 0 to 1 mmol. The conversion and gas yield were nearly constant. In a similar study, brown macroalga Laminaria saccharina was hydrothermally liquefied to bio-crude in a batch reactor (Anastasakis and Ross, 2011). A maximum bio-crude yield of 19.3 wt. % was obtained with a biomass to water ratio of 1 10 at 350°C and 15 min of residence time. The solid residue contained large proportion of calcium and magnesium, whereas the liquid phase was rich in sugars, ammonium, potassium and sodium. 

Scheme 4-275. Carbomagnesation of electron-deficient allenes using tris(acetylacetonato)iron as catalyst.

Allylic alcohols can be isomerized to ketones in the presence of pentacarbonyl-iron as catalyst under photochemical conditions (Scheme... 

K.Kalucki and A.W.Morawski, Graphite intercalation compounds of iron as catalysts for low temperature ammonia synthesis, in Proc. Inter. Carbon Conference, Baden-Baden, FUG, Chine 30 - July 4, 1986,... 

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