Transition substituted iron oxide catalysts

In another study, the effect of silica incorporation into the Fe O lattice was studied (5,49,50) A 20% Fe O on silica catalyst was prepared using conventional techniques. Ir was found that while direct oxidation of the catalyst at 800 K produced the expected a -catalyst was previously reduced in CO/CO2 to produce magnetite, then subsequent oxidation resulted in the formation of y-Fe203 Figure 10 shows MOssbauer spectra of this catalyst after various thermal treatments. In these spectra, the central doublets were demonstrated to be a result of small iron oxide particles which were superparamagnetic at the conditions where the spectrum was recorded. The suppression of the y - oOg to a -Fe203 transition is characteristic of the substitution of roreign cations into the mag-... 

Fe is the active metal for high-temperature WGS reaction. Hence, we introduced a variety of metal dopants (M = Cr, Mn, Co, Ni, Cu, Zn and Ce) for iron oxide (spinel lattice) and screened their effectiveness for high-temperature WGS reaction [1]. The idea was to examine if ferrite formation can occur with dopants and promote the Fe Fe redox couple. The substitution of Fe sites in the ferrite strucmre with other transition/non-transition/inner transition metal atoms leads to the crystallization of an inverse (or mixed) spinel. The stoichiometry of an inverse spinel can be represented as A(i a)Ba[AaB(2 a)]04, where 8 is the degree of inversion, while A and B represent typical divalent and trivalent cations, respectively. The catalysts were synthesized by coprecipitation method using nitrates as precursors. The synthesized catalysts were evaluated for ultra high temperature WGS reaction in the temperature region 400-550 °C and GHSV 60,000 h- ... 

Many transition-metal complexes have been widely studied in their application as catalysts in alkene epoxidation. Nickel is unique in the respect that its simple soluble salts such as Ni(N03)2 6H20 are completely ineffective in the catalytic epoxidation of alkenes, whereas soluble manganese, iron, cobalt, or copper salts in acetonitrile catalyze the epoxidation of stilbene or substituted alkenes with iodosylbenzene as oxidant. However, the Ni(II) complexes of tetraaza macrocycles as well as other chelating ligands dramatically enhance the reactivity of epoxidation of olefins (90, 91). 

Interestingly, coupling of phenols and jS-ketoesters under iron-catalysed oxidative conditions leads selectively to the formation of substituted benzofurans. Notably, the iron catalyst acts as a transition-metal catalyst in the oxidative coupling step and as Lewis acid in the condensation step. The presence of water coordinated to the catalyst and/or protic solvents accelerates the process, likely favouring the (final) tautomerisation step (Scheme 13.12). ... 

PO can be made degradable by means of additives. The types of additives include aromatic ketones (benzo-phenone and substituted benzophenones [47], qui-none), aromatic amines (trisphenylamine), polycyclic aromatic hydrocarbons (anthracene, certain dyes such as xanthene dyes), or transition metal organic compounds. The transition metal compounds of Fe, Co, Ni, Cr, Mn are widely used. Organo-soluble acetyl acetonates of many transition metals are photooxidants and transition metal carboxylates are also thermal pro-oxidants. Co acetylacetonate appears to be an effective catalyst for chemical degradation of PP in the marine environment. The preferred photoactivator system is ferric dibutyldithiocarbamate with a concentration range of 0.01. 1%. Scott has patented the use of organometallic compounds hke iron (ferric) dibutyldithiocarbamate or Ni-dibutyl-dithiocarbamate [48]. Cerium carboxylate [49] and carbon black are also used in such materials [50]. 

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