Iron-based olefin oxidation catalysts

FIGURE 18.2 Ligands for iron-based olefin oxidation catalysts with H2O2 oxidant. 

Mn-promoted Fe-based Fischer-Tropsch Catalysts. 4.1.1 Unsupported Fe-Mn Fischer-Tropsch Catalysts. Iron-based F-T catalysts possess both hydrogenation and WGS activity, imposing a flexible option as a working catalyst for typically coal-derived CO-rich syngas conversion. Iron-based catalysts often contain small amounts of K and some other metals/metal oxides as promoters to improve their activity and selectivity. Mn has been widely used as one of the promoters for unsuppported Fe-based F T catalysts, particularly in promoting the production of C2 C4 olefins. ... 

The discovery of iron complexes that can catalyze olefin czs-dihydroxylation led Que and coworkers to explore the possibility of developing asymmetric dihydroxylation catalysts. Toward this end, the optically active variants of complexes 11 [(1R,2R)-BPMCN] and 14 [(1S,2S)- and (lP-2P)-6-Me2BPMCN] were synthesized [35]. In the oxidation of frans-2-heptene under conditions of limiting oxidant, 1R,2R-11 was foimd to catalyze the formation of only a minimal amount of diol with a slight enantiomeric excess (ee) of 29%. However, 1P-2P-14 and 1S,2S-14 favored the formation of diol (epoxide/diol = 1 3.5) with ees of 80%. These first examples of iron-catalyzed asymmetric ds-dihydroxylation demonstrate the possibility of developing iron-based asymmetric catalysts that may be used as alternatives to currently used osmium-based chemistry [45]. 

To date Sasol has used only iron-based catalysts. Not only is iron much cheaper than the alternative metals, but it also produces more olefins. For the fixed-bed reactors the silica-supported and alkali-promoted catalyst is prepared by precipitation techniques (ref. 2). A recent improvement in catalyst formulation has resulted in a more reactive catalyst as well as a lower cost per reactor charge. The catalyst used in the fluidized-bed reactors is prepared by fusing suitable iron oxides together with the... 

Electrocatalytic oxidations (mainly epox-idation) of alkenes by manganese porphyrins [77, 78] and a Schiff-base [79] and iron and cobalt porphyrins [78] have been achieved. Hydrogen peroxide or the superoxide ion (O ) was generated electrochem-ically by reduction of dioxygen in solvents containing an acid or acid anhydride, the metal compounds as catalysts, and olefins as substrates, in the presence or absence of an axial base. The reaction was believed to take place through the formation of a high valent metal 0x0 porphyrin, produced... 

Oxidation of aliphatic C-H groups with HP is efficiently catalysed by cis-a-aminopyridine manganese complexes in the presence of acetic acid. The reaction demonstrated excellent efficiency (up to TON = 970), site selectivity, and stereospecificity (up to >99%). Manganese(II) and iron(II) complexes based on ligands with a rigid, chiral diamine derived from proline and two benzimidazoles (2) were synthesized and applied in epoxidation reaction with aqueous HP. Mn-complex catalyses the epoxidation of olefins. Isolated yields of 60-99% and up to 95% ee were obtained with 0.01-0.2mol% catalyst loading. The turnover frequencies and turnover numbers reached 59,000 h and 9600, respectively. Iron(II) complex exhibited a... 

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