Reduction promoted

Additives such as rare earth or noble metals are generally introduced into industrial cobalt FTS catalysts as structural or reduction promoters.92 The addition of various promoters to cobalt catalysts has also been shown to decrease the amount of carbon produced during the FTS.84 87 93 94 Also, the addition of promoter elements may decrease the temperature of regeneration, preventing the possible sintering of supported cobalt particles during such treatments.92... 

Chen and Ray [48] in a study on the photocatalytic reduction of environmentally relevant metal ions on Ti02 suspensions, observed that the presence of dissolved oxygen, acting as electron acceptor, inhibits the reduction of metal ions with low reduction potentials, while the presence of organic reductants promotes photocatalytic reduction. 

Scheme 3.9 Mechanistic pathway for dioxygen reduction promoted by dicobalt FTF porphyrins.

Preferential reduction of an a,)3-unsaturated ketones C=C bond is more easily accomplished than preferential reduction of the C=0 bond. However, a keto group can be hydrogenated in preference to a C=C bond after the appropriate choice of the catalyst, usually Pt or Ru . Additives such as FeCl2 (a carbonyl reduction promoter) and zinc acetate (a double bond saturation inhibitor) may be used in conjunction with platinum oxide . The less hindered ketone in 6 is selectively hydrogenated over Pt02 [equation... 

Cu is shown to be much more easily reducible than Ni and Co when interacting with a non-stoichiometric zinc aluminate spinel [13], in agreement with the model suggested above for the Cu-Zn-Al system [12]. The TPR profile of the Ni-Cu-Zn-Al sample indicates that Ni and Cu reduction take place at different temperatures. However, the reduction of Ni in the Ni-Cu-Zn-Al catalyst occurs at a lower temperature than in the rest of the solids, so that the Cu reduction seems to catalyze the Ni reduction. The TPR profile for the Ni-Co-Zn-Al oxide shows only one peak at around 614 °C. This reduction temperature is similar to that obtained with the Ni-Zn-Al catalyst and lower than the temperature required to reduce Co towards Co in a Co-Zn-Al catalyst. This fact indicates that the nickel reduction promotes the cobalt reduction. In this case, a simultaneous reduction of both metallic cations is obtained. 

Biomimetic CO2 reduction promoted by Ni complexes has been reported by Tommasi. The isolable and previously characterized Ni(0) adduct, Ni(PCy3)2(002), reacted with thiols to liberate Ni(PCy3)2(CO)2, Ni(PCy3)2(SR)2, and water. The authors suggest single-electron transfer from PhSH to the Ni(0)-CO2 adduct, followed by proton transfer, as the key mechanistic steps in CO2 reduction. Lower yields resulted when using HCl or H2S in place of PhSH, consistent with proton... 

Intensity of soil reduction promotes increase in root porosity and ROL from root to rhizosphere. There is an increasingly higher rate of oxygen loss as soil redox potential becomes more reduced. 

Reductions Promoted by Low Valent Transition Metal Complexes in Organic Synthesis ... 

ENANTIOSELECTIVE REDUCTIONS PROMOTED BY CHIRAL PHOSPHORIC ACIDS... 

Carbon dioxide is hydrogenated (40-50 atm.) to formic acid in the presence of [RhCl(cod)]2/dppb 5 or [Rh(nbd)(PMe2Ph)3]Bp4. In the latter case dihydride and formate intermediates can be detected spectroscopically. A small group of related papers deal with electrochemical CO2 reductions promoted by various transition metal catalysts. ... 

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