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Moderne Katalysatoren zur Hydrierung von Kohlendioxid

“…Anders als heterogen katalysierte Reduktionen von Kohlendioxid11 verläuft die Hydrierung zu Ameisensäurederivaten in Gegenwart von metallorganischen Komplexen bei vergleichsweise niedriger Temperatur (<100 °C) und zuweilen niedrigem Druck. Wie in Tabelle 1 gezeigt, wurden bei der Hydrierung von Kohlendioxid hohe Umsatzzahlen (TON) mithilfe von Rhodium‐,12 Ruthenium‐ und Iridiumkatalysatoren erzielt.…”

Homogeneous Hydrogenation of Carbon Dioxide

“…It is not clear, given that these higher ratios are possible, why the yield in practice is limited to a ratio of 1.9 : 1, or lower. Rhodium(I) catalyst precursors [20,37] have similar dependence of rate on solvent polarity, with DMSO always being excellent and less-polar aprotic solvents such as acetone, THF, or benzene being inferior. One of the most active catalysts to date, RhCl(TPPTS) 3 , is used in water, despite the very poor solubility of H 2 in that medium.…”

“…Solvent choice is important for optimizing the rate of this reaction. However, methanol was found to be better than DMSO for RhCl(PPh 3 ) 3 [37] and decidedly inferior for [RhCl(COD)] 2 /dppb [20]. For the hydrophobic catalysts, the best solvents so far have been scCO 2 and polar aprotic solvents.…”

Selective and Direct Hydrogenation of CO2 for the Synthesis of Formic Acid over a Rhodium Hydrotalcite (Rh‐HT) Catalyst

“…Most of the CO 2 hydrogenation processes performed with the use of various promoters. The Rh(PPh 3 ) 3 Cl, a Wilkinson catalyst, was first introduced for the hydrogenation of CO 2 using methanol as a solvent, PPh 3 as an additive and Et 3 N as a base with a TON of 2715 . A TON of 1840 was reported, when water was used as a solvent and ionic liquid as a promoter in the presence of a Si(CH 2 ) 3 NH(CSCH 3 )[RuCl 3 (PPh 3 )] catalyst .…”