Hydrogenation supercritical carbon dioxide

Iridium(III) hydride forms complexes with DIOP, BDPP (2,4-bis(diphenyl-phosphino)pentane), NORPHOS, and BINAP ligands to produce amines in 11 -80% ee.679 Similar modest results are obtained in the reduction of N-arylketimines with an iridium(HI) complex with (2S,3 S) -C HIRA PHOS as the chiral ligand.680 The indium complexes with chiral phosphinodihydrooxazoles catalyze the enantioselective hydrogenation of imines in supercritical carbon dioxide with up to 80% ee, but generally lower ee values are observed in... 

Keurentjes et al. performed a continuous hydrogenation of 1-butene in supercritical carbon dioxide.[9,10] A fluorous derivative of Wilkinson s catalyst was prepared in situ by mixing the ligand with [(COD)RhCl]2 under hydrogen / carbon dioxide pressure (Figure 4.37). 

Keywords Asymmetric Hydrogenation m Carbon Dioxide m Carbonylation m Dimethylformamide Enantioselectivity m Formic Acid m Homogeneous Hydrogenation n Palladium Catalysts Radical Reactions m Ruthenium Catalysts m Supercritical Fluids m Solvent Replacement... 

S. Kainz, A. Brinkmann, W. Leitner, A. Pfaltz, Iridium-Catalyzed Enantioselective Hydrogenation of Imines in Supercritical Carbon Dioxide , J. Am Chem Soc 1999, 121, 6421-6429. 

P. G. Jessop, T. Ikariya, R. Noyori, Homogeneous Catalytic Hydrogenation of Supercritical Carbon Dioxide , Nature 1994,368,231-233. 

Very recently Jackson reported the use of supercritical carbon dioxide (SCCO2) in this tandem reaction, lowering the required total pressures of carbon monoxide and hydrogen [54]. 

Amorphous fluoropolymers have many applications in the areas of advanced materials where they are used in applications requiring thermal and chemical resistance. Their manufacture is hindered by their low solubility in many solvents. Many fluoropolymerizations cannot be carried out in hydrocarbon solvents because the radical abstraction of hydrogen atoms leads to detrimental side reactions. Chlorofluorocarbons (CFCs) were thus commonly used, but their use is now strictly controlled due to their ozone depleting and greenhouse gas properties. Supercritical carbon dioxide is a very attractive alternative to CFCs and it has been shown that amorphous fluoropolymers can be synthesized by... 

In recent years, attempts have been made to make use of the advantages of the supercritical carbon dioxide in chemical reactions. The first technical examples concerning the use of carbon dioxide in a pilot-plant scale chemical reaction were heterogeneous catalyzed hydrogenation and radical polymerization [38-42]. Meanwhile, hydrogenation reactions have been scaled up in a 1000 t/a commercial multipurpose plant. 

To study the effect of the Ru/Al Oj catalyst on hydrogen yield for refomung of glucose in supercritical water, the experiments were compared to reactions with and without catalytic runs imder identical conditions. Typical product distributions are shown in Table 6.9 for experiments with and without a Ru/Al Oj catalyst at 973 K with 1 wt.% glucose feed (Byrd et al., 2007). There was a significant reduction in carbon monoxide and methane yields in the presence of the catalyst. The main products of the reaction were hydrogen, methane, carbon dioxide, and carbon monoxide. The low carbon monoxide yield (0.1% by vol.) indicates that the water-gas shift reaction approaches completion. 

Class 5 Liquids with no hydrogen-bond forming capability and no donor atoms, e.g., hydrocarbons, carbon disulfide, carbon tetrachloride, supercritical carbon dioxide, etc. 

Brown, R.A., Pollet, R, McKoon, E., Eckert, C.A., Liotta, C.L., and Jessop, P.G., Asymmetric hydrogenation and catalyst recycling using ionic liquid and supercritical carbon dioxide, /. Am. Chem. Soc., 123,1254-1255,2001. 

The three-phase catalytic hydrogenation of an unsaturated ketone using supercritical carbon dioxide as a solvent was studied in order to simulate the performance of a semi-industrial trickle-bed reactor. It is shown that supercritical CO2 strongly increases the reaction rate (Devetta et al., 1999). 

Weidner, E., Richter, D. Influence of Supercritical Carbon Dioxide and Propane on the Solubility and Viscosity of systems containing Hydrogen and Triglycerides (Soybean Oil). In Proceedings 6th Meeting on Supercritical Fluids, Nottingham, April 1999, I.S.A.S.F. Nancy, France, 1999, 657 - 662. 

High catalytic activities have been achieved by the PYRPHOS- [18], PPCP [20], BICHEP- [21], Et-DuPHOS-Rh [19] complexes among others, allowing the reaction with a substrate-to-catalyst molar ratios (S/C) as high as 50,000. With a [2.2]PHANEPHOS-Rh complex, the reaction proceeds even at -45°C [27], Supercritical carbon dioxide, a unique reaction medium, can be used in the DuPHOS and BPE-Rh-catalyzed hydrogenation [43], A highly lipophilic counteranion such as tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF) or trifluoromethanesulfonate is used to enhance the solubility of the cationic Rh complexes. Under the most suitable reaction conditions of 102 atm of carbon dioxide, 1 atm of hydrogen, and 22°C, a-amino acid derivatives are produced with up to 99.7% ee. 

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