Synthesis of N,N-dimethylformamide from carbon dioxide in aqueous biphasic solvent systems

- CO2 is hydrogenated to formate and condensed with an amine to yield formamides.
- The immobilization of a homogeneous catalyst in nonpolar solvents is investigated.
- Catalyst complex formation and product separation are performed in-situ.
- Several recycling runs demonstrate the concept and the catalyst stability towards air.

This paper presents the homogeneous catalyzed hydrogenation of carbon dioxide to N,N-dimethylformamide (DMF) with an in-situ generated ruthenium catalyst based on RuCl3 × H2O and the phosphine ligand 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl (BISBI). Investigations showed that the complex formation of an active species requires the presence of an amine. The catalyst was recycled by immobilization in a nonpolar alcoholic solvent while the formed product was extracted in-situ into the aqueous phase. The self-assembling reaction system showed stability for 10 recycling runs without a significant loss of activity resulting in an average yield of 31% DMF at 40 bar and 140 °C without the occurrence of any byproducts. Furthermore, a combination of the developed reaction system with ternary amines enables the application of wash amine solutions as carbon dioxide carrier.

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