Aqueous biphasic systems were investigated for the production of formate–amine adducts by metal‐catalyzed CO2 hydrogenation, including typical scrubbing solutions as feedstocks. Different hydrophobic organic solvents and ionic liquids could be employed as the stationary phase for cis‐[Ru(dppm)2Cl2] (dppm=bis‐diphenylphosphinomethane) as prototypical catalyst without any modification or tagging of the complex. The amines were found to partition between the two phases depending on their structure, whereas the formate–amine adducts were nearly quantitatively extracted into the aqueous phase, providing a favorable phase behavior for the envisaged integrated reaction/separation sequence. The solvent pair of methyl isobutyl carbinol (MIBC) and water led to the most practical and productive system and repeated use of the catalyst phase was demonstrated. The highest single batch activity with a TOFav of approximately 35 000 h−1 and an initial TOF of approximately 180 000 h−1 was achieved in the presence of NEt3. Owing to higher stability, the highest productivities were obtained with methyl diethanolamine (Aminosol CST 115) and monoethanolamine (MEA), which are used in commercial scale CO2‐scrubbing processes. Saturated aqueous solutions (CO2 overpressure 5–10 bar) of MEA could be converted into the corresponding formate adducts with average turnover frequencies up to 14×103 h−1 with an overall yield of 70 % based on the amine, corresponding to a total turnover number of 150 000 over eleven recycling experiments. This opens the possibility for integrated approaches to carbon capture and utilization.

CO2 was investigated as carbon source for the synthesis of the polymer precursor toluene‐2,4‐diisocyanate (TDI). A four‐step synthesis was envisaged. The first step, i.e., the Ru‐catalyzed CO2 hydrogenation to [HCOOH·amine] adducts, was carried out under biphasic conditions allowing for straightforward reutilization of the catalyst phase. The investigation of the second step, the esterification of formic acid with methanol to yield methyl formate (MF), is ongoing with a strong focus on the integration with the hydrogenation step. The potential hazards of the third step, the Pd‐catalyzed oxidative carbonylation of toluene‐2,4‐diamine with MF, have been addressed developing a sophisticated protocol for a safe operation with organics/CO/O2 mixtures. For the final step, the carbamate cleavage of toluene‐2,4‐dicarbamate (TDC) towards TDI, monofunctional model substrates and TDC were cleaved in the presence of bifunctional catalysts. The obtained kinetic data allowed to implement the reaction in a continuous stirred‐tank reactor and will serve as starting point for further process optimization.

Catalyst immobilization in decane and repetitive hydrogenation of CO2 to HCOOH-amine with subsequent reactive distillation of the resulting methanolic solution.

Process concepts have been conceived and evaluated for the amine-free homogeneous catalyzed hydrogenation of CO 2 to formic acid (FA). Base-free DMSO-mediated production of FA has been shown to avoid the formation of stable intermediates and presumably the energy-intensive FA recovery strategies. Here, we address the challenges in the development of an overall process: from catalyst immobilization to the FA isolation. The immobilization of the homogeneous catalyst was achieved using a multiphasic approach (nheptane/DMSO) ensuring high retention of the catalyst (> 99%) and allowing facile separation of the catalyst-free product phase. We show that the strong molecular interactions between DMSO and FA on the one hand shift the equilibrium towards the product side, on the other hand, lead to the formation of an azeotrope preventing a simple isolation step by distillation. Thus, we devised an isolation strategy based on the use of co-solvents and computed the energy demands. Acetic acid was identified as best co-solvent and its compatibility with the catalyst system was experimentally verified. Overall, the outlined process involving DMSO and acetic acid as co-solvent has a computed energy demand on a par with state-of-the art aminebased processes. However, the insufficient chemical stability of DMSO poses major limitations on processes based on this solvent.