Rh‐Catalyzed Hydrogenation of CO₂ to Formic Acid in DMSO‐based Reaction Media: Solved and Unsolved Challenges for Process Development

Abstract

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.

Methylformate from CO2: an integrated process combining catalytic hydrogenation and reactive distillation

“…8 offers an attractive alternative to the isolation of formic acid from CO 2 hydrogenation mixtures, which proves to be notoriously difficult. 52 With the increasing availability of methanol 53 from biomass, 54,55 recycled waste, 56 or even CO 2 and hydrogen, 57,58 both reactive components of the methyl formate process can be produced from renewable electricity and resources. Given the broad portfolio of methylformate in direct applications or as intermediate, the CO 2 -based production outlined in this paper holds therefore significant potential within the so-called "Power-to-X" concept.…”

The Role of Biowaste: A Multi-Objective Optimization Platform for Combined Heat, Power and Fuel

“…• Formic acid: produced according to the process described in Jens et al (2019) comprising the reaction of CO 2 and H 2 at 50°c and 94 bar, with subsequent by-products removed by distillation. A reactive distillation column at 200 mbar and 180°c produces formic acid with adequate market purity.…”

To Integrate or Not to Integrate—Techno-Economic and Life Cycle Assessment of CO2 Capture and Conversion to Methyl Formate Using Methanol

“…Thus, if the processes are implemented at the time of writing, an additional step in the process will be required to separate the homogeneous catalyst from the formed MeF before depressurization and MeF recovery by distillation. Such homogeneous catalyst separation is usually performed by biphasic systems or by fixating the catalyst on a support material. , Since this work does only consider the catalyst indirectly, this catalyst separation step is not considered in the simulations. Since this step would be very similar for both routes, it would not change the findings of whether the ICCU process is most efficient or not.…”