Identification of key mechanics in the ruthenium catalyzed synthesis of N,N-dimethylformamide from carbon dioxide in biphasic solvent systems

An Efficient and Practical System for the Synthesis of N,N‐Dimethylformamide by CO2 Hydrogenation using a Heterogeneous Ru Catalyst: From Batch to Continuous Flow

“…However, advancing the homogeneous hydrogenation towards the practical realization remains unfeasible, owing to the serious obstacles in terms of separation of the catalysts from the highly polar product DMF and recycling of the catalyst. Nevertheless, Vorholt and co‐workers recently proposed a continuous stirred tank reactor as feasible for the homogeneous hydrogenation of CO 2 to DMF by using multiphase liquid–liquid extraction to separate DMF from the homogeneous catalyst –. However, this multiphase extraction process may not be preferable and suitable in industry, particularly for a chemical like DMF, the production scale of which is relatively large, because this process is highly laborious, and most importantly, leaching of Ru metal is thus far unavoidable, which in turn reduces the economic viability of the system.…”

“…It is commonly considered that the synthesis of DMF by CO 2 hydrogenation is accompanied by FA generation, followed by dehydration (Figure b). However, there is another possible route that involves the generation of CO via the reverse water gas shift reaction, followed by DMA carbonylation (Figure b) . To acquire insight into the pathway, a series of experiments was carried out.…”

“…Therefore, these results collectively indicate that the formation of DMF is accompanied by FA generation and the pathway related to carbonylation is very unlikely in hydrogenation catalyzed by 1 . Notably, there was no discernible distinction in the point of selectivity for FA versus DMF during the heterogeneous hydrogenation, because FA, if present, in the reaction medium, can be converted to DMF during thermal treatment in the DMF isolation step, which has also been reported by Vorholt and co‐workers during distillation of the solvents in the DMF isolation step –. Henceforth, the word “yield” indicates the combined FA and DMF yields.…”

“…Based on our experience and previous reports, we have proposed a mechanism for the synthesis of DMF via the formate pathway by CO 2 hydrogenation over 1 (Scheme ). The pathway involves the generation of a Ru−H intermediate through substitution of the Cl ligand with H 2 followed by CO 2 insertion into the Ru−H intermediate to generate a Ru−formate species, which then releases the formate from the catalytic cycle by oxidative addition of H 2 and regenerates the Ru−H species.…”

Recent Advances Utilized in the Recycling of Homogeneous Catalysis

“…Kuhlmann et al . developed a biphasic solvent system for the recycling of homogeneous catalyst (Ru‐Macho) in the synthesis of N , N ‐dimethylformamide (DMF) from carbon dioxide (Figure )Several reaction parameters were optimized to understand the key factors of this biphasic setup and mechanism of the reaction. Recently, Prakash and co‐workers developed a tandem efficient and recyclable catalyst system for CO 2 capture in aqueous amine solution and its hydrogenation to methanol in biphasic 2‐MTHF/water system (Figure ) .…”