Pincer Ligand Enhanced Rhodium-Catalyzed Carbonylation of Formaldehyde: Direct Ethylene Glycol Production

Formaldehyde is one of the most important bulk chemicals and is produced on a million tone scale (52 million tons in 2017).([1]) Since the middle of the last century, the challenge has remained to produce the valuable ethylene glycol (EG) directly from the C1 building block formaldehyde in a single step. In the systems reported so far, the reaction conditions were very harsh, often with pressures above 400 bar. However, under milder conditions, the selectivity was on the side of glycol aldehyde (GA) and the hydrogenation product methanol. Only traces of EG could be generated in the presence of a Rh catalyst. Herein, we describe a new Rh catalyst system with pincer ligand, which allows the direct one pot synthesis of EG from easy to handle paraformaldehyde (PFA) at remarkable mild conditions (70 bar, 100 degrees C) and overcomes the aforementioned limitations with yield up to 40%.

Automated summary

Formaldehyde is an important bulk chemical, and the challenge of producing valuable ethylene glycol directly from it has been a difficult one. Existing systems have low efficiency in generating ethylene glycol, but this new Rh catalyst system allows for efficient synthesis under milder conditions.