PEP Review 83-3-4
Direct Process for Ethylene Glycol from Syngas
Published: January 1985
This review examines the technology for producing ethylene glycol directly from syngas (mixtures of hydrogen with carbon monoxide). Research efforts have focused on a high-pressure, liquid-phase process that uses a homogeneous catalyst and a high-dielectric solvent.
The catalyst complex is based on rhodium or ruthenium, generally with a ligand and a nitrogen-containing Lewis base, and often with another modifier. Development work on the catalyst has been aimed at producing a stable system that gives high selectivity to EG and can be recovered with very low losses of precious metal.
Because of competing reactions that produce methanol and propylene glycol, selectivity to EG seldom exceeds 75%, and the reactor product is dilute. Reactor pressure must be at least 8000 psig, with residence times of at least 1.5 hr. Owing to these requirements, the estimated capital is high. Even with optimistic assumptions, we estimate the product value to be highter than the conventional process. Before the syngas process can be commercialized, it will be necessary to improve EG selectivity, lower the operating pressure, increase product concentration, or reduce residence time.