Direct Synthesis of Ethylene Glycol from Carbon Monoxide and Hydrogen by Use of Rhodium Catalyst. The Effect of Amine Promoters and Their Roles

Article abstract of DOI:10.1246/bcsj.61.2865

The influence of addition of amines on the direct synthesis of ethylene glycol (EG) has been investigated using a rhodium catalyst under a high pressure (1800 kg cm^-2).The addition of amines improved the catalyst activity and selectivity for the EG formation and the stability of the catalyst.The addition of amines further resulted in glycerol (GL) formation.Optimum amine/rhodium ratios for the EG formation were 50-100 in tetrahydrofuran solvent with a low polarity and 1-3 in γ-butyrolactone solvent with a high polarity.Optimum N/Rh ratios and IR spectra of reaction solutions suggested that amines promoters serve to accelerate the formation of mononuclear Rh species from the catalyst precursor.It was also suggested that amines promote formation of a Rh-CH2OH complex and insertion of CO.Bulky amines such as triisobutylamine, N-ethylcarbazole, triisopropanolamine, and tribenzylamine were especially effective promoters for the formation of EG and Gl.The effectiveness of bulky amines as the promoter is discussed.