The direct conversion of synthesis gas into ethylene glycol catalyzed by rhodium.

Abstract

Recent advances in the direct conversion of synthesis gas to form ethylene glycol catalyzed by rhodium are summarized. High-rate conversions of synthesis gas are achieved in alkyl-substituted pyrrolidones or urea derivatives used as solvents. The formation of glycol is greatly facilitated by phosphine-promoted rhodium catalysts. The catalytic activity is determined by the electronic and steric effects of the phosphine. The rate of ethylene glycol formation increases with increasing electron-donating properties of the phosphine. The steric hindrance of the ligand inhibits electronic effects on glycol formation. Carboxylic acids (HX) facilitate the formation of ethylene glycol catalyzed by the Rh/phosphine (L) system. Recovered complexes from the resultant solutions were identified as RhX(CO)L2, which are stable under repeated usage. The acids play an important role in the catalytic activity and stability of the rhodium complexes.