Rhodium-based bidentate phosphorus ligand catalyst for direct synthesis of ethylene glycol

Abstract

After decades of development, the reaction conditions for direct synthesis of ethylene glycol (EG) from syngas are still very harsh. The pressure required for the reaction is around 435 atm for the state of the art catalyst HRh(CO)3Pi−Pr3. Herein, a new catalyst 1,2-di(phospholan-1-yl)benzene rhodium dicarbonyl hydride is predicted to relieve the harsh reaction conditions by theoretical simulations. In methanol solvent, the highest energy barrier of the new catalyst is 8.7 kcal/mol lower than that of the old catalyst for the rate determining step, which indicates that the bidentate phosphorus ligand effect can significantly improve the catalytic performance compared with traditional monodentate phosphorus ligand catalysts. It is also found that the energy barrier of this reaction is very high in gas phase but it can be significantly decreased under polar solvents, which explains why the current catalysts for the direct synthesis of EG can only be carried out in solution rather than in gas phase. Here, the pressure required for the reaction is promising to be reduced by using the predicted new catalyst, which is improved for direct synthesis of EG.