Hydroformylation Of Formaldehyde To Glycolaldehyde: An Alternative Synthetic Route For Ethylene Glycol

Hydroformylation of formaldehyde to glycolaldehyde (GA), as a vital reaction in both direct and indirect process of syngas to ethylene glycol (EG), shows great advantages in the aspects of the process complexity and clean production. The hydroformylation of formaldehyde to GA is thermodynamically unfavourable, requiring the development of highly efficient hydroformylation catalytic systems, appropriate reaction conditions and in-depth understanding of the reaction mechanisms. In this review, we have made a detailed summary on the reaction in terms of the reaction network, thermodynamics, metal complex catalysts (including central metals and ligands), reaction conditions (e.g., temperature, pressure, formaldehyde source and solvent) and promoters. Furthermore, the reaction mechanisms, involving neutral and anionic complex in the catalytic cycle, have been summarized and followed by a discussion on the impact of the crucial intermediates on the reaction pathways and product distribution. A brief overview of product separation and catalyst recovery has been presented in the final part. This review gives new insights into the factors that impact on the formaldehyde hydroformylation and reaction mechanisms, which helps to design more efficient catalytic systems and reaction processes for EG production via the hydroformylation route. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.