Alkali-Free Oxidation of Glycolaldehyde and Ethylene Glycol Toward Glycolic Acid Over a Pt/C Catalyst

Abstract

Glycolic acid (GA), a versatile compound widely used in pharmaceuticals, cosmetics, and biodegradable polymers, requires efficient and sustainable synthesis methods to meet industrial demands. This study investigates the selective oxidation of glycolaldehyde (GD) and ethylene glycol (EG) to GA over a carbon-supported platinum (Pt/C) catalyst under alkali-free conditions. Complete GD conversion with exceptional GA selectivity (99.8%) was achieved under mild conditions (30 °C, 2.5 MPa air), while EG oxidation exhibited moderate conversion (∼60%) with >90% GA selectivity. Kinetic analysis revealed distinct oxygen pressure dependencies: GD oxidation exhibited strong oxygen sensitivity, as oxygen adsorption and activation were rate-determining, whereas EG oxidation was predominantly governed by substrate concentration due to the oxygen saturation on the Pt/C surface. Mechanistic studies identified GD as a key intermediate in EG oxidation, with overoxidation pathways limiting GA selectivity at higher temperatures and concentrations. Catalyst characterization demonstrated high Pt dispersion, stable surface chemistry, and structural durability, contributing to its superior performance. This work provides a green, efficient pathway for GA production, offering valuable insights into catalyst design and process optimization for sustainable chemical manufacturing.