Abstract: The selective oxidation of ethylene glycol (EG) to glycolic acid (GA) under ambient pressure constitutes a crucial process for building a green carbon cycle and synthesizing value-added chemicals. This study employed a Pt/C catalytic system to systematically investigate the effects of reaction temperature, oxygen partial pressure, and types of reaction promoter on the reaction performance. The results indicate that the optimal reaction temperature ranges from 60 to 80 °C, with an apparent activation energy of 11.27 kJ/mol. A high GA selectivity of 90% was achieved, and the reaction order with respect to oxygen was determined to be only 0.24, confirming that highly efficient catalysis can be realized under mild positive oxygen pressure. Furthermore, a semi-continuous mild positive-pressure reaction system achieved a GA selectivity of 70%. Screening of reaction promoters revealed that the introduction of ascorbic acid significantly enhanced both reaction conversion and selectivity [with a conversion rate of 46% and total selectivity for glycolaldehyde (GD) and GA reaching 100%]. In contrast, quinone-based promoters, while facilitating active oxygen transport, showed limited improvement in conversion. In situ infrared spectroscopy analysis elucidated the tandem reaction pathway, wherein EG is converted to GA via a GD intermediate.

Key words: ethylene glycol, glycolic acid, glycolaldehyde, Pt/C catalyst, selective oxidation, radical regulation