Base-free selective oxidation of monosaccharide into sugar acid by surface-functionalized carbon nanotube composites

作者：Li, Zengyong; Li, Di; Zhong, Linxin; Li, Xuehui; Liu, Chuanfu^*; Peng, Xinwen^*

来源：CHINESE CHEMICAL LETTERS, 2023, 34(11): 108370.

DOI：10.1016/j.cclet.2023.108370

• Surface functionalization
• Base-free oxidation
• Sugar acid
• Kinetic study
• DFT calculation

Selective oxidation of biomass-derived monosaccharide into high value-added chemicals is highly desirable from sustainability perspectives. Herein, we demonstrate a surface-functionalized carbon nanotubesupported gold (Au/CNT-O and Au/CNT-N) catalyst for base-free oxidation of monosaccharide into sugar acid. Au/CNT-O and Au/CNT-N surfaces successfully introduced oxygen-and nitrogen-containing functional groups, respectively. The highest yields of gluconic acid and xylonic acid were 93.3% and 94.3%, respectively, using Au/CNT-N at 90 & DEG;C for 240 min, which is higher than that of using Au/CNT-O. The rate constants for monosaccharide decomposition and sugar acid formation in Au/CNT-N system were higher, while the corresponding activation energy was lower than in Au/CNT-O system. DFT calculation revealed that the mechanism of glucose oxidation to gluconic acid involves the adsorption and activation of O 2 , adsorption of glucose, dissociation of the formyl C-H bond and formation of O-H bond, and formation and desorption of gluconic acid. The activation energy barrier for the glucose oxidation over Au/CNT-N is lower than that of Au/CNT-O. The nitrogen-containing functional groups are more beneficial for accelerating monosaccharide oxidation and enhancing sugar acid selectivity than oxygen-containing functional groups. This work presents a useful guidance for designing and developing highly active catalysts for producing high-value-added chemicals from biomass.& COPY; 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.