Catalytic wet air oxidation of phenol with functionalized carbon materials as catalysts：Reaction mechanism and pathway

• Published in: Journal of environmental sciences (China) Vol. 26; no. 8; pp. 1741 - 1749
• Main Authors: Wang, Jianbing, Fu, Wantao, He, Xuwen, Yang, Shaoxia, Zhu, Wanpeng
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2014
• Subjects: acetic acid; air; Air - analysis; aqueous solutions; Carbon; Carbon - chemistry; carbon dioxide; carbon fibers; Carbon materials; carbon nanotubes; Catalysis; Catalysts; Catalytic activity; Catalytic wet air oxidation; formic acid; free radicals; maleic acid; malonic acid; Molecular Structure; Oxalic acid; oxidants; Oxidation; Oxidation-Reduction; Pathways; Phenol; Phenol - chemistry; Radical; Reaction pathway; Water; Water Pollutants, Chemical - chemistry; 催化剂; 催化活性; 催化湿式氧化法; 功能化; 反应机理; 多壁碳纳米管; 碳材料; 苯酚; Catalytic wet air oxidation; Phenol; Radical; Carbon materials; Reaction pathway
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/j.jes.2014.06.015

The development of highly active carbon material catalysts in catalytic wet air oxidation（CWAO）has attracted a great deal of attention. In this study different carbon material catalysts（multi-walled carbon nanotubes,carbon fibers and graphite） were developed to enhance the CWAO of phenol in aqueous solution. The functionalized carbon materials exhibited excellent catalytic activity in the CWAO of phenol. After 60 min reaction,the removal of phenol was nearly100% over the functionalized multi-walled carbon,while it was only 14% over the purified multi-walled carbon under the same reaction conditions. Carboxylic acid groups introduced on the surface of the functionalized carbon materials play an important role in the catalytic activity in CWAO. They can promote the production of free radicals,which act as strong oxidants in CWAO. Based on the analysis of the intermediates produced in the CWAO reactions,a new reaction pathway for the CWAO of phenol was proposed in this study. There are some differences between the proposed reaction pathway and that reported in the literature. First,maleic acid is transformed directly into malonic acid. Second,acetic acid is oxidized into an unknown intermediate,which is then oxidized into CO2 and H2O. Finally,formic acid and oxalic acid can mutually interconvert when conditions are favorable.