Deactivation of Au/TiO2 catalyst in the hydrogenation of o-chloronitrobenzene in the presence of CO2

✍ Scribed by Yufen Hao; Ruixia Liu; Xiangchun Meng; Haiyang Cheng; Fengyu Zhao

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 683 KB
• Volume: 335
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2010.11.029

✦ Synopsis

The hydrogenation of o-chloronitrobenzene over Au/TiO 2 was investigated in supercritical carbon dioxide (scCO 2 ), ethanol, H 2 O, and H 2 O/CO 2 at 140 • C. The reaction rate followed the order of H 2 O > H 2 O/CO 2 > ethanol > scCO 2 . Au/TiO 2 was deactivated in the systems containing CO 2 . Changes of Au/TiO 2 catalysts were investigated by means of transmission electron microscopy (TEM), in situ infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance ultraviolet-visible spectra (DR-UV/Vis). Aggregation of Au particles was excluded from origins of deactivation by TEM. Carbonate-like species formed on gold in the presence of CO 2 and H 2 were detected by in situ IR spectroscopy. The results of XPS and DR-UV/Vis reveal that the active species of Au 0 was oxidized in the presence of CO 2 . The possible formation of CO and its influence on the activity of Au/TiO 2 were also discussed. Accordingly, the formation of carbonates, the oxidation of surface Au 0 by CO 2 , and the CO formation are proposed to be the possible factors for the deactivation of Au/TiO 2 .