Oxidation of ethylene by Cu/TiO 2 : reducibility of Cu 2+ in TiO 2 as a possible descriptor of catalytic efficiency

• Published in: Catalysis science & technology 2023-04, Vol.13 (8), p.2330-2339
• Main Authors: Rajendran, K., Sharma, Mandeep, Jaison, Augustine, Ankitha, Menon, Tiwari, Ankit D., Vinod, C. P., Jagadeesan, Dinesh
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/D2CY02170F

Catalytic oxidation using non-noble metal-based catalysts is a promising approach to mitigate pollution due to VOCs in the air. In this work, mesoporous Cu/TiO 2 catalysts containing different concentrations of Cu 2+ (0.2, 1, 3, and 4 wt% Cu w.r.t. Ti) were synthesized using the sol–gel technique. The catalysts were characterized using inductively coupled plasma-optical emission spectrometry, XRD, Raman spectroscopy, N 2 physisorption, cyclic voltammetry, H 2 -TPR and electron microscopy to understand the structure and composition. The thermal catalytic gas phase oxidation of ethylene was studied by heating a mixture of ethylene (1.5 vol%) and air (5.9 vol%) in the presence of the Cu/TiO 2 samples in the temperature range of 298 to 773 K. Cu/TiO 2 showed a higher catalytic activity compared to TiO 2 for the thermal oxidation of ethylene, indicating a strong promotion by doped copper ions. A volcanic behaviour in the catalytic activity was observed with different concentrations of Cu doping, with 1% Cu/TiO 2 showing a 99.5% ethylene conversion at 673 K and 100% selectivity to CO 2 . The activity of 1% Cu/TiO 2 remained consistent without deactivation for 24 h. At low dopant concentrations of Cu (0.2 and 1% Cu/TiO 2 ), the reduction of Cu 2+ to Cu + was observed. An interplay of oxygen vacancies (O V ), Cu + , Cu 2+ and Ti 4+ may be involved in controlling the activity. DRIFT studies indicated the formation of surface bidendate carbonate as a possible intermediate.