Operando investigation of catalytic trichloroethylene combustion over metal-doped CeO2 nanorods

Abstract

The remediation of chlorinated volatile organic compounds is an intractable issue for it typically requires high temperatures and generates undesirable byproducts. This work utilized a series of representative transition metals (i.e., Cr, Cu, V) to modify the morphology, surface oxygen, and acidity of the CeO2 nanorods for trichloroethylene (TCE) treatment. A spectroscopic operando DRIFT − online GCMS reactor was introduced to examine the catalytic performance and elucidate the reaction pathway. Among them, Cr-CeO2 exhibited 50 % (T50) and 90 % (T90) TCE conversions with no byproduct at 171 °C and 241 °C, respectively. The performances of Cu-CeO2 (T90 = 391 °C), V-CeO2 (T90 = 423 °C) and CeO2 (T90 = 494 °C) were inferior to Cr-CeO2 (T90 = 241 °C), with obvious C2Cl4 generated in the TCE oxidation. It reveals that TCE adsorbed on Cr-CeO2 is dechlorinated on acidic sites and oxidized to carbonate/formate intermediates by the surface oxygen then facilely to generate carbon oxides, while TCE is adsorbed as chlorinated species (CH2ClCH2O−) on the other three catalysts which occupy the surface and require higher temperature to be oxidized. The abundant medium-strong acidic sites and surface oxygen species of Cr-CeO2 nanorods are responsible for the low-temperature activation via C-Cl cleavage on acidic sites and fast oxidation of hydrocarbon intermediates in the TCE oxidation, respectively.