Synergistic Enhancement of Hydrolysis–Oxidation Drives Efficient Catalytic Elimination of Chlorinated Aromatics over VO<sub><i>x</i></sub>/TiO<sub>2</sub> Catalysts at Low Temperature
Yunfeng Ma, Jianwen Lai, Bingcheng Lin, Xiaoqing Lin, Jiabao Lv, Fanxiang Meng, Zhongkang Han, Runtong Dong, Rong Jin, Guorui Liu, Masaki Takaoka, Xiaodong Li, Minghui Zheng
Abstract
The efficient catalytic elimination of toxic chlorinated aromatics (i.e., dioxins, chlorobenzenes, etc.) at low temperature is still a great challenge. Based on the VO x /TiO 2 catalyst, a hydrolysis-oxidation strategy (CeO x and WO x doping) was built for desirable low-temperature catalytic activity, product selectivity, H 2 O tolerance, and chlorine desorption. The in situ and ex situ experimental characterizations and density functional theory calculations revealed that hydrolysis sites favored molecular adsorption, C–Cl cleavage, and HCl formation; meanwhile, oxidation sites enhanced the activation of reactive oxygen species and improved oxygen mobility and redox properties. The enhanced oxygen storage/release capacity (33–53 fold) and extended redox cycle (e.g., from V 5+ ↔V 4+ to V 5+ ↔V 4+ ↔V 3+ ) favored the deep oxidation. The introduction of H 2 O triggered the hydrolysis–oxidation process that promoted the catalytic activity and chlorine desorption due to the elevated generation of ·O 2 – and higher-activity ·OH. Furthermore, the water resistance of the VO x /TiO 2 -based catalyst was enhanced after the application of the hydrolysis–oxidation strategy. The V–Ce–W/Ti catalyst exhibited remarkable removal efficiency of dioxins (96.7–98.2%), which was reduced from 0.34–0.48 ng I-TEQ Nm –3 to 0.006–0.016 ng I-TEQ Nm –3 during pilot tests at 160–180 °C, achieving ultralow emissions. This work provides practical guidance for industry development for efficiently eliminating chlorinated organics in flue gas.