SO2 Poisoning Mechanism of the Multi-active Center Catalyst for Chlorobenzene and NOx Synergistic Degradation at Dry and Humid Environments

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique’s environmental flexibility. Herein, Ca, Pb, As, and NO/SO2 were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn–Ca/Pb–O, leading to their inferior catalytic performance with poor CO2 selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO2 introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO2. The formation of unstable sulfites and the released Mn–O structure offset the negative effect from SO2. Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

Section: Results and Disccusionmentioning

confidence: 91%

Section: Characterization Of Catalystsmentioning

confidence: 99%

Evaluation of the Flexibility for Catalytic Ozonation of Dichloromethane over Urchin-Like CuMnO_x in Flue Gas with Complicated Components

Lin

Cai

et al. 2022

“…However, the complex components ( e.g. , As, Pb, SO 2 , H 2 O) in the flue gases of industrial processes often result in mutual interferences in the MPC reaction, which thereby complicates the MPC performance of the V 2 O 5 –WO 3 /TiO 2 catalyst. , Over the years, studies on the resistance to interferences in the NH 3 -SCR process have been extensively explored. − However, few studies have investigated the MPC interference mechanism and anti-interference. , Our previous work demonstrated that the loaded As 2 O 3 species distinctly decreased the oxygen vacancy formation energy at the V–O–V site, which likely contributed to the extensive formation of more toxic polychlorinated byproducts in the MPC reaction. Moreover, the As 2 O 5 species vigorously attacked the neighboring VO sites, forming the As–O–V bands and deactivating the deNO x reaction …”

Section: Introductionmentioning

confidence: 99%

Polymerization State of Vanadyl Species Affects the Catalytic Activity and Arsenic Resistance of the V₂O₅–WO₃/TiO₂ Catalyst in Multipollutant Control of NO_x and Chlorinated Aromatics

Long

Chen

et al. 2023

The conventional V2O5–WO3/TiO2 catalyst suffers severely from arsenic poisoning, leading to a significant loss of catalytic activity. The doping of Al or Mo plays an important role in promoting the arsenic resistance on NH3 selective catalytic reduction (NH3-SCR), but their promotion mechanism remains in debate and has yet to be explored in multipollutant control (MPC) of NO x and chlorinated organics. Herein, our experimental characterizations and density functional theory (DFT) calculations confirmed that arsenic species preferentially adsorb on both Al and Mo to form arsenate, thereby avoiding bonding to the catalytically active V sites. More importantly, Al doping partially converted the polymeric vanadyl species into monomeric ones, thereby inhibiting the near-surface and bulk lattice oxygen mobility of the V2O5–WO3/TiO2 catalyst, while Mo doping resulted in vanadyl polymerization with an enriched V5+ chemical state and exhibited superior MPC activity and CO x selectivity. Our work shows that antipoisoning catalysts can be designed with the combination of site protection and occurrence state modification of the active species.

“…However, over the current well-known NH 3 -SCR catalysts, the temperature window of NH 3 -SCR is difficult to match the CB conversion temperature. , Generally, the redox ability of the NH 3 -SCR catalyst is insufficient, which will result in higher CB conversion temperature, low CO 2 selectivity, and more incompletely oxidized products including regenerated PCDD/Fs . Numerous efforts have been focused on VO x -based catalysts recently, especially VO x /TiO 2 -based catalysts are considered as promising candidates for simultaneously eliminating NO x and chlorinated organics. − The V 2 O 5 –MoO 3 /TiO 2 catalyst investigated by Huang et al exhibited activity with 100% NO conversion within 200–400 °C and more than 90% CB conversion above 300 °C. However, the N 2 selectivity dramatically decreased above 300 °C.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Catalytic Elimination of NO_x and Chlorinated Organics: Cooperation of Acid Sites

Zhang

Shen

et al. 2022

The synergistic catalytic removal of NO x and chlorinated volatile organic compounds under low temperatures is still a big challenge. Generally, degradation of chlorinated organics demands sufficient redox ability, which leads to low N2 selectivity in the selective catalytic reduction of NO x by NH3 (NH3-SCR). Herein, mediating acid sites via introducing the CePO4 component into MnO2/TiO2 NH3-SCR catalysts was found to be an effective approach for promoting chlorobenzene degradation. The observation of in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) and Raman spectra reflected that the Lewis acid sites over CePO4 promoted the nucleophilic substitution process of chlorobenzene over MnO2 by weakening the bond between Cl and benzene ring. Meanwhile, MnO2 provided adequate Brønsted acid sites and redox sites. Under the cooperation of Lewis and Brønsted acid sites, relying on the rational redox ability, chlorobenzene degradation was promoted with synergistically improved NH3-SCR activity and selectivity. This work offers a distinct pathway for promoting the combination of chlorobenzene catalytic oxidation and NH3-SCR, and is expected to provide a novel strategy for synergistic catalytic elimination of NO x and chlorinated volatile organic compounds.