Comparative study of three-way catalytic performance over Pd/CeO2-ZrO2-Al2O3 and Pd/La-Al2O3 catalysts: New insights into microstructure and thermal stability

Chen, Kai; Wan, Jie; Lin, Ji; Zhou, Renxian

doi:10.1016/j.mcat.2022.112361

Cited by 13 publications

(8 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the first period up to 150 s, at a bed temperature below 400 °C, Pd/CZ exhibited higher conversion efficiencies than Pd/Al 2 O 3 . This is consistent with previous reports, − ,− in which the superior intrinsic activity of Pd/CZ was attributed to the presence of active sites at the interface between Pd and CZ. As shown in Figure , the activity difference between these catalysts was especially obvious during a long acceleration period (e.g., 120–145 s, highlighted by yellow color), during which the catalyst was exposed to the exhaust gas at a high space velocity.…”

Section: Results and Discussionsupporting

confidence: 93%

“…In the present study, we investigated the dynamic TWC performance of Pd/CZ and Pd/Al 2 O 3 catalysts using a full-scale chassis dynamometer and a laboratory scale microreactor. Although these catalyst systems have been already investigated and compared in terms of their catalytic performance and thermostability, − their behavior under dynamic perturbation conditions remains unexplored. We especially focused on the transient behavior of these catalysts arising from the oxygen scavenging function of Pd/CZ to elucidate the relationship between the surface state and the catalyst performance.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

et al. 2022

View full text Add to dashboard Cite

In three-way catalytic converters, momentary perturbations of the exhaust gas composition between fuel-rich (reducing) and fuel-lean (oxidizing) conditions near the stoichiometric point affect the catalyst surface and the conversion efficiencies of NO x , CO, and hydrocarbons. However, the specific changes in the surface state of the catalyst under such dynamic conditions have not been elucidated in detail. In this study, in situ diffuse reflectance spectroscopy (DRS) was applied to monitor real-time changes in the surface state of Pd-based catalysts occurring under rich/lean perturbation at intervals of 2 s. The Pd oxidation state was found to fluctuate in synchronism with this perturbation, but its oscillation amplitude was much smaller when supported on CeO2–ZrO2 (CZ) than on Al2O3. Because this buffering effect of CZ due to its oxygen scavenging function mitigates the gradual oxidation of active metallic Pd to less-active Pd oxide, higher reaction rates were achieved especially for NO x and CO under the dynamic perturbation atmosphere. Furthermore, the Pd–CZ interface quickly supplied active oxygen species to prevent coke deposition originating from the decomposition of adsorbed hydrocarbon, which was unavoidable on Pd/Al2O3 under stoichiometric and fuel-rich conditions. This study demonstrates that in situ DRS provides a simple and useful tool for the direct observation of surface state changes under the real reaction atmosphere at the laboratory level. The information obtained is of great use for understanding the role of CZ in transient and unsteady-state catalytic processes and bridging a gap between real on-board TWC performances and laboratory tests.

show abstract

Section: Results and Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

et al. 2022

View full text Add to dashboard Cite

show abstract

“…There are two main groups of spin–orbit complex lines, namely the u series and the v series. The two characteristics, comprised of peaks u ′ (902.0–903.4 eV) and v ′ (884.4–885.5 eV), can be attributed to Ce 3+ , while the six characteristic peaks, comprised of v (881.2–882.2 eV), v ′′ (888.9–889.3 eV), v ′′′ (897.5–898.1 eV), u (900.3–900.8 eV), u ′′ (907.3–907.7 eV), and u′′′ (916.4–916.7 eV), can be assigned to Ce 4+ . ,− Such results reveal that both Ce 3+ and Ce 4+ species exist on the Ce 0.79 /Cu 2.34 -SSZ-13 surface, and Ce 4+ is identified as the major one by calculating the Ce 4+ /Ce 3+ ratio.…”

Section: Results and Discussionmentioning

confidence: 99%

New Insight into the Doping Effect of Transition Metals (Fe, Ti, Mn, and Ce) on the Structure and Catalytic Performance of Cu-SSZ-13 Zeolite Catalysts for the NH₃-SCR Reaction

Wang

Wan

Chen

et al. 2022

Ind. Eng. Chem. Res.

Self Cite

View full text Add to dashboard Cite

Cu-SSZ-13 zeolite catalysts were synthesized via one-pot strategies and further doped with different transition metals (TM = Fe, Ti, Ce, Mn) by ion exchange methods. The synthesized catalysts were assessed by tests of NH3-SCR activity, hydrothermal stability, and antisulfur-poisoning ability along with various characterizations including XRD, XPS, and H2-TPR. Results indicate that different dopants significantly affect the catalytic performance. The Fe doped Fe 0.86 /Cu 2.14 -SSZ-13 catalyst exhibited an expanded operation temperature window, outstanding high-temperature SCR activity, and increased durability against hydrothermal aging as well as SO2 poisoning, while other dopants such as Mn or Ce seem quite unsatisfactory. Isolated Cu2+ and monomeric Fe3+ are revealed as the major active species contributing to low-temperature NH3-SCR activity and efficient high-temperature NO conversion, respectively. TM doping led to substitution of the Cu1 species (isolated Cu2+ near the octatomic ring window) at ion-exchange sites, zeolite framework structure collapse, and migration of active Cu species into more stable sites during hydrothermal aging, as well as agglomeration of Cu/Fe species during SO2 pretreatment. Thus, the TM/Cu-SSZ-13 catalysts presented obvious catalytic activity deterioration after hydrothermal aging or sulfur poisoning.

show abstract

“…As shown in Figure 11a, the catalysts regenerated at various times show similar peak at ∼531.2 eV relating to O 1s, which can be deconvoluted into two sub-bands: The one (O I ) located at 530.9 eV is attributed to the lattice oxygen, while the other peak (O II ) located at 532.0 eV is assigned to the surface activated oxygen. 44 As to Pd 3d, it can be deconvoluted into four peaks, which are attributed to Pd 2+ 3d 3/2 (∼350 eV), Pd 0 3d 3/2 (∼347 eV), Pd 2+ 3d 5/2 (∼331 eV), and Pd 0 3d 5/2 (∼336 eV), respectively (Figure 11b). The detailed information on the Pd oxidation states is summarized in Table S5.…”

Section: Spent Catalyst Treatmentmentioning

confidence: 99%

Plasma Regeneration of Spent Pd/Al₂O₃ Catalysts and Their Electrochemical Performance

Lin

Tao

Starostin³

et al. 2023

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

A dielectric barrier discharge (DBD) plasma was applied to reactivate palladium on alumina (Pd/Al 2 O 3 ) waste catalysts at extreme conditions, addressing a common problem of reusing the spent catalysts instead of discarding them. Experimental studies of the effect of gas composition in the plasma process reveal different extent of coke elimination and different electrochemical performance of the reactivated Pd/Al 2 O 3 catalysts, ranked as Artreated > N 2 -treated > O 2 -treated > untreated spent catalyst at fixed gas flow rate and regeneration time. The effect of the regeneration time and gas flow rate on the electrochemical performance of the reactivated Pd/Al 2 O 3 catalysts was systematically studied. The results show that for Ar and N 2 process gas, the electrochemical performance of the plasma-treated spent catalyst is improved with the increase of the gas flow rate and the treatment time. However, if O 2 is used, then the electrochemical performance of the spent catalyst decreases with the increase of the gas flow rate and the treatment time. The XPS results show that higher oxidation degrees of Pd reduces the electrochemical performance. This study demonstrates a new strategy for reusing the otherwise waste catalyst in a simple and environment-benign solvent-free manner.

show abstract

Comparative study of three-way catalytic performance over Pd/CeO2-ZrO2-Al2O3 and Pd/La-Al2O3 catalysts: New insights into microstructure and thermal stability

Cited by 13 publications

References 55 publications

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

New Insight into the Doping Effect of Transition Metals (Fe, Ti, Mn, and Ce) on the Structure and Catalytic Performance of Cu-SSZ-13 Zeolite Catalysts for the NH₃-SCR Reaction

Plasma Regeneration of Spent Pd/Al₂O₃ Catalysts and Their Electrochemical Performance

Contact Info

Product

Resources

About

Comparative study of three-way catalytic performance over Pd/CeO2-ZrO2-Al2O3 and Pd/La-Al2O3 catalysts: New insights into microstructure and thermal stability

Cited by 13 publications

References 55 publications

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

Surface State Changes of Pd Three-Way Catalysts under Dynamic Lean/Rich Perturbation Compared with Static Condition

New Insight into the Doping Effect of Transition Metals (Fe, Ti, Mn, and Ce) on the Structure and Catalytic Performance of Cu-SSZ-13 Zeolite Catalysts for the NH3-SCR Reaction

Plasma Regeneration of Spent Pd/Al2O3 Catalysts and Their Electrochemical Performance

Contact Info

Product

Resources

About

New Insight into the Doping Effect of Transition Metals (Fe, Ti, Mn, and Ce) on the Structure and Catalytic Performance of Cu-SSZ-13 Zeolite Catalysts for the NH₃-SCR Reaction

Plasma Regeneration of Spent Pd/Al₂O₃ Catalysts and Their Electrochemical Performance