Low‐Temperature H<sub>2</sub> Reduction of Copper Oxide Subnanoparticles

Sonobe, Kazutaka; Tanabe, Makoto; Imaoka, Takane; Chun, Wang‐Jae; Yamamoto, Kimihisa

doi:10.1002/chem.202100508

Cited by 17 publications

(16 citation statements)

References 54 publications

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“…In contrast, PC3/6 does not appear until holding at 500 °C for the Cu-CHA sample. The reduction temperatures and the reduction behavior of Cu ions in Mg-Cu-CHA and K-Cu-CHA correlate with the reduction of Cu ions of nanosized CuO-like clusters to Cu 0 metal . The differences in the reduction behavior of poisoned catalysts can indicate the different sizes of these Cu 2+ oxide-like clusters.…”

Section: Resultsmentioning

confidence: 94%

“…The reduction temperatures and the reduction behavior of Cu ions in Mg-Cu-CHA and K-Cu-CHA correlate with the reduction of Cu ions of nanosized CuO-like clusters to Cu 0 metal. 83 The differences in the reduction behavior of poisoned catalysts can indicate the different sizes of these Cu 2+ oxide-like clusters. Likely larger Cu 2+ oxide clusters are also present in Na-Cu-CHA compared to other poisoned catalysts.…”

Section: Changes Inmentioning

confidence: 99%

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Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Mesilov

Zhuang

et al. 2023

J. Phys. Chem. C

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Biodiesel is an environmentally friendly fuel that may partially replace petroleum diesel in transportation. One possible disadvantage of biodiesel is that alkali and alkaline earth metals can significantly affect Cu speciation and the elemental composition of copper chabazite (Cu-CHA) catalysts used in vehicle emission control units. To investigate this, we perform atomic-scale characterization of Cu-SSZ-13 zeolites contaminated by Mg, K, and Na using inductively coupled plasma-optical emission spectroscopy and Cu K-edge X-ray absorption spectroscopy (XAS) coupled with hydrogen temperature-programmed reduction. The experimental data decomposed by a multivariate curve resolution algorithm are interpreted using theoretical XAS spectra and reactive molecular dynamics. We find that Mg poisoning leads to a more severe dealumination compared to K or Na poisoning. Poisoning of catalysts also leads to the aggregation of isolated Cu ions into CuO x clusters, while alkali and alkaline earth metal ions replace Cu ions in ion-exchange sites. The site preferences of Mg, K, and Na ions in Cu-CHA are thoroughly explored using density functional theory (DFT) calculations, suggesting an explanation of results from elemental analysis. Our study provides important theoretical and experimental insights into the poisoning of Cu-CHA catalysts by biodiesel metal contaminants.

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Section: Resultsmentioning

confidence: 94%

Section: Changes Inmentioning

confidence: 99%

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Mesilov

Zhuang

et al. 2023

J. Phys. Chem. C

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“…For the MW-synthesized HP-CuO, four H 2 -reduction peaks are observed at reduction temperatures of 155, 202, 223, and 278 °C. The two main H 2 -reduction peaks at 202 and 223 °C can be attributed to the reduction of lattice copper species of HP-CuO as Cu(II) → Cu(I) and Cu(I) → Cu . The small H 2 -reduction peak at 152 °C could be related to the reduction of exposed fine Cu species on the surface, whereas the one at the highest reduction temperature of 278 °C could be related to unexposed larger Cu entities within the cavities .…”

Section: Resultsmentioning

confidence: 94%

“…The two main H 2 -reduction peaks at 202 and 223 °C can be attributed to the reduction of lattice copper species of HP-CuO as Cu(II) → Cu(I) and Cu(I) → Cu. 44 The small H 2 -reduction peak at 152 °C could be related to the reduction of exposed fine Cu species on the surface, whereas the one at the highest reduction temperature of 278 °C could be related to unexposed larger Cu entities within the cavities. 45 The CuO prepared by CHM possessed the main H 2 -reduction peak at 243 °C along with two higher-temperature reduction peaks at 255 and 263 °C.…”

Section: Resultsmentioning

confidence: 99%

Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation

2022

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The synthesis of copper oxide (CuO)-based nanomaterials has received a tremendous deal of interest in recent years. Particularly, the design and development of novel CuO structures with improved physical and chemical properties have attracted immense attention, especially for catalysis applications. We report on a rational, rapid, and surfactant-free microwave synthesis (MWS) of hierarchical porous copper oxide (HP-CuO) with a three-dimensional (3D) sponge-like topology using an MWS reactor. The activity of the microwave (MW)-synthesized HP-CuO catalysts for carbon monoxide (CO) oxidation was studied and compared to CuO prepared by the conventional heating method (CHM). Results showed that HP-CuO catalysts prepared by MWS for 10 and 30 min surpassed the CuO catalyst prepared by CHM, exhibiting T 80 of 98 and 115 °C, respectively, as compared to 185 °C of CuO prepared by CHM (T 80 is the temperature corresponding to 80% CO conversion). In addition, the MW-synthesized HP-CuO catalysts outperformed the CHM-synthesized CuO, achieving a 100% CO conversion at 150 °C compared to 240 °C in the case of CuO prepared by CHM. Interestingly, the HP-CuO catalyst expressed workable CO conversion kinetics with a reaction rate of c.a.35 μmol s −1 g −1 at 150 °C and apparent activation energy (E a ) of 82 kJ mol −1 . The HP-CuO catalyst showed excellent cycling and long-term stabilities for CO oxidation up to 4 cycles and 72 h on the stream, respectively. The enhanced catalytic activity and stability of the HP-CuO catalyst appear to result from the unique topological and structural features of HP-CuO, which were revealed by SEM, XRD, Raman, BET, TGA, XPS, and TPR techniques.

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“…Note that the reduction of bulk and nanosized CuO in H 2 is observed below 300 °C. 79,80 No significant reduction of Cu ions is observed for P-Cu at these temperatures (Figure 5b). The XAFS spectra of PC5 (Figure 3) and CuO 70,81 are different.…”

Section: Discussionmentioning

confidence: 94%

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

et al. 2022

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Biodiesel is a promising renewable fuel, which may help to limit our dependence on fossil fuels. However, the presence of contaminants in biodiesel can affect the Cu speciation of the Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, resulting in its deactivation and decreased durability. In situ Cu K-edge X-ray absorption fine structure (XAFS) scanning during a temperature-programmed reduction in hydrogen (H2-TPR) has been applied here for the analysis of Cu speciation in Cu-SSZ-13 catalysts aged using pure and contaminated biodiesel fuels. XAFS data were analyzed using the multivariate curve resolution alternating least-squares (MCR-ALS) method. While only reduction from CuII to CuI was observed at temperatures below 500 °C for the catalyst aged using pure biodiesel, a one-step reduction of CuII to Cu0 at temperatures between 400 and 500 °C was found for the catalyst aged using P-doped biodiesel. The transformation of isolated CuII species to CuII clusters was suggested for the catalyst as a result of aging using P-doped biodiesel. The catalyst aged using S-doped biodiesel showed mainly the reduction of isolated CuII to CuI, which was inhibited as compared to that observed for the catalyst aged using pure biodiesel. The reduction of the catalyst aged using P+S-doped biodiesel led to the reduction of CuII to both CuI and Cu0. The phosphorus was responsible for the formation of CuII clusters during aging of the catalyst using P+S-doped biodiesel. This study reveals that the presence of phosphorus in biofuels should be strictly regulated to avoid major changes in the Cu speciation of Cu-SSZ-13 catalysts.

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Low‐Temperature H₂ Reduction of Copper Oxide Subnanoparticles

Cited by 17 publications

References 54 publications

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

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Low‐Temperature H2 Reduction of Copper Oxide Subnanoparticles

Cited by 17 publications

References 54 publications

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H2-TPR

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Low‐Temperature H₂ Reduction of Copper Oxide Subnanoparticles

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR