Hydrothermally stable Pd/SiO2@Zr Core@Shell catalysts for diesel oxidation applications

Liu, Chih-Han; Chen, Junjie; Toops, Todd J.; Choi, Jae‐Soon; Thomas, Cyril; Lance, Michael J.; Kyriakidou, Eleni A.

doi:10.1016/j.cej.2021.130637

Cited by 12 publications

(6 citation statements)

References 42 publications

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“…The microreactor experiments were performed in a custom‐built reactor system, as reported previously 33,34 . The experimental procedure followed is shown in Scheme 1.…”

Section: Methodsmentioning

confidence: 99%

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Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Chen,

Lee,

Khatri

et al. 2024

AIChE Journal

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Pd/BEA is chosen as a model passive NOx adsorber (PNA) to elucidate the effect of the feed gas composition on the NOx adsorption/desorption behavior. The Brønsted acid and the partially hydrolyzed framework Al (P‐HAl(OH)) sites in HBEA adsorb NO and NO2 under dry conditions. Moreover, the performance of HBEA is not affected by CO, while CO inhibits nitrate formation and promotes NO adsorption via the Pd(NO)(CO) complexes formation over Pd/BEA. H2O inhibits NO adsorption over the Brønsted acid and P‐HAl(OH) sites, and ionic Pd is the only active site for NOx adsorption under wet conditions. Furthermore, NO adsorption over hydrated Pd (Pd2+(OH)(NO)(H2O)3) is weaker than NO adsorption over bare ionic Pd (Z2[Pd2+(NO)], Z[Pd2+(OH)(NO)]). Dehydration of Pd2+(OH)(NO)(H2O)3 forms more stable Z[Pd2+(OH)(NO)] during desorption. The NO adsorption capacity of Pd/BEA improves in the presence of CO under both dry and wet conditions by forming a stable carbonyl–nitrosyl complex.

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“…The microreactor experiments were performed in a custom‐built reactor system, as reported previously 33,34 . The experimental procedure followed is shown in Scheme 1.…”

Section: Methodsmentioning

confidence: 99%

“…The microreactor experiments were performed in a custom-built reactor system, as reported previously. 33,34 The experimental procedure followed is shown in Scheme 1. Specifically, 100 mg of sample (HBEA, Pd/BEA, 250-500 μm) was loaded in a U-shaped quartz reactor (I.D.…”

Section: Microreactor Experimentsmentioning

confidence: 99%

Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Chen,

Lee,

Khatri

et al. 2024

AIChE Journal

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“…Kinetic studies were conducted in a packed-bed reactor as reported previously. , Specifically, 100 mg of Ni/CeO 2 catalyst was diluted with 100 mg of inert quartz sand and loaded in a U-shaped quartz reactor (ID = 8 mm). The feed gas contained a mixture of CH 4 , O 2 , and Ar with a flow rate of 30 sccm (cm 3 /min at STP) and a gas hourly space velocity (GHSV) of ∼18 000 mL g –1 h –1 .…”

Section: Methodsmentioning

confidence: 99%

Mechanistic Understanding of Methane Combustion over Ni/CeO₂: A Combined Experimental and Theoretical Approach

et al. 2021

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Catalytic oxidation of methane (CH4) over nonprecious Ni/CeO2 catalysts has received a lot of attention due to the large natural gas reserves found in North America and the prohibitive cost of palladium-based catalysts, commonly used for CH4 oxidation. However, the catalytic mechanism of CH4 oxidation over Ni/CeO2 still remains unclear. Moreover, the parameters affecting the reaction rates, the interaction between nickel and CeO2, and the reaction intermediates are still not well understood. Herein, kinetic model fitting, CH4 temperature-programmed reduction-mass spectroscopy (CH4 TPR-MS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) calculations were combined to elucidate the mechanism of complete oxidation of CH4 over Ni/CeO2. CH4 TPR-MS showed that the complete oxidation of CH4 over Ni/CeO2 requires 55–120 °C lower compared to bare CeO2 or Ni/quartz sand; complete oxidation of CH4 took place when the surface oxygen species were abundant, while partial oxidation products (CO, H2) were formed when the oxygen species were depleted. In situ DRIFTS showed that CH3, CH2, CO, and CO2 were formed after CH4 activation over Ni/CeO2, while CH3O species were not observed. Combining those findings with kinetic model fitting, a redox Mars–van Krevelen (MvK) mechanism showed the best description of the experimental observations. The MvK mechanism involves the reaction of dissociated oxygen species with gas-phase CH4 while water inhibits the reaction rate by adsorbing on the oxidized sites. Moreover, CH4 activation leads to the reduction of the active sites and oxygen vacancy formation followed by reoxidation of the active sites by gas-phase O2. A CH4 oxidation reaction pathway over Ni/CeO2 is proposed by DFT calculations. In summary, the findings shown here suggest that CH4 oxidation over Ni/CeO2 follows a redox MvK mechanism and provides guidance for the rational design of non-precious-metal catalysts for CH4 oxidation reactions.

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“…The CH 4 oxidation performance of the as-synthesized catalysts was evaluated in a home-built packed bed reactor equipped with an online MKS FTIR gas analyzer (MultiGas 2030). , The catalyst (100 mg, 250–500 μm) was loaded into a U-shaped quartz tube reactor (I.D. = 8 mm) and was stabilized between two small plugs of quartz wool.…”

Section: Experimental Sectionmentioning

confidence: 99%

Cobalt-Induced PdO Formation in Low-Loading Pd/BEA Catalysts for CH₄ Oxidation

et al. 2021

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Palladium (Pd)/zeolite-based catalysts have shown great promise in low-temperature CH4 oxidation reactions. However, improving the low-temperature performance of Pd/zeolite catalysts while simultaneously decreasing Pd usage remains a challenge. Herein, we demonstrate that incorporation of cobalt (Co) into 0.5 wt % Pd/BEA (Pd (0.5)/BEA) can substantially boost the CH4 oxidation performance. In particular, increasing Co loading from 0 to 1 wt % led to a continuous improvement in the CH4 oxidation activity, with T 50 (temperature at which 50% conversion is achieved) decreasing from >500 °C over Pd (0.5)/BEA to 352 °C over Pd(0.5)Co(1.0)/BEA. Moreover, the CH4 oxidation reaction rate of Pd(0.5)Co(1.0)/BEA at 250 °C was 77% greater than that of Pd(1.0)/BEA. Experimental evidence from CH4-temperature programmed reduction, CO diffuse reflectance infrared Fourier transform spectroscopy, H2-temperature programmed reduction, O2-temperature programmed desorption, high-angle annular dark field-scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and apparent activation energy studies suggested that the promotion effect of Co incorporation is attributed to the formation of highly active PdO, instead of less active ionic Pd. Stability tests over Pd(0.5)Co(1.0)/BEA showed comparable CH4 oxidation activity to Pd(1.0)/BEA and slightly improved H2O resistance. Density functional theory calculations revealed that Co is more stable than Pd at the ion-exchange sites (Al sites) of BEA zeolites. Co being more stable than Pd at the ion-exchange sites leads to fewer ion-exchange sites available for Pd and thus less ionic Pd but more PdO nanocluster formation over bimetallic PdCo/BEA catalysts.

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Hydrothermally stable Pd/SiO2@Zr Core@Shell catalysts for diesel oxidation applications

Cited by 12 publications

References 42 publications

Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Mechanistic Understanding of Methane Combustion over Ni/CeO₂: A Combined Experimental and Theoretical Approach

Cobalt-Induced PdO Formation in Low-Loading Pd/BEA Catalysts for CH₄ Oxidation

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Hydrothermally stable Pd/SiO2@Zr Core@Shell catalysts for diesel oxidation applications

Cited by 12 publications

References 42 publications

Condition‐dependent NOx adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Condition‐dependent NOx adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Mechanistic Understanding of Methane Combustion over Ni/CeO2: A Combined Experimental and Theoretical Approach

Cobalt-Induced PdO Formation in Low-Loading Pd/BEA Catalysts for CH4 Oxidation

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Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Condition‐dependent NO_x adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

Mechanistic Understanding of Methane Combustion over Ni/CeO₂: A Combined Experimental and Theoretical Approach

Cobalt-Induced PdO Formation in Low-Loading Pd/BEA Catalysts for CH₄ Oxidation