Characterization of active sites on copper ion-exchanged ZSM-5-type zeolite for NO decomposition reaction

1999 ◽  
Vol 1 (4) ◽  
pp. 649-656 ◽  
Author(s):  
Yasushige Kuroda ◽  
Ryotaro Kumashiro ◽  
Takefumi Yoshimoto ◽  
Mahiko Nagao
Keyword(s):  
Active Sites ◽  
Copper Ion ◽  
Decomposition Reaction ◽  
No Decomposition ◽  
Type Zeolite

Characterization of Active Sites on Copper Ion-Exchanged Mordenite for Dinitrogen Adsorption by Using CO as a Probe Molecule

1997 ◽  
Vol 101 (8) ◽  
pp. 1312-1316 ◽  
Author(s):  
Yasushige Kuroda ◽  
Hironobu Maeda ◽  
Yuzo Yoshikawa ◽  
Ryotaro Kumashiro ◽  
Mahiko Nagao
Keyword(s):  
Active Sites ◽  
Copper Ion ◽  
Probe Molecule

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

Defect engineering and characterization of active sites for efficient electrocatalysis

Nanoscale ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 3327-3345
Author(s):  
Xuecheng Yan ◽  
Linzhou Zhuang ◽  
Zhonghua Zhu ◽  
Xiangdong Yao
Keyword(s):  
Transition Metal ◽  
Active Sites ◽  
Defect Engineering ◽  
Metal Free

This review highlights recent advancements in defect engineering and characterization of both metal-free carbons and transition metal-based electrocatalysts.

Diffuse Reflectance FT-IR Characterization of Active Sites under Reaction Conditions: The Production of Oxygenates in the CO/H2 Reaction

1994 ◽  
Vol 48 (10) ◽  
pp. 1208-1212 ◽  
Author(s):  
J. J. Benítez ◽  
I. Carrizosa ◽  
J. A. Odriozola
Keyword(s):  
Infrared Spectra ◽  
Active Sites ◽  
Diffuse Reflectance ◽  
Reaction Conditions ◽  
In Situ Drifts ◽  
Ft Ir

The reactivity of a Lu2O3-promoted Rh/Al2O3 catalyst in the CO/H2 reaction is reported. Methane, heavier hydrocarbons, methanol, and ethanol are obtained. In situ DRIFTS has been employed to record the infrared spectra under the actual reaction conditions. The structure of the observed COads DRIFTS bands has been resolved into its components. The production of oxygenates (methanol and ethanol) has been correlated with the results of the deconvolution calculation. Specific sites for the production of methanol and ethanol in the CO/H2 reaction over a Rh,Lu2O3/Al2O3 catalyst are proposed.

PREPARATION AND CHARACTERIZATION OF ACTIVATED CARBON FROM OIL PALM EMPTY FRUIT BUNCH WASTES USING ZINC CHLORIDE

2015 ◽  
Vol 74 (11) ◽  
Author(s):  
Riry Wirasnita ◽  
Tony Hadibarata ◽  
Abdull Rahim Mohd Yusoff ◽  
Zainab Mat Lazim
Keyword(s):  
Activated Carbon ◽  
Zinc Chloride ◽  
Oil Palm ◽  
Active Sites ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Proximate Analysis ◽  
Infrared Spectrometry ◽  
Empty Fruit Bunch

An oil palm empty fruit bunch-derived activated carbon has been successfully produced by chemical activation with zinc chloride and without chemical activation. The preparation was conducted in the tube furnace at 500oC for 1 h. The surface structure and active sites of activated carbons were characterized by means of Fourier transform infrared spectrometry and field emission scanning electron microscopy. The proximate analysis including moisture content, ash content, bulk density, pH, and pH at zero charge was conducted to identify the psychochemical properties of the adsorbent. The results showed that the zinc chloride-activated carbon has better characteristics compared to the carbon without chemical activation.  

scholarly journals Influence of Bio-Oil Phospholipid on the Hydrodeoxygenation Activity of NiMoS/Al2O3 Catalyst

Catalysts ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 418 ◽  
Author(s):  
Muhammad Abdus Salam ◽  
Derek Creaser ◽  
Prakhar Arora ◽  
Stefanie Tamm ◽  
Eva Lind Grennfelt ◽  
...  
Keyword(s):  
Active Sites ◽  
Batch Reactor ◽  
Active Phase ◽  
Aluminum Phosphate ◽  
Spent Catalyst ◽  
Bio Oil ◽  
Pore Blockage ◽  
Sulfided Catalyst ◽  
High Degree

Hydrodeoxygenation (HDO) activity of a typical hydrotreating catalyst, sulfided NiMo/γ-Al2O3 for deoxygenation of a fatty acid has been explored in a batch reactor at 54 bar and 320 °C in the presence of contaminants, like phospholipids, which are known to be present in renewable feeds. Oleic acid was used for the investigation. Freshly sulfided catalyst showed a high degree of deoxygenation activity; products were predominantly composed of alkanes (C17 and C18). Experiments with a major phospholipid showed that activity for C17 was greatly reduced while activity to C18 was not altered significantly in the studied conditions. Characterization of the spent catalyst revealed the formation of aluminum phosphate (AlPO4), which affects the active phase dispersion, blocks the active sites, and causes pore blockage. In addition, choline, formed from the decomposition of phospholipid, partially contributes to the observed deactivation. Furthermore, a direct correlation was observed in the accumulation of coke on the catalyst and the amount of phospholipid introduced in the feed. We therefore propose that the reason for the increased deactivation is due to the dual effects of an irreversible change in phase to aluminum phosphate and the formation of choline.

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