New light on the state of active sites in CuZSM-5 for the NO decomposition reaction and N2 adsorptionElectronic supplementary information (ESI) available: XANES and EXAFS spectra of the reference samples (1) Cu metal; (2) Cu2O; (3) CuCl; (4) [Cu(NH3)2]+; (5) CuO; (6) Cu(OH)2; (7) [Cu(hfac)2]. See http://www.rsc.org/suppdata/cp/b3/b304538m/

2003 ◽  
Vol 5 (15) ◽  
pp. 3318 ◽  
Author(s):  
Yasushige Kuroda ◽  
Kazunori Yagi ◽  
Naoko Horiguchi ◽  
Yuzo Yoshikawa ◽  
Ryotaro Kumashiro ◽  
...  
Keyword(s):  
Active Sites ◽  
Decomposition Reaction ◽  
The State ◽  
No Decomposition ◽  
Supplementary Information ◽  
Reference Samples ◽  
Exafs Spectra

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

scholarly journals Properties of Iron-Modified-by-Silver Supported on Mordenite as Catalysts for NOx Reduction

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1156 ◽  
Author(s):  
Perla Sánchez-López ◽  
Yulia Kotolevich ◽  
Evgeny Khramov ◽  
Ramesh Kumar Chowdari ◽  
Miguel Angel Estrada ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Bimetallic Catalysts ◽  
Active Sites ◽  
Nox Reduction ◽  
The State ◽  
Edge Structure ◽  
X Ray ◽  
Disordered Phase ◽  
Activity Test ◽  
X Ray Absorption

A series of mono and bimetallic catalysts based on a Fe-Ag mixture deposited on mordenite was prepared by ion-exchange and evaluated in the catalytic activity test of the de-NOx reaction in the presence of CO/C3H6. The activity results showed that the most active samples were the Fe-containing ones, and at high temperatures, a co-promoter effect of Ag on the activity of Fe catalysts was also observed. The influence of the order of cation deposition on catalysts formation and their physicochemical properties was studied by FTIR (Fourier Transform Infrared Spectroscopy) of adsorbed NO, XANES (X-ray Absorption Near-Edge Structure), and EXAFS (Extended X-ray Absorption Fine Structure) and discussed in terms of the state of iron. Results of Fe K-edge XANES oscillations showed that, in FeMOR catalysts, iron was present in a disordered state as Fe3+ and Fe2+. In FeAgMOR, the prevailing species was Fe3+, while in the AgFeMOR catalyst, the state of iron was intermediate or mixed between FeMOR and FeAgMOR. The Fe K-edge EXAFS results were characteristic of a disordered phase, the first coordination sphere being asymmetric with two different Fe-O distances. In FeAgMOR and AgFeMOR, coordination of Fe-O was similar to Fe2O3 with a few amount of Fe2+ species. We may conclude that, in the bimetallic FeAgMOR and AgFeMOR samples, a certain amount of tetrahedral Al3+ ions in the mordenite framework is replaced by Fe3+ ions, confirming the previous reports that these species are active sites for the de-NOx reaction. Based on the thermodynamic analysis and experimental data, also, it was confirmed that the order of deposition of the components influenced the mechanism of active sites’ formation during the two steps ion-exchange synthesis.

scholarly journals Catalytic and Sulfur-Tolerant Performance of Bimetallic Ni–Ru Catalysts on HI Decomposition in the Sulfur-Iodine Cycle for Hydrogen Production

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8539
Author(s):  
Lijian Wang ◽  
Kang Zhang ◽  
Yi Qiu ◽  
Huiyun Chen ◽  
Jie Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
Large Scale ◽  
Decomposition Reaction ◽  
Catalytic Performance ◽  
Sulfur Poisoning ◽  
Great Promise ◽  
Sulfur Tolerance ◽  
Sulfur Resistance ◽  
Sulfur Deactivation ◽  
The Stability

The sulfur-iodine (SI) cycle holds great promise as an alternative large-scale process for converting water into hydrogen without CO2 emissions. A major issue regarding the long-term stability and activity of the catalysts is their poor sulfur deactivation resistance in the HI feeding process. In this work, the effect of Ru addition for enhancing the activity and sulfur resistance of SiO2-supported Ni catalysts in the HI decomposition reaction has been investigated. The presence of H2SO4 molecules in the HI results in severe sulfur deactivation of the Ru-free Ni/SiO2 catalysts by blocking the active sites. However, Ni–Ru/SiO2 catalysts show higher catalytic activity without sulfur-poisoning by 25% and exhibit more superior catalytic performance than the Ru-free catalyst. The addition of Ru to the Ni/SiO2 catalyst promotes the stability and activity of the catalysts. The experimental trends in activity and sulfur tolerance are consistent with the theoretical modeling, with the catalytic activities existing in the order Ni/SiO2 < Ni–Ru/SiO2. The effect of Ru on the improvement in sulfur resistance over Ni-based catalysts is attributed to electronic factors, as evidenced by theory modeling analysis and detailed characterizations.

scholarly journals Synthesis and characterization of Cu-MFI catalyst for the direct medium temperature range NO decomposition

2016 ◽  
Vol 34 (1) ◽  
pp. 177-184 ◽  
Author(s):  
Karolina Maduna Valkaj ◽  
Vesna Tomašić ◽  
Andrea Katović ◽  
ElżBieta Bielańska
Keyword(s):  
Ion Exchange ◽  
Active Sites ◽  
Catalytic Properties ◽  
Direct Synthesis ◽  
Copper Acetate ◽  
Nitrogen Adsorption ◽  
No Decomposition ◽  
Medium Temperature ◽  
Exchange Method ◽  
Mfi Zeolites

AbstractIn this study the physico-chemical and catalytic properties of copper bearing MFI zeolites (Cu-MFI) with different Si/Al and Si/Cu ratios were investigated. Two different methods for incorporation of metal ions into the zeolite framework were used: the ion exchange from the solution of copper acetate and the direct hydrothermal synthesis. Direct synthesis of a zeolite in the presence of copper-phosphate complexes was expected to generate more active copper species necessary for the desired reaction than the conventional ion exchange method. Direct decomposition of NO was used as a model reaction, because this reaction still offers a very attractive approach to NOX removal. The catalytic properties of zeolite samples were studied using techniques, such as XRD, SEM, EPR and nitrogen adsorption/desorption measurements at 77 K. Results of the kinetic investigation revealed that both methods are applicable for the preparation of the catalysts with active sites capable of catalyzing the NO decomposition. It was found out that Cu-MFI zeolites obtained through direct synthesis are promising catalysts for NO decomposition, especially at lower reaction temperatures. The efficiency of the catalysts prepared by both methods is compared and discussed.

The State of the Active Sites and Deactivation of Mo-ZSM-5 Catalysts of Methane Dehydroaromatization

2005 ◽  
Vol 404 (4-6) ◽  
pp. 201-204 ◽  
Author(s):  
V. I. Zaikovskii ◽  
A. V. Vosmerikov ◽  
V. F. Anufrienko ◽  
L. L. Korobitsyna ◽  
E. G. Kodenev ◽  
...  
Keyword(s):  
Active Sites ◽  
The State ◽  
Methane Dehydroaromatization

Fe-Modified ZSM-5 and β Zeolites for Direct N2O Decomposition

2012 ◽  
Vol 610-613 ◽  
pp. 94-99 ◽  
Author(s):  
Quan Hui Guo ◽  
Juan Li ◽  
Ying Xia Li
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Channel Wall ◽  
Decomposition Reaction ◽  
Catalytic Performance ◽  
Iron Ions ◽  
Exchange Method ◽  
Different Types ◽  
Charge Balancing ◽  
Better Than

Fe-modified ZSM-5 and β zeolites were prepared by adopting liquid ion-exchange method and their catalytic performance was studied in the N2O decomposition reaction. The state of Fe loaded on Fe-zeolites was investigated by means of UV-vis diffuse spectra, infrared spectroscopy, EPR and H2-TPR. The results of IR of hydroxyl stretching and UV-vis investigationSubscript texts indicated that part of the iron-ions was introduced into zeolites at the charge-balancing sites. The results of EPR and H2-TPR investigations showed that the same iron species were loaded on ZSM-5 and β zeolites. However, the results of IR of the perturbed anti-symmetric T-O-T vibrations of iron-ions indicated that different types of ZSM-5 and β zeolites resulted in different distributions of charge-balancing iron cations. The iron-ions could replace Brönsted acid protons at the straight channel wall (α sites), intersection of straight and sinusoidal channels (β sites), and sinusoidal channel wall (γ sites) within the ZSM-5 zeolite. In the case of Fe-β zeolites, iron-ions mainly located in the straight channels. We observed that the catalytic activity of the iron ions located on the α sites of ZSM-5 zeolites was better than those of iron ions located on β and γ sites in N2O direct decomposition, since the former was the most easily reduced from Fe3+to Fe2+in H2. Furthermore, it was found that Fe-β zeolite showed higher catalytic activity than Fe-ZSM-5 zeolite. This difference was attributed to the active sites located almost exclusively in the straight zeolite channels.

Effect of valence of copper in La2−Th CuO4 on NO decomposition reaction

2006 ◽  
Vol 7 (1) ◽  
pp. 29-32 ◽  
Author(s):  
Junjiang Zhu ◽  
Zhen Zhao ◽  
Dehai Xiao ◽  
Jing Li ◽  
Xiangguang Yang ◽  
...  
Keyword(s):  
Decomposition Reaction ◽  
No Decomposition

Dimeric Cu(I) species in Cu-ZSM-5 catalysts: the active sites for the NO decomposition

2005 ◽  
Vol 232 (2) ◽  
pp. 476-487 ◽  
Author(s):  
G MORETTI ◽  
G FERRARIS ◽  
G FIERRO ◽  
M JACONO ◽  
S MORPURGO ◽  
...  
Keyword(s):  
Active Sites ◽  
No Decomposition
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