scholarly journals Probing the Active Sites of ZnO Nanowire Supported Ir Species for CO Oxidation

2019 ◽  
Vol 25 (S2) ◽  
pp. 2204-2205
Author(s):  
Jia Xu ◽  
Yafeng Cai ◽  
Xu Li ◽  
Jingyue Liu
Keyword(s):  
Co Oxidation ◽  
Active Sites ◽  
Zno Nanowire

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

scholarly journals Dynamic active sites over binary oxide catalysts: In situ/operando spectroscopic study of low-temperature CO oxidation over MnOx-CeO2 catalysts

2016 ◽  
Vol 191 ◽  
pp. 179-191 ◽  
Author(s):  
Xiao-man Zhang ◽  
Ya-Qing Deng ◽  
Pengfei Tian ◽  
Huan-huan Shang ◽  
Jing Xu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Spectroscopic Study ◽  
Co Oxidation ◽  
Active Sites ◽  
Binary Oxide ◽  
Oxide Catalysts ◽  
Low Temperature Co Oxidation

scholarly journals CO Oxidation over Metal Oxide (La2O3, Fe2O3, PrO2, Sm2O3, and MnO2) Doped CuO-Based Catalysts Supported on Mesoporous Ce0.8Zr0.2O2 with Intensified Low-Temperature Activity

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 724 ◽  
Author(s):  
Yan Cui ◽  
Leilei Xu ◽  
Mindong Chen ◽  
Chufei Lv ◽  
Xinbo Lian ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Low Temperature ◽  
Metal Oxide ◽  
Metal Oxides ◽  
Co Oxidation ◽  
Active Sites ◽  
Earth Metal ◽  
High Dispersion ◽  
Impregnation Method ◽  
X Ray

CuO-based catalysts are usually used for CO oxidation owing to their low cost and excellent catalytic activities. In this study, a series of metal oxide (La2O3, Fe2O3, PrO2, Sm2O3, and MnO2)-doped CuO-based catalysts with mesoporous Ce0.8Zr0.2O2 support were simply prepared by the incipient impregnation method and used directly as catalysts for CO catalytic oxidation. These mesoporous catalysts were systematically characterized by X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), energy-dispersed spectroscopy (EDS) mapping, X-ray photoelectron spectroscopy (XPS), and H2 temperature programmed reduction (H2-TPR). It was found that the CuO and the dopants were highly dispersed among the mesoporous framework via the incipient impregnation method, and the strong metal framework interaction had been formed. The effects of the types of the dopants and the loading amounts of the dopants on the low-temperature catalytic performances were carefully studied. It was concluded that doped transition metal oxides could regulate the oxygen mobility and reduction ability of catalysts, further improving the catalytic activity. It was also found that the high dispersion of rare earth metal oxides (PrO2, Sm2O3) was able to prevent the thermal sintering and aggregation of CuO-based catalysts during the process of calcination. In addition, their presence also evidently improved the reducibility and significantly reduced the particle size of the CuO active sites for CO oxidation. The results demonstrated that the 15CuO-3Fe2O3/M-Ce80Zr20 catalyst with 3 wt. % of Fe2O3 showed the best low-temperature catalytic activity toward CO oxidation. Overall, the present Fe2O3-doped CuO-based catalysts with mesoporous nanocrystalline Ce0.8Zr0.2O2 solid solution as support were considered a promising series of catalysts for low-temperature CO oxidation.

scholarly journals Wolkenstein’s Model of Size Effects in CO Oxidation by Gold Nanoparticles

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 288 ◽  
Author(s):  
Nigora Turaeva ◽  
Herman Krueger
Keyword(s):  
Gold Nanoparticles ◽  
Co Oxidation ◽  
Active Sites ◽  
Kinetic Equations ◽  
Dissociative Adsorption ◽  
Transition Metal Catalysts ◽  
Band Theory ◽  
Shape Dependence ◽  
Langmuir Hinshelwood Mechanism ◽  
Electron Transfers

The Wolkenstein’s theory of catalysis and the d-band theory of formation chemical bonds between transition metal catalysts and adsorbates were used to develop the approach applied to the kinetics of CO oxidation by gold nanoparticles. In the model, within the framework of the mechanism of the reaction going through dissociative adsorption of oxygen molecules and reaction with gas-phase CO molecules, weak and strong chemisorption states of intermediates (O, CO2) were taken into account in the kinetic equations by introducing reversible electronic steps corresponding to electron transfers between the intermediates and the catalyst. As a result, we obtain the expression for the reaction rate, which exhibits a volcano-shape dependence upon the size of the gold nanoparticles at the conditions when the intermediates fractions are not small compared to the empty active sites of the catalyst. It is supposed that the approach can be also applied to the Langmuir-Hinshelwood mechanism.

CeO2-supported Au and AuCu catalysts for CO oxidation: Impact of activation protocol and residual chlorine on the active sites

2020 ◽  
Author(s):  
Tanna Elyn Rodrigues Fiuza ◽  
Danielle Santos Gonçalves ◽  
Igor Ferreira Gomes ◽  
Daniela Zanchet
Keyword(s):  
Co Oxidation ◽  
Active Sites ◽  
Residual Chlorine

scholarly journals Surface and Catalytic Properties of γ-Irradiated Cr2O3/Al2O3 Solids

1997 ◽  
Vol 15 (6) ◽  
pp. 465-476 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
G.M. Mohamed
Keyword(s):  
Catalytic Activity ◽  
Co Oxidation ◽  
Surface Area ◽  
Pore Volume ◽  
Active Sites ◽  
Catalytic Properties ◽  
Total Pore Volume ◽  
Bet Surface Area ◽  
Two Samples ◽  
Γ Rays

Two samples of Cr2O3/Al2O3 were prepared by mixing a known mass of finely powdered Al(OH)3 with a calculated amount of CrO3 solid followed by drying at 120°C and calcination at 400°C. The amounts of chromium oxide employed were 5.66 and 20 mol% Cr2O3, respectively. The calcined solid specimens were then treated with different doses of γ-rays (20–160 Mrad). The surface and catalytic properties of the different irradiated solids were investigated using nitrogen adsorption at −196°C and the catalysis of CO oxidation by O2 at 300–400°C. The results revealed that γ-rays brought about a slight decrease in the BET surface area, SBET (15%), and in the total pore volume, Vp (20%), of the adsorbent containing 5.66 mol% Cr2O3. The same treatment increased the total pore volume, Vp (36%), and the mean pore radius, r̄ (43%), of the other adsorbent sample without changing its BET surface area. The catalytic activities of both catalyst samples were found to increase as a function of dose, reaching a maximum value at 80–160 Mrad and 40 Mrad for the solids containing 5.66 and 20 mol% Cr2O3, respectively. The maximum increase in the catalytic activity measured at 300°C was 59% and 100% for the first and second catalyst samples, respectively. The induced effect of γ-irradiation on the catalytic activity was an increase in the concentration of catalytically active sites taking part in chemisorption and in the catalysis of CO oxidation by O2 without changing their energetic nature. This was achieved by a progressive removal of surface hydroxy groups during the irradiation process.

Low-temperature CO oxidation on Ag/ZSM-5 catalysts: Influence of Si/Al ratio and redox pretreatments on formation of silver active sites

Fuel ◽  
2017 ◽  
Vol 188 ◽  
pp. 121-131 ◽  
Author(s):  
E. Kolobova ◽  
A. Pestryakov ◽  
G. Mamontov ◽  
Yu. Kotolevich ◽  
N. Bogdanchikova ◽  
...  
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Active Sites ◽  
Low Temperature Co Oxidation

scholarly journals Elucidation of the Active Sites in Single-Atom Pd1/CeO2 Catalysts for Low-Temperature CO Oxidation

ACS Catalysis ◽  
2020 ◽  
Vol 10 (19) ◽  
pp. 11356-11364 ◽  
Author(s):  
Dong Jiang ◽  
Gang Wan ◽  
Carlos E. García-Vargas ◽  
Linze Li ◽  
Xavier Isidro Pereira-Hernández ◽  
...  
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Active Sites ◽  
Single Atom ◽  
Low Temperature Co Oxidation

Identification of Active Sites on High-Performance Pt/Al2O3 Catalyst for Cryogenic CO Oxidation

ACS Catalysis ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8815-8824 ◽  
Author(s):  
Yang Chen ◽  
Yingxin Feng ◽  
Lin Li ◽  
Jingyue Liu ◽  
Xiaoli Pan ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Active Sites ◽  
High Performance ◽  
Al2o3 Catalyst
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