scholarly journals Highly Dispersed Pd Species Supported on CeO2 Catalyst for Lean Methane Combustion: The Effect of the Occurrence State of Surface Pd Species on the Catalytic Activity

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 772
Author(s):  
Yanxiong Liu ◽  
Changhua Hu ◽  
Longchun Bian
Keyword(s):  
Catalytic Activity ◽  
Oxygen Vacancies ◽  
Methane Combustion ◽  
Pd Nanoparticles ◽  
High Concentration ◽  
Ch4 Combustion ◽  
Highly Active ◽  
Δ Phase ◽  
Occurrence State ◽  
Comprehensive Characterization

The correlation between the occurrence state of surface Pd species of Pd/CeO2 for lean CH4 combustion is investigated. Herein, by using a reduction-deposition method, we have synthesized a highly active 0.5% PdO/CeO2-RE catalyst, in which the Pd nanoparticles are evenly dispersed on the CeO2 nanorods CeO2-R. Based on comprehensive characterization, we have revealed that the uniformly dispersed Pd nanoparticles with a particle size distribution of 2.3 ± 0.6 nm are responsible for the generation of PdO and PdxCe1−xO2−δ phase with –Pd2+–O2−–Ce4+– linkage, which can easily provide oxygen vacancies and facilitate the transfer of reactive oxygen species between the CeO2-R and Pd species. As a consequence, the remarkable catalytic activity of 0.5% Pd/CeO2-RE is related to the high concentration of PdO species on the surface of the catalyst and the synergistic interaction between the Pd species and the CeO2 nanorod.

scholarly journals Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Reoxidation Treatment

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 838 ◽  
Author(s):  
Chansong Kim ◽  
Eunpyo Hong ◽  
Chae-Ho Shin
Keyword(s):  
Catalytic Activity ◽  
Low Temperatures ◽  
Methane Combustion ◽  
Reduction Temperature ◽  
Isothermal Reaction ◽  
Ch4 Combustion ◽  
Cyclic Temperature ◽  
Zro2 Catalyst ◽  
Number Of Cycles ◽  
Simple Reduction

The improvement of methane combustion activity was observed in cyclic temperature-programed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/reoxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/reoxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures.

Rapid microwave-assisted hydrothermal synthesis of CeO2 octahedra with mixed valence states and their catalytic activity for thermal decomposition of ammonium perchlorate

2019 ◽  
Vol 6 (7) ◽  
pp. 1735-1743 ◽  
Author(s):  
Jing Shi ◽  
Huixiang Wang ◽  
Yequn Liu ◽  
Xiaobo Ren ◽  
Haizhen Sun ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Catalytic Activity ◽  
Hydrothermal Synthesis ◽  
Ammonium Perchlorate ◽  
Oxygen Vacancies ◽  
Mixed Valence ◽  
High Concentration ◽  
Microwave Assisted ◽  
Valence States

CeO2 octahedra are prepared rapidly and they exhibit improved catalytic activity due to high concentration of oxygen vacancies and exposed (111) facets.

Ethylene Polymerization by Thioether Bridged Dinuclear Titanocene Complex

2011 ◽  
Vol 213 ◽  
pp. 354-357 ◽  
Author(s):  
Yu Jing Nie ◽  
Ming Yang
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
Ethylene Polymerization ◽  
Gel Permeation Chromatography ◽  
Molar Ratio ◽  
Polymerization Temperature ◽  
High Concentration ◽  
Highly Active ◽  
Cyclopentadienyl Ligand ◽  
Broad Molecular Weight Distribution

The thioether bridged metallocene complex [(C5H5)Cl2TiC5H4CH2CH2]2S has been synthesized by treating the dilithium salts of the thioether bridged cyclopentadienyl ligand with two equivalents of C5H5TiCl3 and characterized by 1HMNR and elemental analysis. After activation with methylaluminoxane (MAO), the complex was highly active catalysts for homogeneous ethylene polymerization in toluene. The influence of the molar ratio [MAO]/[Cat], the catalyst concentration, time and temperature have been studied systematically. The catalytic activity of 1 is 3.63×105 g PE/mol•Cat•h. Rising the polymerization temperature decreases the catalytic activity for 1. A high concentration of the catalysts drops the catalytic activity as well as the molecular weight of polyethylene for the complex. High temperature gel permeation chromatography (HT-GPC) proves the production of polyethylene with a broad molecular weight distribution (MWD).

A highly active Pd/H-ZSM-5 catalyst in lean methane combustion prepared via a sol–gel method and treated by reduction–oxidation

2020 ◽  
Vol 44 (10) ◽  
pp. 3940-3949 ◽  
Author(s):  
Chao Fan ◽  
Li Yang ◽  
Li Luo ◽  
Zhiwei Wu ◽  
Zhangfeng Qin ◽  
...  
Keyword(s):  
Sol Gel ◽  
Methane Combustion ◽  
Pd Nanoparticles ◽  
Catalytic Performance ◽  
Oxidation Treatment ◽  
Gel Method ◽  
Sol Gel Method ◽  
Highly Active ◽  
Metal Support ◽  
Metal Support Interactions

The reduction–oxidation treatment can reconstruct Pd nanoparticles, strengthen metal–support interactions and enhance catalytic performance of Pd/H-ZSM-5 in methane combustion.

A-site deficient perovskite: the parent for in situ exsolution of highly active, regenerable nano-particles as SOFC anodes

2015 ◽  
Vol 3 (20) ◽  
pp. 11048-11056 ◽  
Author(s):  
Yifei Sun ◽  
Jianhui Li ◽  
Yimin Zeng ◽  
Babak Shalchi Amirkhiz ◽  
Mengni Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Vacancies ◽  
Electronic Conductivity ◽  
Nano Particles ◽  
Highly Active ◽  
A Site ◽  
Mobile Oxygen

Introduction of A-site deficiency on Ni-doped LaSrCrO3 anodes helps form highly mobile oxygen vacancies and remarkably enhances Ni nanoparticle reducibility, and significantly increases electronic conductivity and catalytic activity.

Preparation of supported AuPd nanoalloys mediated by ionic liquid-like functionalized SBA-15: structural correlations concerning its catalytic activity

2016 ◽  
Vol 40 (8) ◽  
pp. 6636-6642 ◽  
Author(s):  
João Paulo Vita Damasceno ◽  
Camila Marchetti Maroneze ◽  
Mathias Strauss ◽  
Fernando Aparecido Sigoli ◽  
Italo Odone Mazali
Keyword(s):  
Ionic Liquid ◽  
Catalytic Activity ◽  
Pd Nanoparticles ◽  
Highly Active

We report highly active catalysts based on mono- or bimetallic Au and Pd nanoparticles supported in ionic liquid-like modified SBA-15.

scholarly journals Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Re-oxidation Treatment

2019 ◽  
Author(s):  
Chansong Kim ◽  
Eunpyo Hong ◽  
Chae-Ho Shin
Keyword(s):  
Catalytic Activity ◽  
Methane Combustion ◽  
Oxidation Treatment ◽  
Ch4 Combustion ◽  
Cyclic Temperature ◽  
Zro2 Catalyst ◽  
Temperature Programmed ◽  
Number Of Cycles ◽  
Temperature Programmed Reaction ◽  
Simple Reduction

The improvement of the methane combustion activity was observed in cyclic temperature-programmed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/re-oxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programmed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programmed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/re-oxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures.

scholarly journals Rice Husk Derived Porous Silica as Support for Pd and CeO2 for Low Temperature Catalytic Methane Combustion

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Dongjing Liu ◽  
Dominik Seeburg ◽  
Stefanie Kreft ◽  
René Bindig ◽  
Ingo Hartmann ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Nitrate Solution ◽  
Porous Silica ◽  
Methane Combustion ◽  
Pd Nanoparticles ◽  
Highly Active ◽  
Palladium Nitrate ◽  
The Cost ◽  
Supported Pd

The separation of Pd and CeO2 on the inner surface of controlled porous glass (CPG, obtained from phase-separated borosilicate glass after extraction) yields long-term stable and highly active methane combustion catalysts. However, the limited availability of the CPG makes such catalysts highly expensive and limits their applicability. In this work, porous silica obtained from acid leached rice husks after calcination (RHS) was used as a sustainable, cheap and broadly available substitute for the above mentioned CPG. RHS-supported Pd-CeO2 with separated CeO2 clusters and Pd nanoparticles was fabricated via subsequent impregnation/calcination of molten cerium nitrate and different amounts of palladium nitrate solution. The Pd/CeO2/RHS catalysts were employed for the catalytic methane combustion in the temperature range of 150–500 °C under methane lean conditions (1000 ppm) in a simulated off-gas consisting of 9.0 vol% O2, and 5.5 vol% CO2 balanced with N2. Additionally, tests with 10.5 vol% H2O as co-feed were carried out. The results revealed that the RHS-supported catalysts reached the performance of the cost intensive benchmark catalyst based on CPG. The incorporation of Pd-CeO2 into RHS additionally improved water-resistance compared to solely Pd/CeO2 lowering the required temperature for methane combustion in presence of 10.5 vol% H2O to values significantly below 500 °C (T90 = 425 °C).

Deactivation of arenetitanium(II) bromoalane complexes in the cyclotrimerization of butadiene

1986 ◽  
Vol 51 (12) ◽  
pp. 2751-2759 ◽  
Author(s):  
Jindřich Poláček ◽  
Helena Antropiusová ◽  
Lidmila Petrusová ◽  
Karel Mach
Keyword(s):  
Catalytic Activity ◽  
Catalytic System ◽  
Model System ◽  
Highly Active ◽  
Catalytic Stability

The C6H6.Ti(II)(AlBr4)2 (Ib) catalyst deactivates during the butadiene cyclotrimerization to give a solid containing all titanium (mostly as TiBr3) and a mixture of AlBr3 and RAlBr2 compounds dissolved in benzene. The residual cationic catalytic activity of the deactivated Ib system is due to presence of AlBr3. In contrast to TiCl3, the deactivated Ib system and the model system TiBr3 + AlBr3 are not activated by the addition of EtAlCl2 in the presence of butadiene: the highly active benzenetitanium(II) system is re-constituted only after reduction of TiBr3 with Et3Al followed by the addition of EtAlCl2. The addition of Et2AlBr to Ib accelerates the deactivation of the system. Deactivation products of this system contain mainly Ti(II) species which forms benzenetitanium(II) catalytic system after addition of EtAlCl2. All the EtAlCl2 reactivated systems produce (Z, E, E)-1,5,9-cyclododecatriene with high catalytic stability and considerable selectivity (>90%). This behaviour points to the catalysis by benzenetitanium(II) chloroalane complexes containing only low amount of bromine atoms and ethyl groups.

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