scholarly journals NO Reactions Over Ir-Based Catalysts in the Presence of O2

2011 ◽  
Vol 8 (s1) ◽  
pp. S349-S357 ◽  
Author(s):  
Mingxin Guo ◽  
Rongshu Zhu ◽  
Minhua Dong ◽  
Feng Ouyang
Keyword(s):  
Catalytic Activity ◽  
No Reduction ◽  
Active Phase ◽  
No Oxidation ◽  
Impregnation Method ◽  
Iridium Catalysts ◽  
Support Materials ◽  
Surface Active ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

The behaviour of a series of Ir-based catalysts supported on SiO2, ZSM-5 and γ-Al2O3 with various Ir loadings prepared by impregnation method was conducted by temperature programmed reaction (TPR) technique. The result implies that NO is oxidized to NO2while simultaneously being reduced to N2or N2O in the NO reactions over iridium catalysts. The surface active phase over iridium catalysts that promote the NO reactions is IrO2. The catalytic activity increases with the increase of the Ir loading and support materials have a little effect on the catalytic activity. When the loading is less than 0.1%, the catalytic activity was found to be dependent on the nature of support materials and in order: Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2. When the loading is higher than 0.1%, the catalytic activity for NO oxidation is in order: Ir/ZSM-5>Ir/SiO2>Ir/γ -Al2O3, which is correlated with Ir dispersion on the surface of support materials and the catalytic activity for NO reduction is in sequence: Ir/γ -Al2O3>Ir/SiO2>Ir/ZSM-5, which is attributed to the adsorbed-dissociation of NO2. Compared to Pt/γ-Al2O3, Ir/γ-Al2O3catalyst is more benefit for the NO reduction.

Performance of LaBO3/HZSM-5 Catalysts for Eliminating Soot from Diesel Exhaust

2013 ◽  
Vol 634-638 ◽  
pp. 563-566
Author(s):  
Fu Chen Ding ◽  
Cui Tao Ren ◽  
Bin Li ◽  
Hong Wang ◽  
Cui Qing Li
Keyword(s):  
Catalytic Activity ◽  
Catalytic Combustion ◽  
Soot Particle ◽  
Partial Substitution ◽  
Impregnation Method ◽  
Perovskite Type Oxide ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction ◽  
Soot Catalytic Combustion ◽  
Perovskite Type

The LaBO3/HZSM-5 samples were prepared by the impregnation method. The structure of catalysts was examined by XRD. The catalytic activity for the combustion of soot particulate was evaluated by a technique of the temperature-programmed reaction. In the LaBO3/HZSM-5 catalyst, the Mn as B-site ion, the catalyst was the good candidate catalyst for the soot catalytic combustion. In the LaMnO3/HZSM-5 catalyst, the catalytic activity was tunable by changing the metal components of the perovskite-type oxide at B-site, the Fe partial substitution for Mn of LaMnO3/HZSM-5 enhanced the catalytic activity, and the combustion temperature of soot particle was lower than LaMnO3/HZSM-5 sample without substitution, corresponding Tm of 401oC and the selectivity of CO2 77.0%.

The Effect of CeO2 and Fe2O3 Dopants on Ni/ Alumina Based Catalyst for Dry Reforming of Methane to Hydrogen

2011 ◽  
Vol 364 ◽  
pp. 519-523 ◽  
Author(s):  
S. Sivasangar ◽  
Yun Hin Taufiq-Yap
Keyword(s):  
Catalytic Activity ◽  
Vital Role ◽  
Dry Reforming ◽  
Dry Reforming Of Methane ◽  
Impregnation Method ◽  
Environment Friendly ◽  
Fuel Gas ◽  
Wet Impregnation ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

Methane reforming is the most feasible techniques to produce hydrogen for commercial usage. Hence, dry reforming is the environment friendly method that uses green house gases such as CO2and methane to produce fuel gas. Catalysts play a vital role in methane conversion by enhancing the reforming process. In this study Ni/γ-Al2O3was selected as based catalyst and CeO2and Fe2O3dopants were added to investigate their effect on catalytic activity in dry reforming. The catalysts synthesized through wet impregnation method and characterized by using XRD, TEM and SEM-EDX. The catalytic tests were carried out using temperature programmed reaction (TPRn) and the products were detected by using an online mass spectrometer. The results revealed that these dopants significantly affect the catalytic activity and selectivity of the catalyst during reaction. Hence, Fe2O3doped catalyst shows higher hydrogen production with stable catalytic activity.

scholarly journals Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

2021 ◽  
Author(s):  
Petar Djinović ◽  
Janez Zavašnik ◽  
Janvit Teržan ◽  
Ivan Jerman
Keyword(s):  
Catalytic Activity ◽  
Activated Carbon ◽  
Oxidative Dehydrogenation ◽  
Active Phase ◽  
Lattice Oxygen ◽  
Chemisorbed Oxygen ◽  
Catalytically Active ◽  
Temperature Programmed ◽  
Propane Cracking

AbstractCeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

scholarly journals Influence of Sulfur-Containing Sodium Salt Poisoned V2O5–WO3/TiO2 Catalysts on SO2–SO3 Conversion and NO Removal

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 541 ◽  
Author(s):  
Haiping Xiao ◽  
Chaozong Dou ◽  
Hao Shi ◽  
Jinlin Ge ◽  
Li Cai
Keyword(s):  
Photoelectron Spectroscopy ◽  
No Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
So2 Oxidation ◽  
Sodium Salts ◽  
X Ray ◽  
Temperature Programmed ◽  
Physical Features

A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.

Effect of Supports on the Properties of Co-Mo Nitride Catalysts for Ammonia Decomposition

2011 ◽  
Vol 391-392 ◽  
pp. 1215-1219 ◽  
Author(s):  
Zhao Hui Zhao ◽  
Han Bo Zou ◽  
Wei Ming Lin
Keyword(s):  
Elevated Temperatures ◽  
Active Species ◽  
Ammonia Decomposition ◽  
Zeolite Catalysts ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
5A Zeolite ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction ◽  
Effect Of Support

Supported Co–Mo nitride catalysts have been synthesized by incipient-wetness impregnation method and temperature-programmed reaction in N2-H2 mixed gases. The effect of support types, namely carbon nanotubes(CNTs), active carbon(AC), 5A zeolite and Al2O3 on the properties of the prepared catalysts for ammonia decomposition has been investigated by XRD, H2–TPR and SEM techniques. The results showed that CNTs was the optimum support for Co–Mo nitride catalyst. At 550 , NH3 conversions over CoMoNx/AC, CoMoNx/Al2O3 and CoMoNx/5A Zeolite catalysts were only 14.7%, 65.4% and 68.7%, respectively, while NH3 conversion over CoMoNx/CNTs catalyst was up to 84.4%. XRD and H2–TPR results indicated that the active species consist of CoMoO4, MoO3, γ-Mo2N and Co3Mo3N crystallites, which can be reduced at elevated temperatures at H2 atmosphere. The SEM characterization demonstrated that Co-Mo nitrides particles disperse uniformly on the CNTs.

Preparation and Characterization of Cu1-xKxFe2O4 Fibers and the Catalytic Activity for Diesel Engine Exhaust Removal

2010 ◽  
Vol 96 ◽  
pp. 135-139
Author(s):  
Cai Rong Gong ◽  
Hai Feng Chen ◽  
Guo Liang Fan ◽  
Chong Lin Song ◽  
Gang Lv
Keyword(s):  
Catalytic Activity ◽  
Sol Gel ◽  
Complex Oxide ◽  
Average Diameter ◽  
Partial Substitution ◽  
High Catalytic Activity ◽  
Engine Exhaust ◽  
Sol Gel Process ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

A series of complex oxide Cu1-xKxFe2O4 fibers have been prepared via a sol-gel process related electron-spinning procedure, in which x is among 0, 0.05, 0.1 and 0.2 corresponding to the quantity of Cu2+ partial substitution by K+. The average diameter of the fiber was 500 nm. The catalytic activity of the catalysts in removal of NOx and carbon black from diesel exhaust gases were examined in detail using temperature-programmed reaction technique. The results show that after partial substitution of Cu2+ with K+, the catalytic activities have been improved. Cu0.95K0.05Fe2O4 as an optimal catalyst can significantly decrease the ignition temperature (Tig) of the PM, and has high catalytic activity on the removal of NOx.

scholarly journals Synergistic Effects of Co3O4-CeO2 Nanoparticles towards Catalytic Oxidation of Aromatic Hydrocarbons: A Study in Association with Carbon Monoxide and Humidity

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Trung Dang-Bao ◽  
Hong Phuong Phan ◽  
Phung Anh Nguyen ◽  
Pham Phuong Trang Vo ◽  
Van Tien Huynh ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Catalytic Oxidation ◽  
Synergistic Effects ◽  
Active Oxygen Species ◽  
High Dispersion ◽  
High Catalytic Activity ◽  
Impregnation Method ◽  
Temperature Programmed ◽  
The Stability

In this study, a series of Co3O4-CeO2 nanocomposites with various Co3O4 loading were fabricated by the impregnation method using cobalt(II) acetate as the cobalt precursor for the treatment of benzene, toluene, ethylbenzene, and xylene (BTEX). The as-prepared Co3O4-CeO2 nanocomposites were thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brumauer-Emmett-Teller (BET), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed desorption (O2-TPD). The excellent reproduction of active oxygen species caused by the high dispersion of Co3O4 crystals on the CeO2 supports was established. In addition, the reduction peaks of Co3O4-CeO2 nanocomposites were found at much lower temperatures compared to pure CeO2, considering their unique redox property influencing on the high catalytic activity. Among the characterized materials, the 5.0 wt.% Co3O4 supported on CeO2 (5.0Co–Ce) was the best system for catalytic oxidation of xylene, along with excellent performances in the cases of benzene, ethylbenzene, and toluene. Its catalytic activity increased in the order: benzene < xylene < ethylbenzene < toluene . Furthermore, the addition of carbon monoxide (CO) as a coreactant permitted to improve the catalytic performances in such oxidations as well as the stability of as-prepared catalysts, even under humid conditions.

scholarly journals Influence of CeO2 Addition to Ni–Cu/HZSM-5 Catalysts on Hydrodeoxygenation of Bio-Oil

2019 ◽  
Vol 9 (6) ◽  
pp. 1257 ◽  
Author(s):  
Wenhe Wang ◽  
Changsen Zhang ◽  
Guanghui Chen ◽  
Ruiqin Zhang
Keyword(s):  
Carbon Deposition ◽  
Catalyst Support ◽  
Coke Deposition ◽  
Impregnation Method ◽  
High Heating Value ◽  
Active Metal ◽  
Bio Oil ◽  
The Difference ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

Hydrodeoxygenation (HDO) of bio-oil is a method of bio-oil upgrading. In this paper, x%CeO2–Ni–Cu/HZSM-5 (x = 5, 15, and 20) was synthesized as an HDO catalyst by the co-impregnation method. The HDO performances of x%CeO2–Ni–Cu/HZSM-5 (x = 5, 15, and 20) in the reaction process was evaluated and compared with Ni–Cu/HZSM-5 by the property and the yield of upgrading oil. The difference of the chemical composition between bio-oil and upgrading oil was evaluated by GC-MS. The results showed that the addition of CeO2 decreased the water and oxygen contents of upgrading oil, increased the high heating value, reduced acid content, and increased hydrocarbon content. When the CeO2 addition was 15%, the yield of upgrading reached the maximum, from 33.9 wt% (Ni–Cu/HZSM-5) to 47.6 wt% (15%CeO2–Ni–Cu/HZSM-5). The catalytic activities of x%CeO2–Ni–Cu/HZSM-5 (x = 5, 15, and 20) and Ni–Cu/HZSM-5 were characterized by XRD, N2 adsorption–desorption, NH3-Temperature-Programmed Desorption, H2-Temperature-Programmed Reaction, TEM, and XPS. The results showed that the addition of CeO2 increased the dispersion of active metal Ni, reduced the bond between the active metal and the catalyst support, increased the ratio of Bronsted acid to total acids, and decreased the reduction temperature of NiO. When the CeO2 addition was 15%, the activity of catalyst reached the best. Finally, the carbon deposition resistance of deactivated catalysts was investigated by a Thermogravimetric (TG) analysis, and the results showed that the addition of CeO2 could improve the carbon deposition resistance of catalysts. When the CeO2 addition was 15%, the coke deposition decreased from 41 wt% (Ni–Cu/HZSM-5) to 14 wt% (15%CeO2–Ni–Cu/HZSM-5).

scholarly journals H2-TPR, XPS and TEM Study of the Reduction of Ru and Re promoted Co/γ-Al2O3, Co/TiO2 and Co/SiC Catalysts

2016 ◽  
Vol 5 (2) ◽  
pp. 39 ◽  
Author(s):  
H. Romar ◽  
A. H. Lillebo ◽  
P. Tynjala ◽  
T. Hu ◽  
A. Holmen ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Metallic Nanoparticles ◽  
Surface Composition ◽  
Active Phase ◽  
Support Materials ◽  
Metal Support Interaction ◽  
Active Metal ◽  
Metal Support ◽  
Oxide Phases

<p class="1Body">Effects of Ru and Re promoters on Co-CoO<sub>x </sub>catalysts supported on γ-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub> and SiC were investigated to improve the understanding of the role of promoters of the active phase of Co-CoO<sub>x</sub>-Ru and Co-CoO<sub>x</sub>-Re. The influence of promoter addition on the composition and activity of the catalysts was characterized by several methods, such as H<sub>2</sub>-TPR, XPS, chemisorption and TEM. Furthermore, the role of support and metal-support interaction was especially studied and different support materials were compared.</p><p class="1Body">Based on the results, addition of promoter metals (Ru or Re) will most likely improve catalytic activity of Co/γ-Al<sub>2</sub>O<sub>3</sub>, Co/TiO<sub>2</sub> and Co/SiC catalysts by increasing the active metal surface available for chemical reaction and by decreasing the size of the metallic nanoparticles. These changes in the catalytic activity were also associated with the changes in the ratio of metal and metal oxide phases in the surface composition as observed by XPS. Promoter metals also decreased the reduction temperatures needed for the reduction of Co<sub>3</sub>O<sub>4</sub> to CoO and further to metallic cobalt. Significant decrease in reduction temperature was observed especially when ruthenium was used as the promoter.</p>

scholarly journals Studies of New Iridium Catalysts Supported on Modified Silicalite-1—Their Structure and Hydrogenating Properties

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4465
Author(s):  
Michał Zieliński ◽  
Monika Kot ◽  
Mariusz Pietrowski ◽  
Robert Wojcieszak ◽  
Jolanta Kowalska-Kuś ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Phase ◽  
The Novel ◽  
Iridium Catalysts ◽  
Transmission Electron ◽  
Acidic Sites ◽  
Temperature Programmed ◽  
Post Synthesis ◽  
Adsorption Desorption ◽  
Ammonium Compounds

This paper investigates the catalytic properties of the iridium catalysts supported on modified silicalite-1. Post-synthesis modification of silicalite-1, with solutions of ammonium compounds (NH4F and NH4OH), appeared to be an efficient method to generate the acidic sites in starting support. The modification of support led not only to changes in its acidity but also its porosity—formation of additional micro- and mesopores. The novel materials were used as supports for iridium. The iridium catalysts (1 wt.% Ir) were characterized by N2 adsorption/desorption measurements, temperature-programmed reduction with hydrogen (TPR-H2), H2 chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (TPD-NH3), X-ray photoelectron spectroscopy (XPS) and tested in the hydrogenation of toluene reaction. The catalytic activity of iridium supported on silicalite-1 treated with NH4OH (higher porosity of support, better dispersion of active phase) was much higher than that of Ir supported on unmodified and modified with NH4F silicalite-1.

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