scholarly journals Tungsten-Based Catalysts for Environmental Applications

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 703
Author(s):  
Fabien Can ◽  
Xavier Courtois ◽  
Daniel Duprez
Keyword(s):  
Tungsten Oxide ◽  
Precious Metals ◽  
High Specific Surface Area ◽  
Environmental Applications ◽  
Background Information ◽  
Acidic Properties ◽  
Total Oxidation ◽  
Tungsten Oxides ◽  
Pollutant Remediation ◽  
Volatile Organic

This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsorption properties (due to the presence of oxygen vacancies) and a photostimulation response under visible light (2.6–2.8 eV bandgap). Depending on the operating condition of the catalytic process, each of these behaviors is tunable by controlling structure and morphology (e.g., nanoplates, nanosheets, nanorods, nanowires, nanomesh, microflowers, hollow nanospheres) and/or interactions with other compounds such as conductors (carbon), semiconductors or other oxides (e.g., TiO2) and precious metals. WOx particles can be also dispersed on high specific surface area supports. Based on these behaviors, WO3-based catalysts were developed for numerous environmental applications. This review is divided into five main parts: structure of tungsten-based catalysts, acidity of supported tungsten oxide catalysts, WO3 catalysts for DeNOx applications, total oxidation of volatile organic compounds in gas phase and gas sensors and pollutant remediation in liquid phase (photocatalysis).

scholarly journals Influence of Alumina Precursor Properties on Cu-Fe Alumina Supported Catalysts for Total Toluene Oxidation as a Model Volatile Organic Air Pollutant

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 252
Author(s):  
Tadej Žumbar ◽  
Alenka Ristić ◽  
Goran Dražić ◽  
Hristina Lazarova ◽  
Janez Volavšek ◽  
...  
Keyword(s):  
Surface Characterization ◽  
Iron Concentration ◽  
Catalytic Performance ◽  
Air Pollutant ◽  
Molar Ratio ◽  
Homogeneous Distribution ◽  
Total Oxidation ◽  
Alumina Support ◽  
Determining Factors ◽  
Volatile Organic

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

Study on spinel - typed catalyst NiCo2O4 for total oxidation of toluene

2021 ◽  
Vol 10 (4) ◽  
pp. 97-102
Author(s):  
Nhung Nguyen Hong ◽  
Hung Khong Manh ◽  
Thang Le Minh ◽  
Phuong Pham Thi Mai ◽  
Nam Chu Thi Hai
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Sol Gel ◽  
Total Oxidation ◽  
Gel Method ◽  
Sol Gel Method ◽  
Volatile Organic ◽  
Epr Experiments

Toluene is a component of volatile organic compounds which need to be converted into non-poisonous one. Thus, we study the spinel-typed catalyst as NiCo2O4 for total oxidation of toluene because the advantage of spinel catalyst is multi- defective. Based on the sol-gel method, the catalysts NiCo2O4 were successfully prepared with different ratios of Ni/Co. The characteristic properties of catalysts were evaluated by XRD, BET, H2-TPR and EPR experiments. Amongst these ratios, the catalyst with ratio Ni/Co as 0.5 had the best activity in the total oxidation of toluene, as 100% conversion reached at 250 oC.

scholarly journals Cerium Oxide-Tungsten Oxide Core-Shell Nanowire-Based Microsensors Sensitive to Acetone

Biosensors ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 116 ◽  
Author(s):  
Milena Tomić ◽  
Milena Šetka ◽  
Ondřej Chmela ◽  
Isabel Gràcia ◽  
Eduard Figueras ◽  
...  
Keyword(s):  
Tungsten Oxide ◽  
Cerium Oxide ◽  
Chemical Vapor ◽  
Disease Diagnosis ◽  
Core Shell ◽  
Early Disease ◽  
Vacancy Defects ◽  
The Core ◽  
Enhanced Sensitivity ◽  
Volatile Organic

Gas sensitive cerium oxide-tungsten oxide core-shell nanowires are synthesized and integrated directly into micromachined platforms via aerosol assisted chemical vapor deposition. Tests to various volatile organic compounds (acetone, ethanol, and toluene) involved in early disease diagnosis demonstrate enhanced sensitivity to acetone for the core-shell structures in contrast to the non-modified materials (i.e., only tungsten oxide or cerium oxide). This is attributed to the high density of oxygen vacancy defects at the shell, as well as the formation of heterojunctions at the core-shell interface, which provide the modified nanowires with ‘extra’ chemical and electronic sensitization as compared to the non-modified materials.

Modification of Co-Mn-Al Mixed Oxide with Promoters and Their Effect on Properties and Activity in VOC Total Oxidation

2008 ◽  
Vol 73 (8-9) ◽  
pp. 1000-1014 ◽  
Author(s):  
Zuzana Mikulová ◽  
Květuše Jirátová ◽  
Jan Klempa ◽  
František Kovanda
Keyword(s):  
Mixed Oxide ◽  
Oxide Catalyst ◽  
Potassium Concentration ◽  
Impregnation Method ◽  
Reaction Intermediates ◽  
Total Oxidation ◽  
Mixed Oxide Catalyst ◽  
Volatile Organic ◽  
Double Hydroxide ◽  
Oxidation Of Ethanol

The activity and selectivity of the Co-Mn-Al mixed oxide catalyst modified with promoters (Pt, Pd, K and La) in total oxidation of volatile organic compounds (toluene and ethanol) were studied. The promoters were introduced at the stage of coprecipitation of a layered double hydroxide (LDH) precursor or impregnation of the mixed oxide obtained by LDH precursor calcination. In total oxidation of toluene, the most active Co-Mn-Al catalysts were those containing low amounts of potassium regardless of the mode of modification, while in total oxidation of ethanol the catalyst impregnated with a higher potassium concentration (3 wt.%) was the most active. Introduction of Pt and Pd in an amount of 0.5 or 0.1 wt.% into the Co-Mn-Al mixed oxide did not improve its catalytic activity. The impregnation method appears to be a more effective mode for preparation of active catalysts than the method using an addition of promoters at the stage of coprecipitation of the LDH precursor. Undesirable reaction intermediate (benzene) was formed when toluene oxidation was carried out over lanthanum- or palladium-containing catalysts. In total oxidation of ethanol, a number of reaction intermediates were produced acetaldehyde being the main one. The catalysts modified at the stage of LDH precursor coprecipitation exhibited a better selectivity (i.e., a lower acetaldehyde formation) than those modified by impregnation. The best results were obtained with the Co-Mn-Al mixed oxide catalyst modified with potassium.

Tungsten oxide nanostructures and nanocomposites for photoelectrochemical water splitting

Nanoscale ◽  
2019 ◽  
Vol 11 (41) ◽  
pp. 18968-18994 ◽  
Author(s):  
Guangwei Zheng ◽  
Jinshu Wang ◽  
Hu Liu ◽  
Vignesh Murugadoss ◽  
Guannan Zu ◽  
...  
Keyword(s):  
Tungsten Oxide ◽  
Water Splitting ◽  
Photoelectrochemical Water Splitting ◽  
Tungsten Oxides ◽  
Oxide Nanostructures

This paper reviews nanostructural tungsten oxides and their nanocomposites to enhance the activity of photoelectrochemical water splitting.

Total oxidation of isopropanol over manganese oxide modified ZSM-5 zeolite membrane catalysts

RSC Advances ◽  
2015 ◽  
Vol 5 (37) ◽  
pp. 29482-29490 ◽  
Author(s):  
Wang Ling ◽  
Zhang Huiping ◽  
Yan Ying ◽  
Zhang Xinya
Keyword(s):  
Organic Compound ◽  
Manganese Oxide ◽  
Volatile Organic Compound ◽  
Membrane Reactor ◽  
Catalytic Combustion ◽  
Zeolite Membrane ◽  
Total Oxidation ◽  
Volatile Organic

Manganese oxide modified ZSM-5 membrane catalysts were prepared for the catalytic combustion of a volatile organic compound (isopropanol) over a zeolite membrane reactor.

Synthesis, characterization and environmental applications of nanocrystalline zeolites

2017 ◽  
Author(s):  
Vicki H. Grassian ◽  
Sarah C. Larsen
Keyword(s):  
Catalytic Reduction ◽  
Organic Phosphorus ◽  
Environmental Contaminants ◽  
Building Blocks ◽  
Environmental Applications ◽  
Environmental Catalysis ◽  
Hierarchical Zeolite ◽  
Volatile Organic ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

This article describes the synthesis, characterization and environmental applications of nanocrystalline zeolites. It begins by considering the use of nanocrystalline zeolites as building blocks in the preparation of hierarchical zeolite structures, followed by a discussion of the synthesis of silicalite-1 with systematically varied crystal sizes, along with the synthesis of nanocrystalline aluminosilicates, NaZSM-5 and NaY. It then looks at the various applications of nanozeolites and hierarchical zeolite structures for environmental catalysis, adsorption of volatile organic compounds and other environmental contaminants, selective catalytic reduction of nitrogen oxide, and decontamination of organic phosphorus and sulfur-containing compounds. It also examines the unique properties and reactivity of nanocrystalline zeolites and concludes by assessing their potential for future environmental applications.

Synthesis and characterization of tungsten oxide nanorods

2004 ◽  
Vol 19 (12) ◽  
pp. 3665-3670 ◽  
Author(s):  
D.Z. Guo ◽  
K. Yu-Zhang ◽  
A. Gloter ◽  
G.M. Zhang ◽  
Z.Q. Xue
Keyword(s):  
Electron Microscopy ◽  
Tungsten Oxide ◽  
Electric Heating ◽  
Tungsten Oxides ◽  
X Ray ◽  
Preparation Conditions ◽  
Transmission Electron ◽  
Oxide Nanorods ◽  
Electron Energy Loss

Single crystalline nanorods (15–200 nm in diameter and hundreds nanometers in length) have been formed on the carbon-covered W wires by simple electric heating under a vacuum of 5 × 10−4 Pa. The chemical composition and crystalline structure of the nanorods were carefully investigated by various characterization techniques such as scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, energy dispersive x-ray spectroscopy and electron energy loss spectroscopy. After ruling out any possible existence of carbon nanotubes (CNTs), tungsten carbide, W–Fe alloying, and formation of other types of tungsten oxides, monoclinic W18O49 phase has been well identified. The mechanism of nanorod formation of sub-tungsten oxide (∼WO2.7 compared to WO3) will be discussed in relation to the sample preparation conditions.

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