Enhancement of photocatalytic NOx abatement on titania via additional metal oxide NOx-storage domains: Interplay between surface acidity, specific surface area, and humidity

2020 ◽  
Vol 263 ◽  
pp. 118227 ◽  
Author(s):  
Mustafa Çağlayan ◽  
Muhammad Irfan ◽  
Kerem Emre Ercan ◽  
Yusuf Kocak ◽  
Emrah Ozensoy
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Surface Acidity ◽  
Nox Storage ◽  
Nox Abatement

scholarly journals Features of obtaining the catalyst for the synthesis of carbon nanotubes

2019 ◽  
Vol 81 (2) ◽  
pp. 261-267 ◽  
Author(s):  
E. A. Burakova ◽  
G. S. Besperstova ◽  
M. A. Neverova ◽  
A. G. Tkachev ◽  
N. V. Orlova ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Decomposition ◽  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Nanostructured Materials ◽  
Specific Surface Area ◽  
Oxide System ◽  
Decomposition Stage ◽  
Al2o3 Catalyst

In this paper, the features of obtaining a Co-Mo/Al2O3 catalyst to synthesize carbon nanotubes (CNTs) by thermal decomposition were studied. It was revealed that the duration of the pre-catalyst thermal decomposition stage in the process of developing a metal oxide system has a significant impact on its activity in the synthesis of carbon nanostructured materials by chemical vapor deposition (CVD). It was proved that an effective catalyst for CNTs synthesis can be obtained by through thermal decomposition of the pre – catalyst, without calcination of the metal oxide system. The use of the Co-Mo/Al2O3 catalyst, synthesized in such a way, in the CVD process makes it possible to reduce the cost of synthesized CNTs. Using scanning electron microscopy, it was shown that the size of the grains, and specific surface area of the formed Co-Mo/Al2O3 catalyst depend on the thermal treatment conditions of the pre-catalyst. Under the conditions for the implementation of the pre-catalyst thermal decomposition stage (temperature, volume, duration, etc.), it is possible to contro not only the characteristics of the resulting catalyst (specific surface area, efficiency), but also the characteristics of the CNTs (diameter, degree of defectiveness). In the course of experiments, the optimal modes of implementation of the method for obtaining the Co-Mo/Al2O3 catalyst allowed forming a system with a specific surface area of ~ 108 m2/g. The use of the resulting catalyst in the synthesis of nanostructured materials provides a high specific yield of multi-walled CNTs with a diameter of 8-20 nm and a degree of defectiveness of 0.97.

scholarly journals Simultaneous deposition of Au nanoparticles during flame synthesis of TiO2 and SiO2

2003 ◽  
Vol 18 (1) ◽  
pp. 115-120 ◽  
Author(s):  
L. Mädler ◽  
W. J. Stark ◽  
S. E. Pratsinis
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Au Nanoparticles ◽  
Visible Region ◽  
Gold Deposits ◽  
Absorption Bands ◽  
Oxide Support ◽  
Metal Oxide Support

Nanostructured gold/titania and gold/silica particles with up to 4 wt% Au were made by a single-step process in a spray flame reactor. Gold(III)-chloride hydrate and titania- or silica-based metalorganic precursors were mixed in a liquid fuel solution, keeping concentrations in the flame and overall combustion enthalpy constant. The powders were characterized by x-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller, and ultraviolet–visible analysis. The titania or silica specific surface area and the crystalline structure of titania were not affected by the presence of gold in the flame. Furthermore the size of the gold deposits was independent of the metal oxide support (TiO2 or SiO2) and its specific surface area (100 and 320 m2/g, respectively). The gold nanoparticles were nonagglomerated, spherical, mostly single crystalline, and well dispersed on the metal oxide support. Depending on the Au weight fraction (1, 2, and 4 wt%) the Au nanoparticles' mass mean diameter was 3, 7, and 15 nm, respectively, on both titania and silica. The particles showed surface plasmon absorption bands in the ultraviolet–visible region, which is typical for nano-sized gold. This absorption band was red shifted in the case of the titania support, while no shift occurred with the silica support.

scholarly journals Design and Photocatalytic Activity of Mesoporous TiO2/ZrO2 Thin Films

2005 ◽  
Vol 23 (6) ◽  
pp. 497-508 ◽  
Author(s):  
Yu. Gnatyuk ◽  
N. Smirnova ◽  
A. Eremenko ◽  
V. Ilyin
Keyword(s):  
Thin Films ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Surface Acidity ◽  
Sol Gel ◽  
Pluronic P123 ◽  
Vis Spectroscopy ◽  
Gel Technique ◽  
Doped Titania

Optically transparent, crack-free mesoporous titania and zirconia-doped titania thin films were fabricated by the sol—gel technique using the non-ionic amphiphilic triblock copolymer Pluronic P123 as the template. The structure and optical properties of these films were characterized using TEM, low-angle XRD, DTA/TG measurements, UV—vis spectroscopy and hexane adsorption investigations. It was found that addition of ZrO2 into the TiO2 matrix retarded sintering of the films, thereby increasing the specific surface area after treatment up to 500°C. The catalytic activity of the mesoporous TiO2 and TiO2/(5–30%) ZrO2 films in ethanol photo-oxidation increased with increasing specific surface area and surface acidity of the samples.

scholarly journals EFFECT OF PHYSICOCHEMICAL PROPERTIES OF d-METAL OXIDES ON SUNFLOWER OIL TRANSESTERIFICATION

2021 ◽  
pp. 113-120
Author(s):  
Yurii Melnyk ◽  
Stepan Melnyk ◽  
Halyna Mahorivska ◽  
Viktor Reutskyy
Keyword(s):  
Specific Surface ◽  
Metal Oxides ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sunflower Oil ◽  
Aqueous Suspension ◽  
Surface Acidity ◽  
Weak Acid ◽  
Transesterification Reaction ◽  
Acidity And Basicity

The physicochemical indicators of d-metal oxides (NiO, CuO, MnO, FeO, PbO, ZnO) which are heterogeneous catalysts for the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol have been determined. The available specific surface area, surface acidity and basicity, as well as the hydrogen potential change of the catalyst suspension in water were determined for the oxides. The available specific surface area of the oxides was determined by titration of their aqueous suspension with a solution of methylene blue with a predetermined concentration. The surface acidity and basicity of the catalysts were determined by back titration of samples treated with an aqueous solution of ammonia and acetic acid, respectively. It was found that all investigated d-metal oxides have a low specific surface area. The value of specific surface area is in the range of 0.6-1.5 m2/g. The surface acidity and basicity of the catalysts is 0.13-0.27 mmol/g and 0.019-0.066 mmol/g, respectively. It is shown that the change in the aqueous suspension hydrogen potential of the investigated catalysts relative to the distilled water pH is maximum for NiO and ZnO and it is 0.6-0.65, while for CuO this change is the smallest and it is only 0.3. The character of the pH change curves and the pH values of the oxides suspension in equilibrium condition indicate the presence of weak acid sites in the studied catalysts. The indicated catalysts characteristics are compared with the results obtained in the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol. It was found that there is a correlation between the surface acidity of catalyst and the reaction initial rate of triglycerides transesterification by ethanol and butan-1-ol. At the same time, such a correlation is absent for the surface basicity of the catalysts. This is consistent with the data on the catalysis of the triglyceride transesterification reaction only by strong major active sites. It is concluded that the transesterification reaction of sunflower oil triglycerides by ethanol and butan-1-ol occurs predominantly on the weak acid centers of the d-metal oxides.

Synthesis of high-specific-surface-area Li-Al mixed metal oxide: Through nanoseed-assisted growth of layered double hydroxide

2021 ◽  
Vol 203 ◽  
pp. 106006
Author(s):  
Masanori Takemoto ◽  
Yasuaki Tokudome ◽  
Hidenobu Murata ◽  
Kenji Okada ◽  
Masahide Takahashi ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Layered Double Hydroxide ◽  
Specific Surface Area ◽  
High Specific Surface Area ◽  
Mixed Metal Oxide ◽  
Mixed Metal ◽  
Double Hydroxide

scholarly journals Characterization of Commercial Metal Oxide Nanomaterials: Crystalline Phase, Particle Size and Specific Surface Area

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1812
Author(s):  
Michael Bushell ◽  
Suzanne Beauchemin ◽  
Filip Kunc ◽  
David Gardner ◽  
Jeffrey Ovens ◽  
...  
Keyword(s):  
Particle Size ◽  
Metal Oxide ◽  
Specific Surface ◽  
Human Health ◽  
Surface Area ◽  
Specific Surface Area ◽  
Crystalline Phase ◽  
Size Distributions ◽  
Metal Oxide Nanomaterials

Physical chemical characterization of nanomaterials is critical to assessing quality control during production, evaluating the impact of material properties on human health and the environment, and developing regulatory frameworks for their use. We have investigated a set of 29 nanomaterials from four metal oxide families (aluminum, copper, titanium and zinc) with a focus on the measurands that are important for the basic characterization of dry nanomaterials and the determination of the dose metrics for nanotoxicology. These include crystalline phase and crystallite size, measured by powder X-ray diffraction, particle shape and size distributions from transmission electron microscopy, and specific surface area, measured by gas adsorption. The results are compared to the nominal data provided by the manufacturer, where available. While the crystalline phase data are generally reliable, data on minor components that may impact toxicity is often lacking. The crystal and particle size data highlight the issues in obtaining size measurements of materials with broad size distributions and significant levels of aggregation, and indicate that reliance on nominal values provided by the manufacturer is frequently inadequate for toxicological studies aimed at identifying differences between nanoforms. The data will be used for the development of models and strategies for grouping and read-across to support regulatory human health and environmental assessments of metal oxide nanomaterials.

scholarly journals The Structure and Properties of Sepiolite with Partial Lattice Ions Substituted by Aluminum Ions

2021 ◽  
Vol 9 ◽  
Author(s):  
Huiwen Chen ◽  
Junming Geng ◽  
Zepeng Zhang ◽  
Rui Jiang ◽  
Jingya Zhai ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Bonding Strength ◽  
Surface Acidity ◽  
Functional Materials ◽  
Structure And Properties ◽  
Obvious Change ◽  
Aluminum Ions ◽  
Weather Resistance

Sepiolite was modified with Al3+ via hydrothermal reaction. The substitution amount of Al3+ for Mg2+ and Si4+ located at sepiolite lattice and the influence of substitution amount on the structure, specific surface area, and surface acidity of Al-modified sepiolite were investigated. On this basis, indigo–sepiolite composite pigments were prepared by Al-modified sepiolite and indigo via grinding method to evaluate the influence of Al-modified sepiolite on the structure, bonding strength, and weather resistance of composite pigment. The crystal structure of Al-modified sepiolite had no obvious change after modification. Al3+ mainly substituted Mg2+ located at the octahedron of the sepiolite lattice, and the substitution amount was positively related to the dosage of Al3+. The specific surface area of Al-modified sepiolite decreased and the distribution of channel size became wider after Al modification. In addition, the absolute value of zeta potential decreased as well as the solid acid sites increased with the increase of Al substitution in Al-modified sepiolite. For indigo–sepiolite composite pigments, the structure of Al-modified sepiolite had no obvious change as well. The adsorption amount of indigo in composite pigment after treating by DMSO and Al content as well as weak acid amount in Al-modified sepiolite presented linear correlation, indicating that Al modification could enhance the bonding strength between indigo and Al-modified sepiolite by increasing the amount of coordinated water with Al. For indigo, Al-modified sepiolite could brighten the color and reduce the weather resistance of the prepared composite pigment. The results of this study provide a new idea and basis for regulating the structure and properties of clay and for studying the preparation of composite pigment and clay functional materials.

scholarly journals A feasible strategy to balance the crystallinity and specific surface area of metal oxide nanocrystals

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Q. P. Zhang ◽  
X. N. Xu ◽  
Y. T. Liu ◽  
M. Xu ◽  
S. H. Deng ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area

Methanol to C2 and C4 fuels over (Nb/Al)-pillared clay catalysts

RSC Advances ◽  
2016 ◽  
Vol 6 (33) ◽  
pp. 27915-27921 ◽  
Author(s):  
F. C. F. Marcos ◽  
A. F. Lucrédio ◽  
J. M. Assaf ◽  
E. M. Assaf
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Low Cost ◽  
Surface Acidity ◽  
Pillared Clay ◽  
Catalytic Reactions ◽  
Large Specific Surface Area ◽  
Clay Catalysts

Pillared interlayer clay (PILC) is a low cost material, which is characterized by a large specific surface area, high pore volume and surface acidity that make it effective in catalytic reactions.

scholarly journals Mixed Metal Oxide by Calcination of Layered Double Hydroxide: Parameters Affecting Specific Surface Area

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1153
Author(s):  
Su-Bin Lee ◽  
Eun-Hye Ko ◽  
Joo Y. Park ◽  
Jae-Min Oh
Keyword(s):  
Metal Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Calcination Temperature ◽  
Layered Double Hydroxide ◽  
Specific Surface Area ◽  
High Performance ◽  
Mixed Metal Oxide ◽  
Mixed Metal ◽  
Double Hydroxide

Mixed metal oxide (MMO) is one of the widely utilized ceramic materials in various industries. In order to obtain high performance, the specific surface area of MMO should be controlled. Calcination of layered double hydroxide (LDH) is a versatile way to prepare MMO with homogeneous metal distribution and well-developed porosity. Although researchers found that the specific surface area of LDH-originated MMO was relatively high, it had not been systematically investigated how the surface area is controlled under a certain parameter. In this review, we summarized LDH-originated MMO with various starting composition, calcination temperature, and pore developing agent in terms of specific surface area and porosity. Briefly, it was represented that MMOs with Mg-Al components generally had higher specific surface area than Mg-Fe or Zn-Al components. Calcination temperature in the range 300–600 °C resulted in the high specific surface area, while upper or lower temperature reduced the values. Pore developing agent did not result in dramatic increase in MMO; however, the pore size distribution became narrower in the presence of pore developing agents.

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