Oxidation of p-toluic acid to terephthalic acid via a bromine-free process using nano manganese and manganese–copper mixed oxides

2018 ◽  
Vol 42 (8) ◽  
pp. 6343-6353 ◽  
Author(s):  
Mohamed A. Betiha ◽  
Nadia G. Kandile ◽  
Abdelfattah M. Badawi ◽  
Sanaa M. Solyman ◽  
Ahmed S. Afify
Keyword(s):  
Mixed Oxide ◽  
Acid Production ◽  
Terephthalic Acid ◽  
Mixed Oxides ◽  
Free Process ◽  
Green Route ◽  
Technological Opportunities ◽  
Manganese Copper

Challenges and technological opportunities for nano-mixed oxide (Cu–Mn) allowing a green route to valued terephthalic acid production from p-xylene.

Phase Identification in Mixed Oxide Capacitors Using Electron Backscatter Diffraction and X-Ray Diffraction

2000 ◽  
Vol 6 (S2) ◽  
pp. 944-945
Author(s):  
P. M. Adams ◽  
C. T. Hoskinson ◽  
R. Witt
Keyword(s):  
Dielectric Properties ◽  
Mixed Oxide ◽  
Mixed Oxides ◽  
Electron Backscatter Diffraction ◽  
Phase Identification ◽  
Electronic Systems ◽  
Oxide Ceramic ◽  
Backscatter Diffraction ◽  
Titanium Silicon ◽  
New Phase

A group of mixed oxide ceramic capacitors used in several electronic systems recently failed as a result of voltage breakdown in the specified test ranges. These capacitors consist predominantly of mixed oxides of magnesium, titanium, silicon and aluminum (with minor amounts of strontium and calcium) and contain palladium mesh electrodes. Preliminary results suggest that phase transformations have occurred in some lots of capacitors that have been over-fired as a result of a manufacturing change. Several years’ production of capacitors has potentially been affected. The formation of a phase with inferior dielectric properties, and which can exhibit semiconducting properties (P/N junction), probably resulted in the failure of the capacitors. This new phase is typically rich in strontium and is only present at levels of several volume percent. The low concentration of this phase has made its identification difficult. If this new phase could be identified it might be possible to determine/establish if its dielectric properties are consistent with the proposed failure mechanism.

scholarly journals Effect of Mg/Al molar ratio on the basicity of Mg-Al mixed oxide derived from Mg-Al hydrotalcite

2020 ◽  
Vol 10 (6) ◽  
pp. 625
Author(s):  
Said Arhzaf ◽  
Mohammed Naciri Bennani ◽  
Sadik Abouarnadasse ◽  
Hamid Ziyat ◽  
Omar Qabaqous
Keyword(s):  
Thermal Analysis ◽  
Mixed Oxide ◽  
Mixed Oxides ◽  
Molar Ratio ◽  
Acid Molecule ◽  
X Ray Diffraction ◽  
Phenol Adsorption ◽  
X Ray ◽  
Maximum Quantity ◽  
Uv Visible

<p>The fundamental character of the Mg-Al mixed oxide (Mg<sub>n</sub>(Al)O), derived from the Mg-Al hydrotalcite (Mg<sub>n</sub>Al-CO<sub>3</sub>-HT), where n corresponds to the Mg/Al molar ratio (n: 2, 2.5, 3, 3.5 and 4), was studied by using the adsorption of phenol as a probe acid molecule. The hydrotalcite precursors were prepared by the coprecipitation method. Their derived mixed oxides were obtained by thermal treatment at 450°C in a flow of air. The resulting solids were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis             (TG-DTA), nitrogen physisorption (BET) and phenol chemisorption. The phenol adsorption followed by UV-Visible spectrophotometry shows that the basicity increases with the Mg/Al molar ratio, such that maximum quantity of phenol adsorbed (Q<sub>ads</sub> = 0.54 mmol/g <sub>cat</sub>) was obtained with the mixed oxide derived from the Mg-Al hydrotalcite of Mg/Al molar ratio equal to 3.5.</p>

scholarly journals Modification of Surface Properties of Colloidal Suspensions of NixOy-SiO2 Mixed Oxides with Different Ni Contents by the Adsorption Layers of Poly(Vinyl Alcohol)

2020 ◽  
Author(s):  
M. Wiśniewska ◽  
S. Chibowski ◽  
T. Urban ◽  
G. Fijałkowska ◽  
M. Medykowska ◽  
...  
Keyword(s):  
Nickel Oxide ◽  
Mixed Oxide ◽  
Vinyl Alcohol ◽  
Mixed Oxides ◽  
Colloidal Suspensions ◽  
Surface Characteristics ◽  
Limited Range ◽  
Poly Vinyl Alcohol ◽  
Solution Interface ◽  
Adsorption Affinity

Abstract The adsorption and electrokinetic properties of hybrid silica materials composed of nickel and silicon oxides (NixOy-SiO2), characterized by different contents of nickel oxide (from 0.5 to 3 mmol/g SiO2), were examined. These solids were also modified by poly(vinyl alcohol) to change their surface characteristics. The polymer is non-toxic and very well soluble in water. Due to incomplete hydrolysis of the polymer acetate groups, its macromolecules become negatively charged. The limited range of studied pH (6–10) resulted from high solubility of nickel oxide at more acidic pH values. The spectrophotometric, surface charge and electrophoretic measurements indicated that PVA exhibits higher adsorption affinity for the surfaces of mixed oxide with a larger content of nickel in its structure. Moreover, the presence of polymeric layers on the solid surface influences considerably the structure of electrical double layer formed at the mixed oxide-aqueous solution interface.

scholarly journals Co-Mn-Al Mixed Oxides Promoted by K for Direct NO Decomposition: Effect of Preparation Parameters

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 593 ◽  
Author(s):  
Pacultová ◽  
Bílková ◽  
Klegova ◽  
Karásková ◽  
Fridrichová ◽  
...  
Keyword(s):  
Mixed Oxide ◽  
Alkali Metals ◽  
Mixed Oxides ◽  
Oxide Catalysts ◽  
No Decomposition ◽  
Selective Catalyst ◽  
Mixed Oxide Catalysts ◽  
Preparation Conditions ◽  
Fundamental Research

Fundamental research on direct NO decomposition is still needed for the design of a sufficiently active, stable and selective catalyst. Co-based mixed oxides promoted by alkali metals are promising catalysts for direct NO decomposition, but which parameters play the key role in NO decomposition over mixed oxide catalysts? How do applied preparation conditions affect the obtained catalyst’s properties?

scholarly journals Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 613
Author(s):  
Hussein Mahdi S. Al-Aani ◽  
Mihaela M. Trandafir ◽  
Ioana Fechete ◽  
Lucia N. Leonat ◽  
Mihaela Badea ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transition Metal ◽  
Mixed Oxide ◽  
Mixed Oxides ◽  
Catalytic Performance ◽  
Atomic Ratio ◽  
Total Oxidation ◽  
X Ray ◽  
Oxidation Of Methane ◽  
Al2o3 Catalyst

To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

scholarly journals Selective Oxidation of Glycerol Using 3% H2O2 Catalyzed by Supported Nano-Au Catalysts

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 505 ◽  
Author(s):  
Xiaoli Wang ◽  
Gongde Wu ◽  
Tongfa Jin ◽  
Jie Xu ◽  
Shihao Song
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Selective Oxidation ◽  
Mixed Oxide ◽  
Transition Metal Oxides ◽  
Mixed Oxides ◽  
Catalytic Performance ◽  
Glyceric Acid ◽  
Glycerol Conversion ◽  
Composition And Structure

A series of transition metal oxides or mixed oxides supported nano-Au catalysts were prepared for the selective oxidation of glycerol to glyceric acid using 3% H2O2. It was found that the composition and structure of supports significantly influenced the catalytic performance of catalysts. The mesoporous trimetal mixed oxide (CuNiAlO) supported nano-Au catalysts were more active in comparison with the others. In the present catalytic system, the highest glycerol conversion was 90.5%, while the selectivity of glyceric acid could reach 72%. Moreover, the catalytic performance remained after 11 times of reaction.

Formation of mixed oxide powders in flames: Part II. SiO2−GeO2 and Al2O3−TiO2

1992 ◽  
Vol 7 (7) ◽  
pp. 1870-1875 ◽  
Author(s):  
Cheng-Hung Hung ◽  
Philippe F. Miquel ◽  
Joseph L. Katz
Keyword(s):  
Light Scattering ◽  
Mixed Oxide ◽  
Mixed Oxides ◽  
Electrophoretic Method ◽  
X Ray ◽  
Oxide Powders ◽  
Flame Burner ◽  
Carbon Coated ◽  
Oxide Particles ◽  
Counterflow Diffusion Flame

SiO2−GeO2 and Al2O3−TiO2 mixed oxide powders were synthesized using a counterflow diffusion flame burner. SiCl4, GeCl4, Al(CH3)3, and TiCl4 were used as source materials for the formation of oxide particles in hydrogen-oxygen flames. In situ particle sizes were determined using dynamic light-scattering. Powders were collected using two different methods, a thermophoretic method (particles are collected onto carbon coated TEM grids) and an electrophoretic method (particles are collected onto stainless steel strips). Their size, morphology, and crystalline form were examined using a transmission electron microscope and an x-ray diffractometer. A photomultiplier at 90° to the argon ion laser beam was used to measure the light-scattering intensity. The formation of the mixed oxides was investigated using Si to Ge and Al to Ti ratios of 3:5 and 1:1, respectively. Heterogeneous nucleation of the SiO2 on the surface of the GeO2 was observed. In Al2O3−TiO2 mixtures, both oxide particles form at the same temperature. X-ray diffraction analysis of particles sampled at temperatures higher than 1553 K showed the presence of rutile, γ–Al2O3, and aluminum titanate. Although the particle formation process for SiO2−GeO2 is very different from that for Al2O3−TiO2, both mixed oxides result in very uniform mixtures.

Photocatalytic Activity of Fe/Ti Mixed Oxide for Degrading Humic Acid in Water

2013 ◽  
Vol 717 ◽  
pp. 95-100 ◽  
Author(s):  
I.H. Kim ◽  
W.S. Kim ◽  
D.S. Rhee
Keyword(s):  
Titanium Dioxide ◽  
Iron Oxide ◽  
Humic Acid ◽  
Mixed Oxide ◽  
Photocatalytic Oxidation ◽  
Mixed Oxides ◽  
Environmental Pollutant ◽  
Oxide Surface ◽  
Active Components ◽  
Coated Granules

The comparative experiments for removing humic acid as environmental pollutant were conducted by adsorption on iron oxide, photooxidation in the presence of titanium dioxide catalyst and combined adsorption-photooxidation by iron-titanium mixed metal oxides, where all these active components were immobilized on polypropylene granules. The main purpose of the work was the combination of adsorption and photocatalytic oxidation processes to remove humic acid. The granules with iron-titanium mixed oxide for treating humic acid gave much better results with 1.2~3 times higher removal rates comparing to the other two single coated oxides at certain pH values. And the order of removal efficiency according to pH was the same as for single iron oxide-coated granules. The ratio 1:2 of iron oxide/titanium dioxide was found optimal for maximal decolorization of humic acid solution. The total organic carbon decrease of humic acid in each experiments, when it was pre-equilibrated with mixed oxides-coated granules in the dark for 30 min and without pre-equilibration, was very similar. The results suggested that the mechanism of humic acid removal may be not only a respectively combined adsorption and photooxidation by iron oxide and titanium oxides, but an enhanced photooxidation reaction as a result of concentrating humic acid on titanium oxide surface by iron oxide.

Catalytic activity of Mg–Al hydrotalcites and derived mixed oxides for imination reactions via an oxidative-dehydrogenation mechanism

2020 ◽  
Vol 44 (21) ◽  
pp. 8859-8868
Author(s):  
Naresh Vala ◽  
Pradyuman A. Joshi ◽  
Manish Mishra
Keyword(s):  
Catalytic Activity ◽  
Oxidative Dehydrogenation ◽  
Mixed Oxide ◽  
Mixed Oxides ◽  
Tandem Reactions ◽  
Dehydrogenation Mechanism

A Mg–Al hydrotalcite derived mixed oxide (Mg/Al ratio = 3.0) showed excellent catalytic activity in imination and tandem reactions via an oxidative-dehydrogenation mechanism.

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