scholarly journals EFFECT OF DURATION OF OXYCHLORINATION ON DEGREE OF ACCESSIBILITY FOR CATALYSIS OF PLATINUM CENTERS OF PLATINUM-RHENIUM REFORMING CATALYST

2020 ◽  
Vol 63 (5) ◽  
pp. 59-64
Author(s):  
Andrey G. Starostin ◽  
Nikolai B. Khodyashev
Keyword(s):  
Carbon Monoxide ◽  
Absorption Band ◽  
Hydrogen Adsorption ◽  
Molar Ratio ◽  
Frequency Range ◽  
Alumina Support ◽  
Reforming Catalyst ◽  
Platinum Particles ◽  
Linear Vibrations ◽  
Carrier Volume

The work presents the results of a chemisorption analysis of a platinum-rhenium catalyst on an alumina support after regeneration and reduction with hydrogen. Adsorption-desorption diagrams were obtained by stepwise-pulsed chemisorption of carbon monoxide on reforming catalyst samples. With an increase in the number of carbon monoxide injections from 1 to 4, the catalyst sample is poisoned, and subsequent desorption peaks indicate the termination of the interaction. With an increase in the time of oxychlorination, the CO/Pt ratio in the carrier volume increases linearly. The effect of the oxychlorination process on the chemisorption of CO and the subsequent availability of platinum nanoparticles for catalysis has been shown. The absorption on freshly prepared platinum-rhenium catalyst samples reaches a CO/Pt molar ratio of about 0.4. The results show that the duration of oxychlorination for 16–20 h allows us to achieve the value of the ratio CO/Pt, which is in the range of 0.4-0.5. This indicates that the availability of platinum centers in its composition reaches the level of a fresh catalyst, and, on the other hand, taking into account a slight excess of this ratio, we can assume that some of the Re atoms participate in the absorption of CO molecules. The presence of finely dispersed platinum particles in the composition of the regenerated catalyst was confirmed by IR spectroscopy. The analysis of catalyst samples on an IR spectrometer in the frequency range of 1900-2200 cm-1 revealed a rather wide absorption band with a pronounced extremum at 2060 cm-1. In this frequency range, there is another, slightly pronounced extremum at 2149 cm-1. However, for samples with a short duration of oxychlorination, it did not appear. An absorption band with an extremum of 2060 cm-1 can be attributed to linear vibrations of adsorbed CO molecules on the surface of particles of metallic platinum.

A Study of Na2O-TiO2-SiO2 Glasses by Infrared Spectroscopy

1974 ◽  
Vol 28 (3) ◽  
pp. 256-259 ◽  
Author(s):  
Murli H. Manghnani ◽  
John R. Ferraro ◽  
L. J. Basile
Keyword(s):  
Infrared Spectroscopy ◽  
Absorption Band ◽  
Infrared Absorption ◽  
Vibrational Frequency ◽  
Silicate Glasses ◽  
Molar Ratio ◽  
Frequency Range ◽  
Weak Absorption ◽  
Infrared Absorption Spectra ◽  
The Relationship

The infrared absorption spectra of six Na2O-TiO2-SiO2 glasses in the frequency range of 1600 to 200 cm−1 are reported. These glasses, having a SiO2/Na2O molar ratio of 1.07 to 3.54, and containing 20 or 25 mole % TiO2, demonstrate two main absorptions at ∼950 cm−1 and at ∼450 cm−1. A weak absorption at ∼790 cm−1 becomes progressively weaker in intensity, and a weak shoulder at 1050 cm−1 appears with increasing Na2O content. The frequency of the absorption band at ∼950 cm−1 is found to decrease markedly and systematically with a decrease in the SiO2/Na2O molar ratio, whereas the frequency of the band at ∼450cm−1 shows a slight increase. The infrared results may be interpreted in terms of a lowering of symmetry occurring for the SiO4 units. The effect of TiO2 content on the relationship between vibrational frequency is discussed. The frequency composition curves for glasses containing 20 and 25 mole % of TiO2 intersect at SiO2/Na2O ratio ∼2. A reversal in the frequency vs SiO2/Na2O ratio relation was also found at SiO2/Na2O ∼2 for the sodium silicate glasses.

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.

Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation – co-precipitation method

2020 ◽  
Vol 18 (5-6) ◽  
Author(s):  
Buyan-Ulzii Battulga ◽  
Tungalagtamir Bold ◽  
Enkhsaruul Byambajav
Keyword(s):  
Synergetic Effect ◽  
Space Velocity ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Alumina Support ◽  
Co Methanation ◽  
Temperature Range ◽  
Co Precipitation ◽  
Catalyst Distribution

AbstractNi based catalysts supported on γ-Al2O3 that was unpromoted (Ni/γAl2O3) or promoted (Ni–Fe/γAl2O3, Ni–Co/γAl2O3, and Ni–Fe–Co/γAl2O3) were prepared using by the impregnation – co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H2/CO = 3 and in the temperature range between 130 and 350 °C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni–Co/γAl2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 °C). The temperatures for the 20% CO conversion over Ni–Co/γAl2O3, Ni–Fe/γAl2O3, Ni–Fe–Co/γAl2O3 and Ni/γAl2O3 catalysts were 205, 253, 263 and 270 °C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of β type nickel species which had an appropriate interacting strength with alumina support in the Ni–Co/γAl2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni–Fe/γAl2O3. Moreover, it was found that there was no synergetic effect from the binary Fe–Co promotors in the Ni–Fe–Co/γAl2O3 on catalytic activity for CO methanation.

scholarly journals Liquid Phase Hydrogenation of 1-Hexene and 2-Hexene with 30 Å Platinum Particles on Alumina Support.

1980 ◽  
Vol 34a ◽  
pp. 639-644 ◽  
Author(s):  
Magali Boutonnet ◽  
Carlaxel Andersson ◽  
Ragnar Larsson ◽  
Jussi Valkonen ◽  
V. P. Spiridonov ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Alumina Support ◽  
Liquid Phase Hydrogenation ◽  
Platinum Particles

Single-Layer and Double-Layer Microwave Absorbers Based on Graphene Nanosheets/Epoxy Resin Composite

NANO ◽  
2017 ◽  
Vol 12 (07) ◽  
pp. 1750089 ◽  
Author(s):  
Dandan Min ◽  
Wancheng Zhou ◽  
Yuchang Qing ◽  
Fa Luo ◽  
Dongmei Zhu
Keyword(s):  
Absorption Band ◽  
Epoxy Resin ◽  
Microwave Absorption ◽  
Double Layer ◽  
Graphene Nanosheets ◽  
Resin Composite ◽  
Single Layer ◽  
Frequency Range ◽  
Absorption Properties ◽  
Microwave Absorption Properties

Graphene nanosheets/epoxy resin (GN/EP) composites with enhanced microwave absorption properties were prepared. The influence of GNs content on the electromagnetic and microwave-absorbing properties of single-layer GN/EP composites was investigated in the frequency range of 2–18[Formula: see text]GHz. A novel double-layer microwave absorber by combining absorbers with different contents of graphene was designed to achieve absorbers with wide absorption band and optimal microwave absorption. The calculated microwave absorption properties indicated that broader absorption band was obtained by the double-layer GN/EP composites. Reflection loss (RL) values below [Formula: see text]5[Formula: see text]dB can be obtained in the frequency range of 4.4–18[Formula: see text]GHz by the double-layer GN/EP composites at thickness of 3.9[Formula: see text]mm.

Model Catalyst Studies on Vanadia Particles Deposited onto a Thin-Film Alumina Support. 2. Interaction with Carbon Monoxide

2003 ◽  
Vol 107 (34) ◽  
pp. 9003-9010 ◽  
Author(s):  
Norbert Magg ◽  
Javier B. Giorgi ◽  
Ayman Hammoudeh ◽  
Thomas Schroeder ◽  
Marcus Bäumer ◽  
...  
Keyword(s):  
Thin Film ◽  
Carbon Monoxide ◽  
Model Catalyst ◽  
Alumina Support

Template-Method Synthesis of High-Surface-Area Monolithic Carbon Aerogels and Their Applications for Hydrogen and Deuterium Adsorption

2017 ◽  
Vol 16 (05n06) ◽  
pp. 1750010 ◽  
Author(s):  
Bowei Chen ◽  
Xiaojun Wang ◽  
Jiayi Zhu ◽  
Yutie Bi ◽  
Xuan Luo ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Surface Area ◽  
Hydrogen Adsorption ◽  
High Surface ◽  
High Surface Area ◽  
Carbon Aerogel ◽  
Molar Ratio ◽  
Template Method ◽  
Carbon Aerogels ◽  
Polymer Templates

In this work, novel monolithic carbon aerogels obtained by using a polymer template method were characterized and evaluated for their applications in the hydrogen and deuterium adsorption capacity. The properties (i.e., surface area, pore size distribution, hydrogen and deuterium adsorption capacities, etc.) of the carbon aerogels were affected by the polymer templates. The results showed that the carbon aerogel with the molar ratio of polyacrylic acid (PAA) to zinc chloride (ZnCl2) being 0.75:40 was featured the highest surface area (1806 m2/g) and had the highest hydrogen adsorption capacity. Moreover, the deuterium adsorption capacity of the carbon aerogel was to be further elucidated.

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