Structural, Surface and Catalytic Properties of Nano-Sized Ceria Catalysts

Well-dispersed uniform spheres of crystalline CeO2 were prepared by calcining precursor particles obtained by heating ammonium cerium nitrate for 4 h. These spherical substrates were examined using XRD and TEM methods, and by nitrogen adsorption studies at −196 °C. Subsequently, such cerium oxide particles prepared by calcination at 400–600 °C were used as catalysts for the conversion of isopropanol at 250–450 °C, using a flow method. The results obtained showed that increasing the heating temperature of the system investigated from 400 °C to 600 °C stimulated the formation of a well-crystallized CeO2 phase having a crystallite size varying between 10 and 20 nm. Both the surface area and catalytic activity of cerium oxide were found to decrease on increasing the calcination temperature. All solids investigated behaved as dehydrogenation catalysts which were selective towards the formation of acetone. The heat treatment did not alter the mechanism of dehydrogenation of isopropanol, but changed the concentration of active sites involved in the catalyzed reaction without altering their energetic nature.

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Synthesis and characterization of Cu-MFI catalyst for the direct medium temperature range NO decomposition

Materials Science-Poland ◽

10.1515/msp-2016-0018 ◽

2016 ◽

Vol 34 (1) ◽

pp. 177-184 ◽

Cited By ~ 3

Author(s):

Karolina Maduna Valkaj ◽

Vesna Tomašić ◽

Andrea Katović ◽

ElżBieta Bielańska

Keyword(s):

Ion Exchange ◽

Active Sites ◽

Catalytic Properties ◽

Direct Synthesis ◽

Copper Acetate ◽

Nitrogen Adsorption ◽

No Decomposition ◽

Medium Temperature ◽

Exchange Method ◽

Mfi Zeolites

AbstractIn this study the physico-chemical and catalytic properties of copper bearing MFI zeolites (Cu-MFI) with different Si/Al and Si/Cu ratios were investigated. Two different methods for incorporation of metal ions into the zeolite framework were used: the ion exchange from the solution of copper acetate and the direct hydrothermal synthesis. Direct synthesis of a zeolite in the presence of copper-phosphate complexes was expected to generate more active copper species necessary for the desired reaction than the conventional ion exchange method. Direct decomposition of NO was used as a model reaction, because this reaction still offers a very attractive approach to NOX removal. The catalytic properties of zeolite samples were studied using techniques, such as XRD, SEM, EPR and nitrogen adsorption/desorption measurements at 77 K. Results of the kinetic investigation revealed that both methods are applicable for the preparation of the catalysts with active sites capable of catalyzing the NO decomposition. It was found out that Cu-MFI zeolites obtained through direct synthesis are promising catalysts for NO decomposition, especially at lower reaction temperatures. The efﬁciency of the catalysts prepared by both methods is compared and discussed.

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SURFACE CHEMISTRY AND CATALYTIC PROPERTIES OF BORON PHOSPHATE: 1. SURFACE AREA AND ACIDITY

Canadian Journal of Chemistry ◽

10.1139/v65-222 ◽

1965 ◽

Vol 43 (6) ◽

pp. 1680-1688 ◽

Cited By ~ 12

Author(s):

J. B. Moffat ◽

H. L. Goltz

Keyword(s):

Surface Area ◽

Active Sites ◽

Elevated Temperatures ◽

Catalytic Properties ◽

Nitrogen Adsorption ◽

Weight Changes ◽

Kcal Mole ◽

Boron Phosphate ◽

Surface Areas ◽

Nitrogen Adsorption Isotherms

Surface properties of the dehydration catalyst, boron phosphate (BP), prepared by the reaction of triethyl borate and phosphoric acid, were investigated by the use of a microbalance system. During evacuation at elevated temperatures, weight changes of the BP were obtained. Nitrogen adsorption isotherms were measured after each treatment. Surface areas appear to increase, and reach a maximum in the range 200–300 °C. Weight changes are initially large but begin to level off as the temperature is increased. Ammonia isotherms were obtained at 25.00 °C on aliquots of the same BP sample after various pretreatments. Amounts of ammonia remaining adsorbed after evacuation overnight were taken as the quantity chemisorbed. An approximate value of 8.9 kcal/mole of ammonia was obtained for the heat of chemisorption of ammonia by measuring the pressure and weight change as the amount of chemisorbed ammonia is decreased on heating the BP to various temperatures in a closed system. Results are interpreted in terms of change of number of active sites with surface area and the deactivation of sites on loss of water.

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Surface and Catalytic Properties of MoO3-Treated Co3O4/Al2O3 Solids

Adsorption Science & Technology ◽

10.1260/0263617001493620 ◽

2000 ◽

Vol 18 (6) ◽

pp. 561-572 ◽

Cited By ~ 6

Author(s):

A.M. Ghozza ◽

G.A. El-Shobaky ◽

G.M. Mohamed

Keyword(s):

Thermal Decomposition ◽

Aluminium Hydroxide ◽

Active Sites ◽

Catalytic Properties ◽

Nitrogen Adsorption ◽

Ammonium Molybdate ◽

Degree Of Crystallinity ◽

The Degree Of Crystallinity ◽

Calculated Amount ◽

Cobalt Species

The surface and catalytic properties of Co3O4/Al2O3 solids treated with different proportions of MoO3 were investigated, the extent of MoO3 added varying between 0.50 mol% and 5.00 mol% (0.63–5.9 wt%). The pure sample was prepared by thermal decomposition at 600°C of aluminium hydroxide impregnated with a calculated amount of Co(NO3)2 dissolved in the least amount of distilled water. The MoO3-treated samples were prepared by thermal decomposition at 600°C of aluminium hydroxide treated with different proportions of ammonium molybdate followed by treatment with Co(NO3)2 solution. The crystalline phases produced by thermal treatment of the pure and treated samples precalcined at 600°C were characterized using an XRD technique. The surface and catalytic properties of the various catalysts were studied using nitrogen adsorption at −196°C and CO oxidation by O2 at 100–150°C. The results obtained revealed that molybdena treatment of the Co3O4/Al2O3 solids followed by precalcination at 600°C resulted in a decrease in the degree of crystallinity of the Co3O4 phase produced. This treatment effected a progressive small increase in the specific surface area of the treated solids (ca. 10%). However, the catalytic activity was found to be increased considerably by increasing the amount of MoO3 added (184%), reaching a maximum limit at 1.00 mol% MoO3. The activation energies of the catalytic reaction calculated for both the pure and MoO3-treated solids suggested that MoO3 treatment did not modify the energetic nature of the active sites (surface cobalt species) but increased their concentration.

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Fluoride Adsorption Properties of CeO2 Powders and Al Foam Loaded CeO2

Materials Science Forum ◽

10.4028/www.scientific.net/msf.814.118 ◽

2015 ◽

Vol 814 ◽

pp. 118-124 ◽

Cited By ~ 1

Author(s):

Jian Qing Chen ◽

Dong Hui Yang ◽

Yong Wei ◽

Jing Hua Jiang ◽

Ai Bin Ma ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Cerium Oxide ◽

Active Sites ◽

Aluminum Foam ◽

Raw Material ◽

Nitrate Hexahydrate ◽

Fluoride Ions ◽

Oxide Particles ◽

Scanning Electron

Cerium oxide powder and aluminum foam loaded cerium oxide were prepared by hydrothermal method using cerium nitrate hexahydrate and dimethyl oxalate (DMO) as raw material. Cerium oxide precursors and cerium oxide particles were characterized by field emission scanning electron microscopy (FESEM). Aluminum foam loaded cerium oxide was characterized by environment scanning electron microscopy (ESEM). On the basis of calculation and fitting of the experimental data, effect of the particle size on the adsorption rate, desorption rate and concentration of surface active sites of the powder and composite absorbents were studied. Results show that the removal of fluoride ions can be realized by exchange adsorption of oxhydryl on the cerium oxide particles surface and the fluoride ions in the solution.

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Effect of Li2O Doping on the Surface and Catalytic Properties of the Cr2O/Al2O3 System

Adsorption Science & Technology ◽

10.1177/026361749801600601 ◽

1998 ◽

Vol 16 (6) ◽

pp. 415-429 ◽

Cited By ~ 13

Author(s):

G.A. El-Shobaky ◽

A.M. Ghozza ◽

H.G. El-Shobaky

Keyword(s):

Co Oxidation ◽

Catalytic Reaction ◽

Active Sites ◽

Catalytic Properties ◽

Nitrogen Adsorption ◽

Maximum Increase ◽

Exponential Factor ◽

Catalytic Activities ◽

Catalytically Active ◽

Maximum Decrease

Two Cr2O3/Al2O3 samples with the nominal compositions 0.06Cr2O2/Al2O3 and 0.125Cr2O3/Al2O3 (AlCr-I and AlCr-II, respectively) were prepared by mixing a known amount of finely powdered Al(OH)3 with calculated amounts of CrO3, followed by drying at 120°C and calcination at 700°C and 800°C. Doped solid specimens were prepared by treating Al(OH)3 samples with known amounts of LiNO3 dissolved in the minimum amount of distilled water prior to mixing with CrO3. Dopant concentrations of 0.75, 1.50, 3.00 and 6.00 mol% Li2O were employed. The surface and catalytic properties of the pure and doped solids thus prepared were investigated using nitrogen adsorption at −196°C and studies of the catalysis of CO oxidation by O2 over the solid specimens at 300–400°C. The results of such studies showed that Li2O doping followed by calcination at 700°C led to a maximum increase in the specific surface area, SBET, of 26% for AlCr-I and of 55% for AlCr-II when these samples were doped with 3.00 mol% Li2O. The reverse effect was found when the calcination temperature was increased to 800°C, where a decrease of 34% in the SBET value of the AlCr-II sample doped with 3.00 mol% Li2O was detected. The catalytic activities measured at 350°C over the pure and doped solids decreased on increasing the dopant concentration, the maximum decrease in such activity being ca. 33% and 50%, respectively, for the AlCr-I and AlCr-II samples calcined at 700°C. Doping led to noticable changes in the magnitude of the activation energy for the catalytic reaction. Such changes were accompanied by parallel changes in the value of the pre-exponential factor in the Arrhenius equation. These results may indicate that Li2O doping has no effect on the mechanism of the catalytic reaction but modifies (decreases) the concentration of catalytically active sites taking part in chemisorption during the catalysis of CO oxidation by O2.

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Surface and Catalytic Properties of γ-Irradiated Fe2O3/Al2O3 Solids

Adsorption Science & Technology ◽

10.1177/026361749601300302 ◽

1996 ◽

Vol 13 (3) ◽

pp. 153-163 ◽

Cited By ~ 13

Author(s):

G.A. El-Shobaky ◽

A.S. Ahmad ◽

A.M. Ghozza ◽

S.M. El-Khouly

Keyword(s):

Co Oxidation ◽

Surface Area ◽

Catalytic Reaction ◽

Active Sites ◽

Catalytic Properties ◽

Nitrogen Adsorption ◽

Ferric Nitrate ◽

Unit Surface Area ◽

Γ Irradiation ◽

Co Oxidation Reaction

Two specimens of Fe2O3/Al2O3 solids were prepared by impregnating a known mass of finely-powdered Al(OH)3 with calculated amounts of ferric nitrate solutions followed by drying at 120°C and calcination in air at 400°C for 4 h. The mixed solids thus prepared had the nominal molar compositions 0.06Fe2O3/Al2O3 and 0.125Fe2O3/Al2O3 (FeAl-I and FeAl-II). The surface and catalytic properties of various irradiated solids (15–200 Mrad) were studied using nitrogen adsorption at −196°C and catalysis of CO oxidation by O2 at 150–280°C using a static method. The results obtained revealed that γ-irradiation at doses between 15 and 80 Mrad resulted in a progressive decrease (7–22%) in the surface area of the treated solids. Treatment with doses above this limit exerted an opposite effect. γ-Irradiation also resulted in a widening of the pores of the irradiated adsorbents. The catalytic activity of the FeAl-I solid was influenced slightly by γ-rays while the FeAl-II catalyst was significantly modified by this treatment. The reaction rate constant per unit surface area of the catalytic reaction conducted at 280°C over the FeAl-II solid decreased (65%) by exposure to doses up to 120 Mrad, then increased on increasing the dose above this limit. This did not modify the mechanism of the catalytic reaction, but changed the number of catalytically-active sites taking part in chemisorption and catalysis of the CO oxidation reaction without affecting their energetic nature.

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A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

10.26434/chemrxiv.10008545.v2 ◽

2020 ◽

Author(s):

Travis Marshall-Roth ◽

Nicole J. Libretto ◽

Alexandra T. Wrobel ◽

Kevin Anderton ◽

Nathan D. Ricke ◽

...

Keyword(s):

Oxygen Reduction ◽

Active Sites ◽

Catalytic Properties ◽

Reduction Reaction ◽

Iron Phthalocyanine ◽

Electrochemical Studies ◽

Onset Potential ◽

Nitrogen Doped Carbon ◽

Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N4 pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N4 catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen2N2)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen2N2)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen2N2)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen2N2)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen2N2)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen2N2)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen2N2)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen2N2)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H2O2 production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen2N2)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.

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Catalytic Neutralization of Naphthenic Acid from Petroleum Crude Oil by Using Cerium Oxide Catalyst and 2- Methylimidazole in Polyethylene Glycol

Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) ◽

10.2174/2405520413999200819171315 ◽

2020 ◽

Vol 13 ◽

Author(s):

Norshahidatul Akmar Mohd Shohaimi ◽

Norfakhriah Jelani ◽

Ahmad Zamani Ab Halim ◽

Nor Hakimin Abdullah ◽

Nurasmat Mohd Shukri

Keyword(s):

Polyethylene Glycol ◽

Crude Oil ◽

Cerium Oxide ◽

Active Sites ◽

Naphthenic Acid ◽

Naphthenic Acids ◽

Catalyst Loading ◽

High Concentration ◽

Oil Refineries ◽

Al2o3 Catalyst

: The presence of relatively high naphthenic acid in crude oil may contribute to the major corrosion in oil pipelines and distillation units in crude oil refineries. Thus, high concentration Naphthenic Acids crude oil is considered tobe of low quality and is marketed at lower prices. In order to overcome this problem, neutralization method had been developed to reduce the TAN value in crude oil. In this study, crude oil from Petronas Penapisan Melaka was investigated. The parameters studied were reagent concentration, catalyst loading, calcination temperature and reusability of the potential catalyst. Basic chemical used were 2- methylimidazole in polyethylene glycol (PEG 600) with concentration 100, 500 and 1000 ppm. Cerium oxide-based catalysts supported onto alumina prepared with different calcination temperatures. The catalyst was characterized by using Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry Analysis-Differential Thermal Gravity (TGA-DTG) to study physical properties of the catalyst. The Ce/Al2O3 catalyst calcined at 1000°C was the best catalyst due to larger surface area formation which lead to increment of active sites thus will boost the catalytic activity. The result showed that the Ce/Al2O3 catalyst meet Petronas requirement as the TAN value reduced to 0.6 mgKOH/g from original TAN value of 4.22 mgKOH/g. The best reduction of TAN was achieved by using catalyst loading of 0.39% and reagent of 1000 ppm.

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Physicochemical and Catalytic Properties of Spinels Formed by Solid-Solid Interaction Between Fe2O3and V2O5

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19961131 ◽

1996 ◽

Vol 61 (8) ◽

pp. 1131-1140 ◽

Cited By ~ 3

Author(s):

Abd El-Aziz Ahmed Said

Keyword(s):

Vanadium Oxide ◽

Active Sites ◽

Catalyst Surface ◽

Catalytic Properties ◽

Flow System ◽

Oxide Catalysts ◽

X Ray Diffraction ◽

Selective Catalyst ◽

X Ray ◽

Solid Catalysts

Vanadium oxide catalysts doped or mixed with 1-50 mole % Fe3+ ions were prepared. The structure of the original samples and those calcined from 200 up to 500 °C were characterized by TG, DTA, IR and X-ray diffraction. The SBET values and texture of the solid catalysts were investigated. The catalytic dehydration-dehydrogenation of isopropanol was carried out at 200 °C using a flow system. The results obtained showed an observable decrease in the activity of V2O5 on the addition of Fe3+ ions. Moreover, Fe2V4O13 is the more active and selective catalyst than FeVO4 spinels. The results were correlated with the active sites created on the catalyst surface.

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