Surface characteristics and catalytic activity of Al-Pillared (AZA) and FeAl-pillared (FAZA) clays for isopropanol decomposition

1996 ◽  
Vol 106 (3) ◽  
pp. 241-254 ◽  
Author(s):  
A.K. Ladavos ◽  
P.N. Trikalitis ◽  
P.J. Pomonis
Keyword(s):  
Catalytic Activity ◽  
Surface Characteristics ◽  
Isopropanol Decomposition

PHOTO-CATALYTIC ACTIVITY AND PHOTO-ABSORPTION OF PLASMA-SPRAYED NANO-STRUCTURED TiO2 COATINGS

2010 ◽  
Vol 24 (31) ◽  
pp. 6115-6127 ◽  
Author(s):  
MARYAMOSSADAT BOZORGTABAR ◽  
MEHDI SALEHI ◽  
MOHAMMADREZA RAHIMIPOUR ◽  
MOHAMMADREZA JAFARPOUR
Keyword(s):  
Catalytic Activity ◽  
Flow Rate ◽  
Test Chamber ◽  
Catalytic Efficiency ◽  
Surface Characteristics ◽  
Catalytic Performance ◽  
Atmospheric Plasma ◽  
Argon Flow Rate ◽  
Photo Catalytic Activity ◽  
Argon Flow

Titanium dioxide coatings were deposited by utilizing atmospheric plasma-spraying system. The agglomerated P25/20 nano-powder and different spraying parameters (e.g., Argon flow rate and spray distance) were used to determine their influences on the microstructure, crystalline structure, photo-absorption, and photo-catalytic performance of the coatings. The microstructure and phases of as-sprayed TiO 2 coatings were characterized by scanning electron microscope SEM and X-ray diffraction, respectively. Surface characteristics were investigated by Fourier Transform Infrared. Photo-catalytic efficiency of the elaborated samples was also determined in an environmental test chamber set-up and evaluated from the conversion rate of ethanol. The photo-absorption was determined by UV–Vis spectrophotometer. The as-sprayed TiO2 coating was photo-catalytically reactive for the degradation of ethanol. The photo-catalytic activity was influenced by spray conditions. It is found that the photo-catalytic activity is significantly influenced by anatase content, surface area, and surface state. The results showed that the argon flow rate has an influence on the microstructure, anatase content, and photo-catalytic activity of the TiO 2 coatings.

Catalytic Activity in Organic Solvents and Stability of Immobilized Enzymes Depend on the Pore Size and Surface Characteristics of Mesoporous Silica

2000 ◽  
Vol 12 (11) ◽  
pp. 3301-3305 ◽  
Author(s):  
Haruo Takahashi ◽  
Bo Li ◽  
Toshiya Sasaki ◽  
Chie Miyazaki ◽  
Tsutomu Kajino ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Mesoporous Silica ◽  
Pore Size ◽  
Organic Solvents ◽  
Surface Characteristics ◽  
Immobilized Enzymes

scholarly journals Effect of Li2O Doping on the Surface and Catalytic Properties of the Fe2O3–NiO/Al2O3 System

1998 ◽  
Vol 16 (1) ◽  
pp. 21-32 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
N.M. Deraz
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Mixed Oxide ◽  
Active Sites ◽  
Catalytic Properties ◽  
Surface Characteristics ◽  
Appreciable Change ◽  
Surface Areas ◽  
Catalytically Active ◽  
Specific Surface Areas

Ferric–nickel/aluminium mixed oxide solids have the formula Fe2O3–0.42NiO/Al2O3 were treated with Li2O (0.75–3 mol%) and heated in air for 4 h at 500°C and 800°C, respectively. The effects of this treatment on the surface characteristics of these solids and their catalytic properties in relation to CO oxidation by O2 have been investigated. The results reveal that Li2O doping at 0.75 mol% concentration resulted in an increase of 24% and 18%, respectively, in the value of the specific surface areas, SBET, of the solids precalcined at 500°C and 800°C, while the addition of 3 mol% Li2O led to a slight decrease of ca. 10% in the SBET value of the same solids. In contrast, irrespective of whether the doping process involved solids precalcined at 500°C or 800°C, a significant decrease of 37% and 78%, respectively, was observed in the catalytic activity of these materials. This decrease in catalytic activity was not accompanied by any appreciable change in the magnitude of the activation energy for the catalytic reaction, i.e. Li2O doping brings about a decrease in the concentration of catalytically active sites without changing their energetic nature.

scholarly journals Catalytic Decomposition of H2O2 over a γ-Irradiated CuO–ZnO/Al2O3 System

1998 ◽  
Vol 16 (5) ◽  
pp. 381-390 ◽  
Author(s):  
Gehan A. Fagal ◽  
Amina A. Attia ◽  
Hala G. El-Shobaky
Keyword(s):  
Catalytic Activity ◽  
Mixed Oxide ◽  
Catalytic Decomposition ◽  
Nitrogen Adsorption ◽  
Surface Characteristics ◽  
Copper Nitrate ◽  
Oxide Material ◽  
Γ Irradiation ◽  
Exponential Factor ◽  
Γ Rays

A CuO–ZnO/Al2O3, catalyst sample was prepared by wet impregnation methods using Al(OH)3, zinc and copper nitrate solutions followed by drying at 110°C and calcination at 600°C. The nominal molar composition of the resulting material was calculated to be 0.25CuO · 0.03ZnO/Al2O3 Samples of this solid were exposed to varying dosages of γ-irradiation (20–160 Mrad) and the effect of such treatment on their surface characteristics and catalytic activity investigated using nitrogen adsorption studies at −196°C and studies of the decomposition of H2O2 at 30–50°C. The results obtained indicate that doses of γ-rays up to 80 Mrad had no significant effect on the specific surface area. SBET, of the supported mixed oxide material although this quantity increased by 20% when the solid was exposed to γ-irradiation doses of 160 Mrad. In contrast, such treatment brought about a progressive decrease in the catalytic activity of the treated catalyst samples. Thus, the reaction rate constant (k) of the catalyzed reaction measured at 50°C diminished from 8 × 10−2 min−1 to 0.3 × 10−2 min−1 on exposure of the supported mixed oxide material to a dose of 160 Mrad. What was surprising was that the activation energy (δE) of the catalytic reaction decreased as a function of the dose employed whereas it should have been expected to increase in the light of the observed decrease in the catalytic activity. This apparent discrepancy was resolved by recalculating the values of ΔE taking into account any possible changes in the pre-exponential factor of the Arrhenius equation brought about by γ-irradiation. The observed decrease in the catalytic activity due to treatment with γ-rays was attributed, mainly, to the enhanced removal of Brönsted acid centres by the action of such irradiation.

Structural and Adsorption Effects of Some Thiopurine and Thiopyrimidine Derivatives on their Catalytic Activity at the Mercury Electrode

1994 ◽  
Vol 59 (7) ◽  
pp. 1472-1482 ◽  
Author(s):  
Mohamed Sayed Ibrahim
Keyword(s):  
Catalytic Activity ◽  
Catalytic Effect ◽  
Mercury Electrode ◽  
Surface Characteristics ◽  
Reduction Wave ◽  
Ph Values ◽  
Catalytic Wave ◽  
Dc Polarography ◽  
Catalytic Hydrogen ◽  
Catalytic Hydrogen Evolution

6-Thiopurine, 6-thiopurine riboside, 6-thioguanine, 6-thioguanosine, 8-thioguanosine, 2-thiouracil, 4-thiouridine, 2-thiocytosine and 2-thiocytidine are investigated by means of DC polarography and coulometry. In acid medium they give a typical catalytic hydrogen discharge wave, as shown by its parameters and the regeneration of the depolarizer during the electrode process. At pH values above 4.2 a second catalytic wave appears. Both catalytic waves possess pronounced surface characteristics, most likely due to adsorption of the molecules with differing orientations on the electrode surface. The catalytic wave overlaps the reduction wave, which is placed in evidence under conditions where the catalytic effect is absent. Under the same conditions, 2-thiouracil was found to be catalytically inactive, but it induces catalytic hydrogen evolution in Co(II)-containing ammonia buffer. The present results indicate that the position of thio group yields also such distinct change in the catalytic activity of the investigated compounds.

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