The mobility of an alkali promoter as probedin situ during a catalytic reaction: Li in the CO oxidation on Pt

2007 ◽  
Vol 39 (2-3) ◽  
pp. 161-165 ◽  
Author(s):  
Y. Suchorski ◽  
J. Beben ◽  
A. Frac ◽  
V. K. Medvedev ◽  
H. Weiss
1985 ◽  
Vol 162 (1-3) ◽  
pp. 354-360 ◽  
Author(s):  
V. Matolin ◽  
E. Gillet ◽  
M. Gillet

1985 ◽  
Vol 162 (1-3) ◽  
pp. A591-A592
Author(s):  
V. Matolin ◽  
E. Gillet ◽  
M. Gillet

1998 ◽  
Vol 16 (6) ◽  
pp. 415-429 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
H.G. El-Shobaky

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.


1996 ◽  
Vol 13 (3) ◽  
pp. 153-163 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.S. Ahmad ◽  
A.M. Ghozza ◽  
S.M. El-Khouly

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.


1996 ◽  
Vol 100 (3) ◽  
pp. 1048-1054 ◽  
Author(s):  
Tsuyoshi Sueyoshi ◽  
Takehiko Sasaki ◽  
Yasuhiro Iwasawa

2013 ◽  
Vol 133 (12) ◽  
pp. 642-647 ◽  
Author(s):  
Hitomi Kawakami ◽  
Akinori Zukeran ◽  
Koji Yasumoto ◽  
Yoshiyasu Ehara ◽  
Toshiaki Yamamoto

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