Open AccessPhysicochemical Surface and Catalytic Properties of the Na2O-doped CuO–ZnO/Al2O3 System
Author(s) -
G.A. El-Shobaky,
G.A. Fagal,
Abdulkarim S. Ahmed,
M. Mokhtar
Publication year - 1998
Publication title -
adsorption science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.682
H-Index - 36
eISSN - 2048-4038
pISSN - 0263-6174
DOI - 10.1177/026361749801600202
Subject(s) - calcination , dopant , catalysis , crystallite , doping , chemistry , adsorption , oxide , crystallization , specific surface area , inorganic chemistry , chemical engineering , materials science , crystallography , organic chemistry , optoelectronics , engineering
In order to investigate the effect of Na 2 O doping (0.75–4.5 mol%) on metal oxide-support interactions, the surface and catalytic properties of the CuO–ZnO/Al 2 O 3 system have been studied using XRD, nitrogen adsorption at -196°C and the catalytic oxidation of CO by O 2 at 150–200°C. Pure and doped mixed oxide solid samples were prepared via the wet impregnation method using Al(OH)3, NaNO 3 . Zn(NO 3 ) 2 and Cu(NO 3 ) 2 solutions, followed by drying and calcination at 600°C and 700°C.The nominal composition of the solids thus prepared was 0.25CuO:0.06ZnO: Al 2 O 3 . The results obtained showed that Na 2 O doping followed by heating in air at 600°C leads to enhanced crystallization of the CuO crystallites to an extent proportional to the amount of dopant present, while doping followed by heating in air at 700°C hinders the solid–solid interactions between CuO andA12O 3 , and leads to the production of CuAl 2 O 4 . The specific surface area was found to increase progressively as a function of the dopant concentration for the solid calcined at 700°C. The catalytic activity was also found to increase progressively on increasing the amount of dopant added. The maximum increase in the catalytic activity measured at 150, 175 and 200°C over solids calcined at 700°C was 114, 102 and 82%. respectively. The doping process did not modify the mechanism of the catalyzed reaction but rather increased the concentration of catalytically active constituents (surface CuO crystallites) involved in the chemisorption and catalysis of the CO oxidation reaction without affecting their energetic nature.