Abstract
The physicochemical, surface and catalytic properties of 10 and 20
wt% CuO, NiO or (CuO–NiO) supported on cordierite (commercial grade) calcined at 350–700
°C were investigated using XRD, EDX, nitrogen adsorption at −196
°C and CO oxidation by O
2 at 220–280
°C. The results obtained revealed that the employed cordierite preheated at 350–700
°C was well-crystallized magnesium aluminum silicate (Mg
2Al
4Si
5O
18). Loading of 20
wt% CuO or NiO on the cordierite surface followed by calcination at 350
°C led to dissolution of a limited amount of both CuO and NiO in the cordierite lattice. The portions of CuO and NiO dissolved increased upon increasing the calcination temperature. Treating a cordierite sample with 20
wt% (CuO–NiO) followed by heating at 350
°C led to solid–solid interaction between some of the oxides present yielding nickel cuprate. The formation of NiCuO
2 was stimulated by increasing the calcination temperature above 350
°C. However, raising the temperature up to ≥550
°C led to distortion of cuprate phase. The chemical affinity towards the formation of NiCuO
2 acted as a driving force for migration of some of copper and nickel oxides from the bulk of the solid towards their surface by heating at 500–700
°C. The
S
BET of cordierite increased several times by treating with small amounts of NiO, CuO or their binary mixtures. The increase was, however, less pronounced upon treating the cordierite support with CuO–NiO. The catalytic activity of the cordierite increased progressively by increasing the amount of oxide(s) added. The mixed oxides system supported on cordierite and calcined at 450–700
°C exhibited the highest catalytic activity due to formation of the nickel cuprate phase. However, the catalytic activity of the mixed oxides system reached a maximum limit upon heating at 500
°C then decreased upon heating at temperature above this limit due to the deformation of the nickel cuprate phase.