Abstract
▶ The effects of K
2O and Li
2O-doping (0.5, 0.75 and 1.5 mol%) of Fe
2O
3/Cr
2O
3 system on its surface and catalytic properties were investigated. ▶ Pure and differently doped solids were calcined in air at 400–600
°C. The formula of the un-doped calcined solid was 0.85 Fe
2O
3: 0.15 Cr
2O3. ▶ The techniques employed were TGA, DTA, XRD, N
2 adsorption at −196
°C and catalysis of CO oxidation by O
2 at 200–300
°C. ▶ The doping process did not modify the activation energy of the catalyzed reaction but rather increased the concentration of the active sites without changing their energetic nature.
The effects of K
2O and Li
2O-doping (0.5, 0.75 and 1.5
mol%) of Fe
2O
3/Cr
2O
3 system on its surface and the catalytic properties were investigated. Pure and differently doped solids were calcined in air at 400–600
°C. The formula of the un-doped calcined solid was 0.85Fe
2O
3:0.15Cr
2O
3. The techniques employed were TGA, DTA, XRD, N
2 adsorption at −196
°C and catalytic oxidation of CO oxidation by O
2 at 200–300
°C. The results revealed that DTA curves of pure mixed solids consisted of one endothermic peak and two exothermic peaks. Pure and doped mixed solids calcined at 400
°C are amorphous in nature and turned to α-Fe
2O
3 upon heating at 500 and 600
°C.
K
2O and Li
2O doping conducted at 500 or 600
°C modified the degree of crystallinity and crystallite size of all phases present which consisted of a mixture of nanocrystalline α- and γ-Fe
2O
3 together with K
2FeO
4 and LiFe
5O
8 phases. However, the heavily Li
2O-doped sample consisted only of LiFe
5O
8 phase. The specific surface area of the system investigated decreased to an extent proportional to the amount of K
2O and Li
2O added. On the other hand, the catalytic activity was found to increase by increasing the amount of K
2O and Li
2O added. The maximum increase in the catalytic activity, expressed as the reaction rate constant (k) measured at 200
°C, attained 30.8% and 26.5% for K
2O and Li
2O doping, respectively. The doping process did not modify the activation energy of the catalyzed reaction but rather increased the concentration of the active sites without changing their energetic nature.