Abstract
The thermal solid–solid interactions between Co
3O
4 and MoO
3 and their physicochemical properties in the presence and absence of Al
2O
3 have been investigated using thermal analysis (TG–DTG–DTA), X-ray diffraction (XRD) techniques, electron spin resonance (ESR) and catalytic decomposition of H
2O
2 at 30, 40 and 50
°C. The pure and variously doped mixed solids were subjected to heat treatment at 350, 550, 750 and 1000
°C. The amounts of dopant were 1.23, 2.44, 4.76 and 9.09
mol% Al
2O
3. The results revealed that only Co
3O
4 phase was detected for the pure mixed solids calcined at 350, 550 and 750
°C. Doping of the system under investigation with alumina enhanced the formation of crystalline cobalt molybdate phase starting from 350
°C. The degree of crystallinity of CoMoO
4 phase increased with increasing calcination temperature and amount of dopant. Crystalline Al
2(MoO
4)
3 and CoAl
2O
4 phases detected for the solids heavily doped with alumina and calcined at 750 and 1000
°C, respectively as a result of solid–solid interactions between the reacted oxides. CoO phase was detected only for the pure mixed solids and that doped with small amount of alumina and calcined at 1000
°C. The catalytic activity of mixed oxides was higher than that of single oxides obtained at the same temperature. The catalytic activity of Co
3O
4/MoO
3 system progressively decreased with increasing the amount of alumina dopant and with increasing calcination temperature.