Synthesis and investigation of activity of nano-spinels MeCo2O4 (Me: Mn, Ni, Cu) for total oxidation of toluene
Series of spinel MeCo2O4 (Me: Mn. Ni, Cu) were synthesized by citrate method. These oxides were characterized by different methods as XRD, BET, SEM and H2-TPR. The XRD results showed the pure phase MnCo2O4 but also the existence of simple oxides NiO, CuO beside principal phases NiCo2O4, CuCo2O4 respectively. The BET surface areas diminished in the following order: NiCo2O4>MnCo2O4>CuCo2O4. The SEM showed the size of particle in reverse order. The catalytic activity was evaluated towards total toluene oxidation reaction.CuCo2O4 showed the best activity between 300-340°C. This result is in accordance with H2-TPR :the more the catalyst is reducible, the more it is active for VOC total oxidation. However, the total conversion was not reached. This phenomenon seems to be due to the very low surface area of this catalyst. In conclusion, among the three catalysts, MnCo2O4 reached the total conversion of toluene at the lowest temperature of 375oC.
Volatile Organic Compounds (VOC) emitted during many industrial processes and transport activities contribute significantly to atmospheric pollution. Their presence in atmosphere causes the increase in photochemical smog and depletion of stratospheric ozone (1). Catalytic total oxidation of these compounds is potential technology due to less consumption of energy and less formation of by-products. A lot of catalysts was developed such as noble metal based catalysts (2, 3) or transition metal oxides (4, 5). Among them, recently, transition metal oxides well attracted the attention of researchers because they show a good activity and a low price. However, in severe operation conditions, these catalysts were not stable. To improve stability, nowadays, researchers tend to focus their work on mixed oxides such as perovskites ABO3 or spinels AB2O4 (6-10). These mixed oxides show a better stability. In addition, they can stabilize an unstable ion state like B4+ which could considerably improve the catalytic activity (9, 10).
In this work, series of cobaltite spinels MeCo2O4 (Me :Mn, Ni, Cu) were synthesized by citrate method (11). This meth ...