MnO_x Catalyst with High‐Efficiency Degradation Behavior of Toluene: Effect of Cryptomelane

Abstract

A series of MnOx catalysts were prepared by hydrothermal reaction of different pH values, which proved the important influence of preparation conditions on the structure and performance of the catalysts. The results proved that the cryptomelane MnOx catalyst with a pH of 10 (Cat‐2) exhibited the most outstanding performance in catalyzing toluene. The appearance of cryptomelane on Cat‐2 would reduce the chemical valence of Mn, which could increase the content of Mn3+ and the amount of oxygen vacancies. With the increase of Mn3+, the Mn−O bond was broken more easily, and then facilitated the mobility oxygen species, causing the promotion of the catalytic activity. Low‐valence manganese, high‐capacity oxygen vacancies and maximum concentration of lattice oxygen were the most important reasons for the best catalytic activity of Cat‐2. According to the results of in‐situ DRIFT, benzyl, benzaldehyde, benzoic acid were the main intermediate products, which followed the Mars‐van Krevelen mechanism.

Catalytic combustion of toluene performance over MnOx catalysts: Effect of KMnO4 content

“…The mobility of catalysts oxygen species was tested by O 2 ‐TPD. In general, the peaks below 400°C were attributed to the desorption of surface adsorbed oxygen, the peaks between 400°C and 700°C were attributed to the desorption of surface lattice oxygen (Peak I), and the peaks between 700°C and 900°C were ascribed to the desorption of bulk lattice oxygen (Peak II) 56 . In Figure 7b, it could be seen that the desorption peak of surface adsorbed oxygen was not obvious for all catalysts.…”

“…In general, the peaks below 400 C were attributed to the desorption of surface adsorbed oxygen, the peaks between 400 C and 700 C were attributed to the desorption of surface lattice oxygen (Peak I), and the peaks between 700 C and 900 C were ascribed to the desorption of bulk lattice oxygen (Peak II). 56 In…”