Layered δ-MnO2 as an active catalyst for toluene catalytic combustion

Layered delta-MnO2 was successfully synthesized by redox reaction precipitation between KMnO4 and n-butanol. Then, the as-synthesized layered delta-MnO2 was used as catalyst for toluene catalytic combustion and showed excellent catalytic performance. The T-10 and T-90 (the temperatures corresponded to the toluene conversion of 10 % and 90 %) were just 160 degrees C and 199 degrees C, respectively (1000 ppm toluene, GHSV = 60,000 mL/(g h, 20 vol.% O-2/N-2). In addition, the layered delta-MnO2 showed well catalytic stability and humid resistance. The as-prepared catalysts were characterized by XRD, N-2 sorption, SEM, TEM, XPS, H-2-TPR, O-2-TPD and so on. Compared with the referenced epsilon-MnO2 and gamma-MnO2, the higher catalytic activity of layered delta-MnO2 was ascribed to its higher specific surface area, stronger low-temperature reducibility and richer oxygen vacancy. Finally, the toluene catalytic oxidation mechanism over delta-MnO2 was also proposed based on the results of in-situ DRIFTs. And the key successively intermediate species for toluene oxidation over delta-MnO2 were benzyl alcohol, benzoic acid, maleic anhydride and acetate.