Abstract: The birnessite and cryptomelane types of manganese oxide were prepared by the sol-gel method using KMnO₄ and glucose. The optimum conditions were investigated by varying different process variables such as c(glucose)/c(KMnO₄) ratio, calcination temperature, reaction time, and gel treatment methods. The results of X-ray diffraction and atomic absorption spectroscopy indicated that the crystal phases of manganese oxide were controllable with different gel treatment methods. Under the conditions of c(glucose)/c(KMnO₄) = 0.74, t = 20 s and by different gel treatment methods, the birnessite and cryptomelane with high purity and high crystallinity were synthesized. The catalytic performance of both types of manganese oxide for the combustion of dimethyl ether was excellent, but the cryptomelane showed much higher catalytic activity than the birnessite.

Key words: sol-gel method, manganese oxide, controllable synthesis, dimethyl ether, catalytic combustion