Extended synthetic study of α-type manganese oxide with porous structure

Abstract

α-type manganese oxide (α-MnO₂) was synthesized by pyrolysis of manganese carbonate and potassium t-butoxide. The method is valid even when their molar basis fraction is varied from 0% to 100%. For some potassium butoxide content percentages, the calcined material which is mainly α-MnO₂ contained an admixture phase of bixbyite (0–7%) or γ-Mn₂O₃(11–20%) or both the latter phases (7–11%). The acid-treated materials are single phase α-MnO₂ containing various amounts of structural-water. The degree of crystallinity is very high when the material was prepared with a potassium butoxide content of less than 20%, but materials of distorted structure are obtained with over 20%. The materials of high crystallinity contain less than about 0.5 molecules of structural-water per open pore site, but the distorted materials contain about two molecules of the water per site. The degree of ease of deformation, namely, the flexibility of the structure was an index to the amount of ion-exchange uptake on the materials. The possibility of controlling the properties of α-MnO₂ ion-exchange material is suggested by changing potassium butoxide content in this synthetic procedure.