In-Deep Determination of Microporosities of a Silica-Pillared Manganese Oxide by the Multistep Adsorption Mechanism and αs-Plot Methods

A novel silica-pillared manganese oxide (SiHMnO) was synthesized, and its porous structure was exactly determined by assuming a multistep adsorption mechanism (MSAM) using the low-temperature N 2, Ar, and CO adsorption and the α s -comparison plot based on a standard N 2 adsorption isotherm on a nonporous manganese oxide. The MSAM method gave a good agreement in values of micropore volume (0.155−0.160 mL g - 1 ) and external surface area (61−63 m 2 ·g - 1 ) from the three adsorbates. The standard nonporous manganese oxide was selected by comparing those based on crystalline hydrous birnessite (H-Bir). The H-Bir-393 obtained by calcining H-Bir at 393 K is the most appropriate standard nonporous material. The values of micropore volume and external surface area from the α s -plot matched very well with those from the MSAM method. SiHMnO has a very high surface area value (483 m 2 ·g - 1 ) by analysis of an α s -plot in contrast to the smaller one (360 m 2 ·g - 1 ) by the ordinary BET analysis.