Analysis of Nitrogen Adsorption Isotherms for a Series of Porous Silicas with Uniform and Cylindrical Pores: A New Method of Calculating Pore Size Distribution of Pore Radius 1–2 nm

Abstract

Two kinds of the porous silicas with uniform and cylindrical pores were prepared from calcined Na4SiO4and cationic surfactants ([C16H33N(CH3)3]Cl and [C18H37N(CH3)3]Br). In this paper, we call these porous silicas PS-C16 and PS-C18. PS-C16 was calcinedin vacuoat 873–1273 K in order to prepare a series of porous silicas having different pore sizes. All nitrogen adsorption isotherms for a series of the porous silicas show no hysteresis in the adsorption and desorption branches. The nitrogen adsorption isotherms were analyzed by thetmethod, and the pore surface area (Sp), the pore volume (Vp), and the core volume (Vc) were determined. The pore radius (rp), the core radius (rc), and the adsorbed thickness on the pore wall (tpore) were computed from the measured values ofSp,Vp, andVc. We can determine the relationship between the Polanyi adsorption potential and the core radius in the range ofrc= 0.6–1.2 nm. On the basis of the present data, we propose a new method of calculating the pore size distribution in the range ofrp= 1–2 nm.