アルキルベンゼン蒸気吸着による微小表面積の測定法

概要

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Using the vapor of alkylbenzenes such as toluene, ethylbenzene, and n-butylbenzene, having comparatively low saturation pressures, small surface areas could be estimated from the gradient of the linear portion of the Type II adsorption isotherms which were found in many of the solid adsorbents. In this “gradient method”, surface area was obtained from the monolayer volume, which is equated to the gradient values of dv/d(P/Ps), where v is the amount adsorbed and P/Ps is the relative pressure, and from the adsorbate molecular cross-sections calculated from the liquid densities. The surface areas thus obtained agreed, with a precision of ±20%, with the standard N2-BET surface areas for more than 20 solid powder samples. The surface areas for plate-like samples examined, however, were estimated a little larger than the geometrical values, probably because the surface pores of the samples could not completely be removed by surface pretreatment. It was ascertained that this method is useful for the estimation of surface areas, and especially the small areas, not only because the vapor pressures of the alkylbenzenes were low but not too low (e.g., the saturation pressure of n-butylbenzene was 21.3Pa at 0°C), but also because adsorption measurements can easily be carried out at room temperature.
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