N-heptane adsorption and desorption in mesoporous materials

[摘要] Positron Annihilation Lifetime Spectroscopy (PALS) was used for an in situ monitoring of adsorption and desorption processes. The disordered and ordered porous silica as well as the porous polymer were used as adsorbents, while an adsorbate in all the cases was n-heptane. The lifetimes and particularly the intensities of the ortho-positronium(o-Ps) components depend strongly on the adsorbate pressure. The analysis of these dependencies allows us to identify several processes, which are taking place during sorption. At low pressure, an island-like growth of the first layers of the adsorbate on the silica, in a contrary to a swelling of the polymer, is observed. A size of the pores, which remain empty, is estimated at the subsequent stages of the adsorbate condensation and evaporation. The adsorbate thrusting into micropores is deduced at p/p0> 0.6 whilst the mesopores are still not completely filled.

[发布机构] Maria Curie-Sklodowska University, Institute of Physics, Department of Nuclear Methods, pl. M. Curie-Sklodowskiej 1, Lublin; 20-031, Poland^1;Maria Curie-Sklodowska University, Faculty of Chemistry, Department of Adsorption, pl. M. Curie-Sklodowskiej 3, Lublin; 20-031, Poland^2

[效力级别] 化学

[关键词] Adsorption and desorptions;In- situ monitoring;Low pressures;Micropores;Ordered porous;Ortho-positronium (o-Ps) component;Porous polymers;Positron annihilation lifetime spectroscopy