Multiple equilibria describe the complete adsorption isotherms of nonporous, microporous, and mesoporous adsorbents

• DOI: 10.1016/j.micromeso.2021.111563
• Publication Date: 2021-11-15T16:51:41Z
• Authors: Gion Calzaferri; Samuel H. Gallagher; Dominik Brühwiler
• Keywords: Type VI; Zeolite L; Cavity; Stöber-type particle; Type I; 02 engineering and technology; 000 Computer science, knowledge & systems; 500 Science; MCM-41; 01 natural sciences; Type II; 0104 chemical sciences; 540: Chemie; Cluster; Sequential chemical equilibria; 540 Chemistry; 570 Life sciences; biology; Type IV; Adsorption isotherm; 0210 nano-technology

The adsorption of simple gases begins with the formation a monolayer on pristine surface, not always followed by second or more monolayers. Subsequently, cluster cavity filling occurs, depending properties surface. characteristically different shape isotherms related to these processes allows clearly differentiate them. We analyzed argon and N2 quantitatively over entire relative pressure range for adsorbents bearing properties: nonporous Stöber-type particles, microporous zeolite L (ZL) filled indigo (Indigo-ZL), three mesoporous silica pore size. formal equilibria involved in have been derived successfully applied describe adsorbents. No indication regarding top first one was observed particles. Instead, generation, which minimizes surface tension, starts early. behavior ZL Indigo-ZL is different. A sets up some delay. enthalpy is, however, practically identical that seen difference between experimental calculated inflection points very small. shapes differ significantly from those quantitative analysis data proves cavities ends as soon all sites are filled. sum individual fractional contributions, namely ΘmL, appearance Θ2L one, Θcav, yields isotherm Θcalc describes Θexp well. excellent agreement, also case points. value roughly 10% larger than volume smaller adsorbent diameter 2.7 nm, while it same diameters 4.1 nm 4.4 respectively. conclude understanding signature several sequential chemical equilibrium steps provides additional information clusters, cavities, position points, accessible means conventional models. theory reported herein covers type I, II, IV extent VI isotherms.