Entropy in multiple equilibria. Argon and nitrogen adsorption isotherms of nonporous, microporous, and mesoporous materials

Analysis of multiple equilibria compounds with different coordination sites is extended to the description adsorption isotherms focus on low relative pressure range. The entropy evolution described using particle distribution theory which also holds for adsorbents consisting materials bearing more than one type and applies condition that adsorptive-adsorbent binding strength larger adsorptive-adsorbate strength, so monolayer coverage favored. This allows accurately determine enthalpy. No assumption concerning growth mechanism specifics regarding structure surface needed. We find a rigorous basis this leads Langmuir's equation each site independently, total fractional amount bound adsorptive can be as linear combination individual Langmuir isotherms, such has never shape original isotherms. results are successfully applied argon nitrogen nonporous, microporous, mesoporous comparing systems properties active span large observe all experimental data by means two in range up 60%–95%. essentially determined decrease increasing coverage. interactions involved exhibit substantially enthalpies. Interestingly Ar enthalpy ? d s H 1 ? Stöber-type silica three investigated MCM-41 (with pore size 2.7 nm, 4.1 4.4 nm) similar, namely ?11 kJ/mol. situation analogous 2 2, amounts ?8 A significantly 1, ?14.3 kJ/mol, = ? 11.7 kJ / mol measured potassium zeolite L thus reflecting polar nature adsorbent. specific area these samples ranges from 14 m /g 1100 MCM-41(4.1 information provided lc2-L (linear functions) analysis calculating function pressure. inflection points mark point where curvature changes sign, were numerically evaluating second derivatives vanish at compared values obtained BET analysis.