A NEW ADSORPTION MODEL FOR ANALYZING GAS-SOLID EQUILIBRIA IN POROUS MATERIALS

Equilibria involving three probe gases adsorbed on two porous carbonac eous supports are measured at various temperatures. A novel analysis o f the data is offered which uses multiple process equilibria to calcul ate adsorption equilibrium constants for the interaction of the gas wi th the solid. Equilibria involving three distinct processes are found. The equilibrium constants (K-1,K-ads, K-2,K-ads, and K-3,K-ads) are o btained as well as the capacity of the solid for each type of process (n(1), n(2), and n(3)), in millimoles of adsorptive per gram of solid. The first process, K-1,K-ads, involves adsorption of the gas in the s olid's micropores which are of molecular dimensions. The second proces s, K-2,K-ads, involves adsorption in the larger micropores. The third process, K-3,K-ads, involves adsorption by the remaining surface. Mult ilayer formation is likely involved in some processes. The temperature dependencies of the K-ads's produce the enthalpy of adsorption for th ese processes. This analysis is important for, in contrast to BET anal yses, it provides thermodynamic data for different adsorptives that ca n be interpreted in terms of those molecular properties that facilitat e probe-solid interactions and can provide a quantitative definition o f solid reactivity.