An initial evaluation of the thermodynamic or kinetic separation performance of cation-exchanged LTA zeolites for mixtures of propane and propylene

Adsorptive separation of propylene (C3H6) and propane (C3H8) may represent an energy-efficient alternative to conventional cryogenic distillation. In this perspective, a set zeolitic adsorbents LTA type structure (pure-silica zeolite (Si-LTA) cation- (Na+, 33% Li+, 50% Mg2+ Ca2+) containing zeolites) were prepared, then characterized using various techniques such as PXRD, gas adsorption measurement, TGA, XRF, SEM EDX mapping. Thanks in-house manometric dosing setup coupled with Tian-Calvet microcalorimeter, the pure isotherms their corresponding differential enthalpies measured at 303 K for pressures up 5 bar. To fit those data, dual-site Langmuir was selected best model, by Ideal Adsorbed Solution Theory (IAST), thermodynamic selectivities determined. The mass transfer constants also estimated fitting, separately, Linear Driving Force (LDF) isothermal micropore diffusion models kinetic curves, thus allowing be calculated. combination reveals that C3H6 from C3H8 is highly favorable on CaNa-LTA, followed its MgNa-LTA counterpart IAST around 15 5, respectively. On other hand, monovalent cationic zeolites (i.e., Na- LiNa-LTA) show predominance steric effects. Also, except Si-LTA which shows moderate separation, studied materials are potential candidates, in following order CaNa- > MgNa- LiNa- Na-LTA, adsorption-based technologies.