Ordering of n-Alkanes Adsorbed in the Micropores of AlPO₄-5: A Combined Molecular Simulations and Quasi-Equilibrated Thermodesorption Study

Adsorption of n-alkanes from methane to decane (C1-C10) on AlPO₄-5 aluminophosphate was studied by means of Monte Carlo simulations. The additional experimental study with use of quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) yielded high quality adsorption isobars of C5-C10 n-alkanes. The QE-TPDA based isotherms were accurately reproduced in the simulation, thus validating the applied force field. The agreement between experimental and simulated data indicated that the QE-TPDA is a reliable method for studying porosity-related adsorptive properties. The simulations revealed differences in the adsorption mechanism of the n-alkane series, with unmistakable site-based adsorption for short molecules (C1-C5) at saturation. Kinetic properties of the studied systems determined with the use of molecular dynamics exposed chain length dependency of the self-diffusion coefficient, indicating probably a resonant diffusion mechanism.