Liquid phase adsorption differs from gas phase adsorption due to the high density of the adsorbates inside the pores. This results in the intermolecular forces among adsorbate molecules playing a significant role in the adsorption mechanism. Although in principle grand canonical Monte Carlo (GCMC) simulation of an adsorbed phase in contact with a liquid or gas phase is similar, there are several challenges in practice. Because of the high density in the pores under liquid-phase conditions, insertions and deletions of molecules become inefficient in convention GCMC simulations, resulting in poor sampling averages. Previously [1-3] we have shown that through the use of advanced techniques such as configuration biasing and identity swaps, one can perform GCMC simulations for adsorption of n-alkanes with chain lengths up to 10 C atoms in zeolites under liquid phase conditions. However, simulations of adsorption of alkanes with chain lengths exceeding 10 C atoms, especially of mixtures, are still inefficient.

In this study we make use of the parallel tempering technique to improve the efficiency of simulations for long-chain alkane mixtures in zeolites. These simulations helps to us to understand the molecular origins of phenomena such as azeotrope formation and selectivity inversion observed during experiments of adsorption of alkane mixtures.

1. K. M. A. DeMeyer, S. Chempath, J. F. M. Denayer, J. A. Martens, R. Q. Snurr and G. V. Baron, "Packing effects in the liquid-phase adsorption of C5-C22 n-alkanes on ZSM-5.", J. Phys. Chem. B, 107, 10760-10766, 2003

2. S. Chempath, J. F. M. Denayer, K. M. A. DeMeyer, G. V. Baron and R. Q. Snurr, "Adsorption of liquid-phase alkane mixtures in silicalte: simulations and experiment", Langmuir, 20, 150-156, 2004

3. I. Daems, G. V. Baron, S. Punnathanam, R. Q. Snurr and J. F. M. Denayer, "Molecular cage nestling in the liquid-phase adsorption of n-alkanes in 5A zeolite", J. Phys. Chem. C, 111, 2191-2197, 2007