Energetics and siting of sorbed molecules in zeolites by computer simulations. Comparison with calorimetric and structural results. II —n-Alkanes in silicalite

In the first part of this work sorbent/sorbate interactions corresponding to some zeolitic FAU(faujasite)/sorbate and MOR(mordenite)/sorbate systems using the exp-6-1 Buckingham theoretical model have been investigated. This second part concerns MFI(silicalite)/sorbate systems, where it is shown that several almost equipotential sorption sites are available in the channel system for strictly linear C1 to C10 n-alkanes. For the C11–C18 range (n-undecane to n-octadecane) the n-alkane in the zig-zag channels looses its strictly linear and protracted configuration. Two structural examples corresponding to n-hexane and n-decane reveal that the molecular alkane distribution in the zeolitic channel system depends on its nature and porefilling. The calculated sorption energy for the n-alkanes varies linearly versus the aliphatic C1–C18 chain-length. As for MOR/alkane systems, it is found that in the present case hexane isomers have comparable calculated sorption heats.