By using a force-field molecular dynamics method, an investigation was made of the intracrystalline diffusion of ethene and propene in four different zeolites at various temperatures (table 10). The self-diffusion coefficients were described by:

ethane in CHA:      D(m2/s) = 5.3 x 10-9exp[-9.64(kJ/mol)/RT]

propene in CHA:      D(m2/s) = 1.9 x 10-9exp[-23.23(kJ/mol)/RT]

ethane in MFI:      D(m2/s) = 3.1 x 10-8exp[-3.38(kJ/mol)/RT]

propene in MFI:      D(m2/s) = 2,1 x 10-8exp[-6.28(kJ/mol)/RT]

ethane in BEA:      D(m2/s) = 1.1 x 10-7exp[-3.87(kJ/mol)/RT]

propene in BEA:      D(m2/s) = 9.6 x 10-8exp[-5.78(kJ/mol)/RT]

ethane in FAU:      D(m2/s) = 1.0 x 10-7exp[-4.82(kJ/mol)/RT]

propene in FAU:      D(m2/s) = 1.1 x 10-7exp[-7.04(kJ/mol)/RT]

A strong restriction on the diffusion of propene in CHA was observed because the self-diffusion coefficient ratio of ethene to propene was larger than 18 and the diffusion activation barrier of propene was more than 20kJ/mol in CHA. This ratio decreased with increasing temperature in the four zeolites.

Insight into the Topology Effect on the Diffusion of Ethene and Propene in Zeolites: a Molecular Dynamics Simulation Study. C.Wang, B.Li, Y.Wang, Z.Xie: Journal of Energy Chemistry, 2013, 22[6], 914–8