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Diffusion of C2H6 and C2H4 in DDR Zeolite

Vidoni, Adam, Ruthven, Douglas M.
Industrial & Engineering Chemistry Research 2012 v.51 no.3 pp. 1383-1390
activation energy, adsorption, carbon dioxide, crystals, diffusivity, engineering, ethane, ethylene, methane, silica, zeolites
Diffusion of ethane and ethylene in large crystals of DDR clathrisil (the pure silica analogue of ZSM-58) has been studied in detail by the zero length column (ZLC) technique. The behavior of ethane and ethylene is very similar with respect to both kinetics and equilibria. Measurements were made with two different DDR samples with both He and CO₂ as the carrier gas. In contrast to methane neither the equilibrium nor the diffusivity of ethane (or ethylene) is significantly affected by the presence of CO₂, suggesting noncompetitive adsorption. Although the diffusivity of the C₂ hydrocarbons is about an order of magnitude smaller than that of methane the activation energies are similar or even smaller. Also, in contrast to the behavior of methane, the data show clear evidence of a small but significant surface resistance (in addition to the intracrystalline diffusional resistance).