A diffusion study of small hydrocarbons in DDR zeolites by micro-imaging

Transport Phenomena in Nanoporous Materials

“…In terms of irreversible thermodynamics, it is applicable if there is no cross-correlation between the fluxes and the gradients of the chemical potentials of differently labelled molecules. "eight-ring" zeolites, [120,147] including the structure types LTA [146,148] and DDR, [21,117,149] have proven to be ideal candidates for this type of analysis for normal alkanes and alkenes. "eight-ring" zeolites, [120,147] including the structure types LTA [146,148] and DDR, [21,117,149] have proven to be ideal candidates for this type of analysis for normal alkanes and alkenes.…”

“…[79,145,146] This requirement is, in particular, fulfilled if the guest molecules have to overcome, on their diffusion path through the pore space, pronounced constrictions such as, e.g., narrow "windows" between adjacent cavities. "eight-ring" zeolites, [120,147] including the structure types LTA [146,148] and DDR, [21,117,149] have proven to be ideal candidates for this type of analysis for normal alkanes and alkenes. Now also in ZIF-8 diffusion of short-chain length hydrocarbons is found to follow this pattern.…”

The hydrocarbon-bearing clathrasil chibaite and its host–guest structure at low temperature

“…Various clathrates have gained interest because of their application as potential materials for gas storage and gas separation of H 2 as well as the greenhouse gases CO 2 and CH 4 (Burggraaf et al, 1998;Algieri et al, 2003;Min et al, 2003;Navrotsky et al, 2003;van den Berg et al, 2004van den Berg et al, , 2005Hong et al, 2005;House et al, 2006;Di Profio et al, 2007;Dong et al, 2008;Kanezashi et al, 2008;Zheng et al, 2008;Eslamimanesh et al, 2012). The cages have small pore openings and so guest species are trapped inside the crystal structure; thus, diffusion of the atoms and molecules out of the cages is slow in comparison with most microporous zeolite structures (Binder et al, 2013;Hu et al, 2014;Fujiyama et al, 2015;O'Malley et al, 2016). Clathrate frameworks consisting of only SiO 2 are referred to as clathrasils.…”

Measurement of the surface diffusion coefficient for adsorbed gas in the fine mesopores and micropores of shale organic matter

“…Many valuable works have been achieved about the laboratorial methods of measuring gas diffusion coefficients in rocks like mudstone [33][34][35][36], coal [3,33,[37][38][39][40] and shale [1,41], in porous media like carbon materials [25,42,43], zeolites [44][45][46], alumina [27,47], and in high pressure fluids [48,49]. In rocks the measured coefficients ranged from 10 À16 to 10 À4 cm 2 /s due to the differences of rock types and testing methods [34,41,66].…”

“…In zeolites and carbon materials, the surface diffusion coefficient was measured to be 10 À12 -10 À4 cm 2 /s [29,44,45,47]. The common laboratorial methods can be simplified as: Predict the flux or permeability of the bulk gas transport with Hagen-Poiseuille equation or slip/Knudsen model based on the characteristics of the flow channels; compare the predicted value with the measured flux or permeability, and then the contribution of adsorbed phase transport was obtained, based on which the coefficient was also calculated [25,29].…”