Selective adsorption of N2 over CH4 in flexible Sr2+- and Ba2+-UPRM-5 (TEA) titanium silicates: Effect of activation temperature

Adsorption equilibria and kinetics of CH4 and N2 on commercial zeolites and carbons

“…However, while zeolite 4A and MSC-3K 172 are also methane selective at equilibrium, their uptake of N2 is sufficiently faster than that of CH4 that they are kinetically selective for N2 over CH4. In both cases the kinetic selectivity [53] is modest (1.4 to 2.2) at the conditions studied in this work, in comparison for example with those reported for Sr-UPRM-5 [54] ( =25.42) and Sr-ETS-4…”

Long- and Local-Range Structural Changes in Flexible Titanium Silicates with Variable Faulting upon Thermal Treatment and Corresponding Adsorption and Particle Size Polydispersity-Corrected Diffusion Parameters for CO2/CH4 Separation

“…As reported recently for Sr 2+ -UPRM-5 prepared using TEA + , these materials have a set of two accessible pore channels each with different dimensions . Adsorption studies made for ETS-4, which also contains a bimodal pore system, have shown that this feature results in poor prediction of adsorption–desorption diffusivities when traditional phenomenological transport models are employed. , The narrower channels in UPRM-5 correspond to the 8-MR pore system previously mentioned, which is characteristic of flexible titanium silicates. ,, The other dominant pore system is a result of the structural faulting, which is controlled by the choice of SDA and effectively results in larger pore dimensions . Per the discussion of the XRD results, the 8-MR pores or channel system in Sr 2+ -UPRM-5 (TPA) and Sr 2+ -UPRM-5 (TBA) seems to be the most affected by thermal contraction during thermal activation.…”

“…42 Adsorption studies made for ETS-4, which also contains a bimodal pore system, have shown that this feature results in poor prediction of adsorption−desorption diffusivities when traditional phenomenological transport models are employed. 28,36 The narrower channels in UPRM-5 correspond to the 8-MR pore system previously mentioned, which is characteristic of flexible titanium silicates. 26,42,47 The other dominant pore system is a result of the structural faulting, which is controlled by the choice of SDA and effectively results in larger pore dimensions.…”

“…36,57 Table S4 in Supporting Information shows Henry's law constants calculated from the adsorption equilibrium data shown in Figure 4. Figure 6 shows the resulting kinetic selectivity values at selected pressures.…”

“…For instance, the use of tetra­propyl­ammonium (TPA + ) and tetra­butyl­ammonium (TBA + ) improved the UPRM-5 structural and textural characteristics for the adsorption of CO 2 in a considerable fashion . A recent study by Yu et al also showed the potential of using Sr 2+ -UPRM-5 prepared with tetra­ethyl­ammonium (TEA + ) for the selective N 2 removal in natural gas upgrading . The contraction property of UPRM-5 upon thermal treatment was used to reverse selectivity in favor of N 2 , as has been done before for ETS-4. , …”