“…Pascual et al predicted that hexane molecules could adsorb in the 8-ring cages when the pressure is higher than 10 kPa, and this unusual behavior has not been confirmed by experiments. In contrast, our simulation shows that before the bulk saturation pressure is reached, hexane molecules can only adsorb in the 10-ring channels, as shown in Figure , which is consistent with the experimental observations. ,− 3 Distribution of hexane in FER zeolites at 74 kPa and 333 K. The centers of mass of the hexane molecules are represented by black dots.…”
Section: Resultssupporting
confidence: 89%
“…In contrast, our simulation shows that before the bulk saturation pressure is reached, hexane molecules can only adsorb in the 10-ring channels, as shown in Figure 3, which is consistent with the experimental observations. 11, [31][32][33] From Figure 2a-f we can see our simulations based on the new UA force field show systematic lower adsorption capacities in pure silica FER-type zeolite than the experimental values for all of the alkanes tested, which can be attributed to the presence of protons in the experimental zeolite samples. To test this hypothesis, we performed some simulations using the force field of Calero et al, 30 an extended version of the force field of Dubbeldam et al that takes into account the effects of protons, for alkanes in protonated zeolites, as shown in Figure 2b-d,f.…”
Section: Validation Of the Applicability Of The New Force Fieldmentioning
The recently proposed united atom force field by Dubbeldam et al. (Phys. ReV. Lett. 2004, 93, 088302) for the adsorption of alkanes in MFI-type zeolites was extended to other zeolites in this work. Its applicability to FER-type zeolites was evaluated in detail, for which the Henry coefficients, the isosteric heat of adsorption, the adsorption isotherms, as well as the locations of alkanes in the FER-type zeolites were computed and compared to experimental values. The results show that the new force field works well for FER zeolites. Furthermore, its applicability to MWW-, MTW-, CFI-, LTA-, and STF-type zeolites was investigated, and we found that the experimental isotherms could be accurately predicted except for STF-type zeolites. This work shows that the new united atom force field proposed by Dubbeldam et al. is applicable to most pure silica zeolites.
“…Pascual et al predicted that hexane molecules could adsorb in the 8-ring cages when the pressure is higher than 10 kPa, and this unusual behavior has not been confirmed by experiments. In contrast, our simulation shows that before the bulk saturation pressure is reached, hexane molecules can only adsorb in the 10-ring channels, as shown in Figure , which is consistent with the experimental observations. ,− 3 Distribution of hexane in FER zeolites at 74 kPa and 333 K. The centers of mass of the hexane molecules are represented by black dots.…”
Section: Resultssupporting
confidence: 89%
“…In contrast, our simulation shows that before the bulk saturation pressure is reached, hexane molecules can only adsorb in the 10-ring channels, as shown in Figure 3, which is consistent with the experimental observations. 11, [31][32][33] From Figure 2a-f we can see our simulations based on the new UA force field show systematic lower adsorption capacities in pure silica FER-type zeolite than the experimental values for all of the alkanes tested, which can be attributed to the presence of protons in the experimental zeolite samples. To test this hypothesis, we performed some simulations using the force field of Calero et al, 30 an extended version of the force field of Dubbeldam et al that takes into account the effects of protons, for alkanes in protonated zeolites, as shown in Figure 2b-d,f.…”
Section: Validation Of the Applicability Of The New Force Fieldmentioning
The recently proposed united atom force field by Dubbeldam et al. (Phys. ReV. Lett. 2004, 93, 088302) for the adsorption of alkanes in MFI-type zeolites was extended to other zeolites in this work. Its applicability to FER-type zeolites was evaluated in detail, for which the Henry coefficients, the isosteric heat of adsorption, the adsorption isotherms, as well as the locations of alkanes in the FER-type zeolites were computed and compared to experimental values. The results show that the new force field works well for FER zeolites. Furthermore, its applicability to MWW-, MTW-, CFI-, LTA-, and STF-type zeolites was investigated, and we found that the experimental isotherms could be accurately predicted except for STF-type zeolites. This work shows that the new united atom force field proposed by Dubbeldam et al. is applicable to most pure silica zeolites.
“…The intracrystalline diffusivity is a strong function of concentration and varies by nearly two orders of magnitude. In Figure 4, as in all other Figures, the concentration is expressed as a fraction of the equilibrium concentration of methanol adsorbed by ferrierite at 80 mbar, which is estimated from our work and published data [21] to be 0.163 cm 3 g À1 % 4 mmol g À1 % 8.5 molecules/unit cell. All experiments consisted of consecutive cycles of adsorption and desorption on the same single crystal, [22] a technique which is unprecedented.…”
How many guests? Interference microscopy is used to monitor the concentration of guest molecules in a ferrierite zeolite. The micropore diffusivities are determined as a function of loading through the microscopic application of Fick's second law. This method can be used to study isotropic and anisotropic diffusion, as well as to locate and quantify surface barriers and internal defects.
“…Fig. 4 shows the measured isotherm of the equilibrium concentrations of the adand desorption runs compared with the data at 303 K from the literature [27]. It is not reasonable to calculate the absolute methanol concentration by comparing with the literature values [27] because the specific pore volume determined by nitrogen adsorption differs significantly from the sample under study (> 20 %).…”
Section: Adsorption Isotherm and Determining Absolute Concentrationmentioning
confidence: 99%
“…4 shows the measured isotherm of the equilibrium concentrations of the adand desorption runs compared with the data at 303 K from the literature [27]. It is not reasonable to calculate the absolute methanol concentration by comparing with the literature values [27] because the specific pore volume determined by nitrogen adsorption differs significantly from the sample under study (> 20 %). However, the absolute concentration can be estimated by comparing the band intensity of the IR signal of the gas phase with the signal of the adsorbed methanol as well as taking account of the geometry of the cuvette and the structure of the ferrierite [21,28,29].…”
Section: Adsorption Isotherm and Determining Absolute Concentrationmentioning
The application of interference microscopy has provided an important breakthrough in the study of the transport of guest molecules in nanoporous materials, making it possible to observe the transient intracrystalline concentration profiles resulting from a well-defined change (usually a step) in the ambient gas pressure. This approach was used to study adsorption and desorption kinetics in several zeolite systems. The advantages of this technique, especially when combined with infrared absorption measurements, are illustrated by experimental results obtained in a study of the methanol-ferrierite system.
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