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Cavalcante, Célio L.; Azevedo, Diana Cristina Silva de; Souza, I.G.; Silva, A. Cristina M.; Alsina, Odelsia Leonor Sánchez de; Lima, V.E.; Araújo, Antônio S.

doi:10.1023/a:1008947132186

Cited by 17 publications

(5 citation statements)

References 9 publications

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“…Ortho-selectivity has also been experimentally observed previously for two aluminophosphate molecular sieves, AlPO 4 -5 and AlPO 4 -11 (Barthomeuf and Mallmann 1990;Chiang et al 1991;Cavalcante et al 2000). This has been further studied by molecular simulation by Lucena et al (2006Lucena et al ( , 2008.…”

Section: Selectivity Measurements For P-xylene and O-xylene Mixtures supporting

confidence: 55%

“…They suggested that the selectivity in the separation of C 8 aromatics by adsorption on AlPO 4 -5 (preference for o-xylene) is related its high cohesive energy. Chiang et al (1991) and Cavalcante et al (2000) studied the sorption and diffusion of p-xylene and oxylene in crystals of AlPO 4 -5 and AlPO 4 -11, respectively. Their data indicated that, at saturation capacities, equilibrium favored o-xylene, probably due to face-to-face packing orientation of the molecules within the micropores.…”

Section: Symbols Cmentioning

confidence: 99%

“…Various traditional techniques, such as batch, thermogravimetry, chromatographic breakthrough and pulse experiments, can be used to measure adsorption equilibrium of xylenes in zeolites (Santacesaria et al 1982;Li et al 1991;Cottier et al 1997;Cavalcante et al 2000;Tournier et al 2001;Minceva and Rodrigues 2004). Another method that has been more recently applied is the headspace chromatography (Torres et al 2001;Buarque et al 2005;Oliveira et al 2009), which allows the use of a much smaller quantity of liquid and higher solid to liquid ratio, thus increasing the magnitude of the change in concentration and the accuracy of the experimental results (Torres et al 2001).…”

Section: Symbols Cmentioning

confidence: 99%

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Studies of C8 aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique

et al. 2010

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A headspace technique, that consists in analyzing the composition of the vapor phase in equilibrium with the condensed phase of a mixture in a sealed vial containing the adsorbent sample, has been recently applied to acquire equilibrium data for adsorption of xylenes in liquid phase. In this study, we used this technique to measure experimental binary equilibrium data for C 8 aromatics in Y and mordenite zeolitic molecular sieves. For the Y zeolite, we also measured C 8 aromatics quaternary equilibrium data. Measurements were made at temperatures between C 40-80°C. A more tedious, but traditional, chromatographic pulses method was also used to validate some of the results.

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Section: Selectivity Measurements For P-xylene and O-xylene Mixtures supporting

confidence: 55%

Section: Symbols Cmentioning

confidence: 99%

Section: Symbols Cmentioning

confidence: 99%

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Studies of C8 aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique

et al. 2010

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“…At all events, much longer or more tortuous pore channels with fewer openings are formed in the chainlike crystals than those in the normal isolated ZSM-5 crystals. Therefore, the difference among three xylene isomers in their diffusion behavior is greatly enlarged, which can significantly enhance the adsorption selectivity of chainlike ZSM-5 toward a specific xylene isomer. − As given in Table , the ratio of diffusion coefficient of p -xylene to that of o -xylene in the chainlike ZSM-5 zeolite reaches 3.17, which is much higher than that in the isolated ZSM-5 zeolite (1.09). A similar phenomenon was also observed for the fibrous MFI crystals synthesized under microwave irradiation. , Such a result adequately demonstrates the superiority of chainlike ZSM-5 zeolites synthesized in this work as a highly selective adsorbent or catalyst concerning guest molecules similar in their dimension.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Chainlike ZSM-5 Zeolites: Determination of Synthesis Parameters, Mechanism of Chainlike Morphology Formation, and Their Performance in Selective Adsorption of Xylene Isomers

Quan

Wang

et al. 2017

ACS Appl. Mater. Interfaces

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Chainlike zeolites are advantageous to various applications as a catalyst or an adsorbent with specific selectivity; however, it is often very difficult to get desired morphology due to the complexity of zeolite synthesis process. In this work, appropriate parameters for the synthesis of perfect chainlike ZSM-5 zeolites were well determined, which illustrates that the chain length can be controlled by the composition of synthesis mixture, the amount of residual alcohol in the synthesis system, and the crystallization time. Moreover, the mechanism of chainlike crystal growth was investigated by analyzing the surface species during the synthesis process, with the help of density functional theory (DFT) calculation. The results indicate that the formation of disk crystals with proper dimension and flat surface having abundant hydroxyl groups is crucial to the growth of chainlike ZSM-5 crystals; the condensation of Si-OH groups on the (010) facet is energetically more favorable than that on other facets, leading to the growth of MFI crystals along the b-orientation. Through finely tuning the multifarious synthesis parameters, chainlike ZSM-5 zeolites with controllable length in b-orientation are obtained without using any other extra organic additives except the necessary template agent such as tetrapropylammonium hydroxide (TPAOH). Owing to the increased tortuosity of pore channels in the chainlike ZSM-5, the difference between p-xylene and o/m-xylenes in their adsorption behavior and diffusivity is greatly enhanced. These results help to clarify the formation mechanism of zeolites with chainlike morphology and then bring forward an effective approach to get zeolite materials with specific properties in adsorption and catalysis.

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“…The zero length column, ZLC, is one of the most used chromatographic methods for measuring kinetic parameters of a gas diffusing into an adsorbent. This method has been extensively used for crystals − and for pellets. ,− With this method, mass and heat transfer effects, together with axial dispersion, can be minimized, thus allowing for direct measurement of diffusivity parameters. The diffusivity parameters are extracted from the desorption curve of a presaturated sample purged with an inert flow.…”

Section: Theoretical Sectionmentioning

confidence: 99%

Adsorption of Propane and Propylene in Pellets and Crystals of 5A Zeolite

Grande

Gigola

Rodrigues

2001

Ind. Eng. Chem. Res.

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Equilibrium and kinetic data for propane and propylene adsorption in pellets (Grace Davison) and crystals (PQ Corp.) of 5A zeolite are presented in the temperature range 323−423 K. The pellet adsorption loading measured by gravimetry is 1.7 mmol/g for propylene and 1.3 mmol/g for propane at 100 kPa and 423 K. The selectivity for propylene increases with temperature and is in the range 1.08−1.35 at 100 kPa, being higher at lower pressures. The kinetic data measured by zero-length-column (ZLC) chromatography indicate that the transport of sorbate in the pellets is controlled by macropore diffusion; pore diffusivities are in the range 0.018−0.027 cm2/s for both gases. Crystal diffusivities are in the range (1.1−7.2) × 10-11 cm2/s for propane and (0.2−6.2) × 10-11 cm2/s for propylene.

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Cited by 17 publications

References 9 publications

Studies of C8 aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique

Studies of C8 aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique

Synthesis of Chainlike ZSM-5 Zeolites: Determination of Synthesis Parameters, Mechanism of Chainlike Morphology Formation, and Their Performance in Selective Adsorption of Xylene Isomers

Adsorption of Propane and Propylene in Pellets and Crystals of 5A Zeolite

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