New Generation of Zeolite Materials for Environmental Applications.

Kabalan, Ihab; Lebeau, Bénédicte; Nouali, Habiba; Toufaily, Joumana; Hamieh, Tayssir; Koubaissy, Bachar; Bellat, Jean‐Pierre; Daou, T. Jean

doi:10.1021/acs.jpcc.5b10052

Cited by 34 publications

(28 citation statements)

References 65 publications

(128 reference statements)

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“…Prior to the adsorption measurements, the calcined samples were out-gassed at 300 °C overnight under vacuum. For the other fluids considered in this work, dynamic adsorption measurements were performed under different atmospheres of volatile organic compounds ( n -hexane, p -xylene, acetone) and controlled values of relative pressure p / p 0 = 0.5 ( p is the pressure and p 0 the saturation vapor pressure at a given temperature T of the considered organic compound) using a thermogravimetric balance Setaram TG92 instrument 30 . The experiments were done under flow.…”

Section: Methodsmentioning

confidence: 99%

Reminiscent capillarity in subnanopores

et al. 2019

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Fluids in large and small pores display different behaviors with a crossover described through the concept of critical capillarity. Here we report experimental and simulation data for various siliceous zeolites and adsorbates that show unexpected reminiscent capillarity for such nanoporous materials. For pore sizes D exceeding the fluid molecule size, the filling pressures p are found to follow a generic behavior kBT ln p ∼ γ/ρD where γ and ρ are the fluid surface tension and density. This result is rationalized by showing that the filling chemical potential for such ultra-small pores is the sum of an adsorption energy and a capillary energy that remains meaningful even for severe confinements. A phenomenological model, based on Derjaguin’s formalism to bridge macroscopic and molecular theories for condensation in porous materials, is developed to account for the behavior of fluids confined down to the molecular scale from simple parameters.

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Section: Methodsmentioning

confidence: 99%

Reminiscent capillarity in subnanopores

et al. 2019

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“…Zeolites are crystalline silicates with well-defined microporous structures and superior thermo- and chemo-stability. They are widely used in many industrial fields of great significance, including as porous support or catalysts in conversion of chemicals [1,2,3,4,5], as adsorbents for removal and recovery of heavy metal ions from water [6,7,8] and for selective gas adsorption and separation [9], etc [10,11,12,13]. Zeolites for industrial applications are conventionally synthesized through hydrothermal processes, where the oligomerization of poly-silicic acids is crucial [3].…”

Section: Introductionmentioning

confidence: 99%

Oligomerization of Silicic Acids in Neutral Aqueous Solution: A First-Principles Investigation

Liu

Meng

2019

IJMS

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Crystallite aluminosilicates are inorganic microporous materials with well-defined pore-size and pore-structures, and have important industrial applications, including gas adsorption and separation, catalysis, etc. Crystallite aluminosilicates are commonly synthesized via hydrothermal processes, where the oligomerization of silicic acids is crucial. The mechanisms for the oligomerization of poly-silicic acids in neutral aqueous solution were systematically investigated by extensive first-principles-based calculations. We showed that oligomerization of poly-silicic acid molecules proceeds through the lateral attacking and simultaneously proton transfer from the approaching molecule for the formation of a 5-coordinated Si species as the transition state, resulting in the ejection of a water molecule from the formed poly-silicic acid. The barriers for this mechanism are in general more plausible than the conventional direct attacking of poly-silicic acid with reaction barriers in the range of 150–160 kJ/mol. The formation of linear or branched poly-silicic acids by intermolecular oligomerization is only slightly more plausible than the formation of cyclic poly-silicic acids via intramolecular oligomerization according to the reaction barriers (124.2–133.0 vs. 130.6–144.9 kJ/mol). The potential contributions of oligomer structures, such as the length of the linear oligomers, ring distortions and neighboring linear branches, etc., to the oligomerization were also investigated but found negligible. According to the small differences among the reaction barriers, we proposed that kinetic selectivity of the poly-silicic acids condensation would be weak in neutral aqueous solution and the formation of zeolite-like structures would be thermodynamics driven.

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“…The first one in the temperature range 30 -110 °C corresponds to the physisorbed water and the second one in the temperature range 110 -700 °C corresponds to the oxidation of the organic matter (bifunctionnal structuring agent). Since each unit cell of ZSM-5 contains 2 organic cations, a weight loss of 16.5 wt% is expected [12,32,53]. However, for all analyzed materials the weight loss corresponding to the oxidation of the organic cations is higher indicating an excess of bi-functional structure directing agent and/or some dehydroxylation of remaining amorphous silicate phases.…”

Section: Complementary Characterization Of Zsm-5 Nanosheet Beadsmentioning

confidence: 95%

“…Zeolites are very good candidates for physisorption of small molecules into their micropores. The capacity and kinetics of pollutant adsorption, which might be sensitive to diffusion phenomena, surface and porous volume, could be improved by using nanocrystals or hierarchical zeolites (micro/mesoporous or micro/macroporous) [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Hierarchical ZSM-5 beads composed of zeolite nanosheets obtained by pseudomorphic transformation

Moukahhal

Daou

Josien

et al. 2019

Microporous and Mesoporous Materials

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The concept of pseudomorphic transformation was used to transform amorphous mesoporous silica beads with different size (20, 50 and 75 µm) into hierarchical MFI-type zeolite beads composed of ZSM-5 nanosheets. The beads were synthesized under hydrothermal conditions at different temperatures and treatment times, with and without mechanical stirring? (à quelle étape?). The influence of the different synthesis parameters was investigated by X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Fluorescence, Nitrogen adsorption-desorption measurements, 27 Al solid-state Nuclear Magnetic Resonance, Energy-Dispersive X-Ray analysis and Thermogravimetric analysis.Well-crystallized 20 µm ZSM-5 nanosheets beads similar in size and shape to the original mesoporous amorphous silica beads were obtained after a hydrothermal treatment at 150 °C for 5 days in a tumbling oven and 2 days in static at 120 °C. The influence of the bead size on the pseudomorphic transformation was studied in order to prepare well-crystallized ZSM-5 nanosheets beads of 50 and 75 µm. Results showed that the required time of the static treatment at 120°C increases when the size of the parent silica spheres increases. This is explained by the fact that crystallization starts from the outer bead surface toward the center.

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New Generation of Zeolite Materials for Environmental Applications.

Cited by 34 publications

References 65 publications

Reminiscent capillarity in subnanopores

Reminiscent capillarity in subnanopores

Oligomerization of Silicic Acids in Neutral Aqueous Solution: A First-Principles Investigation

Hierarchical ZSM-5 beads composed of zeolite nanosheets obtained by pseudomorphic transformation

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