Characterization of aluminosilicate zeolites by UV Raman spectroscopy

Yu, Yi; Xiong, Guang; Li, Can; Xiao, Feng‐Shou

doi:10.1016/s1387-1811(01)00271-2

Cited by 243 publications

(193 citation statements)

References 40 publications

(60 reference statements)

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“…Raman spectra due to silicate and aluminosilicate rings in zeolites are so weak and often obscured by a broad fluorescence background. Recently, high-quality spectra have been reported by using ultraviolet laser as excitation source [12]. In this work, with the careful treatment as mentioned above, high-quality spectra were obtained using a Raman spectrometer (JASCO Corp., NRS-1000) equipped with green laser (532 nm).…”

Section: Raman Spectroscopymentioning

confidence: 99%

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

et al. 2008

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Ferrierite type zeolite can be synthesized without using any organic structure-directing agent from Na-or (Na, K)-or K-aluminosilicate system. (Na, K)-ferrierite is synthesized from wide range of OH/SiO 2 region of the reactant mixture compared with Na-and K-ferrierite. The crystallization process of ferrierite in each system is investigated in detail by X-ray diffraction and Raman spectroscopy. The role of potassium and sodium cations and cooperative effect of two cations in the formation of the framework of ferrierite are elucidated.

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Section: Raman Spectroscopymentioning

confidence: 99%

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

et al. 2008

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“…A UV source also circumvents possible interference of fluorescence. 33,36,72 Full and consistent assignment of all observed 29 Si NMR and Raman spectroscopic signals successfully was achieved through combination of experiment with molecular modeling using the B3LYP density functional (as described in the Experimental Section). Accumulated 29 Si NMR spectra recorded during the evolution of R-0.2 ( Figure 1) revealed the presence of a monomer (Q 0 , δ = -82.5 ppm), dimer (Q 1 , δ = -89.36 ppm), and two types of Q 2 silicon atoms connected to two silicate units.…”

Section: ' Introductionmentioning

confidence: 97%

²⁹Si NMR and UV−Raman Investigation of Initial Oligomerization Reaction Pathways in Acid-Catalyzed Silica Sol−Gel Chemistry

et al. 2011

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ABSTRACT:The initial molecular steps of the acid-catalyzed silica sol-gel process departing from tetraethylorthosilicate (TEOS) were investigated by in situ 29 Si NMR and UV-Raman spectroscopy. The use of a substoichiometric H 2 O:TEOS molar ratio (rvalue 0.2-1.2) slowed the silicate oligomerization reaction and allowed unraveling the initial steps of silica condensation. Molecular modeling confirmed Raman signal and 29 Si NMR shift assignment. A comprehensive listing of all Raman and 29 Si NMR assignments is provided, including unique Raman assignments of cyclosilicates and the linear tetramer. The combination of experiment and modeling allowed an analysis of the reaction kinetics. The derived kinetic model and the experimental observation both revealed that the H 2 O: TEOS molar ratio had a strong influence on the reaction kinetics but not on the reaction pathways. The multianalytical approach led to development of an oligomerization scheme. As dominant oligomerizations, chain growth, cyclodimerization, and branching were identified. Under the investigated conditions, chains did not grow longer than pentamer, and ring sizes were limited to 6-rings. Chains of 4 Si atoms and 4-rings were abundant species. Branched rings and chains were formed by attachment of dimers and trimers. Gelation proceeded from branched 4-rings and branched chains with limited hydroxyl functionalities.

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“…by XRD techniques, two additional weak bands at 225 and 314 cm À1 were observed in the Raman spectrum. Yu et al [63] assigned these bands to the bending modes of 8-membered and 6-membered rings of the zeolite L framework, respectively. An additional new band at 600 cm À1 was recorded in the final fully crystalline products.…”

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confidence: 99%

Factors That Control Zeolite L Crystal Size

Itani

Bozhilov

Clet

et al. 2011

Chemistry A European J

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Time-series hydrothermal syntheses from two organic-cation-free gels with different compositions were employed to study the factors that control the final size of zeolite L crystals. The first gel had a starting K/Al ratio of 10, whereas in the second one it was three times lower. The relatively simple chemical composition of the starting gels and the combination of complementary characterization methods allowed us to track down the different stages of transformation of the initial amorphous gels into zeolite crystals and the factors that control the nucleation and growth processes. The role of the starting mixture components in the formation of the primary amorphous particles was explored. It was found that the profoundly different reaction kinetics in the two systems are caused by the difference in diffusion rates, which in turn are controlled by the extent of the polymerization reactions at room temperature during mixing of the starting components prior to hydrothermal treatment. As a consequence, nucleation is fast and ubiquitous in the first system with higher water content and K/Al ratio, whereas it is slow and sporadic in the second system with lower water content and K/Al ratio. Ultimately, these differences in the kinetics lead to the formation of two distinctly different patterns of crystal-size distribution, with a large number of small nanocrystals in the first sample and fewer large crystals in the second sample. The new findings put zeolite crystal growth on a rational basis that would enable the control of zeolite crystal size in similar organic-template-free systems.

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Characterization of aluminosilicate zeolites by UV Raman spectroscopy

Cited by 243 publications

References 40 publications

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

²⁹Si NMR and UV−Raman Investigation of Initial Oligomerization Reaction Pathways in Acid-Catalyzed Silica Sol−Gel Chemistry

Factors That Control Zeolite L Crystal Size

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Characterization of aluminosilicate zeolites by UV Raman spectroscopy

Cited by 243 publications

References 40 publications

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

Cooperative Effect of Sodium and Potassium Cations on Synthesis of Ferrierite

29Si NMR and UV−Raman Investigation of Initial Oligomerization Reaction Pathways in Acid-Catalyzed Silica Sol−Gel Chemistry

Factors That Control Zeolite L Crystal Size

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²⁹Si NMR and UV−Raman Investigation of Initial Oligomerization Reaction Pathways in Acid-Catalyzed Silica Sol−Gel Chemistry