Effect of aluminum and gallium concentration on the crystallization rate of TPA/MFI zeolites synthesized with MeNH2 in the absence of inorganic cations

Giannetto, G.; Santos, F. Dos; Monque, R.; Galiasso, R.; Gabélica, Z.

doi:10.1016/0144-2449(95)00073-f

Cited by 22 publications

(5 citation statements)

References 19 publications

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“…Clearly, the pure gallosilicate sodalites crystallize with larger average sizes (Fig. 4), which is in good agreement with previous reports of sodalites [8,27] and zeolites [43]. The morphology of the gallosilicate sodalites (rhombodecahedral) is clearly visible, while the alumosilicate are found as agglomerations.…”

Section: Average Crystal Sizesupporting

confidence: 90%

Isomorphous framework cation substitution in the alumosilicatesodalites: synthesis, structural and spectroscopic studies of nitritecontaining phases

Murshed¹,

Baer²,

Gesing³

2008

Zeitschrift Für Kristallographie

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Partial substitution of aluminium with gallium in the Na 8 [Al 1Ày Ga y SiO 4 ] 6 (NO 2 ) 2 sodalite system (y ¼ 0-1) revealed an extensive isomorphous miscibility. Each composition (y ¼ 0-1) is isotypic to either the alumosilicate or gallosilicate end members (y ¼ 0 or 1, respectively). The Al/Ga ratio was controlled by selective initial stoichiometries in the direct hydrothermal syntheses. The samples were investigated by X-ray powder diffraction, SEM, FTIR and 29 Si MAS NMR spectroscopies. The gallium concentration in the framework was calculated using the X-ray data Rietveld refinement, which was always lower than the feed concentration in each composition. The cell parameter and tilt angle increased, while the T--O--T angle and six-ring window dimension decreased with increasing gallium content in the framework. The Al/Ga--O distance is the mean of Al--O and Ga--O distances and increases with increasing gallium content. In contrast, the Si--O distance fluctuates close to 163 pm with increasing gallium insertion. The broadening of the XRD peaks in the patterns with mid-range gallium concentrations (y ¼ 0.35-0.70) is associated with the formation of Al-rich and Garich domains, which is explained in terms of Al/Ga--O distances and average crystal size with respect to Al/Ga ratio in the framework. The domains are assumed to be smaller than the coherence length of the X-ray radiation but large enough to detect by MAS NMR techniques.

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Section: Average Crystal Sizesupporting

confidence: 90%

Isomorphous framework cation substitution in the alumosilicatesodalites: synthesis, structural and spectroscopic studies of nitritecontaining phases

Murshed¹,

Baer²,

Gesing³

2008

Zeitschrift Für Kristallographie

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“…All the samples are clearly crystalline and possess the classical MFI features of the ZSM‐5 zeolite structure . From HZ‐1 to HZ‐5, the diffraction peaks of the samples become higher and stronger as the Al content decrease gradually, which suggests that the increasing Al content has a negative effect on the crystallization rate . Also, it is noted that the dealumination step is accompanied by a loss in crystallinity in each sample, but not with the appearance of a new crystalline phase.…”

Section: Resultsmentioning

confidence: 91%

“…[41] From HZ-1 to HZ-5, the diffraction peaks of the samples become highera nd stronger as the Al content decrease gradually,w hich suggestst hat the increasing Al content has an egative effect on the crystallization rate. [42] Also, it is noted that the dealumination step is accompanied by al oss in crystallinity in each sample, but not with the appearance of a new crystalline phase.W ith decreasing Si/Al ratio, the loss of crystallinity is clearer,i ndicating that more Al located on the externals urfaces or mesoporousw alls are dealuminated,b ut the crystal lattice is still well maintained.…”

Section: Resultsmentioning

confidence: 98%

The Role of External Acidity of Hierarchical ZSM‐5 Zeolites in n‐Heptane Catalytic Cracking

et al. 2018

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The hierarchical ZSM‐5 zeolite, which contains mesopores in addition to intrinsic micropores, is expected to enhance the bulky molecular diffusion and accessibility of acid sites. These sites, distributed in the internal surface (micropore) or external environment (including external surface and mesopore walls), play different roles in chemical reactions. To explore the effect of internal/external acidity on the reaction, in this study, a series of hierarchical ZSM‐5 zeolites with similar pore structures but different external acid properties were synthesized. Tartaric acid was employed to poison the acidic sites in the external environment selectively and extract Al from the framework. The catalytic cracking of n‐heptane (the main compound of naphtha) was chosen as a model reaction. The results show that elimination of external active sites tends to reduce the coke formation. The more external acid sites are selectively eliminated, the better catalytic performance can be achieved because of suppressing the bimolecular reactions of ethylene and propylene.

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“…Unlike previous methods [8,10,30], our method relies neither on complicated and expensive hard templates nor on compounds with hydrophobic groups. Methylamine was used as a mineralizing agent in the works reported by Gabelica et al [34,[39][40][41][42][43], however, only bulk micro-sized zeolite crystals were obtained. Zeolites in Gabelica's works were prepared by hydrothermal method under high temperature and pressure, which was not beneficial for formation of nano-sized zeolite crystals, comparing to the preparation process in mild conditions in this work.…”

Section: Resultsmentioning

confidence: 97%

Facile synthesis of hierarchical nanocrystalline ZSM-5 zeolite under mild conditions and its catalytic performance

Sun

et al. 2011

Journal of Colloid and Interface Science

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Effect of aluminum and gallium concentration on the crystallization rate of TPA/MFI zeolites synthesized with MeNH2 in the absence of inorganic cations

Cited by 22 publications

References 19 publications

Isomorphous framework cation substitution in the alumosilicatesodalites: synthesis, structural and spectroscopic studies of nitritecontaining phases

Isomorphous framework cation substitution in the alumosilicatesodalites: synthesis, structural and spectroscopic studies of nitritecontaining phases

The Role of External Acidity of Hierarchical ZSM‐5 Zeolites in n‐Heptane Catalytic Cracking

Facile synthesis of hierarchical nanocrystalline ZSM-5 zeolite under mild conditions and its catalytic performance

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