Control of crystallization rate and morphology of zeolite silicalite-1 in solvent-free synthesis

Zhang, Junjia; Lü, Xiaofei; Wang, Zhengbao

doi:10.1016/j.micromeso.2019.03.044

Cited by 18 publications

(14 citation statements)

References 47 publications

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“…At x = 3.5 (W-3), the obtained crystals were in nanorod morphology, while a mixing of nanorods and prismatic crystals were observed at x = 5.0 (W-8), demonstrating the significant effect of mineralizer content on the morphological properties of K-MER zeolite (Figure 6a). A similar observation was also reported by Zhang et al where the addition of a higher amount of NaOH as mineralizer promotes the crystal growth at a specific axis, resulting in the crystallization of silicalite-1 zeolite with spherical shape instead of common coffin shape [31]. Further increasing the K2O content (x = 7.0: W-9) led to the formation of K-MER zeolite with only pure prismatic-shape crystals (Figure 6c).…”

Section: Effect Of K2o Contentsupporting

confidence: 87%

Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

et al. 2020

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MER-type zeolite is an interesting microporous material that has been widely used in catalysis and separation. By carefully controlling the synthesis parameters, a procedure to synthesize K-MER zeolite crystals with various morphologies has been developed. The silica, water and mineralizer content in the synthesis gel, as well as crystallization time and temperature, have a profound impact on the crystallization kinetics, resulting in zeolite solids with various degrees of crystallinity, crystal sizes and shapes. K-MER zeolite crystals with nanorod, bullet-like, prismatic and wheatsheaf-like morphologies have been successfully obtained. The catalytic performances of the K-MER zeolites in cyanoethylation of methanol, under novel non-microwave instant heating, have been investigated. The zeolite in nanosize form shows the best catalytic performance (94.1% conversion, 100% selectivity) while the bullet-like zeolite gives poorest catalytic performance (44.2% conversion, 100% selectivity).

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Section: Effect Of K2o Contentsupporting

confidence: 87%

Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

et al. 2020

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“…This seems to be case for the zeolites milled at the H 2 O/SiO 2 =1.7 molar ratio, Figure 7. The positive effect of the H 2 O/SiO 2 ratio on the crystallinity of the zeolites could be associated with the fact that water can facilitate the hydrolysis and condensation of silica species in the solvent‐less synthesis [16,62] . Another possibility, which does not exclude the aforementioned, is that water can play the role of lubricant during milling.…”

Section: Resultsmentioning

confidence: 99%

“…The positive effect of the H 2 O/SiO 2 ratio on the crystallinity of the zeolites could be associated with the fact that water can facilitate the hydrolysis and condensation of silica species in the solvent-less synthesis. 16,67 Another possibility, which does not exclude the aforementioned, is that water can play the role of lubricant during milling. Therefore, lower amounts of water during milling may lead to harsher mechanical stresses.…”

Section: Crystallinitymentioning

confidence: 99%

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

et al. 2021

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The so-called mechanochemical method for the synthesis of zeolites reduces the generation of liquid residues and gaseous pollutants as compared to the conventional solvothermal method. Different types of zeolites have been synthesized at the laboratory scale with this method using mostly pestle and mortar. However, such an approach hinders both the systematic comprehension of the effects of the input variables of the milling process and its further scale-up towards the synthesis of the zeolites and their catalytic application. This work investigates the influence of key factors involved in the ball milling stage of the mechanochemical route for the synthesis of MFI done with the assistance of a commercial MFI seed and in the absence of solvents over the most salient physicochemical properties of this type of materials, i.e. the recovery percentage, production cost, morphology, surface area and porosity, crystallinity, acidity of the protonated MFI and catalytic performance. The synthesis of the materials was planned and executed following a full 2 4 factorial experiment whose input variables were the Na2O/SiO2 and H2O/SiO2 molar ratios and the milling time and speed. The effects of both main and interaction factors over key physicochemical properties, and catalytic behavior of the synthesized materials on the alkylation of phenol with tert-butyl alcohol were established within the explored sampling space. Results showed that the Na2O/SiO2 molar ratio plays a key role for the mechanochemical synthesis of MFI, since this variable may direct the synthesis to the preferential production of MOR instead of MFI. On the other hand, it was found that the milling time and speed and their interactions markedly impact the textural properties of MFI. Furthermore, the triple interaction between the input variables affected the concentration of Lewis acid sites of the produced materials. These effects were rationalized by considering that sodium can act as a structure directing agent during the mechanochemical synthesis of MFI and also can promote the incorporation of aluminum to its structure. On the other hand, the milling time and speed are non-linearly correlated to the milling energy required for forming the aluminosilicate precursor that crystallizes during the hydrothermal stage of the process. Overall, all the zeolites synthesized by the mechanochemical route were less crystalline than both the MFI used as seed and an MFI synthesized by solgel. This was associated to the formation of amorphous agglomerates around the zeolitic crystals. Finally, the catalytic behavior of the mechanochemical MFI zeolites in the studied reaction was found to be linearly and positively correlated with both the concentration of BrØnsted of sites and with the density of acid sites. The catalytic tendencies were consistent with the proposal of a stepwise Langmuir-Hinshelwood mechanism for the alkylation of phenol with tert-butyl alcohol.

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“…Recently, Zhang et al found that the increase of the NaOH/SiO 2 ratio from 0.14 to 0.19 elongates the crystal size from 10.5 mm Â 2.6 mm to 14 mm Â 9.2 mm along a and c axes respectively in the synthesis of ZSM-5 from the F-containing gel. 89 Another strategy to alter the crystal exposure degree is the introduction of organic additives that are selectively adsorbed on certain crystal facets, and thus, hindering their growth. This is manifested in the synthesis of ZSM-5 by adding an amino acid or a polymer to the gel.…”

Section: Aimed Control Of the Exposure Degree Of Crystal Facetsmentioning

confidence: 99%

Improvement of adsorption and catalytic properties of zeolites by precisely controlling their particle morphology

Yang

Wang

et al. 2022

Chem. Commun.

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Control of crystallization rate and morphology of zeolite silicalite-1 in solvent-free synthesis

Cited by 18 publications

References 47 publications

Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

Improvement of adsorption and catalytic properties of zeolites by precisely controlling their particle morphology

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