scholarly journals Effect of Alkali-Free Synthesis and Post-Synthetic Treatment on Acid Sites in Beta Zeolites

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3434
Author(s):  
Kinga Mlekodaj ◽  
Joanna E. Olszowka ◽  
Venceslava Tokarova ◽  
Edyta Tabor ◽  
Ales Kasparek ◽  
...  
Keyword(s):  
Total Concentration ◽  
Textural Properties ◽  
Acid Sites ◽  
Beta Zeolite ◽  
Synthesis Methods ◽  
Channel System ◽  
Beta Zeolites ◽  
Amorphous Aluminosilicate ◽  
Standard Beta ◽  
Brønsted And Lewis Acid

Beta zeolites with Si/Al around 14 were prepared using three new alkali-free synthesis methods based on the application of amorphous aluminosilicate precursor and calcined in ammonia or air. All samples exhibit structural and textural properties of standard beta zeolite. Comprehensive study by 27Al and 29Si MAS NMR, together with FTIR adsorption of d3-acetonitrile and pyridine were used to characterize the influence of both the synthesis and calcination procedure on the framework Al atoms and related Brønsted and Lewis acid sites. While calcination in ammonia preserves all framework Al atoms, calcination in air results in 15% release of framework Al, but without restrictions of the accessibility of the beta zeolite channel system for bulky pyridine molecules. Terminal (SiO)3AlOH groups present in the hydrated zeolites were suggested as a precursor of framework Al-Lewis sites. Surprisingly, the mild dealumination of the air-calcined zeolites result in an increase of the concentration of Brønsted acid sites and a decrease of the total concentration of Lewis sites with the formation of the extra-framework ones.

scholarly journals Nature of Synergy between Brønsted and Lewis Acid Sites in Sn–Beta Zeolites for Polyoxymethylene Dimethyl Ethers Synthesis

ChemSusChem ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 4421-4431 ◽  
Author(s):  
Christophe J. Baranowski ◽  
Maneka Roger ◽  
Ali M. Bahmanpour ◽  
Oliver Kröcher
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Polyoxymethylene Dimethyl Ethers ◽  
Beta Zeolites ◽  
Brønsted And Lewis Acid

Understanding the roles of different acid sites in Beta zeolites with different particle sizes catalyzed liquid-phase transalkylation of diethylbenzene with benzene

2021 ◽  
Author(s):  
Chuanyu Yang ◽  
Zhongwen Dong ◽  
Weifeng Chu ◽  
Yanan Wang ◽  
Dongpu Zhao ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Beta Zeolite ◽  
Particle Sizes ◽  
Synthesis System ◽  
Beta Zeolites

A series of Beta zeolite catalysts with controllable particle sizes and similar Si/Al ratios were prepared by introducing imidazole (IMD) into the synthesis system and used for a liquid-phase transalkylation...

scholarly journals Mesoporous Beta Zeolite Catalysts for Benzylation of Naphthalene: Effect of Pore Structure and Acidity

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 504 ◽  
Author(s):  
Wenming Hao ◽  
Weimin Zhang ◽  
Zaibin Guo ◽  
Jinghong Ma ◽  
Ruifeng Li
Keyword(s):  
Catalytic Performance ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Beta Zeolite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Type ◽  
Beta Zeolites ◽  
Acidic Sites ◽  
Xrd Patterns

To improve the catalytic performance of zeolite catalysts in reactions involving bulky molecules, a series of mesoporous Beta zeolite were prepared using organic functionalized fumed silica as the silicon source, which were thoroughly characterized in terms of porosity and acidity. The peaks in X-ray diffraction (XRD) patterns showed broadening, and the external surface area and mesoporosity increased progressively when the content of organic functionalization increased. An infrared (IR) spectroscopy study of adsorbed probe molecules, including pyridine (Py-IR), 2,6-ditertbutylpyridine (DTBPy-IR) and pivalonitrile (Pn-IR), showed that the improvement of mesoporosity increased the accessibility of acidic sites. In the catalytic benzylation of naphthalene with benzyl chloride (BC) over the mesoporous Beta zeolite catalysts, the conversion of BC was significantly increased when the accessibility of Brönsted acid sites improved. The increase of mesoporosity not only improved the diffusion ability of the reactants and products, but also increased the accessibility of acid sites, which greatly enhanced the activity of the mesoporous Beta zeolite catalysts. It is highlighted that the interdependence of mesoporosity, acid type, acid concentration, and strength of the mesoporous Beta zeolites on the catalytic performance in the benzylation of naphthalene with BC was comprehensively studied.

Rapid, Non-Toxic Synthesis of Beta Zeolites

2018 ◽  
Author(s):  
Felix Hemmann ◽  
Jonathan Hackebeil ◽  
Andreas Lißner ◽  
Florian Mertens
Keyword(s):  
Hydrofluoric Acid ◽  
Molecular Sieves ◽  
Toxic Chemicals ◽  
Lewis Acidity ◽  
Beta Zeolite ◽  
Seeded Growth ◽  
Related Research ◽  
Beta Zeolites ◽  
Growth Method ◽  
Fast Synthesis

Molecular sieves with beta zeolite topology are promising catalysts for various reactions as they exhibits extraordinary Lewis acidity. However, their industrial application and related research in academica is hindered because their synthesis is time consuming and typically involves toxic chemicals as hydrofluoric acid. Therefore, tetraethylammonium fluorid was tested as a non-toxic fluotide source for the synthesis of beta zeolites. In combination with the previously reported nano-seeded growth method, a fast synthesis of beta zeolites only involving non-toxic chemicals was possible. Synthesized zeolites show comparable selectivity in the Bayer-Villinger oxidation as conventional zeolites synthesized with hydrofluoric acid.<br>

scholarly journals Characterization and Catalytic Behaviour of Co3(PO4)2–AlPO4 Catalysts

1998 ◽  
Vol 16 (4) ◽  
pp. 285-293 ◽  
Author(s):  
M.R. Mostafa ◽  
F.Sh. Ahmed
Keyword(s):  
Pore Radius ◽  
Surface Acidity ◽  
Total Pore Volume ◽  
Textural Properties ◽  
Acid Sites ◽  
Adsorption Of Nitrogen ◽  
Amorphous Structures ◽  
Ft Ir ◽  
Catalytic Behaviour ◽  
The Mean

Co3(PO4)2, AlPO4 and the binary system Co3(PO4)2-AlPO4 with different compositions were prepared by the coprecipitation method. The structural properties of these samples were determined using XRD, DTA and FT-IR techniques. The textural properties were determined from the adsorption of nitrogen at 77 K. The surface acidity was measured by a calorimetric titration method. The samples were tested as catalysts in the dehydration of ethanol and isopropanol using a pulse microcatalytic technique. The data obtained from XRD and FT-IR indicate the amorphous structures of the prepared catalysts. An increase in Co3(PO4)2 content led to a decrease in the surface area and in the total pore volume and an increase in the mean pore radius. The surface acidity of the catalyst depends on the chemical composition; the surface acidity increased with an increase in the AlPO4 content. The dehydration temperature and the distribution of acid sites are important parameters in determining the selectivity and activity of the catalyst.

Characterization and catalytic properties of a saponite clay modified by acid activation

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 633-643 ◽  
Author(s):  
F. Kooli ◽  
W. Jones
Keyword(s):  
Infrared Spectroscopy ◽  
Room Temperature ◽  
Textural Properties ◽  
Acid Sites ◽  
Single Type ◽  
Activation Process ◽  
Acid Activation ◽  
Strongly Correlated ◽  
Lewis Site ◽  
Adsorbed Pyridine

AbstractA natural saponite was acid activated at room temperature or 90°C with different acid/clay ratios and the products were characterized by powder X-ray diffraction, infrared spectroscopy and thermogravimetry. The leaching of Mg from the octahedral sheets is enhanced by an increase in the acid/clay ratio and by an increase in temperature of activation. Textural properties are reported, and it appears that they are strongly correlated to the presence of a noncrystalline silica phase which is formed during the acid activation process. The desorption of cyclohexylamine indicates that for samples activated at 90°C the number of acid sites in the acidactivated saponites decreases following severe acid treatment. Infrared spectroscopy of adsorbed pyridine on samples after calcination at 500°C suggests that acid activation at 90°C produces a single type of Bronsted site but two types of Lewis sites whereas activation at room temperature results in only one type of Lewis site in addition to a Brønsted site. The two Lewis sites are suggested to originate from residual Al in the clay structure and to AI exsolved from the layers during activation. The dehydration of pentan-1-ol has been used as a further probe to measure acidity by monitoring the degree of conversion and selectivity for the different samples.

On the nature of framework Brønsted and Lewis acid sites in ZSM-5

Zeolites ◽  
1997 ◽  
Vol 19 (4) ◽  
pp. 288-296 ◽  
Author(s):  
G.L. Woolery ◽  
G.H. Kuehl ◽  
H.C. Timken ◽  
A.W. Chester ◽  
J.C. Vartuli
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid
Sign in / Sign up

Export Citation Format

Share Document