The catalytic effect of boron substitution in MCM-41-type molecular sieves

2004 ◽  
Vol 82 (5) ◽  
pp. 631-640 ◽  
Author(s):  
V Sundaramurthy ◽  
I Eswaramoorthi ◽  
N Lingappan
Keyword(s):  
Molecular Sieves ◽  
Boron Content ◽  
Acid Sites ◽  
Mas Nmr ◽  
Catalyst Characterization ◽  
Secondary Products ◽  
Hydrogen Shift ◽  
Wide Range ◽  
Ft Ir ◽  
Mcm 41

A series of B-MCM-41 samples has been synthesized with a wide range of boron content (SiO2:B2O3 ratio from 20 to 200), using ethyl silicate ester-40 (ES-40) as the silica source and characterized by XRD, BET, FT-IR, 11B-MAS NMR, SEM, pyridine adsorption, TPDA, and chemical analysis. The interplanar d100 spacing varies from 40 to 45 Å, depending on the Si:B ratio. On calcination, a significant amount of four-coordinated boron is converted into less stable three-coordinated boron, and some boron is removed from the framework. The degree of deboronation increases with an increase of boron content of the sample. The B substitution in the MCM-41 framework results in only weak and mild acid sites. The isomerization of 1-hexene is found to be influenced by the boron content in the framework. The isomerization leads to both a hydrogen shift and skeletal rearrangement. The selectivity ratios of cis-2-hexene to trans-2-hexene and 2-hexene to 3-hexene were found to decrease with an increase of temperature and a decrease of the SiO2:B2O3 ratio of the catalysts. Skeletal isomerization starts at 250 °C, forming secondary products, and increases with an increase of temperature and an increase of boron content of the catalysts. Key words: ES-40, B-MCM-41, deboronation, catalyst characterization, XRD, BET, FT-IR, 11B-MAS NMR, SEM, 1-hexene isomerization, 2-hexene.

A Novel Iron Silicate Mesoporous Material Synthesis and Its Characterization

2018 ◽  
Vol 24 (8) ◽  
pp. 5532-5536
Author(s):  
M. A Mary Thangam ◽  
Chellapandian Kannan
Keyword(s):  
Mesoporous Materials ◽  
Molecular Sieves ◽  
Mesoporous Material ◽  
Synthesis Method ◽  
Acid Sites ◽  
Mesoporous Molecular Sieves ◽  
Isomorphous Substitution ◽  
Main Role ◽  
Material Synthesis ◽  
Ft Ir

The mesoporous materials have variety of applications in several field particularly it has a main role in Catalysis, Petrochemical industries and Adsorption. Normally the porous material has well ordered 3Dimensional structure, huge surface area, high thermal stability and active acid sites. The properties of these materials can be varied because it is mostly depends on its template, synthesis method and isomorphous substitution of metal ions. There are two major mesoporous materials which are aluminosilicate and aluminophosphate. In this present investigation AlCl3 and FeCl3 are used in equal amount for the synthesis of mesoporous material. The synthesized material is characterized by FT-IR, XRD, TGA, BET, EDAX and TPD. Morphological images were studied by SEM. These characterization techniques confirm the formation of mesoporous molecular sieves.

Synthesis of Al-Containing Mesoporous Molecular Sieves and their Catalytic Performance to Isomerization Reaction of Endo-Tetrahydrodicyclo-Pentadiene

2011 ◽  
Vol 233-235 ◽  
pp. 234-237 ◽  
Author(s):  
Sa Liu ◽  
Jian Wei Guo ◽  
Chu Fen Yang ◽  
Long Huan Li ◽  
Yi Hua Cui
Keyword(s):  
Catalytic Activity ◽  
Molecular Sieves ◽  
Catalytic Performance ◽  
Mesoporous Molecular Sieves ◽  
Isomerization Reaction ◽  
Inorganic Acid ◽  
Ft Ir ◽  
Desorption Isotherms ◽  
Adsorption Desorption ◽  
Mcm 41

Al-containing mesoporous molecular sieves(Al-MCM-41) were synthesized at ambient temperature. The structures of samples were characterized by XRD, N2-adsorption/desorption isotherms and FT-IR, etc. The evaluation results showed that Al-MCM-41 had higher catalytic activity for isomerization conversion of endo-tetrahydrodicyclo-pentadiene (endo-TCD) into exo-tetrahydrodicyclo-pentadiene (exo-TCD) and adamantane (AdH). Loading inorganic acid on the surface of Al-MCM-41 led increase of its catalytic activity and the yield of adamantane.

scholarly journals Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 211
Author(s):  
Yongxin Zhang ◽  
Long Lin ◽  
Xiaoming Zheng ◽  
Chunyan Liu ◽  
Quanren Zhu ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Precipitation Method ◽  
Catalyst Characterization ◽  
Lewis Acid Sites ◽  
Modified Zeolite ◽  
Weight Percentage ◽  
Ft Ir

In this study, a series of SnO2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2 and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.

Brønsted and Lewis Acid Sites in Dealuminated ZSM-12 and β Zeolites Characterized by NH3-STPD, FT-IR, and MAS NMR Spectroscopy

2000 ◽  
Vol 104 (17) ◽  
pp. 4122-4129 ◽  
Author(s):  
Wenmin Zhang ◽  
Panagiotis G. Smirniotis ◽  
M. Gangoda ◽  
Rathindra N. Bose
Keyword(s):  
Nmr Spectroscopy ◽  
Lewis Acid ◽  
Acid Sites ◽  
Mas Nmr ◽  
Lewis Acid Sites ◽  
Ft Ir ◽  
Brønsted And Lewis Acid

Synthesis and Catalytic Application of Mesoporous Molecular Sieves MCM-41 Containing Niobium and Tantalum

2007 ◽  
Vol 124-126 ◽  
pp. 1761-1764 ◽  
Author(s):  
Hun Jung ◽  
Kwang Deog Jung ◽  
Oh Shim Joo ◽  
Sun Jin Kim
Keyword(s):  
Vapor Phase ◽  
Molecular Sieves ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Beckmann Rearrangement ◽  
Mesoporous Molecular Sieves ◽  
Cyclohexanone Oxime ◽  
Catalytic Application ◽  
Mcm 41

Niobium- and tantalum-containing mesoporous molecular sieves MCM-41 have been synthesized, and applied as a catalyst for vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam. NbMCM-41 catalyst exhibited high catalytic performance in the vapor phase Beckmann rearrangement of cyclohexanone oxime. The oxime conversions were almost 100% and the lactam selectivities were around 80%. The lactam selectivities of NbMCM-41 catalyst were higher than those of AlMCM-41 catalyst. However, TaMCM-41 catalyst exhibited lower catalytic performance than AlMCM-41 catalyst, and it was fast deactivated with time. These results may be due to the acidity difference among the catalysts. The results from NH3-TPD showed that NbMCM-41 catalyst possessed weak and medium acid sites, while TaMCM-41 catalyst possessed only very weak acid sites. AlMCM-41 catalyst also exhibited only weak acid sites.

Synthesis and Characterization of MCM-41 Molecular Sieves Nanoparticals

2013 ◽  
Vol 662 ◽  
pp. 214-217 ◽  
Author(s):  
Li Qin Wang ◽  
Yang Han ◽  
Xiu Jun Fu ◽  
Hai Tao Wu ◽  
E Chang ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Room Temperature ◽  
Mesoporous Structure ◽  
Decomposition Temperature ◽  
Surface Areas ◽  
Type Iv ◽  
Typical Type ◽  
Ft Ir ◽  
Adsorption Desorption ◽  
Mcm 41

Nanoparticals of MCM-41 molecular sieves were synthesized at near room temperature with cetyltrimethylammonium bromide (CTAB) as template agent. The prepared samples were characterized by the means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), N2 adsorption tests, thermogravimetric and differential thermal analysis (TG-DTA). The results suggested that morphology of MCM-41 molecular sieves samples with high crystallinity was almost uniform spherical, and the particles size was almost less than 100 nm. The adsorption-desorption isotherms were corresponded to typical type IV isotherms with the hysteresis loop of type H2, which showed the samples had mesoporous structure. The pore size distribution of samples were 1.69 nm and 3.58 nm, and the specific surface areas was up to 752.23 m2/g. The decomposition temperature of template agent CTAB was around 327 °C, while the framework for MCM-41molecular sieves was stable. So MCM-41 molecular sieve samples synthesized at near room temperature had excellent physical properties.

Rice Straw and Rice Straw Ash as Precursor for Synthesis of Mesoporous Molecular Sieves MCM-41

2012 ◽  
Vol 550-553 ◽  
pp. 1391-1394
Author(s):  
Xiao Hong Tang ◽  
Bao Jun Li ◽  
Cheng Wei Li
Keyword(s):  
Rice Straw ◽  
Molecular Sieves ◽  
Mesoporous Structure ◽  
Mesoporous Molecular Sieves ◽  
X Ray Diffraction ◽  
Ft Ir ◽  
Temperature Programmed ◽  
Adsorption Desorption ◽  
Straw Ash ◽  
Mcm 41

In this paper, rice straw (RS) and rice straw ash (RSA) were employed to synthesize mesoporous molecular sieves MCM-41 in an open-vessel. The structure of as-synthesized MCM-41 was characterized by X-ray diffraction (XRD) pattern, Fourier transform infrared (FT–IR) spectrum, NH3-Temperature Programmed Desorption (TPD), and N2 adsorption-desorption isotherms. RS-MCM-41 and RSA-MCM-41 possess the same typical hexagonal mesoporous structure with high long-range order and crystalline degree as those of MCM-41 from water glass (SDS-MCM-41).

Synthesis and Characterization of the ZSM-5/MCM-41 Composite Molecular Sieves

2011 ◽  
Vol 480-481 ◽  
pp. 165-169 ◽  
Author(s):  
Li Qin Wang ◽  
Ning Yu ◽  
Yang Han ◽  
Xiang Ni Yang ◽  
Xiu Li Zhao
Keyword(s):  
Molecular Sieves ◽  
Cetyltrimethylammonium Bromide ◽  
Decomposition Temperature ◽  
High Thermal Stability ◽  
Hydrothermal Crystallization ◽  
X Ray ◽  
Ft Ir ◽  
Prepared Composite ◽  
Mcm 41

The ZSM-5/MCM-41 composite molecular sieves were synthesized in the method of hydrothermal crystallization in the presence of cetyltrimethylammonium bromide (CTMABr) as template agent. The prepared composite molecular sieves were characterized by the means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and the thermogravimetric and differential thermal analysis (TG-DTA). The experimental results showed that as-prepared ZSM-5/MCM-41 composite molecular sieves kept both crystal structure and compositions of ZSM-5 zeolites and MCM-41 molecular sieves. The decomposition temperature of the template agent was 293°C, and the decomposition temperature of the molecular sieve framework was higher than 800 °C. We supposed that the obtained ZSM-5/MCM-41 composite molecular sieves had high thermal stability, framework rigidity and structural stability, and could combine the properties of ZSM-5 zeolites and MCM-41 molecular sieves successfully.

Synthesis and Characterization of the Y/MCM-41 Composite Molecular Sieves

2011 ◽  
Vol 480-481 ◽  
pp. 159-164 ◽  
Author(s):  
Li Qin Wang ◽  
Xiang Ni Yang ◽  
Yang Han ◽  
Ning Yu ◽  
Xiu Li Zhao
Keyword(s):  
Pore Size ◽  
Molecular Sieves ◽  
Average Pore Size ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Decomposition Temperature ◽  
Average Pore ◽  
Y Zeolites ◽  
Ft Ir ◽  
Mcm 41

The Y/MCM-41 composite molecular sieves were synthesized in the method of hydrothermal crystallization with cetyltrimethylammonium bromide (CTMABr) as the template agent. The as-prepared composite molecular sieves were characterized by the means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), the thermogravimetric and differential thermal analysis (TG-DTA) and the nitrogen adsorption test. The experimental results were shown as follows: the Y/MCM-41 composite molecular sieves kept properties of Y-zeolites and MCM-41 molecular sieves. In the XRD and FT-IR spectra, it can be found both characteristic peaks of Y-zeolites and MCM-41 molecular sieves. The pore size distribution plot indicated that the Y/MCM-41composite molecular sieves had micro-mesoporous structure, and the average pore size were about 1.5 nm and 15 nm. The decomposition temperature of the template agent was at 320 °C, and the calcined temperature of Y-zeolites was at about 560 °C. There showed an endothermic process constantly in the DTA curve, and there was little mass loss in the TG curve, indicating the obtained Y/MCM-41 composite molecular sieves had higher thermal stability.

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