Mechanism of Ti(IV) incorporation onto the zeolite framework probed with xafs

2004 ◽  
pp. 325-333
Author(s):  
S.J. Cho ◽  
J.H. Kwak ◽  
R. Ryoo ◽  
H.K. Yoon
Keyword(s):  
Zeolite Framework

Study of Coke Distribution in HZSM-5 by 129-Xe NMR

1992 ◽  
Vol 57 (4) ◽  
pp. 733-738 ◽  
Author(s):  
Jean L. Bonardet ◽  
M. C. Barrage ◽  
Jack P. Fraissard ◽  
Ludmila Kubelková ◽  
Jana Nováková ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Zeolite Framework

The location of coke formed during conversion of methanol or acetone on HZSM-5 zeolites has been examined using 129-Xe NMR spectroscopy. The results show that the type of reaction and the method of regeneration have great importance for the location of carbonaceous residues inside or outside the zeolite framework.

scholarly journals Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4508
Author(s):  
Zeinab Mcheik ◽  
Ludovic Pinard ◽  
Joumana Toufaily ◽  
Tayssir Hamieh ◽  
T. Jean Daou
Keyword(s):  
Catalytic Activity ◽  
Amorphous Materials ◽  
Essential Role ◽  
Aluminum Content ◽  
Catalytic Properties ◽  
Hexadecyltrimethylammonium Bromide ◽  
Zeolite Framework ◽  
Ctab Concentration ◽  
Porous Volume ◽  
Synthesis Medium

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L−1, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.

scholarly journals Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 313
Author(s):  
Heidy Ramirez-Mendoza ◽  
Mafalda Valdez Lancinha Pereira ◽  
Tom Van Gerven ◽  
Cécile Lutz ◽  
Ignacio Julian
Keyword(s):  
Catalytic Activity ◽  
Ion Exchange ◽  
Active Sites ◽  
Chemical Properties ◽  
Successful Implementation ◽  
Metal Dispersion ◽  
Zeolite Framework ◽  
Dispersed Catalysts ◽  
Methane Dehydroaromatization ◽  
Ultrasound Assisted

The activity and selectivity of Mo/ZSM-5, benchmarking catalyst for the non-oxidative dehydroaromatization of methane, strongly depend on the cluster size, spatial distribution, and chemical environment of the Mo-based active sites. This study discloses the use of an ultrasound-assisted ion-exchange (US-IE) technique as an alternative Mo/ZSM-5 synthesis procedure in order to promote metal dispersion along the zeolite framework. For this purpose, a plate transducer (91.8 kHz) is employed to transmit the ultrasonic irradiation (US) into the ion-exchange reactor. The physico-chemical properties and catalytic activity of samples prepared under the said irradiation procedure and traditional impregnation (IWI) method are critically evaluated. Characterization results suggest that US neither affects the crystalline structure nor the particle size of the parent zeolite. However, US-IE promotes molybdenum species dispersion, avoids clustering at the external fresh zeolite surface and enhances molybdate species anchoring to the zeolite framework with respect to IWI. Despite the improved metal dispersion, the catalytic activity between catalysts synthesized by US-IE and IWI is comparable. This suggests that the sole initial dispersion enhancement does not suffice to boost the catalyst productivity and further actions such ZSM-5 support and catalyst pre-conditioning are required. Nevertheless, the successful implementation of US-IE and the resulting metal dispersion enhancement pave the way toward the application of this technique to the synthesis of other dispersed catalysts and materials of interest.

Modification of Hydrogen Zeolite with CeO2 and its Catalysis Application for Preparing Aspirin

2014 ◽  
Vol 809-810 ◽  
pp. 884-889
Author(s):  
Zhen Tan ◽  
Hui Ying Chen ◽  
Bi Hao Lan ◽  
Xiang Wen Tong ◽  
Xiao Mei Ba
Keyword(s):  
Heat Treatment ◽  
Calcination Temperature ◽  
Catalytic Efficiency ◽  
Optimal Conditions ◽  
Calcination Time ◽  
Zeolite Framework ◽  
High Efficient ◽  
Zeolite Particle ◽  
Before And After ◽  
Impregnation Temperature

Hydrogen zeolite was modified with CeO2 by impregnation - filtration - heat treatment. Hydrogen-zeolite samples before and after modification were characterized by XRD and SEM. The catalytic efficiency of modified hydrogen-zeolite was investigated. Such modification conditions were explored: as the CeO2 percentage, calcination temperature, calcination time, impregnation temperature. The results show that the optimal CeO2 percentage is 0.5%, calcination temperature is 600°C, calcination time is 2h, impregnation temperature is 75°C. The aspirin yield reaches 78.3% under the optimal conditions, compared with that (64.8%) catalyzed by sulfuric acid and that (70.4%) catalyzed by unmodified zeolite. XRD, SEM characterizations show that Ce ions can be doped into the zeolite framework. And the modification makes the zeolite particle size become smaller, which is reduced to 50.5nm from 56.76nm. A high efficient and eco-enviromently catalyst was got by modification.

Aluminum distribution in mordenite-zeolite framework: A new outlook based on density functional theory calculations

2021 ◽  
pp. 122725
Author(s):  
Joel Antúnez-García ◽  
D.H. Galván ◽  
Vitalii Petranovskii ◽  
Fabian N. Murrieta-Rico ◽  
Rosario I. Yocupicio-Gaxiola ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Zeolite Framework ◽  
Functional Theory ◽  
Aluminum Distribution

Study on the synthesis of antibacterial plastic by using silver nanoparticles doped in zeolite framework

2021 ◽  
Vol 6 (1) ◽  
pp. 32-36
Author(s):  
Anh Quoc Le ◽  
Van Phu Dang ◽  
Ngoc Duy Nguyen ◽  
Kim Lan Nguyen Thi ◽  
Kim Lang Vo Thi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silver Nanoparticles ◽  
Average Particle Size ◽  
Bactericidal Effect ◽  
Ethanol Solution ◽  
Average Particle ◽  
Γ Irradiation ◽  
Zeolite Framework ◽  
Ion Exchange Reaction ◽  
Transmission Electron

Silver nanoparticles (AgNPs) doped in the zeolite framework (AgNPs/Z) were successfully synthesized by γ-irradiation in ethanol solution of silver ion-zeolite (Ag+/Z) prepared by ion exchange reaction between silver nitrate (AgNO3) and zeolite 4A. The effects of the Ag+ concentration and irradiation dose on the formation of AgNPs/Z were also investigated. AgNPs/Z with the silver content of about 10,000 ppm and the average particle size of AgNPs of about 27 nm was characterized by ultraviolet-visible spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM). Firstly, AgNPs/Z was added into PP resins for creation of PP-AgNPs/Z masterbatch (Ag content of ~10.000 ppm) and then PP-AgNPs/Z plastics were preapared by mixing masterbatch with PP resins. The antibacterial activity of the PP-AgNPs/Z plastics was investigated against Gram-negative bacteria Escherichia coli (E. coli). The results showed that PP-AgNPs/Z plastic contained 100 ppm of Ag possessed a high antibacterial property, namely the bactericidal effect was more than 96 % on the platic surface. In conclusion, possessing many advantages such as: vigorously antibacterial effect and good dispersion in plastic matrix, AgNPs/Z is promising to be applied as bactericidal agent for plastic industry.

The Effects of Preparation Methods on Iron Structures of Iron-Supported HZSM-5 and their Catalytic Performance for Methanol Dehydration

2016 ◽  
Vol 723 ◽  
pp. 633-639
Author(s):  
Waenkaew Pantupho ◽  
Arthit Neramittagapong ◽  
Nuttawut Osakoo ◽  
Jatuporn Wittayakun ◽  
Sirinuch Loiha
Keyword(s):  
Flow Reactor ◽  
Fixed Bed ◽  
Catalytic Performance ◽  
Active Species ◽  
Iron Complex ◽  
Methanol Dehydration ◽  
Low Carbon ◽  
Zeolite Framework ◽  
Preparation Methods ◽  
Binuclear Iron

Iron-supported HZSM-5 catalysts were prepared by hydrothermal (Fe-HZSM-5_HYD) and impregnation methods (Fe/HZSM-5_IMP). The active species of binuclear-iron complex and iron-substituted zeolite framework, confirmed by EXAFS analysis, were observed on Fe/HZSM-5_IMP and Fe-HZSM-5_HYD, respectively. The catalysts were used for production of dimethyl ether (DME) by methanol dehydration at 200-350 °C using fixed bed flow reactor. Fe/HZSM-5_IMP showed higher catalytic conversion than Fe-HZSM-5_HYD. However, the Fe/HZSM-5_IMP catalyst was less selective to DME product and strongly deactivated for 24h. The deactivation might due to transformation of binuclear-iron to the a-iron site which was strong acidic strengh. The iron-substituted zeolite framework of Fe-HZSM-5_HYD showed high stability toward methanol dehydration. Moreover, the catalyst showed advantages of good selective to DME and low carbon deposition on surface. These results suggested that the iron-substituted zeolite framework structure could improve catalytic performance for mrthanol dehydration.

Replication of Mesoporous Aluminosilicate Molecular Sieves (RMMs) with Zeolite Framework from Mesoporous Carbons (CMKs)

2004 ◽  
Vol 16 (16) ◽  
pp. 3168-3175 ◽  
Author(s):  
Ayyamperumal Sakthivel ◽  
Shing-Jong Huang ◽  
Wen-Hua Chen ◽  
Zon-Huang Lan ◽  
Kuei-Hsien Chen ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Mesoporous Carbons ◽  
Zeolite Framework ◽  
Mesoporous Aluminosilicate

scholarly journals Flexibility windows in faujasite with explicit water and methanol extra-framework content

2015 ◽  
Vol 44 (13) ◽  
pp. 5978-5984 ◽  
Author(s):  
Stephen A. Wells ◽  
Ka Ming Leung ◽  
Peter P. Edwards ◽  
Asel Sartbaeva
Keyword(s):  
Zeolite Framework ◽  
Explicit Water ◽  
Water Contents

Geometric simulations reveal limits on flexibility in a zeolite framework (faujasite) with extra-framework methanol and water contents explicitly present.

“Secondary” descriptor development for zeolite framework design: an informatics approach

2003 ◽  
Vol 254 (1) ◽  
pp. 147-160 ◽  
Author(s):  
Arun Rajagopalan ◽  
Changwon Suh ◽  
Xiang Li ◽  
Krishna Rajan
Keyword(s):  
Zeolite Framework ◽  
Framework Design
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