scholarly journals Si–OH Nest and Al Distribution of Silicalite-1 Core/Al-ZSM-5 Shell Zeolites for Methane Dehydroaromatization Reaction

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 647
Author(s):  
Do-Young Hong ◽  
Hyun Su Kim ◽  
Haoxiang Zhang ◽  
Su Kyung Kang ◽  
Elsa Tsegay Tikue ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Microstructural Analysis ◽  
Synthesis Method ◽  
Growth Period ◽  
Acid Sites ◽  
Core Shell ◽  
Methane Dehydroaromatization ◽  
Aggregative Growth ◽  
Channel Lengths ◽  
Coke Deactivation

Silicalite-1 core/Al-ZSM-5 shell zeolite crystals were prepared in various sizes for use as catalysts in methane dehydroaromatization (MDA), and the growth kinetics and corresponding physicochemical properties of this core–shell zeolite were investigated. Al-ZSM-5 was grown on silicalite-1 seeds at various Si/Al ratios. Core–shell catalysts of all size variations exhibited similar deactivation trends in the MDA reaction, with minor changes in aromatic yields despite clear differences in reaction channel lengths and acid-site properties. This outcome was shown to originate from the unique growth kinetics of the Al-ZSM-5 layer on silicalite-1 seeds, in which the Al species in the sol used in the synthesis were consumed quickly during the early aggregative growth period. This led to an interesting spatial distribution of Al in the Al-ZSM-5 layer, in that the inner layer was relatively Al-rich. This distribution is advantageous because it can inhibit coke deactivation, which often occurs at the catalyst surface during MDA. However, a substantial quantity of Si–OH nests, which inhibit the effective loading of Mo species at the acid sites of the crystals, were detected in the microstructural analysis of large crystals. Therefore, this study shows that silicalite-1 core/Al-ZSM-5 shell zeolites can be prepared for use as coke-resistant catalysts for the MDA reaction. Further work is required, however, to design a synthesis method which reduces the number of Si–OH nests formed.

Core–shell ZnSe–CdSe quantum dots: a facile approach via decomposition of cyclohexeno-1,2,3-selenadiazole

RSC Advances ◽  
2014 ◽  
Vol 4 (34) ◽  
pp. 17526-17532 ◽  
Author(s):  
Sreenu Bhanoth ◽  
Priyesh V. More ◽  
Aditi Jadhav ◽  
Pawan K. Khanna
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Synthesis Method ◽  
Core Shell ◽  
Cdse Quantum Dots ◽  
First Time

For the first time ever cyclohexeno-1,2,3-selenadiazole (SDZ) has been employed for the synthesis of core–shell ZnSe–CdSe quantum dots thus promoting an eco-friendly and reasonably less toxic synthesis method for such quantum dot hetero-structures.

Simple Strategy Generating Hydrothermally Stable Core–Shell Platinum Catalysts with Tunable Distribution of Acid Sites

ACS Catalysis ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 2796-2804 ◽  
Author(s):  
Houlin Wang ◽  
Minghan Liu ◽  
Yue Ma ◽  
Ke Gong ◽  
Wei Liu ◽  
...  
Keyword(s):  
Platinum Catalysts ◽  
Acid Sites ◽  
Core Shell ◽  
Simple Strategy ◽  
Stable Core

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.

Iron-Carbon Core-Shell Nanoparticles Obtained with Different Conditions of Synthesis

2017 ◽  
Vol 899 ◽  
pp. 221-226 ◽  
Author(s):  
M.M. Lima ◽  
J.P.Z. Gonçalves ◽  
C. Soares ◽  
Humberto Gracher Riella ◽  
S.C. Fernandes ◽  
...  
Keyword(s):  
Synthesis Method ◽  
Processing Parameters ◽  
Effect Of Temperature ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Shell Mass ◽  
The Core ◽  
Iron Precursor ◽  
Co Precipitation ◽  
Core Shell Nanoparticles

Core–shell Fe2O3@C nanoparticles are very studied due to its biocompatibility with plant and animals cells and due its special properties of chemical adsorption. Thus, the definition of an easy synthesis method of these nanoparticles is very important to the scientific studies and to future applications of these materials. For example, the properties of these nanoparticles depend of the combination between some processing parameters, as the temperature, time, chemical composition, atmosphere and others. The mass yield of the synthesis processes depend of these parameters and are important information. In this work the effect of temperature and of the concentration of the iron precursor were evaluated on the characteristics of the proposed nanoparticles. The nanostructures of Fe2O3 coated with carbon (Fe2O3@C) were synthetized by adapted co-precipitation hydrothermal rote. In 40.0 ml of distilled water was added 1.800 g of glucose, 6.006 g of urea, 0.500 g of polyethylene Glycol (PEG 1500) and different concentrations of iron nitrate Fe (NO2)3.9H2O and different temperature values were applied. The Fe2O3@C core-shell were characterized by scanning electron microscopy (SEM/FEG), Energy Dispersive Scanning (EDS) and X-ray Diffractions (XRD). Results showed that nanoparticles form clusters with different sizes that are dependent on the temperature values and Fe (NO3)3.9H2O concentration. The core-shell mass has a linear relation with the iron precursor mass and the reaction temperatures influences the microstructure of the core-shell nanoparticles.

Core–shell nanoparticles by silica coating of metal oxides in a dual-stage hydrothermal flow reactor

2016 ◽  
Vol 52 (16) ◽  
pp. 3434-3437 ◽  
Author(s):  
H. L. Hellstern ◽  
A. Mamakhel ◽  
M. Bremholm ◽  
B. B. Iversen
Keyword(s):  
Continuous Flow ◽  
Flow Reactor ◽  
Synthesis Method ◽  
Silica Coating ◽  
Core Shell ◽  
Narrow Size Distribution ◽  
Shell Nanoparticles ◽  
Coated Nanoparticles ◽  
Dual Stage ◽  
Core Shell Nanoparticles

A green, fast, high-throughput, continuous-flow hydrothermal synthesis method is explored for preparation of silica coated nanoparticles with narrow size distribution.

Methane dehydroaromatization by Mo-supported MFI-type zeolite with core–shell structure

2013 ◽  
Vol 453 ◽  
pp. 295-301 ◽  
Author(s):  
Zhonghao Jin ◽  
Su Liu ◽  
Lei Qin ◽  
Zhicheng Liu ◽  
Yangdong Wang ◽  
...  
Keyword(s):  
Shell Structure ◽  
Core Shell ◽  
Methane Dehydroaromatization ◽  
Type Zeolite ◽  
Core Shell Structure

scholarly journals Eu-Doped Zeolitic Imidazolate Framework-8 Modified Mixed-Crystal TiO2 for Efficient Removal of Basic Fuchsin from Effluent

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7265
Author(s):  
Wanqi Zhang ◽  
Hui Liu ◽  
Zhechen Liu ◽  
Yuhong An ◽  
Yuan Zhong ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Shell Structure ◽  
Mixed Crystal ◽  
Synthesis Method ◽  
Core Shell ◽  
Photocatalytic Efficiency ◽  
Basic Fuchsin ◽  
Zeolitic Imidazolate Framework ◽  
X Ray ◽  
Core Shell Structure

Zeolitic imidazolate framework-8 (ZIF-8) was doped with a rare-earth metal, Eu, using a solvent synthesis method evenly on the surface of a mixed-crystal TiO2(Mc-TiO2) structure in order to produce a core–shell structure composite ZIF-8(Eu)@Mc-TiO2 adsorption photocatalyst with good adsorption and photocatalytic properties. The characterisation of ZIF-8(Eu)@Mc-TiO2 was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET) and ultraviolet–visible light differential reflectance spectroscopy (UV-DRs). The results indicated that Eu-doped ZIF-8 was formed evenly on the Mc-TiO2 surface, a core–shell structure formed and the light-response range was enhanced greatly. The ZIF-8(Eu)@Mc-TiO2 for basic fuchsin was investigated to validate its photocatalytic performance. The effect of the Eu doping amount, basic fuchsin concentration and photocatalyst dosage on the photocatalytic efficiency were investigated. The results revealed that, when 5%-Eu-doped ZIF-8(Eu)@Mc-TiO2 (20 mg) was combined with 30 mg/L basic fuchsin (100 mL) under UV irradiation for 1 h, the photocatalytic efficiency could reach 99%. Further, it exhibited a good recycling performance. Thus, it shows certain advantages in its degradation rate and repeatability compared with previously reported materials. All of these factors suggested that, in an aqueous medium, ZIF-8(Eu)@Mc-TiO2 is an eco-friendly, sustainable and efficient material for the photocatalytic degradation of basic fuchsin.

scholarly journals Hierarchical H-MOR Zeolite Supported Vanadium Oxide for Dimethyl Ether Direct Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 628 ◽  
Author(s):  
Wenfeng Wang ◽  
Xiujuan Gao ◽  
Ru Feng ◽  
Qi Yang ◽  
Tao Zhang ◽  
...  
Keyword(s):  
Vanadium Oxide ◽  
Pore Structure ◽  
Dimethyl Ether ◽  
Active Sites ◽  
Synthesis Method ◽  
Product Distribution ◽  
Acid Sites ◽  
Synthesis Methods ◽  
Direct Oxidation ◽  
Post Synthesis

A series of hierarchical H-MOR zeolites with different pore structure were designed and synthesized by alkaline and alkaline-acid post-synthesis methods. The catalytic performance of hierarchical H-MOR zeolite-supported vanadium oxide was investigated for dimethyl ether (DME) direct oxidation. Different pore structures apparently affect the distribution of oxidation product distribution, especially the selectivity of DMMx and CO. The formation of mesopores for 10%V2O5/deAlmm-H-MOR markedly improved the DMMx selectivity up to 78.2% from 60.0%, and more notably, CO selectivity dropped to zero compared to that of 10%V2O5/H-MOR. The hierarchical H-MOR zeolites were confirmed to be successfully prepared by the post-synthesis method. Due to the presence of mesoporous structure, the dispersion of vanadium oxide species was enhanced, which could improve the reducibility of vanadium oxide species and also make better contact with the acid sites of zeolite to exert the synergistic effect of the bifunctional active sites. More importantly, the creation of mesopores was proved to be favorable to the mass transfer of intermediate and products to avoid the occurrence of secondary reaction, which could effectively suppress the formation of by-products. This work is helpful for us to provide a novel insight to design the catalyst with suitable pore structure to effectively synthesize diesel fuel additives from DME direct oxidation.

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