نتایج جستجو برای: modified zeolites

تعداد نتایج: 255306  

2015
Yuanyuan Yue Haiyan Liu Pei Yuan Chengzhong Yu Xiaojun Bao

Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanosc...

2011
Aleksandra Daković

The potential of surfactant modified zeolites as adsorbents for mycotoxins and as carrier of the pharmaceutical drugs was investigated. Ochratoxin A OCHRA (mycotoxin) and diclofenac sodium DS (anti-inflamatory drug) were used as model substances. Surface of the clinoptilolite was modified with different amounts of quaternary ammonium ions (hexadecyltrimethyl ammonium HDTMA or octadecyldimethylb...

Journal: :Journal of Catalysis 2022

• Stabilization of silicogermanates by substitution Germanium for other elements. A treatment using silicon tetrachloride successfully stabilized a silicogermanate. Transformation non-stable silicogermanate into stable aluminosilicogermanate. Introduction acid sites zeolites through post-treatments. An active extra-large pore zeolite catalytic transformation bulky molecules. Owing to their pore...

Journal: :Molecules 2017
Magdi El Fergani Natalia Candu Simona M Coman Vasile I Parvulescu

The one-pot production of succinic acid from glucose was investigated in pure hot water as solvent using Nb (0.02 and 0.05 moles%)-Beta zeolites obtained by a post-synthesis methodology. Structurally, they are comprised of residual framework Al-acid sites, extra-framework isolated Nb (V) and Nb₂O₅ pore-encapsulated clusters. The Nb-modified Beta-zeolites acted as bi-functional catalysts in whic...

2012
Brigitte Servatius Herman Servatius

We study the background associated with phenomena observed in zeolites using combinatorial and geometric techniques. We define combinatorial d-dimensional zeolites and show that not all combinatorial zeolites have a unit distance realization inR , and of those that have a unit distance realization, not all have non-overlapping unit-distance realizations. Only few classes of finite 2-d zeolites ...

Journal: :Journal of the American Chemical Society 2008
Jun Huang Yijiao Jiang V R Reddy Marthala Michael Hunger

The direct experimental evidence shows that ethylbenzene disproportionation is a transition state shape selective reaction on zeolites: a bimolecular reaction mechanism via diphenylethane-mediated pathway on large-pore zeolites X and Y (ca. 0.74 nm) and a monomolecular reaction mechanism on medium-pore zeolites ZSM-5 (ca. 0.56 nm) via the ethoxy-mediated intermolecular ethyl group transfer. The...

Abstract Background and purpose: Natural zeolites are widely used for the purification of water and wastewater. Nevertheless the selectivity of clinoptilolite (a common zeolite mineral) for cadmium is known to be particularly low. In order to enhance the zeolites’ sorption capacity for cadmium, we treated natural clinoptilolite with sulfuric acid solutions and investigated the sorption of ca...

Journal: :Chemical communications 2001
T Wada M Shikimi Y Inoue G Lem N J Turro

Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by (R)- or (S)-1-methylheptyl benzoate immobilized in zeolite supercages afforded the respective enantiomer pair, (-)- and (+)-(E)-isomer (1E) in 5% enantiomeric excess, whilst racemic 1E was obtained upon homogeneous-phase photosensitization with the same antipodal sensitizer pair, thus demonstrating for the first time tha...

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