Topic
Zeolite
About: Zeolite is a research topic. Over the lifetime, 35635 publications have been published within this topic receiving 739192 citations. The topic is also known as: zeolites & zeolite mineral group.
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TL;DR: It is shown that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolites that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell.
Abstract: Zeolites-microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1 nm, often goes hand-in-hand with diffusion limitations that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which reduces diffusion path lengths and thus improves molecular diffusion. This has been realized by synthesizing zeolite nanocrystals, by exfoliating layered zeolites, and by introducing mesopores in the microporous material through templating strategies or demetallation processes. But except for the exfoliation, none of these strategies has produced 'ultrathin' zeolites with thicknesses below 5 nm. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolite nanosheets that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The large number of acid sites on the external surface of these zeolites renders them highly active for the catalytic conversion of large organic molecules, and the reduced crystal thickness facilitates diffusion and thereby dramatically suppresses catalyst deactivation through coke deposition during methanol-to-gasoline conversion. We expect that our synthesis approach could be applied to other zeolites to improve their performance in a range of important catalytic applications.
1,839 citations
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TL;DR: A review of the recent development of natural zeolites as adsorbents in water and wastewater treatment can be found in this paper, where the properties and modification of natural zerosite are discussed and the modified zerosites achieving higher adsorption capacity for organics and anions.
1,794 citations
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TL;DR: The results show that natural zeolites hold great potential to remove cationic heavy metal species from industrial wastewater.
1,456 citations
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TL;DR: The intercalation of polynuclear hydroxy metal cations and metal cluster cations in smectites affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolite catalysts.
Abstract: Recent advances in the intercalation of metal complex cations in smectite clay minerals are leading to the development of new classes of selective heterogeneous catalysts. The selectivity of both metal-catalyzed and proton-catalyzed chemical conversions in clay intercalates can often be regulated by controlling surface chemical equilibria, interlamellar swelling, or reactant pair proximity in the interlayer regions. Also, the intercalation of polynuclear hydroxy metal cations and metal cluster cations in smectites affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolite catalysts.
1,456 citations
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TL;DR: In this article, the Na-exchanged clinoptilolite in presence of ammonium ions has been analyzed and the selectivity of the Na exchange is calculated by plotting the exchange isotherms relative to the various cations.
1,364 citations