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Deizi V Peron - One of the best experts on this subject based on the ideXlab platform.
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external surface phenomena in dealumination and desilication of large single crystals of zsm 5 zeolite synthesized from a sustainable source
Microporous and Mesoporous Materials, 2019Co-Authors: Deizi V Peron, Vladimir L Zholobenko, James Henrique Dos Santos De Melo, Mickael Capron, Nicolas Nuns, Michele Oberson De Souza, Liliana Amaral Feris, Nilson Romeu Marcilio, Vitaly V OrdomskyAbstract:Abstract Zeolite dealumination and desilication are common methods, which improve accessibility of the active sites located inside the zeolite crystallites and tune the zeolite acidity. The exact mechanism of these post-synthesis zeolite treatments remains under discussion. In this paper, a series of dealuminated and desilicated ZSM-5 Zeolites are prepared using single or combined post-synthesis dealumination and desilication of large zeolite single crystals with oxalic acid and sodium hydroxide. The ZSM-5 zeolite has been synthesized using silica extracted from fly ash. Zeolite desilication results in the potholes, leaf-type structures and other clearly visible defects on the surface of zeolite crystallites, while the effect of dealumination is less pronounced. The low temperature nitrogen adsorption suggests the formation of mesopores in the Zeolites formed by the voids between and in the irregular zeolite crystallites produced during post-synthesis treatments. 27Al and 29Si MAS NMR in combination with XRD data are indicative of only minor modifications of the bulk zeolite structure during dealumination and desilication. The total Bronsted acidity only slightly decreases and is not affected by the type of zeolite post-synthesis treatment. After desilication of large single crystals of ZSM-5, noticeable enhancement of the Bronsted acidity on the zeolite external surface has been detected by FTIR of adsorbed collidine. The Zeolites with higher acidity on the external surface have shown higher activity in the anisole acylation with hexanoic acid. A combination of characterization techniques suggests that the dealumination and desilication of the large crystals of ZSM-5 zeolite using post-synthesis treatments respectively with acid and alkali selectively starts at the zeolite external surface.
Vitaly V Ordomsky - One of the best experts on this subject based on the ideXlab platform.
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external surface phenomena in dealumination and desilication of large single crystals of zsm 5 zeolite synthesized from a sustainable source
Microporous and Mesoporous Materials, 2019Co-Authors: Deizi V Peron, Vladimir L Zholobenko, James Henrique Dos Santos De Melo, Mickael Capron, Nicolas Nuns, Michele Oberson De Souza, Liliana Amaral Feris, Nilson Romeu Marcilio, Vitaly V OrdomskyAbstract:Abstract Zeolite dealumination and desilication are common methods, which improve accessibility of the active sites located inside the zeolite crystallites and tune the zeolite acidity. The exact mechanism of these post-synthesis zeolite treatments remains under discussion. In this paper, a series of dealuminated and desilicated ZSM-5 Zeolites are prepared using single or combined post-synthesis dealumination and desilication of large zeolite single crystals with oxalic acid and sodium hydroxide. The ZSM-5 zeolite has been synthesized using silica extracted from fly ash. Zeolite desilication results in the potholes, leaf-type structures and other clearly visible defects on the surface of zeolite crystallites, while the effect of dealumination is less pronounced. The low temperature nitrogen adsorption suggests the formation of mesopores in the Zeolites formed by the voids between and in the irregular zeolite crystallites produced during post-synthesis treatments. 27Al and 29Si MAS NMR in combination with XRD data are indicative of only minor modifications of the bulk zeolite structure during dealumination and desilication. The total Bronsted acidity only slightly decreases and is not affected by the type of zeolite post-synthesis treatment. After desilication of large single crystals of ZSM-5, noticeable enhancement of the Bronsted acidity on the zeolite external surface has been detected by FTIR of adsorbed collidine. The Zeolites with higher acidity on the external surface have shown higher activity in the anisole acylation with hexanoic acid. A combination of characterization techniques suggests that the dealumination and desilication of the large crystals of ZSM-5 zeolite using post-synthesis treatments respectively with acid and alkali selectively starts at the zeolite external surface.
Takao Masuda - One of the best experts on this subject based on the ideXlab platform.
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kinetics of n hexane cracking over zsm 5 Zeolites effect of crystal size on effectiveness factor and catalyst lifetime
Chemical Engineering Journal, 2012Co-Authors: Hiroki Konno, Takuya Okamura, Takahito Kawahara, Teruoki Tago, Yuta Nakasaka, Takao MasudaAbstract:Abstract The catalytic cracking of n -hexane over ZSM-5 zeolite (MFI-type zeolite, Si/Al = 150 and 240) catalysts was examined at reaction temperatures ranging from 823 to 923 K under atmospheric pressure. The reaction rate constants and activation energies of n -hexane cracking over ZSM-5 Zeolites with various crystal sizes and Si/Al ratios were evaluated. The catalytic cracking of n -hexane was first order with respect to the n -hexane concentration, and the activation energies of n -hexane cracking over ZSM-5 Zeolites were found to be approximately 123–128 kJ mol −1 . Compared with the macro-sized zeolite, the nano-sized Zeolites exhibited high n -hexane conversion with stable activity for 50 h. This is because the cracking reaction with nano-sized zeolite proceeded under reaction-limiting conditions, whereas the reaction with macro-sized zeolite proceeded under transition conditions between reaction- and diffusion-limiting conditions. As a result, the application of nano-zeolite to the catalytic cracking of n -hexane was effective and gave light olefins with high yield and excellent stable activity.
Zhenghua Ping - One of the best experts on this subject based on the ideXlab platform.
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structure property relationships in sorption of vapours with different polarities in Zeolites and zeolite filled poly dimethylsiloxane
Physical Chemistry Chemical Physics, 1999Co-Authors: Hu Yang, Yingcai Long, Quang Trong Nguyen, Zhenghua PingAbstract:Three faujasite (FAU) zeolite samples with different Si:Al ratios and OH contents were prepared from a NaY-type zeolite and their structure was studied by XRD, 29Si NMR, 27Al NMR and IR. These studies showed that the SiCl4 treatment mainly dealuminated the starting NaY zeolite, while the additional hydrothermal treatment reduced the OH groups on the zeolite surface, and the final acid treatment removed further the residual Al traces in the framework. The sorption measurement shows that the zeolite affinity to a non-polar organic solvent increases with increasing Si:Al ratio and decreasing surface OH groups. When Zeolites were used to fill a poly(dimethylsiloxane) membrane, the affinity of the sorption sites and their capacity decreased, leading to a low contribution of the Zeolites to the sorption capacity of the composite membranes. The sorption selectivity of zeolite-filled membranes was consistent with that of pure Zeolites at low solvent activities, but at high activities, the sorption property of the PDMS matrix prevailed.
Oliver Schäf - One of the best experts on this subject based on the ideXlab platform.
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The effects of the Fenton reaction are limited by Zeolites in vitro
Microporous and Mesoporous Materials, 2015Co-Authors: Julien Fromonot, Pierre Suchon, Laurie Bruzzese, Nathalie Kipson, E. Fenouillet, Bernard Mallet, Régis Guieu, Oliver SchäfAbstract:We report the effects of zeolite pore systems in limiting the oxidation of ascorbic acid (vitamin C) in plasma using the mixing of FeCl2 and H2O2 (“Fenton solution”) as an oxidant. We tested three homemade Zeolites and nineteen natural Zeolites. Six polar Zeolites were effective in restricting the oxidation of vitamin C and the majority of them acted by chelation of ferrous/ferric chloride. Faujasite (FAU13x) was the most active ROS scavenger. On the other hand, two natural Zeolites, Goosecreekite and Stilbite (GOOnat and STInat), inhibited the oxidation of vitamin C by action on the reduction of hydrogen peroxide concentration to form H2O. Our hypothesis suggests that effective Zeolites have the advantage of never being saturated in the time. Here, for the first time, we identified a substrate (zeolite) which acts directly on the two substrates (Fe2+/H2O2) to limit ROS formation.
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The Reconstruction of Natural Zeolites - The reconstruction of natural Zeolites
2003Co-Authors: Habbib Ghobarkar, Oliver Schäf, Y. Massiani, Philippe KnauthAbstract:"The Reconstruction of Natural Zeolites" summarizes the known properties of natural Zeolites and, importantly, shows how they can be synthesized by simulating the conditions of natural formation. Systematically, a direct correlation between the glassy precursor composition and that of the zeolite product is established. The zeolite crystal morphology obtained at given synthesis conditions allows direct conclusions on the conditions of formation in nature.
