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https://www.readbyqxmd.com/read/29148783/in-situ-assembly-of-nanoparticles-into-hierarchical-beta-zeolite-with-tailored-simple-organic-molecule
#1
Kai Zhang, Zewei Liu, Xin Yan, Xuelong Hao, Min Wang, Chao Li, Hongxia Xi
A hierarchically structured beta zeolite with intercrystalline mesopores was successfully synthesized via in situ assembly of nanoparticles by employing a simple organic molecule N2-p-N2, tailored form polyquaternium surfactant, with no hydrophobic long chain. The obtained material was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms and computer simulation. These results indicated that the tailored template molecule N2-p-N2 without hydrophobic long chain tail still can direct the zeolite crystallization, the hydrophobic long chain tail is not necessary during the mesoporous Beta zeolite formation...
November 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29148727/substrate-assisted-in-situ-confinement-pyrolysis-of-zeolitic-imidazolate-frameworks-to-nitrogen-doped-hierarchical-porous-carbon-nanoframes-with-superior-lithium-storage
#2
Wei Tian, Jialiang Liu, Yixian Wang, Jingyan Liu, Yanpeng Li, Mingbo Wu
Porous carbons generated from the direct pyrolysis of metal organic frameworks (MOFs) have showed great potential as a kind of promising electrode materials for lithium-ion batteries (LIBs). However, several common drawbacks, such as the inevitable structural damage during carbonization process and intrinsic micropore-dominated feature of MOFs-derived products, largely impede the exposure of active sites and mass transfer, thus usually resulting in inferior electrochemical performances. In this work, an effective and controllable approach was reported to construct nitrogen-doped hierarchical porous carbon nanoframes (N-HPCFs) through in situ pyrolysis transformation of small-sized zeolitic imidazolate frameworks (ZIFs) that are in advance combined with a two-dimensional substrate templated from g-C3N4...
November 17, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29147509/composition-driven-cu-speciation-and-reducibility-in-cu-cha-zeolite-catalysts-a-multivariate-xas-ftir-approach-to-complexity
#3
A Martini, E Borfecchia, K A Lomachenko, I A Pankin, C Negri, G Berlier, P Beato, H Falsig, S Bordiga, C Lamberti
The small pore Cu-CHA zeolite is attracting increasing attention as a versatile platform to design novel single-site catalysts for deNO x applications and for the direct conversion of methane to methanol. Understanding at the atomic scale how the catalyst composition influences the Cu-species formed during thermal activation is a key step to unveil the relevant composition-activity relationships. Herein, we explore by in situ XAS the impact of Cu-CHA catalyst composition on temperature-dependent Cu-speciation and reducibility...
October 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/29144129/efficient-mechanochemical-synthesis-of-polyoxometalate%C3%A2-zif-complexes-as-reusable-catalysts-for-highly-selective-oxidation
#4
Xiaoxiao Zhao, Yunpeng Duan, Fei Yang, Wei Wei, Yanqing Xu, Changwen Hu
One-pot mechanochemical synthesis was demonstrated to be an efficient strategy to synthesize host-guest POM⊂rho-ZIF complexes (POM = polyoxometalate; rho-ZIF = zeolitic imidazolate framework with rho topology) with high crystallinity. In this work, the metastable rho-ZIF with large interior cavities and windows was used as host matrix for encapsulating and immobilizing bulky guest molecules with high loading efficiency and chemical stability. As novel catalysts, POM⊂rho-ZIF complexes were found effective for the selective oxidation of a series of sulfides to sulfoxides...
November 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29143700/improved-three-dimensional-3d-resolution-of-electron-tomograms-using-robust-mathematical-data-processing-techniques
#5
Toby Sanders, Ilke Arslan
Electron tomography has become an essential tool for three-dimensional (3D) characterization of nanomaterials. In recent years, advances have been made in specimen preparation and mounting, acquisition geometries, and reconstruction algorithms. All of these components work together to optimize the resolution and clarity of an electron tomogram. However, one important component of the data-processing has received less attention: the 2D tilt series alignment. This is challenging for a number of reasons, namely because the nature of the data sets and the need to be coherently aligned over the full range of angles...
November 16, 2017: Microscopy and Microanalysis
https://www.readbyqxmd.com/read/29142616/scaling-relations-for-acidity-and-reactivity-of-zeolites
#6
Chong Liu, Ionut Tranca, Rutger A van Santen, Emiel J M Hensen, Evgeny A Pidko
Zeolites are widely applied as solid acid catalysts in various technological processes. In this work we have computationally investigated how catalytic reactivity scales with acidity for a range of zeolites with different topologies and chemical compositions. We found that straightforward correlations are limited to zeolites with the same topology. The adsorption energies of bases such as carbon monoxide (CO), acetonitrile (CH3CN), ammonia (NH3), trimethylamine (N(CH3)3), and pyridine (C5H5N) give the same trend of acid strength for FAU zeolites with varying composition...
October 26, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
https://www.readbyqxmd.com/read/29139603/catalytic-transfer-hydrogenation-of-biomass-derived-carbonyls-over-hafnium-based-metal-organic-frameworks
#7
Avelino Corma, Pilar García-García, Sergio Rojas-Buzo
A series of highly crystalline, porous, hafnium-based metal-organic frameworks (MOFs) have shown to catalyze the transfer hydrogenation reaction of levulinic ester to produce γ-valerolactone using isopropanol as hydrogen donor and the results are compared with the zirconium-based counterparts. The role of the metal center in Hf-MOFs has been identified and reaction parameters optimized. NMR studies with isotopically labeled isopropanol evidences that the transfer hydrogenation occurs via a direct intermolecular hydrogen transfer route...
November 15, 2017: ChemSusChem
https://www.readbyqxmd.com/read/29139299/integrating-zeolite-type-chalcogenide-with-titanium-dioxide-nanowires-for-enhanced-photoelectrochemical-activity
#8
Chengyu Mao, Yanxiang Wang, Wei Jiao, Xitong Chen, Qipu Lin, Mingli Deng, Yun Ling, Yaming Zhou, Xianhui Bu, Pingyun Feng
Developing photoanodes with efficient visible-light harvesting and excellent charge separation still remains a key challenge in photoelectrochemical water splitting. Here zeolite-type chalcogenide CPM-121 is integrated with TiO2 nanowires to form a heterostructured photoanode, in which crystalline CPM-121 particles serve as a visible light absorber and TiO2 nanowires serve as an electron conductor. Owing to the small band gap of chalcogenides, the hybrid electrode demonstrates obvious absorption in visible-light range...
November 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29137479/the-role-of-the-carbohydrates-in-plasmatic-membrane
#9
P Sprovieri, G Martino
In the following paper, authors describe glycans present on cell membranes as they affect the folding, the spatial arrangement, the behavior and the interaction with the substrate of some membrane proteins. Authors describe the synthesis and assembly of a glycan on a protein, the formation of N-glycans, the maturation of an N-glycan in different cellular compartments, the structure of the glycocalyx and how it interacts with any pathogens. The study of the E-cadherin and the potassium channel to demonstrate how glycans affect the spatial arrangement, the stability and activity of the glycoproteins on the membranes...
November 10, 2017: Physiological Research
https://www.readbyqxmd.com/read/29134091/synthesis-of-zeolites-na-a-and-na-x-from-tablet-compressed-and-calcinated-coal-fly-ash
#10
Tao Hu, Wenyan Gao, Xin Liu, Yifu Zhang, Changgong Meng
Zeolites Na-A and Na-X are important synthetic zeolites widely used for separation and adsorption in industry. It is of great significance to develop energy-efficient routines that can synthesize zeolites Na-A and Na-X from low-cost raw materials. Coal fly ash (CFA) is the major residue from the combustion of coal and biomass containing more than 85% SiO2 and Al2O3, which can readily replace the conventionally used sodium silicate and aluminate for zeolite synthesis. We used Na2CO3 to replace the expensive NaOH used for the calcination of CFA and showed that tablet compression can enhance the contact with Na2CO3 for the activation of CFA through calcination for the synthesis of zeolites Na-A and Na-X under mild conditions...
October 2017: Royal Society Open Science
https://www.readbyqxmd.com/read/29132107/removal-of-phosphate-from-water-by-lanthanum-modified-zeolites-obtained-from-fly-ash
#11
Joanna Goscianska, Magdalena Ptaszkowska-Koniarz, Marcin Frankowski, Malgorzata Franus, Rafal Panek, Wojciech Franus
The possibility and effectiveness of removal of phosphate from aqueous solutions with the use of new low-cost synthetic zeolites obtained from fly ash and modified with lanthanum, was studied. Physicochemical properties of the zeolites were characterized by different techniques such as X-ray diffraction, low-temperature nitrogen sorption and scanning electron microscopy. It has been established that lanthanum is preferentially located in the zeolites channels and cages, which is related to the ion-exchange method of modification...
November 10, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29131466/understanding-the-reactive-adsorption-of-h2s-and-co2-in-sodium-exchanged-zeolites
#12
Evgenii O Fetisov, Mansi S Shah, Christopher Knight, Michael Tsapatsis, Joern Ilja Siepmann
Purifying sour natural gas streams containing hydrogen sulfide and carbon dioxide has been a long-standing environmental and economic challenge. In the presence of cation-exchanged zeolites, these two acid gases can react to form carbonyl sulfide and water (H2S + CO2 <=> H2O + COS), but this reaction is rarely accounted for. In this work, we carry out reactive first-principles Monte Carlo (RxFPMC) simulations for mixtures of H2S and CO2 in all-silica and Na- exchanged forms of zeolite beta to understand the governing principles driving the enhanced conversion...
November 13, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29128763/improving-the-hydrocarbon-production-via-co-pyrolysis-of-bagasse-with-bio-plastic-and-dual-catalysts-layout
#13
Huiyan Zhang, Peter Keliona Wani Likun, Rui Xiao
Catalytic fast pyrolysis (CFP) of bagasse and bio-plastic (chicken feather keratin) and their mixtures were conducted to produce aromatic hydrocarbons over a HZSM-5, USY, and dual-catalysts layout. The effects of temperature, co-feeding ratios, feed-to-catalyst ratios and dual catalysts on hydrocarbon yields and selectivities were investigated. The results show a general improvement in the aromatic hydrocarbons yields in all cases compared to non-catalytic and pure biomass pyrolysis. The aromatic hydrocarbons increased by 10 fold with the increase of temperature from 400°C to 700°C...
November 8, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29127821/study-on-adsorption-of-rhodamine-b-onto-beta-zeolites-by-tuning-sio2-al2o3-ratio
#14
Zhi-Lin Cheng, Yan-Xiang Li, Zan Liu
The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO2/Al2O3 ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO2/Al2O3 ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations...
November 8, 2017: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/29119721/integrated-transmission-electron-and-single-molecule-fluorescence-microscopy-correlates-reactivity-with-ultrastructure-in-a-single-catalyst-particle
#15
Bert Marc Weckhuysen, Hans Gerritsen, Sajjad Mohammadian, Sam Kalirai, Pieter Bruijnincx, Florian Meirer, Eelco Vogt, Zoran Ristanovic, Frank Hendriks
Establishing structure-activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure-reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC catalyst particle using this novel SMF-TEM high-resolution combination...
November 9, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29119626/construction-of-zeolite-like-cluster-organic-frameworks-from-3d-4d-3d-3d-heterometallic-superterahedral-secondary-building-units-syntheses-structures-and-properties
#16
Xixiong Li, Shou-Tian Zheng, Li-Dan Lin, Chu-Chu Deng, Dan Zhao
Two zeolite-like cluster organic frameworks based on Cd-Cu/Mn-Cu heterometallic supertetrahedral secondary building units have been successfully constructed under solvothermal conditions, namely, Cu[Cd4Cu6(L)4(H2O)18](Ac)9*DMA*3H2O (1), and Cu[Mn4Cu6(L)4(Ac)3(H2O)12](Ac)6*CH3CN*13H2O (2), where H3L= 2-(hydroxymethyl)-2-(pyridin-4-yl)-1,3-propanediol, Ac = CH3COO-, DMA= N,N'-Dimethylacetamide. Single-crystal X-ray structural analysis reveal that both 1 and 2 exhibit 3-dimensional zeolite-like architectures with similar 4-connected conponents but possess definitely different topologies of diamondoid (Dia) and uncommon Ionsdaleite (Ion), respectively...
November 8, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29115309/structural-reconstruction-a-milestone-in-the-hydrothermal-synthesis-of-highly-active-sn-beta-zeolites
#17
Zhiguo Zhu, Hao Xu, Jingang Jiang, Haihong Wu, Peng Wu
A novel structural reconstruction strategy is proposed to prepare an active Sn-Beta catalyst with high Sn contents and a hydrophobic nature. Compared with post-synthesized Sn-Beta and state-of-the-art classic fluoride-mediated Sn-Beta-F, this Sn-Beta zeolite exhibits unparalleled active site-based turnover frequency for desirable products and in particular catalyst weight-based space-time-yields in various redox reactions of ketones.
November 8, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29112777/elucidating-the-distribution-and-speciation-of-boron-and-cesium-in-bcsx-zeolite-catalysts-for-styrene-production
#18
Antonio J Martín, Sharon Mitchell, Olivier Scholder, René Verel, Roland Hauert, Laetitia Bernard, Christopher Jensen, Meinhard Schwefer, Javier Pérez-Ramírez
An improved understanding of the nature and distribution of boron and cesium species in BCsX zeolites is prerequisite to guide future developments in the environmentally attractive yet challenging production of styrene via the side-chain alkylation of toluene with methanol. Here, standard characterization and catalytic tests are complemented by integrated visualization through time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy and detailed assessment by 133Cs and 11B nuclear magnetic resonance spectroscopy, to correlate the properties and performance during the successive ion exchange and impregnation steps in the preparation of both powders and millimeter-sized granules...
November 7, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29112390/aerobic-oxidations-of-light-alkanes-over-solid-metal-oxide-catalysts
#19
Joseph T Grant, Juan M Venegas, William P McDermott, Ive Hermans
Heterogeneous metal oxide catalysts are widely studied for the aerobic oxidations of C1-C4 alkanes to form olefins and oxygenates. In this review, we outline the properties of supported metal oxides, mixed-metal oxides, and zeolites and detail their most common applications as catalysts for partial oxidations of light alkanes. By doing this we establish similarities between different classes of metal oxides and identify common themes in reaction mechanisms and research strategies for catalyst improvement. For example, almost all partial alkane oxidations, regardless of the metal oxide, follow Mars-van Krevelen reaction kinetics, which utilize lattice oxygen atoms to reoxidize the reduced metal centers while the gaseous O2 reactant replenishes these lattice oxygen vacancies...
November 7, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/29108622/encapsulation-of-lipase-within-metal-organic-framework-mof-with-enhanced-activity-intensified-under-ultrasound
#20
Shamraja S Nadar, Virendra K Rathod
The enzyme under lower-intensity ultrasonic irradiation leads to favorable conformational changes, thereby enhancing its activity. In this study, lipase activity was augmented upto 1.6-folds after ultrasonic treatment at 22kHz and 11.38Wcm(-2) for 25min. This highly activated lipase was encapsulated within zeolite imidazolate framework-8 (ZIF-8) as a metal-organic framework (MOF) material via facile one-step biomineralization method by simply mixing aqueous solution of 2-methylimidazole (13.3mmol) and zinc acetate (1...
January 2018: Enzyme and Microbial Technology
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