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Synthesis of zeolite membranes
Haiyang Jiang,Baoquan Zhang,Y. S. Lin,Yongdan Li
Chinese Science Bulletin , 2004, DOI: 10.1360/03wb0146
Abstract: Zeolite membranes offer great application potentials in membrane separation and/or reaction due to their excellent separation performance and catalytic ability. Up to present, various synthesis methods of zeolite membranes have been developed, including embedded method, in-situ hydrothermal synthesis method, and secondary growth method etc. Compared with the in-situ hydrothermal synthesis method, the secondary growth method possesses a variety of advantages such as easier operation, higher controllability in crystal orientation, microstructure and film thickness, leading to much better reproducibility. This review provides a concise summary and analysis of various synthesis methods reported in the literature. In particular, the secondary growth method was discussed in detail in terms of crystal orientation, defects and crystal grain layers. Some critical issues were also highlighted, which were conducive to the improvement in the synthesis technology of zeolite membranes.
Magneto-orbital effect without spin-orbit interactions --- noncentrosymmetric zeolite-templated carbon structure  [PDF]
Takashi Koretsune,Ryotaro Arita,Hideo Aoki
Physics , 2012, DOI: 10.1103/PhysRevB.86.125207
Abstract: A peculiar manifestation of orbital angular momentum is proposed for a zeolite-templated carbon system, C36H9. The structure, being a network of nanoflakes in the shape of a "pinwheel", lacks inversion symmetry. While the unit cell is large, the electronic structure obtained with a first-principles density functional theory and captured as an effective tight-binding model in terms of maximally-localized Wannier functions, exhibits an unusual feature that the valence band top comes from two chiral states having orbital magnetic momenta of $\pm 1$. The noncentrosymmetric lattice structure then makes the band dispersion asymmetric, as reminiscent of, but totally different from, spin-orbit systems. The unusual feature is predicted to imply a current-induced orbital magnetism when holes are doped.
Synthesis and characterization of carbon cryogel/zeolite composites  [PDF]
Biljana Babi?,Maja Kokune?oski,Jelena Gulicovski,Marija Prekajski
Processing and Application of Ceramics , 2011,
Abstract: A novel method for synthesis of carbon cryogel/zeolite composites was obtained. Method considers forming of carbon cryogel from the sol-gel polycondenzation of resorcinol and formaldehyde, followed by freeze drying, and subsequent pyrolysis in presence of different amount of zeolite. Characterization of composite materials by nitrogen adsorption shows that samples are micro- and mesoporous and that specific surface area decrease with increasing the amount of zeolite in samples. XRD method confirms amorphous structure of carbon cryogel and crystalline structure of zeolite, i.e. structure of zeolite has not been destroyed by carbonization process. SEM and EDX analyses reveal homogenous distribution of zeolite through out carbon cryogel and corresponding composition.
Synthesis of zeolite LTA from thermally treated kaolinite
Ríos Reyes,Carlos Alberto; Williams,Craig Denver; Castellanos Alarcón,Oscar Mauricio;
Revista Facultad de Ingeniería Universidad de Antioquia , 2010,
Abstract: x-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, 29si and 27al nuclear magnetic resonance and thermogravimetric analyses have been used to examine the synthesis of zeolite lta and associated phases from metakaolinite. however, the synthesis product was controlled by the experimental method, taking into account that the classic hydrothermal transformation of the starting material produced a mixture of different zeolite-type structures, whereas the alkaline fusion approach promoted the crystallization of pure zeolite lta.
On the formation process of silicon carbide nanophases via hydrogenated thermally induced templated synthesis  [PDF]
Mark. H. Ruemmeli,Ewa Borowiak-Palen,Thomas Gemming,Martin Knupfer,Kati Biedermann,Ryszard J. Kalenczuk,Thomas Pichler
Physics , 2004, DOI: 10.1007/s00339-004-3048-5
Abstract: A thermally induced templated synthesis for SiC nanotubes and nanofibers using ammonia or nitrogen as a carrier gas, single wall carbon nanotubes (SWCNT) as templates as well as gaseous Si is presented. The bundles of SWCNT act as both the carbon source and as a nanoframe from which SiC structuctures form. Depending on the duration of the thermally induced templated reaction, for a fixed temperature, carrier gas, and gas pressure, various SiC nanostructures are obtained. These structures include SiC nanorods coated in C, SiC nanorods, SiC nanotubes, and SiC nanocrytals. From our analysis using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), electron energy-loss spectroscopy (EELS), electron diffraction (EDX), optical absorption spectroscopy and Raman spectroscopy as probes we prove that H has a key role on the morphology and stochiometry of the different SiC nanostructures.
Metal clusters in zeolite 4A obtained by synthesis process  [PDF]
E. David
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The goal of this paper is to study the possibility of obtaining of the supported metal clusters in zeolite 4A that are a new class of composite materials with application in sorption and catalytic processes.Design/methodology/approach: The materials were fabricated by synthesis process involving organo-metallic chemistry on surfaces, gas-phase cluster chemistry and chemistry in zeolite cages. The magnesium clusters in zeolite 4A(Mg/Z4A) has been prepared by ion exchange, followed by calcination and reduction processes. The metals are introduced as cationic form, which replace cations such as natrium from zeolite and then treated by heating in oxidized mixture or air and reduced in hydrogen. The activation and reduction treatments give the highest metal dispersions. The texture studies, X-ray diffraction , transmission electron microscopy (TEM) and atomic absorption were used for to characterize these materials.Findings: Through this study it was determined the structures and properties of (Mg/Z4A) composites and then these properties were compared with zeolite 4A properties without metal addition. It was found that Mg/Z4A have new properties, with high catalytic effect and the reducing process are decisively regarding the size and the placement of the metal magnesium particles into zeolite 4A.Research limitations/implications: It is noticed, that increase of the reducing temperature over 600oC promotes the forming of metal clusters with great sizes at the external surface of zeolite 4A and the catalitycal activity is diminished. The activation and reduction treatments give the highest metal dispersions, but the most uniform metal clusters are not easily formed.Practical implications: Obtained results allowed to optimize the catalytic activity of the supported metals on zeolite.Originality/value: This work contains several new aspects, which are: the conditions for performing the magnesium metal clusters in zeolite 4A cages, wide range of investigated materials and combining the microstructure of the material with the susceptibility of the formation of the metal clusters in zeolite 4A surface. Also, composite materials have been obtained following a simple and low-cost route.
Synthesis of cubic Y zeolite using a pulsed microwave heating system
Araújo, L.R.G. de;Cavalcante Jr., C.L.;Farias, K.M.;Guedes, I.;Sasaki, J.M.;Freire, P.T.C.;Melo, F.E.A.;Mendes-Filho, J.;
Materials Research , 1999, DOI: 10.1590/S1516-14391999000200011
Abstract: cubic y zeolite were successfully synthesized using microwave heating for 18 - 25 min, whereas 10 - 50 h are required by hydrothermal heating technique depending upon the lattice si/al ratio. to this end, we used a commercial microwave oven modified in order to provide pulsed microwave pumping on the synthesis mixtures. the obtained samples were analyzed by x-ray diffraction, bet surface area and infrared spectroscopy measurements. as a result, we verify that y zeolite samples obtained from hydrogels containing low aluminum contents, present a good degree of crystallinity and then can be suitable for using in adsorption and catalysis experiments.
Synthesis of cubic Y zeolite using a pulsed microwave heating system
Araújo L.R.G. de,Cavalcante Jr. C.L.,Farias K.M.,Guedes I.
Materials Research , 1999,
Abstract: Cubic Y zeolite were successfully synthesized using microwave heating for 18 - 25 min, whereas 10 - 50 h are required by hydrothermal heating technique depending upon the lattice Si/Al ratio. To this end, we used a commercial microwave oven modified in order to provide pulsed microwave pumping on the synthesis mixtures. The obtained samples were analyzed by X-ray diffraction, BET surface area and infrared spectroscopy measurements. As a result, we verify that Y zeolite samples obtained from hydrogels containing low aluminum contents, present a good degree of crystallinity and then can be suitable for using in adsorption and catalysis experiments.
One-Pot Synthesis of Dimethyl Carbonate over Basic Zeolite Catalysts  [PDF]
Wenshuai Xu, Shengrong Ji, Wei Quan, Jianqiang Yu
Modern Research in Catalysis (MRC) , 2013, DOI: 10.4236/mrc.2013.22A004
Abstract:

One-pot synthesis of dimethyl carbonate (DMC) from methanol, propylene oxide (PO) and carbon dioxide has been investigated using the basic zeolites as catalysts. Among the zeolites studied, Beta showed the best catalytic performance for DMC production. That the desilication of zeolite structure resulted in a hierarchical porosity of Beta, leading to more amount of KOH can be loaded on the surface of zeolite and therefore enhancing the base strength of the catalyst was proposed to be the reason for improved catalytic performance.

Monte Carlo Study of the Nucleation Process during Zeolite Synthesis  [PDF]
Minghong G. Wu,Michael W. Deem
Physics , 2001, DOI: 10.1063/1.1430742
Abstract: An atomic-scale model for silicate solutions is introduced for investigation of the nucleation process during zeolite synthesis in the absence of a structure directing agent. Monte Carlo schemes are developed to determine the equilibrium distribution of silicate cluster sizes within the context of this model. How the nucleation barrier and critical cluster size change with Si monomer concentration is discussed. Distance and angle histograms as well as ring size distributions are calculated and compared with known zeolite structures. The free energies of critical clusters are compared with those for small clusters of alpha-quartz.
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