Search results for "ZEOLITE"
showing 10 items of 203 documents
Stabilized Ru[(H2O)(6)](3+) in Confined Spaces (MOFs and Zeolites) Catalyzes the lmination of Primary Alcohols under Atmospheric Conditions with Wide…
2018
[EN] Imines are ubiquitous intermediates in organic synthesis, and the metal-mediated imination of alcohols is one of the most direct and simple methods for their synthesis. However, reported protocols lack compatibility with many other functional groups since basic supports/media, pure oxygen atmospheres, and/or released hydrogen gas are required during reaction. Here we show that, in contrast to previous metal-catalyzed methods, hexa-aqueous Ru(III) catalyzes the imination of primary alcohols with very wide functional group tolerance, at slightly acid pH and under low oxygen atmospheres. The inorganic metal complex can be supported and stabilized, integrally, within either faujasite-type …
Sorption Studies on Large ZSM-5 Crystals: The Influence of Aluminium Content, The Type of Exchangeable Cations and the Temperature on Nitrogen Hyster…
1988
Abstract In comparison to polycrystalline powder large ZSM-5 crystals are best suited for high resolution sorption experiments. The nitrogen isotherms on HZSM-5 at 77 K reveal a pronounced hysteresis loop. The shape and position of the hysteresis relative to the pressure axis has been found to be affected by the aluminium content of the zeolite, the type of framework cation and the sorption temperature. The occurence of the hysteresis and its changes are assigned to a transition from a liquidlike to a solid-like adsorbed phase of nitrogen. The micropore volume v mp derived from the argon and nitrogen isotherm (s. Fig. 2b, first plateau) and calculated according to DUBININ-RADUSHKEVICH was c…
Communication: Evidence of structural phase transitions in silicalite-1 by infrared spectroscopy
2013
The adsorption of trichloroethylene, perchloroethylene, and p-xylene on a MFI (Mobile-FIve) zeolite is studied using in situ FTIR spectroscopy at 298 K. Spectra of self-supported zeolites in contact with increasing pressures of pure gas were recorded at equilibrium in the mid-infrared domain. Analysis of the evolution of the shape and location of vibrational bands of the zeolite as a function of the amount adsorbed allowed the observation of structural modifications of the adsorbent for the first time by infrared spectroscopy.
MOF‐derived/zeolite hybrid catalyst for the production of light olefins from CO2
2020
ispartof: ChemCatChem vol:12 issue:22 pages:5750-5758 status: published
Selective adsorption of ethyl mercaptan on NaX zeolite.
2008
Adsorption on microporous solid is an alternative technique to remove mercaptans from natural gases. The present study gives equilibrium adsorption data on NaX faujasite for some pure gases representative of natural gas impurities (ethyl mercaptan, toluene and n-heptane) and their binary mixtures. The first part of the paper is devoted to the adsorption of pure gases. Experimental results show that the zeolite has a high adsorption affinity for ethyl mercaptan, toluene and n-heptane. In the second part, we examine adsorption isotherms for binary mixtures of ethyl mercaptan and toluene or n-heptane over a large domain of composition. Coadsorption enthalpies are also determined. These experim…
Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension
2015
[EN] Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedure that extends the life of Mo/zeolite based catalysts by combining reaction periods of 1.5 h with 0.5 h regeneration steps in a continuous cyclic mode and methane activation after each regeneration…
Physicochemical Characterization of Isomorphously Substituted FeZSM-5 during Activation
2002
Physicochemical characteristics of isomorphously substituted FeZSM-5 both after preparation and after activation have been determined by gas (Ar and N2) physisorption, 27Al and 29Si magic-angle spinning–nuclear magnetic resonance, NH3 temperature-programmed desorption, transmission electron microscopy, H2 temperature-programmed reduction (TPR), 57Fe Mossbauer spectroscopy, and voltammetric response techniques. The activation of as-synthesized FeZSM-5 comprises calcination at 823 K and a subsequent steam treatment (300 mbar of H2O in N2) at 873 K. Calcination leads to complete removal of the template. During this process a significant fraction of iron is dislodged to extraframework positions…
Anion template effect and the polymerization degree
2005
Two 2D (M1 and M2) and one 1D (M3) metal‐organic frameworks (MOFs) have been prepared from pyridine functionalized tetradentate ligand tetrakis(nicotinoxymethyl)methane TNM with silver tetrafluoroborate, nickel chloride, and copper hexafluorophosphate. M1 manifests a previously unpresented mode of 4,4 threefold parallel interpenetration for 2D MOFs. Large channels (vdW diameter 9.4 Å) through eclipsed 2D layers of M2 were observed. While the open space percentage in the noninterpenetrated M2 was 38.0 %, the triple interpenetration of the sheets of M1 reduced the void to 10.8 %. With the same ligand and a similar, weakly coordinating anion as that in M1, the structure M3 was rendered one‐dim…
Investigation of nitrogen and helium cryosorption on molecular sieves
1994
Abstract The helium-containing plasma exhaust gases of Tokamaks can be pumped by cryopumps using cryosorption panels coated with solid porous materials. The best pumping characteristics are achieved with activated charcoal and molecular sieves at temperatures below 10 K. In order to select the most suitable material with respect to cryosorption properties and reactivation behaviour, comparative tests on various molecular sieve types differing in cavity structure, pore size and polarity were carried out. Nitrogen and helium adsorption isotherms were determined at LN 2 temperature and at 14.5 K, respectively, expecting that an extrapolation mechanism between the adsorption properties of both …
Hydrogenation of Aromatics in Diesel Fuels on Pt/MCM-41 Catalysts
1997
Abstract The hydrogenation activity of Pt supported on two mesoporous MCM-41 samples differing in their chemical composition has been studied by following the kinetics of the hydrogenation of naphthalene at 225–275°C reaction temperature and 5.0 MPa total pressure and by comparing the kinetic parameters obtained with Pt supported on a mesoporous amorphous silica-alumina (MSA) and other conventional supports, such as commercial amorphous silica-alumina (ASA), zeolite USY, γ-alumina, and silica. The two mesoporous MCM-41 and MSA materials having very high surface areas allowed for a better dispersion of the Pt particles, and they showed a superior overall hydrogenation activity as compared to…