Low Temperature Studies Of Rare Gases Adsorbed On Molecular Sieve Materials

1991 ◽  
Vol 233 ◽  
Author(s):  
Graham F. Mccann ◽  
I. Gameson ◽  
W.J. Steado ◽  
T. Rayment ◽  
P.J. Barrie ◽  
...  
Keyword(s):  
Low Temperature ◽  
Phase Transformations ◽  
Adsorption Isotherms ◽  
Low Temperatures ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Variable Temperature ◽  
Rare Gases ◽  
X Ray Diffraction ◽  
X Ray

ABSTRACTX-ray diffraction (XRD) and adsorption isotherms have long been traditional methods of characterising molecular sieves. By combining these techniques at low temperatures with variable temperature 129-Xe N.M.R. we now have a fuller understanding of the behaviour of sorbed layers inside these materials. In particular we have observed phase transformations of Xe in a polyhydroxyaluminium-pillared montmorillonite molecular sieve and have developed a model consistent with the data. In addition, using XRD, an interpillar distance of ca. 30Å was calculated. We present the first detailed low temperature studies of 129-Xe N.M.R. on these systems.

scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

Influence of Substituting Al by Mg-Co and Mn-Co on the Properties of AlPO4-5

1992 ◽  
Vol 57 (4) ◽  
pp. 750-755 ◽  
Author(s):  
Liao Changsheng
Keyword(s):  
Catalytic Activity ◽  
Infrared Spectra ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Surface Acidity ◽  
Chemical Compositions ◽  
Hydrothermal Crystallization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystallization Method

Two kinds of crystalline microporous metal aluminophosphate molecular sieves, magnesium cobalt aluminophosphate (MgCoAPO-5) and manganese cobalt aluminophosphate (MnCoAPO-5), were synthesized by hydrothermal crystallization method in order to improve the surface acidity and catalytic activity of AlPO4-5. The results of X-ray diffraction, infrared spectra and chemical compositions of MgCoAPO-5 and MnCoAPO-5 indicate that Mg-Co or Mn-Co enter the framework of AlPO4-5 molecular sieve without disrupting the microporous framework. However, the results of catalytic studies show that MgCoAPO-5 and MnCoAPO-5 possess much higher surface acidity and catalytic activity than the unmodified AlPO4-5.

Investigating the properties and performance of 3A molecular sieves as an adsorbent to prevent coke formation in olefin dehydration process

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zoya Moslempour ◽  
Sepehr Sadighi ◽  
Ali Dashti ◽  
Ali Ahmadpour
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Coke Formation ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Na Ions ◽  
Temperature Programmed ◽  
And Performance ◽  
Physical And Chemical

Abstract To study the affinity of 3A aluminosilicate adsorbents to prevent oligomerization of olefin molecules and forming green oil, physical and chemical properties of 3A molecular sieves are measured by using characterization techniques such as temperature-programmed desorption (TPD), nitrogen (N2) and water adsorptions, X-ray diffraction (XRD), X-ray fluorescence (XRF), crushing strength, and carbon dioxide (CO2) adsorption. Moreover, coke formation affinities of the understudy adsorbents are evaluated in a bench-scale system using 1-butene and 1,3-butadiene at temperatures of 220 and 260 °C, and outcomes are validated against the actual data gathered from an industrial scale olefin dehydration plant. Results confirm that the type of binder and the amount of ion exchange affect the performance of a 3A molecular sieve nominated for dehydrating olefinic streams. The binder with the least amount of acidity is preferred, and at least 35% of Na ions of the 4A zeolite should be exchanged with K ions to make it applicable for synthesizing an appropriate 3A molecular sieve. Furthermore, to control the oligomerization and inhibit green oil formation, the CO2 adsorption and acidity of Trisiv shape molecular sieves with the sizes of 1/4 inch should be less than 0.5 wt % and 1.7 mmol NH3/g, respectively. For extrudate shape with the sizes of 1/16 inch CO2 adsorption and acidity should be less than 0.2 wt % and 2.2 mmol NH3/g, respectively.

Low-Temperature (<300°C) Phosphate Ceramics from Reactive Aluminas

1989 ◽  
Vol 179 ◽  
Author(s):  
M. R. Silsbee ◽  
R. A. Steinke ◽  
D. M. Roy ◽  
D. K. Agrawal ◽  
R. Roy
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Low Temperatures ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Exciting Potential

AbstractReactive aluminas, including rapidly calcined gibbsites, offer exciting potential for forming ceramic materials at low temperatures. New x-ray amorphous aluminas will react with water at room temperatures to form compacts with 10–50 MPa tensile strengths, via viscous slurries. The cementious behavior of these materials has been examined. The results of TGA, x-ray diffraction, SEM, mechanical properties, and other characterization techniques, as applied to these systems, will be discussed.

Variable temperature and high-pressure crystal chemistry of perovskite formamidinium lead iodide: a single crystal X-ray diffraction and computational study

2017 ◽  
Vol 53 (54) ◽  
pp. 7537-7540 ◽  
Author(s):  
Shijing Sun ◽  
Zeyu Deng ◽  
Yue Wu ◽  
Fengxia Wei ◽  
Furkan Halis Isikgor ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Low Temperature ◽  
Tetragonal Phase ◽  
Computational Study ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
X Ray ◽  
Tetragonal Phase Transition

Single crystals of [(NH2)2CH]PbI3 undergo a cubic-to-tetragonal phase transition at low temperature and high pressure.

Kinetically asymmetric charge and discharge behavior of LiNi0.5Mn1.5O4 at low temperature observed by in situ X-ray diffraction

2014 ◽  
Vol 2 (37) ◽  
pp. 15414-15419 ◽  
Author(s):  
Ikuma Takahashi ◽  
Haruno Murayama ◽  
Kenji Sato ◽  
Takahiro Naka ◽  
Koji Kitada ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Discharge Behavior

Thermodynamically reversible LiNi0.5Mn1.5O4 electrodes kinetically behave asymmetrically during charging and discharging at low temperatures.

Preparation and Luminescence of Host-Guest (SBA-15)-(Arsenano-III) Nanocomposite Materials

2013 ◽  
Vol 785-786 ◽  
pp. 537-541
Author(s):  
Xiao Dong Li
Keyword(s):  
Low Temperature ◽  
Absorption Spectra ◽  
Molecular Sieves ◽  
Diffuse Reflectance ◽  
Nitrogen Adsorption ◽  
Nanocomposite Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Prepared Composite ◽  
Adsorption Desorption

The nanosized channels of SBA-15 molecular sieves were used as template and arsenano-III (ASA-III) was trapped inside the SBA-15 molecular sieves by means of liquid grafting method. The prepared nanocomposite materials were characterized by the powder X-ray diffraction, low temperature nitrogen adsorption-desorption and solid diffuse reflectance absorption spectra. The powder X-ray diffraction indicated the structure of the (SBA-15)-(ASA-III) still remains two-dimensional hexagonal mesostructrure. The low temperature nitrogen adsorption-desorption research showed that the ASA-III was present on the inner surface and partially occupied the channels of the molecular sieve. The UV-Vis solid state diffuse reflectance absorption spectra of the prepared composite materials showed the steroconfinmment effect of the host SBA-15 channels on the guest ASA-III and the guest was in the channels of the SBA-15 host. Luminous spectra showed that the prepared (SBA-15)-(ASA-III) nanocomposite materials have the investigating optical properties.

scholarly journals Separation of Ethanol-Water MixtureUsing Type-A Zeolite Molecular Sieve

2010 ◽  
Vol 7 (2) ◽  
pp. 483-495 ◽  
Author(s):  
Juan Camilo Díaz ◽  
Iván Darío Gil-Chávez ◽  
Liliana Giraldo ◽  
Juan Carlos Moreno-Piraján
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Type A ◽  
Water Mixture ◽  
X Ray Diffraction ◽  
Experimental Procedure ◽  
X Ray ◽  
Promoter Characterization ◽  
Reactive Mixture

This paper presents an experimental procedure for the synthesis of a type-A zeolite molecular sieve, usable in the separation of an ethanol-water mixture. The type-A zeolite molecular sieve is obtained from a reactive mixture formed by a source of alumina, a source of silica and a promoter. Characterization of the molecular sieves obtained in this work was undertaken using X-ray diffraction (XRD), adsorption isotherms and scanning electron microscopy (SEM). The results from the characterization procedures showed that part of the product presented a pore diameter suitable for the separation of an ethanol-water mixture.

Polynuclear Gold Complexes of the Carbodiimide Unit [N=C=N]2-

1996 ◽  
Vol 51 (6) ◽  
pp. 801-805 ◽  
Author(s):  
W. Schneider ◽  
K. Angermaier ◽  
H. Schmidbaur
Keyword(s):  
Low Temperature ◽  
Ground State ◽  
Variable Temperature ◽  
Trinuclear Complex ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nmr Data ◽  
Site Exchange ◽  
High Yields ◽  
State Configuration

Abstract The reaction of N,N′-bis(trimethylsilyl)carbodiimide with equimolar quantities of tris[(triphenylphosphine)gold]oxonium tetrafluoroborate in dichloromethane at -40°C gives high yields of a trinuclear complex {[(Ph3P)Au]2NCN[Au(PPh3)]}+ BF4-(1). According to variable temperature NMR data the cation is fluxional in solution with a rapid site exchange of the [(Ph3P)Au] units, but has an unsymmetrical (N,N,N′) low temperature ground state configuration. A single crystal X-ray diffraction study has shown that in the crystal lattice these cations are associated further into cyclic, hexanuclear dimers through two short head-to-tail Au-Au contacts (auriophilicity). Treatment of complex 1 with one equivalent of [(Ph3P)Au]+ BF4- in tetrahydrofuran affords a tetranuclear complex {[(Ph3P)Au]2NCN[Au(PPh3)]2}2+ 2BF4- (2). The ambient temperature NMR spectra of 2 suggest a fluxional, pseudo-symmetrical structure, but at low temperature a set of three 31P signals (1:2:3 intensity) indicates an aggregation into higher nuclearity species with non-equivalent [Au(PPh3)] units

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