Coexistence of structure I and II hydrates formed from a mixture of methane and ethane gases

2003 ◽  
Vol 81 (1-2) ◽  
pp. 479-484 ◽  
Author(s):  
S Takeya ◽  
Y Kamata ◽  
T Uchida ◽  
J Nagao ◽  
T Ebinuma ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Gas Hydrates ◽  
X Ray Diffraction ◽  
Mixed Gas ◽  
Growth Processes ◽  
X Ray ◽  
Gas Concentration ◽  
In Situ Observations

X-ray diffraction measurements were conducted to determine the hydrate structures formed from a mixture of CH4 and C2H6 gases at 263 K. With increasing initial fractions of C2H6 in the gas, the crystal structures of the hydrate were structure I, structure I + structure II, structure II, structure I + structure II, and structure I. In situ observations of the growth processes of the mixed gas hydrates under constant gas concentration suggest that the coexistence of structure I and structure II hydrate were caused by occurrences of metastable hydrate structure. PACS No.: 82.75Fq

Measurements of physical properties of gas hydrates and in situ observations of formation and decomposition processes via Raman spectroscopy and X-ray diffraction

2003 ◽  
Vol 81 (1-2) ◽  
pp. 351-357 ◽  
Author(s):  
T Uchida ◽  
S Takeya ◽  
L D Wilson ◽  
C A Tulk ◽  
J A Ripmeester ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Physical Properties ◽  
Gas Hydrates ◽  
Hydrate Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrate Layer ◽  
Decomposition Processes ◽  
In Situ Observations

Gas hydrate properties and phase transition kinetics were studied using Raman spectroscopic and X-ray diffraction methods. These techniques have the advantage of measuring physical properties such as crystal structure, gas composition, and cage occupancy of gas molecules without decomposing the sample. In situ observations using these techniques are indicative of formation and decomposition processes in gas hydrates. Raman spectroscopy is used for the analysis of gas concentrations and gas compositions of gas hydrates. The ν1 symmetrical C–H stretching vibration mode of methane molecules in the hydrate phase shows a doublet, and the relative intensity of the peaks determines the cage-occupancy ratio. However, as the Raman method is not standard for this application, we evaluated the method by analyzing the same methane hydrate sample using NMR and Raman scattering in a laboratory in Canada and also comparing the data with the Raman measurements made on the same sample in a laboratory in Japan. The data were consistent with all three measurements. In addition, in situ measurements of hydrate formation and decomposition were done by X-ray diffraction. The transformation of ice into CO2 hydrates occurred in two steps: at first a CO2 hydrate layer rapidly formed a coating on the ice surface and then the CO2 hydrate slowly grew according to the diffusion rates of CO2 and H2O molecules through the hydrate layer to the reaction sites. The same methods were used to observe the self-preservation effect of methane hydrates. PACS Nos.: 82.80Ch, 61.10Nz

Dimethyl-, Disilyl- and Digermylsulfide: Different Intermolecular Contacts in the Solid State

2004 ◽  
Vol 59 (6) ◽  
pp. 635-638 ◽  
Author(s):  
Norbert W. Mitzel ◽  
Udo Losehand
Keyword(s):  
Solid State ◽  
Low Temperature ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermolecular Contacts

The compounds (H3C)2S, (H3Si)2S and (H3Ge)2S have been crystallised in situ on a diffractometer and their crystal structures determined by low-temperature X-ray diffraction. The molecules are present as monomers in the crystals. The aggregation of the molecules through secondary intermolecular contacts in the crystal is different: (H3C)2S is weakly associated into dimers by S···S contacts, whereas (H3Si)2S and (H3Ge)2S form Si···S and Ge···S contacts in an ice-analogous aggregation motif. Important geometry parameters are (H3C)2S: C-S 1.794(av) Å , C-S-C 99.2(1)°; (H3Si)2S: Si- S 2.143(1) Å , Si-S-Si 98.4°; (H3Ge)2S Ge-S 2.223(2) and 2.230(2) Å , Ge-S-Ge 98.2(1)◦.

In situ X-Ray Diffraction Method to Study Natural Gas Hydrates

1998 ◽  
Vol 278-281 ◽  
pp. 335-341 ◽  
Author(s):  
C.C. Tang ◽  
M.C. Miller ◽  
Robert J. Cernik ◽  
S.M. Clark ◽  
C.A. Koh ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Hydrates ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Natural Gas Hydrates

Copper Phosphonatoethanesulfonates: Temperature Dependent in Situ Energy Dispersive X-ray Diffraction Study and Influence of the pH on the Crystal Structures

2012 ◽  
Vol 51 (22) ◽  
pp. 12540-12547 ◽  
Author(s):  
Mark Feyand ◽  
Annika Hübner ◽  
André Rothkirch ◽  
David S. Wragg ◽  
Norbert Stock
Keyword(s):  
Diffraction Study ◽  
Crystal Structures ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray

Synthesis and Structures of Simple (Silylmethyl)(methyl)ethers

2003 ◽  
Vol 58 (8) ◽  
pp. 759-763 ◽  
Author(s):  
Norbert W. Mitzel
Keyword(s):  
Crystal Structures ◽  
Structural Parameters ◽  
Structural Basis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Donor Acceptor

The compound Cl3SiCH2OCH3 was prepared by reacting ClCH2OCH3 with the Cl3SiH/NEt3 reagent. H3SiCH2OCH3 and F3SiCH2OCH3 were synthesized from Cl3SiCH2OCH3 by reduction with LiAlH4 and by fluorination with SbF3, respectively. The crystal structures of the low-melting compounds H3SiCH2OCH3 and F3SiCH2OCH3 were determined by X-ray diffraction of in situ grown crystals. Both compounds do not show any observable β -donor-acceptor interactions, but behave structurally like usual dialkylethers or silanes, as is obvious from the structural parameters in H3SiCH2OCH3 (<SiCO 108.4(3)-109.4(3)°, <COC 111.0(4)-111.6(4)°) and in F3SiCH2OCH3 (<SiCO 107.1(1), <COC 111.2(2)°). Earlier postulates of Si· · ·O interactions in compounds with SiCO units could thus not be confirmed on a structural basis.

The Crystal Structures of Chlorodimethyl( dimethylamino)silane and Dimethyl-bis-(dimethylamino)silane

2003 ◽  
Vol 58 (7) ◽  
pp. 708-710 ◽  
Author(s):  
Norbert W. Mitzel ◽  
Krunoslav Vojinović
Keyword(s):  
Single Crystals ◽  
Crystal Structures ◽  
Low Temperatures ◽  
Structural Parameters ◽  
X Ray Diffraction ◽  
X Ray

Single crystals of chlorodimethyl(dimethylamino)silane, Me2NSiMe2Cl, and dimethyl-bis-(dimethylamino)silane, (Me2N)2SiMe2, have been grown in situ from the melt at low temperatures and their structures determined by X-ray diffraction. Important structural parameters (Å / °): Me2NSiMe2Cl (C2/m) Si-N 1.686(2), Si-C 1.851(1), Si- Cl 2.109(1), N-Si-Cl 111.7(1), C-Si-Cl 105.1(1), C-N-C 112.8(2), Si-N-C 123.4(1); (Me2N)2SiMe2 (P21/c) Si-N(1) 1.725(1), Si-C(1) 1.868(1), N(1)-Si-N(2) 105.7(1), C(3)- N(1)-C(4) 111.6(1), Si-N(1)-C(3) 122.4(1), Si-N(1)-C(4) 120.0(1).

Nucleation and growth processes of α-Fe nanocrystals in amorphous NdFeBCoDy: In situ x-ray diffraction studies

2005 ◽  
Vol 86 (9) ◽  
pp. 092501 ◽  
Author(s):  
W. Li ◽  
X. H. Li ◽  
H. Y. Sun ◽  
J. W. Zhang ◽  
X. Y. Zhang
Keyword(s):  
Nucleation And Growth ◽  
X Ray Diffraction ◽  
Growth Processes ◽  
X Ray
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