Study of Coke Distribution in HZSM-5 by 129-Xe NMR

1992 ◽  
Vol 57 (4) ◽  
pp. 733-738 ◽  
Author(s):  
Jean L. Bonardet ◽  
M. C. Barrage ◽  
Jack P. Fraissard ◽  
Ludmila Kubelková ◽  
Jana Nováková ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Zeolite Framework

The location of coke formed during conversion of methanol or acetone on HZSM-5 zeolites has been examined using 129-Xe NMR spectroscopy. The results show that the type of reaction and the method of regeneration have great importance for the location of carbonaceous residues inside or outside the zeolite framework.

scholarly journals Synthesis of Germanosilicate Zeolite HPM-12 Using a Short Imidazolium-based Dication: Structure-Direction by Charge-to-Charge Distance Matching

2019 ◽  
Author(s):  
Peng Lu ◽  
Luis Gómez-Hortigüela ◽  
Zihao Gao ◽  
Miguel Camblor
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Crucial Role ◽  
Mas Nmr ◽  
Zeolite A ◽  
Zeolite Framework ◽  
Large Shift ◽  
Varying Length ◽  
C Nmr

<p> A short imidazolium based dication, with only three methylene units in the space linker, selectively directs the crystallization towards zeolite HPM-12 (*UOE) as long as there is enough germanium present in the synthesis gel. The integrity of the dication is proved by dissolution of the zeolite and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, where significant effects of organic concentration and presence and concentration of HF need to be taken into account. In the as-made HPM-12 zeolite, a large shift of 9 ppm of one resonance in the <sup>13</sup>C MAS NMR is due to the particular conformation of the dication imposed by confinement in the zeolite framework, as found by DFT calculations. The structure-directing ability of this kind of dications with varying length of the linker suggests that matching of the distance between positive charges (imidazolium moieties) and negative charges (double four rings in which fluoride resides) plays a crucial role during crystallization.</p>

The Chemistry of Detrital Aluminum in Zeolites Studied by Multinuclear NMR Spectroscopy and Other Techniques

1987 ◽  
Vol 111 ◽  
Author(s):  
Richard H. Jarman
Keyword(s):  
Nmr Spectroscopy ◽  
Thermogravimetric Analysis ◽  
High Resolution ◽  
Nmr Spectra ◽  
Compositional Data ◽  
Analysis Data ◽  
State Of Charge ◽  
Zeolite Framework ◽  
Multinuclear Nmr Spectroscopy ◽  
Type Zeolite

AbstractHigh resolution 27Al NMR spectroscopy has been used to study the dealumination of the A-type zeolite ZK4. The aluminum removed from the lattice during calcination undergoes reversible changes in coordination when treated in acidic and basic media. 2 5 Si NMR spectroscopy reveals that the changes are confined to the detrital aluminum species and do not affect the zeolite framework. Thermogravimetric analysis data combined with compositional data available from 29Si NMR spectra have been used to probe the state of charge of the detrital aluminum species and the nature of defects present in the lattice.

scholarly journals Synthesis of Germanosilicate Zeolite HPM-12 Using a Short Imidazolium-based Dication: Structure-Direction by Charge-to-Charge Distance Matching

2019 ◽  
Author(s):  
Peng Lu ◽  
Luis Gómez-Hortigüela ◽  
Zihao Gao ◽  
Miguel Camblor
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Crucial Role ◽  
Mas Nmr ◽  
Zeolite A ◽  
Zeolite Framework ◽  
Large Shift ◽  
Varying Length ◽  
C Nmr

<p> A short imidazolium based dication, with only three methylene units in the space linker, selectively directs the crystallization towards zeolite HPM-12 (*UOE) as long as there is enough germanium present in the synthesis gel. The integrity of the dication is proved by dissolution of the zeolite and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, where significant effects of organic concentration and presence and concentration of HF need to be taken into account. In the as-made HPM-12 zeolite, a large shift of 9 ppm of one resonance in the <sup>13</sup>C MAS NMR is due to the particular conformation of the dication imposed by confinement in the zeolite framework, as found by DFT calculations. The structure-directing ability of this kind of dications with varying length of the linker suggests that matching of the distance between positive charges (imidazolium moieties) and negative charges (double four rings in which fluoride resides) plays a crucial role during crystallization.</p>

Unitary bounds and controllability of quantum evolution in NMR spectroscopy

1999 ◽  
Vol 96 (12) ◽  
pp. 1739-1744 ◽  
Author(s):  
T. S. UNTIDT, S. J. GLASER, C. GRIESIN
Keyword(s):  
Nmr Spectroscopy ◽  
Quantum Evolution
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