Sol-Gel Kinetics: 29Si NMR and a Statistical Reaction Model

1988 ◽  
Vol 121 ◽  
Author(s):  
Roger A. Assitik ◽  
Bruce D. Kay
Keyword(s):  
Chemical Speciation ◽  
Functional Group ◽  
Sol Gel ◽  
Early Time ◽  
Reaction Model ◽  
29Si Nmr ◽  
Mathematical Framework ◽  
Time Behavior ◽  
Acid Catalyzed ◽  
Group Distribution

ABSTRACTThe early time behavior of an acid catalyzed Si(OCH3),4 (TMOS) sol-gel was studied by high resolution 29Si nuclear magnetic resonance (NMR). Both the water producing and the alcohol producing condensation reactions were found to contribute significantly to the overall condensation rate. A general theoretical kinetic formalism which specifically treats the temporal evolution of the various chemical function groups about a specific silicon atom was developed. The experimentally observed functional group distribution was in agreement with the distribution predicted by a simplified statistical reaction model. The mathematical framework for the study of chemical speciation at the next-to-nearest functional group level was developed. This framework was used to assign several fine structure resonances, and to show that the formation of various dimeric species is also largely statistical in nature.

29Si NMR and UV−Raman Investigation of Initial Oligomerization Reaction Pathways in Acid-Catalyzed Silica Sol−Gel Chemistry

2011 ◽  
Vol 115 (9) ◽  
pp. 3562-3571 ◽  
Author(s):  
Anouschka Depla ◽  
David Lesthaeghe ◽  
Titus S. van Erp ◽  
Alexander Aerts ◽  
Kristof Houthoofd ◽  
...  
Keyword(s):  
Sol Gel ◽  
Silica Sol ◽  
Reaction Pathways ◽  
29Si Nmr ◽  
Uv Raman ◽  
Acid Catalyzed ◽  
Oligomerization Reaction

29Si NMR Study of Distribution of Oligomers in Polycondensation of Tetraethoxysilane

1996 ◽  
Vol 61 (5) ◽  
pp. 691-703 ◽  
Author(s):  
Jiří Brus ◽  
Jiří Karhan ◽  
Petr Kotlík
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Sol Gel ◽  
29Si Nmr ◽  
Nmr Study ◽  
Nmr Spectrometry ◽  
Concentration Changes ◽  
Acid Catalyzed ◽  
The Moment

29Si NMR spectrometry has been used to determine the number molecular weight distribution of polymerization degrees of a system of oligomers formed in the sol-gel polycondensation of tetraethoxysilane (TEOS). On the basis of identification of the oligomers, monitoring of the concentration changes during the initial phase of the sol-gel polycondensation, and from the deviations observed between the experimentally determined number molecular weight distribution of polymerization degrees and the Flory-Stockmayer model it has been proved that cyclization represents a significant process in the acid-catalyzed polycondensation with substoichiometric amount of water (ratio of amounts TEOS/H2O = 1 : 1). The cyclization becomes important at the moment when the reaction mixture contains increased amounts of the linear tetramer and pentamer. The cyclization products form a basis for formation of polycyclic, highly condensed building units whose gradual aggregation produces the gel.

Liquid state 29Si NMR study on the sol-gel reaction mechanisms of ormosils

1993 ◽  
Vol 159 (1-2) ◽  
pp. 65-72 ◽  
Author(s):  
Takashi Iwamoto ◽  
Kazuki Morita ◽  
John D. Mackenzie
Keyword(s):  
Reaction Mechanisms ◽  
Liquid State ◽  
Sol Gel ◽  
29Si Nmr ◽  
Nmr Study

High field 1H NMR Studies of Sol-Gel Kinetics

1986 ◽  
Vol 73 ◽  
Author(s):  
Bruce D. Kay ◽  
Roger A. Assink
Keyword(s):  
Equilibrium Distribution ◽  
Sol Gel ◽  
Nmr Studies ◽  
H Nmr ◽  
Rate Limiting Step ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Product Species ◽  
Rate Limiting ◽  
Kinetics Of

ABSTRACTHigh resolution 1H NMR spectroscopy at high magnetic fields is employed to study the reaction kinetics of the Si(OCH3)4:CH3OH:H2O sol-gel system. Both the overall extent of reaction as a function of time and the equilibrium distribution of species are measured. In acid catalyzed solution, condensation is the rate limiting step while in base catalyzed solution, hydrolysis becomes rate limiting. A kinetic model in which the rate of hydrolysis is assumed to be independent of the adjacent functional groups is presented. This model correctly predicts the distribution of product species during the initial stages of the sol-gel reaction.

scholarly journals Explicit Deconvolution of Well Test Data Dominated by Wellbore Storage

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
K. Razminia ◽  
A. Hashemi ◽  
A. Razminia ◽  
D. Baleanu
Keyword(s):  
Test Data ◽  
Material Balance ◽  
Early Time ◽  
Time Behavior ◽  
Well Test ◽  
Deconvolution Method ◽  
Pressure Data ◽  
Practical Applications ◽  
Wellbore Storage ◽  
Storage Effects

This paper addresses some methods for interpretation of oil and gas well test data distorted by wellbore storage effects. Using these techniques, we can deconvolve pressure and rate data from drawdown and buildup tests dominated by wellbore storage. Some of these methods have the advantage of deconvolving the pressure data without rate measurement. The two important methods that are applied in this study are an explicit deconvolution method and a modification of material balance deconvolution method. In cases with no rate measurements, we use a blind deconvolution method to restore the pressure response free of wellbore storage effects. Our techniques detect the afterflow/unloading rate function with explicit deconvolution of the observed pressure data. The presented techniques can unveil the early time behavior of a reservoir system masked by wellbore storage effects and thus provide powerful tools to improve pressure transient test interpretation. Each method has been validated using both synthetic data and field cases and each method should be considered valid for practical applications.

Study of Acetic Acid-Catalyzed Nanocomposite Organic/Inorganic Ureasil Sol−Gel Ionic Conductors

Langmuir ◽  
2003 ◽  
Vol 19 (18) ◽  
pp. 7587-7591 ◽  
Author(s):  
E. Stathatos ◽  
P. Lianos ◽  
B. Orel ◽  
A. Surca Vuk ◽  
R. Jese
Keyword(s):  
Acetic Acid ◽  
Sol Gel ◽  
Ionic Conductors ◽  
Acid Catalyzed
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