29Si Nmr Study of Hydrolyzed Teos-Rteos (R: Methyl, Ethyl, Phenyl) Systems

1998 ◽  
Vol 519 ◽  
Author(s):  
J. Mendez-Vivar ◽  
A. Mendoza-Bandala ◽  
A. Gutierrez ◽  
G. Cao
Keyword(s):  
29Si Nmr ◽  
Methyl Ethyl ◽  
Molar Ratios ◽  
Condensation Reactions ◽  
Nmr Study ◽  
Hydrolysis And Condensation

AbstractSols composed of Tetraethoxysilane (TEOS) and RTEOS (R: methyl, ethyl, phenyl) catalyzed with HCl were prepared. The molar ratios TEOS :RTEOS:EtOH:H20:HC1 were (1.0-0.8947):(5.26×10−2-0.1579):0.95:1.0:7×10−4, respectively. The sols were analyzed by 29 Si NMR immediately after mixing the reagents in order to study the hydrolysis and condensation reactions. A predominant self-condensation was observed in the TEOS-ETEOS sol, compared to cross-condensation. This result was opposite to the behaviour of the TEOS-MTEOS and TEOS-PTEOS sols.

scholarly journals Lipozyme 435-Mediated Synthesis of Xylose Oleate in Methyl Ethyl Ketone

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3317
Author(s):  
Maria Carolina Pereira Gonçalves ◽  
Jéssica Cristina Amaral ◽  
Roberto Fernandez-Lafuente ◽  
Ruy de Sousa Junior ◽  
Paulo Waldir Tardioli
Keyword(s):  
Oleic Acid ◽  
Methyl Ethyl Ketone ◽  
Molar Ratio ◽  
Methyl Ethyl ◽  
Sugar Ester ◽  
Molar Ratios ◽  
Emulsion Capacity ◽  
Ping Pong ◽  
Commercial Sugar ◽  
Repeated Use

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.

scholarly journals The structure directing effect of cations in aqueous silicate solutions. A 29Si-NMR study

1990 ◽  
Vol 45 ◽  
pp. 255-268 ◽  
Author(s):  
P.W.J.G. Wijnen ◽  
T.P.M. Beelen ◽  
J.W. De Haan ◽  
L.J.M. Van De Ven ◽  
R.A. Van Santen
Keyword(s):  
29Si Nmr ◽  
Nmr Study ◽  
Directing Effect

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

29Si NMR study on the structure of lead-silicate glasses

1984 ◽  
Vol 64 (1-2) ◽  
pp. 287-290 ◽  
Author(s):  
Takamitsu Fujiu ◽  
Makoto Ogino
Keyword(s):  
Silicate Glasses ◽  
Lead Silicate ◽  
29Si Nmr ◽  
Nmr Study

scholarly journals Hydration Degree of Alkali-Activated Slags: A 29Si NMR Study

2011 ◽  
Vol 94 (12) ◽  
pp. 4541-4547 ◽  
Author(s):  
Gwenn Le Saoût ◽  
Mohsen Ben Haha ◽  
Frank Winnefeld ◽  
Barbara Lothenbach
Keyword(s):  
29Si Nmr ◽  
Hydration Degree ◽  
Nmr Study ◽  
Alkali Activated
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