Characterization of γ-alumina doped with Li and K by infrared studies of CO adsorption and27Al-NMR

1994 ◽  
Vol 1 (1-2) ◽  
pp. 87-94 ◽  
Author(s):  
Sergio R. de Miguel ◽  
Osvaldo A. Scelza ◽  
Alberto A. Castro ◽  
Javier Soria
Keyword(s):  
Co Adsorption ◽  
Infrared Studies

Characterization of autohydrolysis aspen (P. tremuloides) lignins. Part 4. Residual autohydrolysis lignin

1979 ◽  
Vol 57 (19) ◽  
pp. 2612-2616 ◽  
Author(s):  
Morris Wayman ◽  
Miranda G. S. Chua
Keyword(s):  
Enzymatic Hydrolysis ◽  
Time Varying ◽  
Residual Lignin ◽  
Aspen Wood ◽  
Milled Wood Lignin ◽  
Wood Meal ◽  
Nitrobenzene Oxidation ◽  
Infrared Studies ◽  
Lignocellulosic Residue

Lignocellulosic residue remaining after autohydrolysis of extractive-free aspen wood meal at 195 °C for periods of time varying from 5 to 120 min followed by extraction with 90% dioxane was subjected to enzymatic hydrolysis to obtain residual lignin. Infrared studies indicated that in the early stages of autohydrolysis residual lignin resembles protolignin, but as autohydrolysis proceeds it changes to resemble more and more the extracted lignin. Residual lignin was found to be higher in carbon but lower in hydrogen and oxygen than aspen milled wood lignin. The methoxyl content was also lower than the reference lignin. From alkaline nitrobenzene oxidation, residual lignin is seen to become more condensed with increasing autohydrolysis time. The insolubility of residual lignin is attributed to the existence of strong bonds between this lignin and carbohydrate.

scholarly journals Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 123 ◽  
Author(s):  
Andrea Bellmann ◽  
Christine Rautenberg ◽  
Ursula Bentrup ◽  
Angelika Brückner
Keyword(s):  
Diffuse Reflection ◽  
Co Adsorption ◽  
In Situ Ftir ◽  
Diffuse Reflection Spectroscopy ◽  
Reflection Spectroscopy ◽  
Oxide Supports ◽  
In Situ Ftir Spectroscopy ◽  
Vis Spectroscopy

UV–Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co–ZSM-5, Co/Na–ZSM-5, Co/Al–SBA-15, and Co/Al2O3–SiO2. Because all sample types show comparable UV–Vis spectra with a characteristic band triplet, the former described UV–Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co–zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al–SBA-15 and Co/Al2O3–SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV–Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required.

13C NMR Characterization of Polychloroprene Microstructure II. Relaxation, NOE, and Quantitative Measurements

1978 ◽  
Vol 51 (4) ◽  
pp. 668-676 ◽  
Author(s):  
M. M. Coleman ◽  
E. G. Brame
Keyword(s):  
Free Radical ◽  
Spin Relaxation ◽  
13C Nmr ◽  
Quantitative Measurements ◽  
Nmr Characterization ◽  
Infrared Studies ◽  
Excellent Method ◽  
Quantitative Results ◽  
Structural Irregularities

Abstract Spin relaxation, NOE, and quantitative measurements have been performed on chloroprene polymers prepared by free radical techniques in the range −150 to +90°C. 13C NMR has proved to be an excellent method for the characterization of polychloroprene microstructure. From our quantitative results it would appear that the concentration of cis-1,4 structural irregularities has been considerably overestimated in previous infrared studies. In addition, the relative amount of trans-1,4 inversions (HT) appears to be somewhat higher than previously reported.

Infrared studies of NO adsorption and co-adsorption of NO and O2 onto cerium-exchanged mordenite (CeNaMOR)

1995 ◽  
Vol 4 (6) ◽  
pp. 455-465 ◽  
Author(s):  
E. Ito ◽  
Y.J. Mergler ◽  
B.E. Nieuwenhuys ◽  
H. van Bekkum ◽  
C.M. van den Bleek
Keyword(s):  
Co Adsorption ◽  
No Adsorption ◽  
Infrared Studies
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