Pyrolysis structural studies

Schulten H-F, Schnitzer M. Structural studies on soil humic acids by Curie-point pyrolysis-gas chromatography/mass spectroscopy. Soil Sci. 1992 153 205-224. 

Ion Exchange and Pyrolysis. A typical specimen of zeolite 0 contains approximately eight cations per unit cell, of which about six are sodium ions, and the remaining two are tetramethylammonium ions. The positions of these ions within the zeolitic framework can be determined by x-ray structural studies or by ion-exchange experiments if the structure of the framework is known. 

Usami, T., Itih, T., Ohtani, H., Tsuge, S. (1990) Structural study of polyacrylonitrile libers during oxidative thermal degradation by pyrolysis-gas chromatography, solid state 13C Nuclear magnetic resonance and Fourier transform infrared spectroscopy, Macromolecules 23, 2460-2465. 

Structural Studies Using Pyrolysis and Chemical Degradation 280... 

Structural Studies of Humic Substances. Solid-state C NMR has played a major role in past studies of the chemical structure of humic substances isolated from soil as mentioned above. Recent studies have focused on the examination of humic substances from various environments to establish variabihties which might be indicative of structure and structural evolution.(29-34) Also, combined use of NMR with other analytical methods such as analytical pyrolysis, chemical degradative methods, and solution NMR studies has proved vduable in elucidating structural components. However, the complexity of humic substances has precluded all but inferred structures based on these combined studies. 

When using field desorption, however, it is occasionally difficult to distinguish the fragment ions from impurities and the products of various reactions (surface reactions, pyrolysis). The study of uni- and bimolecular decomposition spectra is very useful, since it enables one to go beyond the simple identification of artifacts to the elucidation of molecular structures. 

Structural studies on melanoidins are in their infancy, but it does appear that they can contain intact carbohydrate fragments, particularly if oligosaccharides are involved. Pyrolysis yields a range of compounds containing aromatic heterocycles, which contribute to the odour of cooked food, with many having furan rings. ... 

Believing that the chemical modification of natural biopolymers could produce materials having many of the physical properties desired for technical applications, he pursued structural studies of synthetic gums, such as the dextrins from pyrolysis of starch (with G. M. Christensen,... 

In this Section, structural studies of the products of pyrolysis of the glucan, dextran, 1,6-anhydro- 3-D-glucopyranose (levoglucosan), and D-glucose will be briefly outlined. 

The range of pyrolysis products is a function of the composition and structure of the pyrolysed sample, which accounts for the applicability of Py—GC in quantitative analysis and structural studies. Determining the composition of polymer systems (mixtures and copolymers) and establishing the structure of the analysed polymers are practically important and complex problems. Py—GC is used successfully in solving these problems and is one of the few methods that can be employed in investigating insoluble polymers. 

Grasset, L. and Ambles, A., Structural study of soil humic acids and humin using a new preparative thermochemolysis technique, J. Anal. Appl. Pyrolysis, 47, 1-12, 1998. 

SoLLi, H. Leplat, T. P. 1986. Pyrolysis-gas chromatography of asphaltenes and kerogens from source rocks and coals—a comparative structural study. Organic Geochemistry, 10, 313-329. 

Figure 12.39 Series of transmission FTIR spectra for (a) Nikkoso precursor AN/MA/ITA, (b) Oxidized in air for 20 min 215°C/15 min 235°C, (c) Oxidized in air for 20 min 215°C/180 min 235°C, (d) Oxidized in air for 20 min 215°C/1800 min 235°C. Source Reprinted from UsamlT, ItohT, Ohtani H.Tsuge S, Structural study of polyacrylonitrile fibers during oxidative thermal degradation by Pyrolysis— Gas Chromatography, Solid State C Nuclear Magnetic Resonance and Fourier Transform Infrared Spectroscopy, Macromolecules, 23, 2460-2465, 1990.

Usami T, Itoh T, Ohtani H, Tsuge S, Structural study of polyacrylonitrile fibers during oxidative thermal degradation by Pyrolysis—Gas Chromatography, Sohd State C Nuclear Magnetic Resonance and Fourier Transform Infrared Spectroscopy, Macromolecules, 23, 2460 2465, 1990. 

Wang and Smith [74] used pyrolysis - gas chromatography to elucidate the composition of, and carry out structural studies on, vinyl chloride-vinylidene chloride copolymers. 

In none of these samples was it possible to find structures that were comparable with the structures previously published by other authors [35]. In their investigations, carbon black was liberated from the matrix by solution and subsequent filtration. In contrast, we find different structures that support the assumption of a concentration of the carbon black in layers. The structures found after pyrolysis by studies with the scanning electron microscope may be flat (Fig. 19.33), wavelike, tubular, or foamlike (Fig. 19.34). These observations can be interpreted with the aid of the model of an interpenetrating network of layers with different structures, as has already been proposed in Ref. 36. 

This Py-GC method can be used to determine both the composition and microstructure of CPE. The determination of the composition and structure of CPE is achieved through the detection of the pyrolysis trimers and the application of two critical assumptions for the polymer system. The chlorine contents of all polymers tested are in excellent agreement with NMR measurements and the product composition specification. To distinguish the structural differences of polymers with the same composition, there are several structure-related terms that have been derived to reveal the structural difference, such as the percent of grouped monomers, the NASL of grouped monomers, and the percentage of chlorine atoms in PVC-like structures. The composition and microstructure of CPE is a direct reflection of the CPE preparation method and the degree of chlorination. In other words, the composition and microstructure of CPE can be used to rationalise the physical-mechanical properties obtained from different chlorination processes. This method extends the capabilities of pyrolysis from the quantitative and structural study of copolymer systems into the realm of chemically modified homopolymers. 

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