Coal aromatic/aliphatic ratios

The nmr analyses of the bottoms products given in Table IV show the material to have a large aliphatic content. The aromatic/aliphatic ratios of the fractions are higher than for the whole coal because of the presence of combined phenol reaction with Tetralin reduces these ratios considerably, presumably by transfer of much of this material to the solvent-range product, but some of it must remain in the bottoms as the aromatic/aliphatic ratio of the composite bottoms product from the fractions is higher than that from the whole coal. It was not possible to calculate the contribution that the diluents, excess solvent and combined phenol, made to the aromatic H, but the large monoaromatic content of the bottoms product must be due, in part, to these. 

Distribution of protons by type and overall aromatic/aliphatic proton ratios for the original fractions and bottoms products, as determined by proton nmr. Proton distribution for fraction D and the whole coal are not included as these materials were only partly soluble and the resultant spectra were not representative of the whole material. 

For each coal, at the maximum in hydrogen content, or H/C atomic ratio, the aliphatic hydrogen content (determined by H NMR analysis) accounted for over 90% of the total hydrogen. The aliphatic hydrogen contents were 10.5% for the subbituminous coal,PSOC-1403, and 6.9% for the bituminous coal, PSOC-1266. The high aliphatic hydrogen content was associated with the presence of polymethylene chains. The early release of paraffinic material, as n-alkanes and as long chain substituents to aromatic structures, under conditions of mild pyrolysis has been observed in other research (13-15. ... 

Partial pyrolysis-gas chromatograms of representative immature kerogens or coals from the four sequences studied are shown in Figure 2. The abundance of thiophenes relative to aliphatic and aromatic hydrocarbons in the partial FID chromatograms differs markedly for the four samples shown. This is reflected by the ratio of the peak area of 2,3-dimethylthiophene relative to those due to 1,2-dimethylbenzene and n-non-l-ene (Le. TR = [2,3-dimethylthiophene]/[l,2-dimethylbenzene+n-non-... 

The ratio of aliphatic protons to aromatic protons for the heavy oil was 4.01/1 and of methylene to methyl 1/1.75. For the asphaltenes, the ratio of aliphatic protons to aromatic protons was 3.49/1 and of methylene to methyl 1/1.1. The asphaltenes were observed to melt at HG C. Molecular weights obtained by vapor phase osmometry (o-xylene solvent) were 407 for the heavy oil and 638 for the asphaltenes. There appears to be little difference in the relative yield of heavy oils and asphaltenes from depolymerized coal as compared with the "as received" coals. Acknowledgements... 

A regression analysis applied to a series of coals, chars, and tars with widely differing ratios of aliphatic-to-aromatic hydrogen has been used to calibrate the aliphatic and aromatic C-H absorption intensities. 

Because of the complexity of the infrared spectra of coals most quantitative studies have been limited to the determination of hydroxyl groups and aliphatic and aromatic C-H. Brown ( ) attempted to obtain a measure of the relative proportions of these latter groups by measuring the ratio of the peak heights of the aromatic and aliphatic C-H stretching modes at 3030 and... 

Comparision with NMR To check the accuracy of the determination of aromatic and aliphatic carbons, eighteen coals for which quantitative FT-IR data were obtained were also studied by NMR by Bernard Gerstein et al, (46) at Ames Laboratory The ratios of aromatic to total carbon obtained by the two methods are compared in Fig 15 There is good agreement between results of the two methods ... 

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