Methyl groups in coals

In 1947, Kinney (15) drew attention to a direct relationship between the amount of acetic acid formed on oxidizing coal with nitric acid and potassium dichromate and the yields of methane obtained by low temperature carbonization. The oxidation method leading to acetic acid is a variation of the standard Kuhn-Roth procedure, and hence what Kinney indicated as the methane yielding structure is obviously the methyl groups in coal. However, the relationship he pointed out can only be qualitative since true C-methyl content (as shown in the present work) cannot be obtained by any... 

The foregoing results and discussions indicate that methane is specifically derived from the methyl groups in coal. If the above hypothesis is agreed to, then the following conclusions emerge ... 

These conclusions are however subject to the validity of the tacit assumption made here that the small proportion of ethane (2-3%) which invariably accompanies methane formation owes its origin also to the methyl groups in coal. Dicker et al. (9) however are of the opinion that ethane mainly origi-... 

Bhupendra K. Mazumdar We have not worked on the nature of the methyl groups in coal but have sought to assess the total methyl content by interpreting the sources of methane formation during low temperature (600°C.) pyrolysis. 

Further, the fusain samples we examined contained methyl groups (in amounts comparable to those in higher rank coals). The presence of such group in fusains would itself rule out the forest fire theory or any other concept which envisages exposure to high temperatures (600°C.) in forming fusains. 

Reduction apparently creates fresh hydroaromatic structure (at the expense of the aromatics), and thus the methyl groups attached to the aromatic structures are likely to become amenable to quantitative estimation (by the Kuhn-Roth procedure), provided that the particular aromatic ring is reduced to hydroaromatic. Significantly, the reduced samples of the lower rank coals did not yield much higher values for methyl groups than the original samples. Thus, it would appear that Kuhn-Roth estimation does not completely measure the true C-methyl content in coals, especially in high rank coal samples. 

The presence of a considerable proportion of methylated bodies in low temperature tar and its origin must be explained. The fact that the yield of methane remains largely the same even when tar formation is completely inhibited would indicate that the methyl groups of coal possibly do not participate in forming the methylated bodies in tar. It is not unlikely, therefore, that such methylated bodies in tar are synthesized during pyrolytic reaction of the hydroaromatic structure (via methylenes). 

The technique for estimating the total aliphatic carbon (especially methyl carbon) in coal may require further refinements. However, in view of the foregoing discussions on the self-consistency of the estimated methyl content with other forms of carbon in coal, it seems unlikely that there are side chains longer than methyl group in normal coals. 

Laszlo A. Heredy There is NMR spectroscopic evidence for the presence of both a- and /3-CHa groups in coal, based on depolymerization work with phenol-BF.3 reagent. For example, isopropyl groups were shown to be present in a high volatile bituminous coal. Is there a distinct difference in the behavior of these two types of CHs groups with respect to the reagent used in wet analytical methyl group determination ... 

Alkylation of solvent represents still another pathway for changing the properties of a recycle solvent. If we consider alkylation in terms of the transfer to methyl groups from coal to solvent components, then there are several structural and physical changes that occur to the solvent. Alkylation will increase the hydrogen content of the solvent at the expense of coal since the solvent molecule will have a C-H replaced by C-CH. This represents an increase in the aliphatic content and conversely a decrease in the aromatic content of the solvent. Kleinpeter (7) has indicated that alkylation of condensed aromatics is a problem. High aliphatic character will decrease the ability of the solvent to act as a physical solvent for coal liquefaction products. 

The pH dependency of this methylation reaction and the existence of base-labile methyl groups in the coal derivatives implicate the ionization and methylation of acidic -OH sites. However, the 14C results alone do not preclude the reaction of other sites of comparable acidity. To determine if this factor is important, the pH 12 PSOC 1197 derivative was analyzed by... 

Alkyl Isoquinolines. Coal tar contains small amounts of l-methylisoquinoline [1721-93-3] 3-methylisoquinoline [1125-80-0] and 1,3-dimetliylisoquinoline [1721-94-4J. The 1- and 3-methyl groups are more reactive than others in the isoquinoline nucleus and readily oxidize with selenium dioxide to form the corresponding isoquinoline aldehydes (174). These compounds can also be obtained by the hydrolysis of the dihalomethyl group. The 1- and 3-methyhsoquinolines condense with benzaldehyde in the presence of zinc chloride or acetic anhydride to produce 1- and 3-styryhsoquinolines. Radicals formed by decarboxylation of carboxyUc acids react to produce 1-aIkyhsoquinolines. 

Figure 3 shows the effect of reaction temperature on the liquefaction reactivity of methylated (3 hrs, 100/1 methanol/HCl wt. ratio) and untreated Wyodak coals using DHP solvent. Mildly treating the coal (approx. 0.2 methyl groups added/100 carbon atoms) resulted in THF conversion improvements of about 21 wt% at 315 C, 23 wt% at 350 C, and 14 wt% at 400 C. Clearly, mild pretreatment enhances reactivity over the entire range of observed conversion levels. This result is very significant since it shows that our pretreatment procedure is beneficial at conversion levels of commercial interest, and thus, represents more than a laboratory curiosity. 

Phenols are a major chemical lump present in coal liquids. Phenols have basically one or more aromatic ring structures with alkyl substituents. Methyl, ethyl and propyl are the most common alkyl substituents. The smallest specie is the one with a hydroxyl group attached to a benzene ring. Addition of a methyl group produces three isomers - o-, m-, and p-cresols. It appears that all three are present in more or less same proportion. The number of possible isomers increases as the possible number and size of alkyl substituents increases. It is expected that higher... 

In m-xylene the two methyl groups agree in activating the same positions, and this is the only one of the three isomeric xylenes which can be nitrated satisfactorily to yield a trinitro derivative. Since the three isomers occur in the same fraction of coal tar and cannot readily be separated by distillation, it is necessary to separate them by chemical means. When the mixed xylenes are treated with about their own weight of 93 per cent sulfuric acid for 5 hours at 50°, the o-xylene (b.p. 144°) and the m-xylene (b.p. 138.8°) are converted into water-soluble sulfonic acids, while the p-xylene (b.p. 138.5°) is unaffected. The aqueous phase is removed, diluted with water to about 52 per cent acidity calculated as sulfuric acid, and then heated in an autoclave at 130° for 4 hours. The m-xylene sulfonic acid is converted to m-xylene, which is removed. The o-xylene sulfonic acid, which remains in solution, may be converted into o-xylene by autoclaving at a higher temperature. The nitration of m-xylene is conveniently carried out in three steps. The effect of the two methyl... 

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