Pyridine solubles

The production of such high concentrations of radicals leads to a very unstable situation and if the radicals are not stabilized via H-donation, they undergo a variety of undesired reactions such as condensation, elimination or rearrangement (7). Neavel has shown that at short times ( 5 min) a vitrinite enriched bituminous coal can be converted to 80% pyridine soluble form in even non-donor reaction solvents (naphthalene) (8). But if reaction times are extended, the soluble products revert to an insoluble form via condensation reactions. Such condensation reactions were... 

Working co-operatively with others, we have found some indication that certain alilphatic linkages between aromatic nucleii are involved in the rapid dissolution of coal. The absolute aliphatic hydrogen content as determined by P. Solomon using FTIR (22) shows a very good linear relationship with conversion of coal in 3 minutes to pyridine soluble materials (Figure 14a). 

In solvent refining, coal is converted to a pyridine-soluble product after very short residence time at reaction conditions. 

Table I compares the conditions and results of this operation to those for conventional SRC for Illinois 6 coal. At the short residence time, the coal conversion determined by pyridine solubility is 89% compared to 95% at conventional SRC conditions. The hydrogen consumption and production of light gases are reduced significantly at short residence time, while the SRC yield is increased.

In this Laboratory, several potential liquid-phase treating agents have been studied at 225-275°C—that is, at temperatures well below 325°C, which appears to be the initiation temperature for pyrolysis of the coals studied here. Working with Wyodak coal in a ZnC -water melt at 250°C, Holten and coworkers (2,3) discovered that addition of tetralin increased the pyridine solubility of product to 75%, compared to 25% without tetralin. About 10 wt-% of water is required in the melt, because pure ZnC melts at 317°C. 

We have now found that replacing water in the melt by methanol leads to large increases in pyridine solubility of product from the treatment, even without tetralin addition. In this paper we characterize the effects of temperature, time, hydrogen pressure, reaction stoichiometry, and addition of various inorganic and organic additives. Because oxygen removal Present Address Chevron Research Co., Box 1627, Richmond, CA 94804. 

In addition to knowing the total MTC solubility, it was important to determine the amount of methanol or other solvent retained by the MTC. This quantity, the incorporation ratio (R, gm incorporated organic material/gm coal-derived organic material), was determined by a carbon balance on the reaction. By assuming that any solvent retained in the dried MTC is pyridine-soluble, and subtracting it from the total dissolved material, the minimum solubility of the coal-derived material may be calculated. This quantity, the corrected solubility, is an indicator of the true solubilizing effect on the coal by the particular run conditions. ... 

Effect of Product Wash. For several runs, the product slurries were divided after water quenching of the MTC, and 15 ml HC1 was added to the cold water wash. Figure 7 shows the increase in benzene and total MTC solubility as a result of the HC1 wash. Acid-washing produces total pyridine solubility from a 65% soluble water-washed MTC. The effect of acid washing on benzene solubility is less marked, with a maximum increase of 10-15% when the water-washed benzene solubility is 25%. The maximum benzene solubility with either water or acid wash is 40%. 

Figure 8. Relations between benzene solubility and total (pyridine) solubility 273 g ZnCl2, 50 g coal Wash (M)> benzene ( 7), HzO (%), HCl...

We have discovered that ZnC, in combination with methanol, constitutes an active liquid-phase catalytic medium for conversion of coal to pyridine-soluble material. There are several possible explanations for this effect improved contact between coal and melt higher activity of the ZnCl2 in the methanol medium methylation of cleaved bonds resulting in reduced char formation and extraction of the reaction products leaving the coal more accessible. 

Extractive solvents reduce the solubilization donor solvents increase it, but involve incorporation. A relation between benzene and pyridine solubility is dependent on wash conditions. Finally, oxygen recovery and corrected solubility are related, the relationship varying with the solvent used. 

The methanol-insoluble product was also upgraded relative to the starting coal. Its H/C ratio was 0.86, its sulfur and nitrogen levels were 0.8% and 1.2%, respectively, and it has fully pyridine soluble. 

To summarize our effort, we found that C0/H20/K0H systems converted Illinois No. 6 coal to a material which was fully pyridine soluble, 51% benzene soluble, and 18% hexane soluble. As with the basic alcoholic systems, there were significant reductions in organic sulfur levels, and moderate reductions in nitrogen levels. 

In outline of what follows we will begin by brief reference to previous work on coal liquefaction. The present approach will then be motivated from considerations of coal structure and hydro-gen-donor activity. A theoretical section follows in the form of a pericyclic hypothesis for the coal liquefaction mechanism, with focus on the hydrogen transfer step. Experiments suggested by the theory are then discussed, with presentation of preliminary results for hydrogen transfer among model substrates as well as for the liquefaction of an Illinois No. 6 coal to hexane-, benzene-, and pyridine-solubles by selected hydrogen donors. 

Results showing the effectiveness of the A1- and A2-dialins in coal liquefaction relative to control solvents, naphthalene, Decalin, and fetralin, are presented in Tables 3.1 and 3.2. In both these tables, each row provides the conversion of the coal sample to each of hexane-, benzene-, and pyridine-solubles (plus gases) by the indicated solvent. Table 3.1 contains data derived at a temperature of 400 C and a reaction time of 0.5 hr. Among the control solvents, it can be seen that the naphthalene... 

The dialins were also found to be more effective donor solvents than Tetralin in the liquefaction of an Illinois No. 6 HVA bituminous coal. For example, at 400 C and 0.5 hr reaction time, A2-dialin yielded 16% more pyridine-solubles and 37% more hex-... 

Finally, a mixture containing equal parts of A1- and A2-dialin was found to be a more effective donor solvent than either of the A1- or A2-dialins separately. At 400 C and 0.5 hr reaction time, the mixture of donors yielded 11% more pyridine-solubles and 8% more hexane-solubles than the average for the separate donors. 

The uncrosslinked portion of the coal is obtained by Soxhlet-extraction of the coal with pyridine. Pyridine is a particularly good solvent for coals, and it is thought to remove a majority of the uncrosslinked molecules from the coal matrix. There is evidence that the pyridine-soluble portion is representative of the larger, crosslinked portion,(12) although this aspect remains... 

The extent to which these Flory interaction parameters apply to the pyridine-insoluble portion of the Illinois No. 6 coal is open to question. We cannot address this aspect fully here, but we have noted that the pyridine-soluble and -insoluble portions of the Illinois No. 6 coal studied here have similar carbon, hydrogen and oxygen contents. Maciel has observed that the aromaticities of the two portions of an Illinois No. 6 coal are similar as well.(12) Based on this alone, it seems that the pyridine-soluble portion is representative of the larger, crosslinked portion, at least for the Illinois No. 6 coal, but this aspect remains controversial,(12) so caution is warranted. 

Primary Conversions and Influence of Mobile Phase Yields for the various H-donor and non-donor solvent extractions of Linby coal at 400% are summarised in Table III the conversions for the THF-extracted coal include the extracted material. Surprisingly, pre-extraction with THF significantly increases primary conversions in the polynuclear aromatic compounds (PACs) investigated. These findings appear to be contrary to those of other liquefaction (16) and pyrolysis (17) studies where prior removal of chloroform-extractable material significantly reduced conversions. However, Rincon and Cruz (18) have reported recently that pre-swelling coals in THF increases conversions for both anthracene oil and tetralin. The fact that Point of Ayr (87% dmmf C) coal yielded over 80% pyridine-solubles in pyrene (C.E. Snape, unpublished data) without pre-extraction is consistent with the earlier results of Qarke et al (19) for anthracene oil extraction where UK coals... 

Conversions to pyridine-solubles for non-THF-extracted Linby coal were much greater with naphthalene than with phenanthrene and pyrene (Table m, pre-soaking at 250% has little effect on conversions) and, even after THF extraction, naphthalene conversions are comparable to those of pyrene. 

Although Neavel obtained high yields of pyridine-solubles with naphthalene at short contact times for some US bituminous coals (201. conversions were much lower after longer extraction times. This trend is not evident for Linby coal... 

The lower yields of pyridine-solubles obtained with tetralin compared to 9,10-dihydrophenanthrene (Table ni) and even to naphthalene and pyrene for the THF-extracted coal (Table m. Figures 1 and 2) again are probably attributable to tetralin being largely vaporised at liquefaction temperatures. 

Figure 1. Conversion of THF-extracted Linby coal with naphthalene at 400 C. Pyridine-solubles and THF-solubles.

Poly(methyl methacrylate) films Pyridine-soluble, phenyl-capped Cd incorporated in polymers... 

Table A. Analytical Data and Structural Parameters of the Pyridine-Soluble, Benzene-Insoluble Part of a Vitrinite and the Corresponding Pyridine-Insoluble Residue After THQ Treatment Compared with Those of the Starting Materials...

Pyridine solubles (toluene insolubles) 777A Asphaltenes... 

Figure 3. Effect of pyridine solubles (toluene insolubles) and of asphaltenes on viscosity...

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