Wyodak coal studies

A recent study in these laboratories (75) on calcium carbonate precipitation from Wyodak coal has confirmed the relationship between ion-exchangeable calcium and the appearance of calcium carbonates during liquefaction. These experiments were performed on samples of the subbituminous coal which had been demineralized, to ensure that all carboxylic acid groups were in the acidic form, and subsequently exchanged with varying amounts of calcium ions. 

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. 

Alkylation Studies. Several preliminary experiments were completed to compare the extent of alkylation obtained with our coal pretreatment method to that obtained with Sternberg and Liotta alkylation. Results for Wyodak coal are summarized in Table III. Clearly, our procedure provides a very mild alkylation treatment compared with the other two methods and does not appear to be sensitive to differences in alkyl chain length (methyl vs. propyl). The increase in THF solubiliw was also small this result again suggests only a small extent of alkylation and in addition, shows that only minimal ion exchange (for example Ca by H ) occurred in the coal mineral matter. The effect of each pretreatment method on low severity liquefaction reactivity is discussed in the next section. 

Such bridges in coal structure have been reported only recently. Alkyl substituted methylene and ethylene bridges have been detected in a Wyodak coal by Benjamin et al.. In the present study, some of the branched chain bridges may have been formed by rearrangement of the straight chain bridges during transalkylation. ... 

H-Coal naphthas and distillates derived from Illinois No. 6 (Burning Star Mine) and Wyodak coals were supplied by Hydrocarbon Research, Inc. The naphthas and distillates were blended in the appropriate proportions to obtain a whole syncrude derived from each coal. Properties of these syncrudes are shown in Table I. For comparison, Table I also shows properties of the SRC-II syncrude used in the study described in the previous chapter. The SRC-II syncrude was derived from a West Virginia coal (Pittsburgh Seam, Blacksville No. 2 Mine of the consolidated Coal Company). The H-Coal and SRC-II syncrudes are not directly comparable because the coals used to derive these syncrudes differ. 

Wyodak coal from Wyoming was selected as a suitable low-rank Western coal for this study. It is inexpensive to produce and is available in an abundant supply. Additionally, the regulations in Wyoming permit the extraction of coalbed methane, making it attractive for C02 sequestration and coalbed methane recovery. Coal would be mined from this region gasified to produce hydrogen then the C02-rich off gas would be injected into unmineable coal beds. 

Table 1. Wyodak coal analysis for this study...

Figure 4. TEMPOL ESR spin label studies in Wyodak coal (a) coal radicals prior to spin label addition (b) ESR spectrum immediately after TEMPOL addition, showing carbon radical in coal and the narrow triplet spin label spectrum (the chemical form of the TEMPOL is indicated in the inset) (c) the narrow TEMPOL spectrum broadens with time.

A variety of solvents including hexane, acetone, tetrahydrofuran, toluene and perchloroethylene have been used in these studies together with four analytical strategies. No sulfur has been detected. This feature is well illustrated in Figure 1, which displays the contrasting results for the pristine Wyodak sample, APCSP-2, and another exposed sample of this low sulfur coal. Elemental sulfur at the 0.002% level is easily detected in the exposed sample, none is observed in the pristine sample. 

The SRC s used in this study were obtained from the SRC process demonstration unit operated by Southern Services Inc. in Wilsonville, Alabama. Three SRC s were studied and these products were derived from the following coals Illinois No. 6 Burning Star, Illinois No. 6 Monterey, and Wyodak (Amax). The as-received SRC s were wet owing to a water quench and therefore each SRC was dried carefully before sampling and analysis. The vacuum resid was prepared by laboratory vacuum distillation of an atmospheric resid obtained from a commercial refinery source. The identification and source of the coal liquid samples used in this study along with other pertinent information are presented in Table I. 

To determine whether of not the reductive step does indeed cause an increase in the population of free radicals, we studied two coals, Illinois No. 6 from the Monterey mine and a subbituminous coal from the Wyodak mine, both before treatment and after about 3 days of reductive procedure. To obtain an idea of the maximum possible free radical population, we titrated the solution prior to filtration to determine the amount of alkali metal consumed per gram of coal. Thus if every alkali metal atom generated a radical anion in the coal, we should see approximately 5 to 10 mmol of spin per gram of coal. 

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