Extraction of a North Dakota Lignite with Supercritical Aliphatic Solvents

摘要

Figure 5 suggests that the supercritical fluid solvents used were extracting more of the compounds that would devolatilize below approx.400 exp 0 C with increased operating temperature necessary with the longer solvent chain length. The analyses of the extracts revealed the presence of aliphatic esters, alcohols, acids and alkanes with litle or no aromatics being extracted. Separations and quantitative infrared spectroscopy have been performed on the chloroform-methanol soluble fractions (approx.50 wt %) from the supercritical pentane and hexane extractions. The yields from this preliminary data averaged 0.19%, 0.06%, and 0.26% for the waxy esters, aliphatic alcohols and the fatty acids, respectively. Proton NMR showed that the aromatic content of the extracts tended to increase slightly with increasing operating temperature. Capillary GC analyses on whole samples and silica gel column separated samples using a 15 m SE-54 column provided data on the distribution of normal and cyclic alkanes, waxy esters, and fatty alcohols and acids. The series of n-alkanes occurred between C sub 21 and C sub 33 with a maximum concentration of the C sub 29 alkane. A number of triterpanes and C sub 15 to C sub 20 cyclic alkanes were present. The fatty alcohols were found to be mainly C sub 24 . The fatty acids were converted to their methyl esters for analysis. A series of esters was observed with maximum concentration at C sub 24 and C sub 26 . From the composition and yield data, it appears that extraction of Indian Head lignite with supercritical aliphatic solvents with critical temperatures below 325 exp 0 C still has the characteristics of nonspecific extraction. 10 references, 5 figures, 5 tables. (ERA citation 10:023384)