Abstract
Coal liquid was extracted by supercritical carbon dioxide at 308 and 328K under the pressure of 6-20MPa. And the effect of diethylene glycol (DEG) as an entrainer on supercritical fluid extraction for coal liquid was examined.
From the experimental results in which DEG was not added, it was suggested that solubility of coal liquid to supercritical carbon dioxide was normalized by density of carbon dioxide. Solubility of normal-paraffin was larger than that of aromatic compound as long as both compounds having similar boiling points were compared each other. But, as the difference of these solubilities was not so much large, the selectivity of normal-paraffins to aromatic compounds was small.
When DEG was used, solubilities of polar molecules such as cresol and phenol decreased to 1/3-1/10 times as much as solubilities obtained without DEG. On the other hand, solubilities of non-polar compounds were enhanced. As the enhancement factors of normal-paraffines were larger than those of non-polar aromatic compounds, the selectivity of normal-paraffines to non-polar aromatic compounds were improved by DEG as an entrainer as well as the selectivity of polar molecules.
