Production and screening of carbon products precursors from coal. Quarterly report, January 1--March 31, 1998

It was reported last quarter that attempts to reduce the ash content of the Hydrocarbon Technology, Inc. (HTI) bottoms material following N-methyl pyrrolidone (NMP) extraction and centrifugation produced a coal-derived pitch with an ash content of 0.7 wt%. Additional processing by pressure filtration through a 0.2 {micro}m Teflon filter produced a coal-derived pitch with an ash content of 0.5 wt%. The latter result indicates that the ash-forming constituents are sub-micron in dimensions. Because the ash exhibited the color of an iron oxide, the assumption was made that the ash-forming matter is primarily iron based. Thus, a portion of the inorganics may be soluble in a dilute solution of HCI acid. To test this assumption, 200 g of the coal liquid were redissolved in 1.5 L of NMP. Table 1 compares some data of the properties of the acid-washed coal liquid with those from centrifugation alone. It is evident that the acid treatment was effective in reducing the quantity of ash significantly. In addition, because some of the lighter coal components were discarded with the supernatant liquid, the coke yield, real density, and softening point temperature all increased