In several coal/plastics liquefaction runs performed by Hydrocarbon Technologies, Inc. (HTI), a substantial amount of incompletely converted high-density polyethylene (HDPE) was present in ash-free recycle resid streams when either the ROSE-SR unit was used in Run POC-2, or the pressure filter unit was used in Runs CMSL-8 and CMSL-9. This indicates that the HDPE is less reactive than coal at the liquefaction conditions used. In these ash-free streams, there is no solid organic or inorganic material arising from the coal, and the incompletely converted HDPE can be recovered by extraction and filtration with tetrahydrofuran (THF) at room temperature. The HDPE (or HDPE-like material, which could also consist of heavy waxes) is THF insoluble. However, in ashy streams, there are both inorganic ({open_quotes}ash{close_quotes}) and organic (unconverted coal) components present from liquefaction of the coal, that interfere with an easy and clean separation of the HDPE from the coal/plastics liquefaction stream sample. Therefore, CONSOL developed an analytical procedure for HDPE in the ashy stream samples based on extraction of HDPE from the sample using hot (150{degrees}C) decalin (decahydronaphthalene), in which the HDPE is soluble. The decalin extraction is both preceded and succeeded by extractions and washes with THF at room temperature, to remove the coal-derived components from the sample
