OCR Text |
Show substituted carbonyls and ferrocene-type compounds (Khalil, 1980). d. Non-volatile inorganic compounds are either the mineral matter of original coal which have remained unchanged or new inorganic compounds formed during the liquefaction process. These compounds usually constitute the suspended particles of the coal liquids and accumulate in the residue of distillation. Suspended particles of coal-derived liquids are usually inorganic in nature. Filteration, hydrocycloning, centrifugation, and antisolvent and critical-sol vent deashing can remove large particles, leaving micron and submicron size particles suspended in the oil (Katz and Rogers, 1977). Overall, concentration of most trace elements in coal-derived liquids is less than the parent coal. However certain elements like titanium and bromine, tend to concentrate in coal-derived liquids (Filby et al., 1982). Volatile compounds show higher concentrations in lighter distillates, while heavy compounds accumulate in the distillation bottoms. Chlorine, probably due to the formation of chlorinated organic compounds such as chlorinated phenols and aryl halides, shows higher concentrations in the middle distillate (Filby et al., 1982). Certain elements, like B, Ti and Fe, have higher tendancy to form organometal1ic compounds (Lett et al., 1979). The concentration of trace elements and their chemical forms are most affected by the feed coal properties and the processing conditions. The nature of trace elements in petroleum is quite different from coal-derived liquids and is somewhat better understood. While titanium and iron are the predominant trace elements in coal-derived liquids, 1.5.9 |