Pyrite removal from Illinois #6 coal by CrCl2 reduction and effect of pyrite on the coprocessing of Illinois #6 coal with waste automotive oil

Pyrite was removed from Illinois #6 coal by HF/HCl washes and by CrCl2 redu ction. The effect of pyrite on the coprocessing of Illinois #6 coal with wa ste automotive oil was investigated. ICP results show that the standard HF/ HCl treatment still leaves about 65% of the pyrite in the Illinois #6 coal, but acidic CrCl2 reduction can remove 95.9% of the pyrite from the same co al without causing significant alteration of the organic matter as shown by examination of samples before and after treatment by infrared and C-13 NMR spectroscopy as well as by atomic ratios (H/C, N/C and S-organic/C). XPS r esults show that compared to untreated Illinois #6 coal, the inorganic comp osition on the surface of CrCl2 treated Illinois #6 coal changes very littl e except for loss of pyrite, whereas the inorganic composition of HF/HCl tr eated Illinois #6 coal changes substantially. A comparison between untreate d coal and CrCl2 treated Illinois # 6 coal was made by TOF-SIMS (Time-of-Fl ight Secondary-Ion Mass Spectroscopy). Nearly total removal of pyrite from Illinois #6 coal by CrCl2 decreases the conversion yield of the coal to THF solubles to 16.2%, compared to 60.9% for untreated Illinois #6 coal and 53 .4% for HF/HCl treated Illinois #6 when each of these coals is coprocessed with waste automotive oil under the same reaction conditions. This comparis on of conversion yields of the coal further supports the conclusion reached previously that pyrite functions as a catalyst aiding in dissolution of th e coal to form gas, oil, asphaltenes and char. (C) 1999 Elsevier Science B. V. All rights reserved.