Changing some properties of lignites by pre-processing.

Six different Turkish lignites ( Beypazarı, Kangal, Mengen,Tunç.1, Tunç.2 ve yatağan) have been subjected to the soxhlet extractions wiht 21 solvents from three different groups ; non-hydrogen bonding, hydrogen bonding and alkyl amine solvents; at their boiling points. In addition toluene extractions were carried out in an autoclave at 350°C. The soxhlet extractions continued until the solvent in the thimble section became clear, but the autoclave extractions were carried out for one hour. The lignites have been pretreated with 0,1 N HCl (at room temperature), and with EtONa/EtOH (at 150°C in an autoclave) and the pretreated lignites have been extracted again with the same solvents as described above. Extraction yields of raw samples and of pretreated samples, the effects of the pretreatment and solvent properties on the yields have been investigated. In addition, effectiveness of the solvents for swelling of the lignites, the types and contents of acidic functional groups in the lignites, the relations of these groups with calcium ion, and the effects of the pretreatments on these functional groups have also been studied. Both the extracts and solid residues have been analyzed by analytical or spectroscopik methods. The result indicated that extraction yields change depending on both the type of lignite and that of the solvent at low temperature. The yields were low with non-hydrogen bonding solvent, but high with hydrogen bonding and alkly amine solvents. However, complete removal of the amines, with 7 or more carbons, from coal and coal extracts were not possible due to their strong adductions. Relatively good relations were found between the extraction yields and solvent's solubility parameter ( ), donor number (DN) and coal swelling features. While the HCl pretreatment affects mainly the inorganic structure, the EtONa/EtOH pretreatment affects the organic structure of the lignites. Both the extraction yields and swelling properties increased after the HCl pretreatment in comparison to the raw lignites; and the increments were higher with hydrogen bonding solvents than those with non-hydrogen bonding solvents. The lignites underwent partial dissolution during the EtONa/EtOH pretreatment and the residues were enriched withrespect to the functional groups. Based on these results, it was suggested that a portion of ester and ether linkages in the lignites have been broken during the pretreatments. All extracts contain both aromatic and aliphatic structures. It has been determined, on the other side, that, pyridien and THF extracts contain greater amounts of condensed aromatic structures than other solvent extracts where as n-pentane extracts are mostly aliphatic in natüre. DTA result indicated that thermal decomposition temperatures of the lignites have been shifted in comparison to the original lignites after the pretreatments. These temperatures lowered after HCl pretreatments but increased after EtONa/EtOH pretreatments. These results indicate that the structures and reactivities of the lignites have been change by the pretreatments.