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    DISSOLUTION OF 2 TURKISH LIGNITES IN TETRALIN UNDER HYDROGEN OR NITROGEN - EFFECTS OF THE EXTRACTION PARAMETERS ON THE CONVERSION
    (Butterworth-Heinemann Ltd, 1992) CEYLAN, K; OLCAY, A
    Two Turkish lignites were extracted with tetralin in a batch autoclave under nitrogen or hydrogen atmosphere. The isothermal extraction temperatures ranged from 325 to 425-degrees-C at 25-degrees-C intervals and the isothermal extraction periods were 0, 30, 60 and 120 min. After removal of char and solvent, the remaining products, which were completely soluble in tetrahydrofuran, were separated into three fractions: preasphaltenes (benzene insolubles), asphaltenes (benzene soluble, n-pentane insolubles) and oils (n-pentane solubles) by successive extractions with benzene and n-pentane. The variations in coal conversion and soluble product composition were investigated with respect to the extraction conditions. The conversion was low below 350-degrees-C but high above 375-degrees-C. As the conversion of the lignites increases, transformation of tetralin to naphthalene also increases. An increase in extraction period affects the product composition but not the percentage conversion, at temperatures of 400-degrees-C and above. In general, the effect of type of gaseous atmosphere on the total conversion was minor. Depending on the extraction conditions, however, the gaseous atmosphere affected the soluble product composition.
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    DISSOLUTION OF LIGNITES IN TETRALIN UNDER HYDROGEN OR NITROGEN - EFFECTS OF EXTRACTION CONDITIONS ON SULFUR DISTRIBUTION AMONG THE PRODUCTS
    (Butterworth-Heinemann Ltd, 1994) CEYLAN, K; OLCAY, A
    Removal and distribution of sulfur among the extraction products of two Turkish lignites (Beypazari and Tuncbilek) were investigated. Extraction was carried out in tetralin at 325-425-degrees-C under nitrogen or hydrogen. Increasing extraction time and temperature increased the amount of sulfur in both soluble and gaseous products. Most of the sulfur in Beypazari lignite was found in the soluble products, whereas most of that in Tuncbilek lignite passed into the gaseous products. The extraction process did not affect the ash sulfur, but the combustible sulfur content of the char decreased with increasing extraction time and temperature. The results suggest that these two lignites have substantially different sulfur functionalities, and that besides the extraction conditions, the structure of the sulfur in the original lignite has an important effect on the extent of sulfur removal and on the distribution of sulfur among the products. Prolonged extraction at high temperatures results in desulfurization of the soluble products, and interaction between H2S and char is likely under these conditions.
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    LOW-TEMPERATURE CARBONIZATION OF TUNCBILEK LIGNITE - EFFECTIVENESS OF CARBONIZATION FOR DESULFURIZATION
    (Elsevier Science Bv, 1989) CEYLAN, K; OLCAY, A
    [Abstract Not Available]
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    SUPERCRITICAL-DIOXANE EXTRACTION OF TUNCBILEK LIGNITE
    (Marcel Dekker Inc, 1995) DEMIRCI, B; OLCAY, A
    After preextraction with ethanol-benzene (1:2) in a Soxhlet apparatus Tuncbilek lignite was extracted with dioxane at 330 degrees C in an autoclave at different pressures and for different exposure times. The extracts were fractionated and many of the compounds they contain were identified by gas chromatography/mass spectrometry. The formation and yields of these compounds are discussed in terms of the structure of the parent fuel and the mechanism of extraction.