CHARACTERIZATION OF SUCCESSIVE EXTRACT FRACTIONS RELEASED FROM A SAMPLE OF COAL DURING LIQUEFACTION IN A FLOWING-SOLVENT REACTOR

Product fractions released from coal during successive temperature and time intervals have been recovered in a flowing-solvent liquefaction reactor. These experiments have been carried out using tetralin, quinoline, and hexadecane as vehicles; the selection was based on the H-donor ability of tetralin, the high solvent power of the essentially nondonor solvent quinoline and the absence of both solvent power and donor ability of hexadecane. The successive extract fractions have been characterized using size exclusion and planar chromatography, FT-IR and UV-fluorescence spectroscopy. Monitoring changes in structure between successive product fractions has required the use of analytical methods which allow the discrimination of effects due to products from the reactions of the liquefaction solvent (vehicle): size exclusion chromatography (SEC), the tandem use of SEC with UV-fluorescence spectroscopy (UV-F) and planar chromatography have proved useful in this respect. Successive extract fractions released from Point of Ayr coal in tetralin and quinoline showed progressively increasing molecular mass distributions with increasing intensity of reaction conditions (temperature and time). Parallel increases have been observed in the densities of large aromatic fused-ring systems during the UV-F spectroscopy of SEC-elution-time-resolved cuts from individual extract fractions. Planar chromatography has also served to establish an order of polarity between the set of successive extract fractions as a function of increasing reaction intensity. While our findings suggest therefore that fractions released from coal during earlier stages of the liquefaction process appear more amenable to further processing, quantitative differences in the ease of hydrocracking of these fractions remain to be demonstrated.