Sequential low-temperature depolymerization and liquefaction of US coals. Progress report No. 6, January 1--March 31, 1988

Abstract

Earlier results on the reactions of a Pittsburgh {number_sign}8 (PA) coal sample, designated below as PB(PA) coal, were described in Progress Report no. 4. Additional work on this coal was performed during the reporting period, as follows: The study of the effect of FeCl{sub 3} catalyst concentration upon the efficiency of the HT depolymerization step was extended. Low FeCl{sub 3} concentrations, in particular in the range of 3.0 to 7.5 wt%, were investigated at four different HT temperatures (275, 290, 300, and 310{degrees}C). It was found that even at the lowest concentration employed (3.0 wt%) FeCl{sub 3} is efficient at 290--310{degrees}C in causing extensive depolymerization (viz. cleavage of alkylene, e.g., methylene linkages) in the PB(PA) coal framework, as reflected by partial solubilization in THF (7--11 wt%) and attendant high degree of activation of the coal for the subsequent BCD step. Additional BCD experiments with the mildly hydrotreated PB(PA) coal, i.e. , with the partially depolymerized coal product from the HT step, were also performed. In particular, the effect of increased BCD temperature, above 290{degrees}C, upon product composition was determined. It was found (see Figure 1) that increase in BCD temperature from 290{degrees} to 310{degrees}C results in a slight increase inmore » the overall yield of THF solubles. On the other hand, this temperature increase causes a major decrease in the yield of the desirable cyclohexane-soluble (oil) fraction and a corresponding increase in the yield of asphaltol and asphaltene products. This clearly indicates that BCD temperatures above 290{degrees}C cause undesirable changes in the composition of the final depolymerized product from PB(PA) coal. « less

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