Coliquefaction of coal and black liquor to environmentally acceptable liquid fuels

Previous work in our laboratories has demonstrated that addition of lignin to coal during liquefaction significantly increases the depolymerization of coal and enhances the quality of the liquid products. It is believed that thermolysis of the lignin results in the formation of phenoxy and other rea ctive radicals at temperatures too low for significant thermolysis of the c oal matrix such radicals are effective and active intermediates that depoly merize coal by cleaving methylene bridges. It has been reported that alkali is also effective for extraction of liquids from coal. The work presented here combines these two reactive agents by utilizing the black liquor waste stream from the Kraft pulping process for coal depolymerization. That wast e stream contains large amounts of lignin and sodium hydroxide, as well as other components. To permit comparative evaluations of the extent of coal d epolymerization by coprocessing coal and black liquor, reference runs were performed with tetralin alone, sodium hydroxide in tetralin, and lignin in tetralin. Results indicated that the sodium hydroxide-tetralin system resul ted in almost 67% conversion at 375 degrees C, 1 hour. The black liquor sys tem exhibited a lower conversion of 60%, indicating some inhibition of the depolymerization reactions by components in the black liquor.