EFFECT OF PROCESS CONDITIONS ON CO-LIQUEFACTION KINETICS OF WASTE TIRE AND COAL

Thermal and catalytic liquefactions of waste (recycled) tire and coal were studied both separately and using mixtures with different tire/co al ratios. Runs were made in a batch tubing bomb reactor at 350-425 de grees C. The effect of hydrogen pressure on the product slate was also studied. Mixtures of tire components and coal were used in order to u nderstand the role of the tire as a solvent in co-liquefaction. In the catalytic runs, a ferric-sulfide-based catalyst impregnated in situ i n the coal was used. Both the tire components and the entire tire exhi bit a synergistic effect on coal conversion. The extent of synergism d epends on temperature, H-2 pressure and the tire/coal ratio. Experimen ts with coal and tire components show that the synergistic effect of t ire is due to the rubber portion of the tire and not the carbon black. The synergism mainly leads to an increase in the yields of asphaltene s, which are nearly double those in the coal-only runs at 400 degrees C. The conversion of coal increases dramatically using the catalyst, b ut the catalytic effect is attenuated somewhat in the presence of tire , especially at high tire/coal ratios. The data were analyzed using a consecutive reaction scheme for the liquefaction of coal to asphaltene s and thence to oil+gas, both reactions being of second order; a secon d-order conversion of tire to oil+gas; and an additional synergism rea ction when both coal and tire are present, first-order in both coal an d tire. Parallel schemes were assumed for thermal (uncatalyzed) and ca talyzed reactions. The uncatalyzed liquefaction of coal has a low appa rent activation energy, 36 kJ/mol, compared to those for the synergism reaction (84 kJ/mol) and the catalytic coal liquefaction (158 kJ/mol) . The conversion of asphaltenes to oil+gas is relatively independent o f temperature and of the presence of the catalyst. The catalyst appear s to play a significant role in the conversion of coal to asphaltenes, but a negligible role in the synergism reaction. (C) 1998 Elsevier Sc ience B.V. All rights reserved.