EFFECTS OF HYDROGEN PRESSURE AND TEMPERATURE ON FREE-RADICALS PRODUCED IN COAL-TIRE COPROCESSING

In-situ ESR (Electron spin resonance) spectroscopy of free radicals is used to investigate the coprocessing of Blind Canyon coal with Michel in tire rubber for temperatures up to 480 degrees C and under H-2 and argon pressures up to 1000 psig. Comparing the free radical intensitie s of the coal and the tire alone with those obtained for the 1:1 coal- tire mixtures, determined under 500 and 1000 psig of H-2 and under 100 0 psig of inert argon, the following observations are made. First, a s trong synergism between the coal and the tire polymer is indicated, as the intensity of the ESR-active free radicals in the coal-tire mixtur e under H-2 pressure are enhanced severalfold beginning at approximate to 200 degrees C and peaking near 350 degrees C. Second, increasing t he H-2 pressure from 500 to 1000 psig reduces the free radical intensi ty, most likely because of enhanced hydrogenation. Third, the tire pol ymer gives a weak ESR-active signal whose characteristics change drama tically between 140 degrees C and 200 degrees C, indicating a phase ch ange in the tire material. The synergistic effect observed here is con sistent with the reported improved yields in direct liquefaction exper iments using coal-tire mixtures.