2-STAGE CATALYTIC COLIQUEFACTION OF COAL AND WASTE TIRE

Two-stage catalytic liquefaction of coal and waste tire was studied us ing two bituminous coals, Blind Canyon and Illinois No. 6, and a sub-b ituminous coal, Wyodak. The tire sample was a mixture of waste, recycl ed tires. In the first stage, the tire was liquefied separately at 350 or 400 degrees C under N-2 or H-2 to obtain tire oil. In the second s tage, each coal was liquefied, in turn, with tire oil at 350-450 degre es C and 1000 psi of H-2 (cold) using various tire-oil/coal ratios. A few second-stage runs were carried out with coal and vacuum-pyrolized tire oil obtained from a commercial source. Some of the second-stage r uns were catalytic. For these, a ferric-sulfide-based catalyst was imp regnated in situ in the coal. In general, the use of tire oil shows an improvement in coal conversion. In the absence of catalyst, the effec ts are similar with tire oils prepared under different conditions. Wit h the catalyst, the increase upon adding tire oil is greatest when the tire oil is prepared at 400 degrees C in a hydrogen atmosphere. A syn ergistic effect can be quantified by adding to the conversion (or oil yield) for catalyst plus coal the increase in conversion (or Oil yield ) observed when tire oil is added to coal in the absence of catalyst a nd comparing this number to the conversion (or oil yield) when the fee d is coal plus tire oil plus catalyst. In general, the improvements ar e most pronounced at the higher temperatures of the second stage and a t higher ratios of tire oil to coal. For all three coals, the effects of tire oil are greater than those due to the whole tire in single-sta ge coliquefaction, especially with a catalyst present at high tire-oil /coal ratios. A kinetic analysis shows that the thermal reactions of c oal and tire oil have lower activation energies in the second stage of two-stage-liquefaction compared to those in single-stage Liquefaction . A similar effect is noted for the catalytic reactions, at least for the bituminous coals. This indicates that two-stage liquefaction is be neficial, particularly at mild temperatures in the second stage. Furth er, the activation energies for the synergistic rate constants are hig her for the catalytic reactions than for; the thermal reactions, indic ating that diffusion effects in the coal may be important in the nonca talytic processes.