MODELING THE KINETICS OF COAL DEPOLYMERIZATION DURING HYDROLIQUEFACTION - HYDROGEN DONATION AND THE RELEASE OF NITROGEN AND SULFUR-COMPOUNDS

Coal liquefaction was conducted in a stirred batch reactor in the presence of tetralin (at tetralin/coal mass ratios of 4.7-7.0) and of hydrogen (at partial pressures of 10.5-13.7 MPa), at temperatures of 360-470-degrees-C, and for 600 min at 360-degrees-C and 435-450 min at the other temperatures. Liquid-phase samples collected periodically were analysed by gas chromatography, using f.i.d., n.p.d. (for nitrogen compounds) and f.p.d. (for sulfur compounds). The results (concentration of compounds in the reacting mixture vs. time) were analysed by a kinetic model describing the coal depolymerization process as a surface reactive phenomenon, and according to which the concentration vs. time of any compound or group of compounds produced directly from coal but not undergoing successive reactions is represented by exponential equations having a common characteristic time. The kinetic analysis indicated among other things that under the experimental conditions, nitrogen compounds released from the coal are essentially stable, whereas those containing sulfur undergo successive reactions. The rate constants and the activation energies of the reactions entering the kinetic model were calculated.