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A mathematical model is presented which describes mass and energy transport during rapid pyrolysis of fibrous cellulose particles. Radiative heat transfer within porous cellulose is modeled by using the method of zones. The kinetic model for pyrolysis developed by Bradbury et al. is extended to include secondary decomposition of condensible liquids (tars) formed. Solution of the governing equations shows that both mass-and heat-transfer resistances influence product composition from pyrolysis even for cellulose particles as small as 0.5 mm in diameter. Heating rate has little influence on product composition, but increasing the total pressure results in a decreased condensible product yield. Radiative heat transfer plays a minor role within the solid for the conditions simulated. The model is useful for identifying critical parameters and conditions in pyrolysis and for predicting trends in product yields.

Heavy distillate prepared from Powhatan No. 5 coal by hydroliquefaction was separated into nine fractions by preparative liquid chromatography. The neutral oils fraction (73% of the coal liquid) was investigated in catalytic hydroprocessing experiments with a flow microreactor at 325 to 400 OC and a range of pressures (>lo0 atm) and space velocities. The catalyst was a standard suifided Nl-Moly-Al,O,. The predominant reaction was hydrodesulfurization. Individual compounds were determined by gas chromatography, and quantitative kinetics was determined for conversion of the major organosulfur compounds, dibenzothiene, &nethyklibenzothbphene, and an unidentified isomer of methyklibenzothiophene. Each reaction was first order in the organic reactant. The rate constant for dibenzothiophene conversion at 355 O C (5.8 X L/g of catalyst s) Is in good agreement with the literature value for dibenzothiophene reacting alone with H2 in a paraffin solvent. Inhibition of the hydrodesulfurization reactions by polycyclic aromatlc hydrocarbons (the major components of the neutral oils) was negligible. A coakbrived liquid such as the neutral oilslacking organonitrogen compounds-might be an attractive commercial feedstock, provided that it could be separated economically from the remainder of the coalderived liquid.

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