Intraparticle mass transfer in coal pyrolysis is described by ternary diffusion and viscous flow, in conjunction with a simple pore model to predict concentration profiles for gases and tar. At low pressures, product yields depend on particle size only, while at high pressures they depend on pressure and particle size. Limited experimental data from a subbituminous coal confirm these trends. Data from a bituminous coal show different trends, as expected from the drastic changes the pore structure undergoes during pyrolysis.

A kinetic study of catalyzed and non-catalyzed coal char hydrogasification was accomplished using a thermobalance (0-1000°C, 0-1000 psi). Rate data were correlated with a kinetic model in which the activation enthalpy was presumed to be a linear function of extent of reaction. Deposition of catalysts (KHCO 3 , K 2 CO 3 , and ZnCl 2 ) on the char and subsequent gasification resulted in substantially increased reaction rates. The effectiveness of the catalysts were in the order KHCO 3 = K 2 CO 3 > ZnCl 2 . Electron microprobe and scanning electron microscopy of chars revealed good catalyst distribution throughout the char particles. / T , he reaction of hydrogen with coal and coal chars to produce gaseous hydrocarbons (hydrogasification) has received considerable attention for at least 35 years since Dent et al. in 1937 first reported on the hydro gasification synthesis (I). The reaction proceeds in two steps. In the initial stage, reaction rates are extremely rapid as the volatile matter and more reactive components of the coal are gasified. Subsequent rapid hydrogenolysis of the higher homologs formed yields methane. In the second stage of the reaction the structure of the remaining carbon char is more graphitic in character, resulting in a much slower hydrogasification rate. Here we report on the catalysis of the slow, second stage of the hydrogasification reaction.There have been numerous reports and patents on the catalysis of a similar reaction-the liquid-phase hydrogenation of coal to liquid and gaseous products. Hydrogenation reactions are generally performed at several hundred atmospheres and at 400°-500°C where the hydrocarbon products formed are substantially liquid. The ability of tin-halogen compounds, ammonium molybdate, and many other materials to catalyze 217