Effectiveness factors in a nonisothermal reaction system

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Abstract
Hydrogenation rates of ethylene on a copper‐magnesium oxide catalyst were measured for fine catalyst particles and ½ in. spherical pellets from 60° to 160°C. Experimental effectiveness factors for this exothermic reaction system ranged from 0.2 to 25, depending upon the temperature and density of the catalyst pellets. The activation energy for the particles was 11,800 cal./g. mole (above 120°C.), while E for the pellets decreased to zero at high temperatures. Reasons for this behavior are discussed.The effective thermal conductivity of the catalyst pellets was measured as a function of density and the effective diffusivity was estimated from pore size and pore volume measurements. In principle this information and the rate data for the particles are sufficient to predict effectiveness factors for the pellets. However available prediction methods are based upon first or second order rate equations which do not fit the ethylene hydrogenation reaction.