657.    DAMKOHLER, G.  [Excess Temperature in Catalyst Grains.]  Ztschr. Physik. Chem., vol. 193, 1943, pp. 16-28; Chem. Abs., vol. 39, 1945, p. 2689.

      The maximum excess temperature, θ_max in a stationary catalyst grain during reaction is independent of the chemical reaction velocity, as well as the radius of the grain and is determined solely by the heat of reaction Q, the internal diffusion coefficient D_ji, the internal thermal conductivity λ_4, and the external concentrate c of the reactants.  The following equation was derived:

      θ_max. ≈ QD_ji (c_jr-c_jo) /ν_j λ₄ where c_jo

  is the equilibrium concentration of reactants and ν_j is the stoichiometric coefficient of constituent j.  Calculated θ_max for SO₂ oxidation was 0.42°, for NH₃ synthesis 0.20° at 20 atm. and 0.57° at 1,000 atm., for MeOH synthesis 1.0°, for butane synthesis from CO and H₂ 3.0°.  This behavior of an individual catalyst grain is quite different from that of a converter where chemical reaction velocity and dimensions of the reaction vessel are of importance.