370.     BROETZ, W., AND SPENGLER, H.  [Physicochemical Behavior of Fischer-Tropsch Catalysts.]  Brennstoff-Chem., vol. 31, 1950, pp. 97-102; Chem. Abs., vol. 44, 1950, p. 6249.

      Conversion behavior of a porous catalyst depends not only on its special chemical properties but also on the structure of its pore system, which makes up its inner surface and provides the path for the transport of the reactants.  The following determinations were made for the purpose of clarifying the pore structure of Fischer-Tropsch catalysts:  (1) Determination of the grain and lattice volumes of unreduced catalysts.  From the data thus obtained the pore volumes and porosity as well as the change in volume through reduction of the catalyst are determined.  (2) Plotting a structure curve in order to find out how the micropore space is divided among the various pore radii.  (3) Determination of the average pore radius of the macropores by means of a perfusion method.  By this means there results for CO and H₂ an excess flow, which is designated as surface diffusion and explains the otherwise determined complete utilization of the catalyst grain.  (4) Determination of the inner surface by plotting an adsorption isotherm.  In connection with surface determination, absorption measurements of CO and H₂ show that the temperature region of Fischer-Tropsch synthesis corresponds to the beginning chemisorption of this gas.  The heat of adsorption of CO and H₂ is calculated from the adsorption isotherms.  (See abs. 3243.)