2285. MILLS, G. A., BOEDEKER, E. R., AND OBLAD, A. G. Chemical Characterization of Catalysts. I. Poisoning of Cracking Catalysts by Nitrogen Compounds and Potassium Ion. Jour. Am. Chem. Soc., vol. 72, 1950, pp. 1554-1560; Chem. As., vol. 44, 1950, p. 6611.
Basic organic N compounds, such as quinoline, are held on SiO2-Al2O3 (-MgO, -ZrO2) catalyst surfaces by physical and chemical forces. These forces are widely different so that at 250°-500° the physically held quinoline can be distinguished from that chemically held. At a given temperature, the amount of physically held N compound is increased with an increase in its partial pressure. The amount chemisorbed is decreased with an increase in temperature. The cracking activity of the catalysts studied was proportional to their capacity to chemisorb quinoline at cracking temperatures. Catalysts that have basic N compounds chemisorbed or that have K added by base exchange are poisoned for cracking. From a study of partial poisoning an exponential relationship was found between the amount of certain N compounds chemisorbed and the yield of C6H6 from the dealkylation of cumene. A relatively small fraction of the total surface of SiO2-metal oxide cracking catalysts is responsible for catalytic activity. The chemical properties exhibited by this part of the surface identify the active principal as an acid.
MINACHEV, K. M. See abs. 3179.