1959. KREBS, R. W. AND LEWIS, W. K. (Standard Oil Development Co.). Method and Apparatus for Carrying Out Exothermic Catalytic Reactions. United States Patent 2,627,522, Feb. 3, 1953; appl. filed Oct. 29, 1948, Serial No. 57,366; 7 claims (Cl. 260-449.6). Chem. Abs., vol. 47, 1953, p. 4146.

The exothermic fluid-type reaction zone is subdivided into at least 2 sections, arranged in series with respect to the flow of reactants. The gaseous reactants are first passed at a relatively high velocity upward through a reaction zone containing heat-exchange surfaces immersed in the catalyst. Then the gases are passed at a relatively low velocity conducive to formation of a dense fluidized catalyst phase through a 2d reaction zone that is free of heat exchange surfaces. Catalyst cooled below the reaction temperature in the 1^st section flows with the high velocity gases continuously into the 2d section to absorb the heat of reaction. The catalyst from the 2d section is continuously returned to the 1^st section for cooling. The rate of catalyst circulation is controlled so that optimum reaction temperatures are maintained in the 2d section. 10 United States patents cited.