Structure and Sintering Properties of Representative Cracking Catalysts

Structure and Sintering Properties of Representative Cracking Catalysts 

A preliminary overall picture of cracking catalyst structures is available in the first three horizontal rows of the composite plot of Fig. 2 and the corresponding data of Table I. Isotherms presented in the lowest row are discussed in Sec. IV. Only the general features of these representative types of cracking catalysts are indicated here, since the detailed plots of individual isotherms will be considered in subsequent sections on sintering. Cracking catalysts of principal interest are represented by three types silica-magnesia silica-alumina and activated clay. 

The silica-magnesia catalysts, DA-5 and Nalco, in the virgin state, along with Davison silica gel have practically their entire area and pore volume contributed by the very smallest of pores that are encountered in catalyst structures that is, pores in the 10 to 15 A. radius range. It is apparent in Fig. 2 that for these materials there is no appreciable adsorption at the high relative pressures. This indicates the absence of large pores. One and one-half monolayers according to the BET theory effectively fill the pore volume of the DA-5 and the Davison silica gel, and only two monolayers are required for Nalco. Very little hysteresis is observed for any of these three materials. 

The synthetic silica-alumina catalysts, TCC Beads, Aerocat, and Diakel, are composed of pores appreciably larger but with average pore radius values almost exclusively in the small pore range of 15 to 25 A. (Ries, Johnson, Melik, and Kreger, 48 Shull, Elkin, and Roess, 57). The complete absence of large pores is indicated for the TCC Beads and the Aerocat Microspheres. In the case of silica-alumina catalysts, the hysteresis loops have considerable breadth and area in contrast to the silica-magnesia isotherms. 

The clay type catalysts such as TCC clay and Fluid Filtrol have a considerably wider pore size distribution which includes pores having radii much greater than those of the synthetic silica-alumina and silica-magnesia. There is appreciable adsorption in the high relative pressure region, and the hysteresis loops are broad (Oulton, 42 Ries, Johnson, Melik, and Kreger, 48 Ritter and Drake, 53). 

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III. Structure and Sintering Properties of Representative Cracking Catalysts.. . 99... 

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