Surface-type supports

Surface-type supports. Many different materials are used for surface functionalization, including beads made from sintered polyethylene, cellulose fibers (cotton, paper, Sepharose, and LH-20), porous highly cross-linked polystyrene or polymethacrylate, controlled pore glass, and silicas. 

Surface-type supports Materials developed for surface functionalization, for example, cellulose fibers, and highly cross-linked polystyrene. 

The high specific surface area supports (10 to 100 m2/g or more) are natural or man-made materials that normally are handled as fine powders. When processed into the finished catalyst pellet, these materials often give rise to pore size distributions of the macro-micro type mentioned previously. The micropores exist within the powder itself, and the macropores are created between the fine particles when they... 

The catalyst consists of V205 supported on silica gel with K2S04 and other promoters also present. The physical property values tabulated below are typical of the low or intermediate surface area supports that one might expect to use in this application. DeMaria et al. (8) did not report data of these types for their catalyst. 

Figure 9.36. Representation of internal surface reverse phase (ISRP) type support. Courtesy of Regis Chemical.

Tlie purpose of supports is similar to that of the structural promoters in aiming at u high meta) disper.sion and catalyst surface. Typical supports are alurttina and silica [15], but also inert supports such as carbon [65,66] or polystyrene-type polymers [67] have been investigated, giving highly-active iron or cobalt catalysts. 

Metal particles do not grow with random orientations on the surface of the support but, instead, under well-defined crystallographic relationships. Note for example the alignment of the diffraction spots of ceria and Rh in the DDPs shown in Figures 4.17(b) and 4.17(c). As demonstrated further on, this is a consequence of an epitaxial relationship between the fluorite-type supports and the f.c.c. metal particles. 

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