Styrene hydrogenation, shape selectivity

The neutral molecular sieve, aluminum phosphate (ALPO, Chapter 10) can also serve as a shape selective support for metal catalysts. These catalysts are normally prepared by the incipient wetness process followed by appropriate drying and reduction procedures. Fig. 13.19 illustrates the selectivity observed using a Ni/ALPO catalyst to hydrogenate a mixture of styrene and a methyl styrene (Eqn. 13.13). The rates of hydrogenation of cyclic alkenes over a Rh/ALPO catalyst decreased in the order cyclopentene cyclohexene > cycloheptene > cyclooctene but no selectivity was observed in a competitive hydrogenation of a mixture of cyclohexene and cyclooctene. 75... 

For hydrophobic elastomers such as NR and styrene butadiene rubber, carbon black usually has been selected as filler due to the hydrophobic surface characteristics and special particle shapes of carbon black which provide good dispersion. However, the dispersion of polar filler in hydro-phobic rubbers matrix is difficult because of its hydrophilic surface. The hydroxyl groups exist on the surface of polar filler provide strong filler-filler interactions which resulted in poor filler dispersion. The polar surface of filler formed hydrogen bonds with polar materials in a rubber compound. As known, the silica surface is acidic and forms strong hydrogen bonds with basic materials. ... 

A gel that is commercially available has the trade name ELAMUS. It is made of a hydrogenated styrene-butadiene block copolymer that is synthesized by solution polymerization. It is swollen by a liquid plasticizer. To maintain shape, a crosslinked structure resembling that of human tissue is formed (see Fig. 4) [5]. The characteristics of this gel are that even if the same polymer main chain is used, various properties can be tailored by changing the low molecular weight material that swells the polymer. By selecting appropriate compatibility and miscibility to allow the polymer molecules to be mobile, gel properties can be tailored. 

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