Hydrogenated polystyrene, preparation

An example of the Michael chemistry, typical of all quinones bearing a replaceable hydrogen, is the preparation of a sulfone (6) (in 55% yield), which was ultimately converted to a polystyrene redox polymer (11). 

Polymer—Cp—MCl complexes have been formed with the Cp-group covalendy bound to a polystyrene bead. The metal complex is uniformly distributed throughout the bead, as shown by electron microprobe x-ray fluorescence. Olefin hydrogenation catalysts were then prepared by reduction with butyl hthium (262). 

In the early 1970 s, Bayer et al. reported the first use of soluble polymers as supports for the homogeneous catalysts. [52] They used non-crosslinked linear polystyrene (Mw ca. 100 000), which was chloromethylated and converted by treatment with potassium diphenylphosphide into soluble polydiphenyl(styrylmethyl)phosphines. Soluble macromolecular metal complexes were prepared by addition of various metal precursors e.g. [Rh(PPh3)Cl] and [RhH(CO)(PPh3)3]. The first complex was used in the hydrogenation reaction of 1-pentene at 22°C and 1 atm. H2. After 24 h (50% conversion in 3 h) the reaction solution was filtered through a polyamide membrane [53] and the catalysts could be retained quantitatively in the membrane filtration cell. [54] The catalyst was recycled 5 times. Using the second complex, a hydroformylation reaction of 1-pentene was carried out. After 72 h the reaction mixture was filtered through a polyamide membrane and recycled twice. 

Partial hydrogenation of acetylenic compounds bearing a functional group such as a double bond has also been studied in relation to the preparation of important vitamins and fragrances. For example, selective hydrogenation of the triple bond of acetylenic alcohols and the double bond of olefin alcohols (linalol, isophytol) was performed with Pd colloids, as well as with bimetallic nanoparticles Pd/Au, Pd/Pt or Pd/Zn stabilized by a block copolymer (polystyrene-poly-4-vinylpyridine) (Scheme 9.8). The best activity (TOF 49.2 s 1) and selectivity (>99.5%) were obtained in toluene with Pd/Pt bimetallic catalyst due to the influence of the modifying metal [87, 88]. 

Polystyrene can be prepared as follows A mixture of styrene, detergent (Na-dodecanoate), and water is agitated ultrasonically to produce a fine emulsion. On the addition of hydrogen peroxide (initiator), PS is obtained as a polymer, which can be extracted after filtration. The polymer molecular weight is determined by various methods (such as light scattering and osmotic pressure). 

HPS was developed by the Laboratory of Sorption Processes (INEOS RAS). It was synthesized by the introduction of methylene bridges between neighboring phenyl rings of linear polystyrene, thus the porous structure was obtained. Preparation of palladium nanoparticles occurred by the adsorption of freshly prepared Na2[PdCl4] solution (Na2[PdCl4] is hydrolyzed in time) into the HPS matrix. The reduction of palladium compound by hydrogen led to the formation of palladium nanoparticles. 

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