Catalysis in Micellar Microheterogeneous Systems

Several writers53,169 have stressed the point that micellar catalysis has analogies with heterogeneous catalysis on solid surfaces because the solubilisation of substrate in the core of a micelle containing catalytically active sites is conceptually related to adsorption on surfaces and the number of micelles to surface area. 

Rh/19 (n=1,2,3,6) catalysts were used in the hydroformylation of 1-octene in the presence of conventional tensides such as the sodium salt of the dodecyl-benzene sulfonic acid (0.5 wt.%) in an 1-octene/nonane/methanol/water (60/34/50/ 56) mixture.121 With Rh/19 (n=6) the TOF achieved was 28 h. 1,21 

Na5[Co+(CO)3(19)2]5 was used as catalyst for the hydroformylation of 1-hexene and 1-octene in a two phase system without leaching of cobalt into the organic phase.122 The products obtained were almost exclusively aldehydes (4-38%) and very little (0.4-3%) or no alcohol formation122 in contrast with cobalt/phosphine catalysed hydroformylation in organic solvents which give alcohols. The n/i ratios of the aldehydes were low (1.1-2.5),122 however, and never approached that expected for a phosphine modified cobalt catalyst in non-aqueous media324,325,393 (see Table 8). 

Rh/76 (Table 4 n=l, x=0, R= Me, Bu), which should be able to induce micelle formation, were used as catalysts in the biphasic hydroformylation of 1-dodecene.371 The conversion was 80%, the n/i ratio 60/40 with no carry-over of the rhodium catalyst into the organic phase.371 

Replacement of the sodium cation of the tppts by an ammonium group such as Me(CH2)i3N+Me3 also imparts surfactant properties to the tppts 

---