Microemulsions with Balanced Catalytic Surfactants

3 Multiphase Microemulsions with Balanced Catalytic Surfactants 

There are two types of bipbasic microemulsion systems one with an excess oil in equilibrium with an oil-in-water microemulsion (Winsor I system) and one with an excess water phase in equihbrium with a water-in-oil microemulsion (Winsor 

II system). The WI system is particularlyrelevant with regard to the ease of workup since the product is extracted into the excess oil phase and the catalyst remains in the microemulsion phase. However, it is still sensitive to dilution by water arising from H2O2 disproportionation. This can be avoided by using pervaporation membrane [71]. A further improvement has been brought by three-hquid phase microemulsion systems based on balanced catalytic surfactants [72]. This new kind of catalysts is carefully designed in order to provide spontaneously a Winsor 

Under well-chosen conditions (the so-called optimal formulation), the interfacial tension T ater/oU between the aqueous and the oil phases is ultralow and, as a consequence, a Winsor III system appears spontaneously. In that case, it becomes a very effective reaction medium with the following features  

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DSO via molybdate-catalyzed disproportionation of HjOj provides a readily scalable alternative to photooxidation. It can be carried out in commonly available stirred-tank reactors. However, the reaction does not work at low temperatures and organic media are limitedto alcoholic polar solvents (methanol or the safer ethylene glycol) or to microstructured media such as one-, two-, or three-phase microemulsion systems. The latter based on balanced catalytic surfactants advantageously combine low surfactant concentration with easy product isolation and catalyst recycling via simple phase separation. Safe processing may be further enhanced by microreactors, which minimize peroxide hold-up. 

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