Cationic catalysts polysiloxanes

Solid acid catalysts, consisting of polysiloxane bearing alkylsulfonic acid groups (MCM-41), are comparable in their catalytic activity to those of the polystyrene-based cation exchange resins. These catalysts can be used in the preparation of para-Bisphenol-A by the alkylation of phenol with acetone. Other application of these catalysts lie in the alkylation of phenol with isobutene at 90-130 O . 

The use of solid acid catalysts, consisting of polysiloxanes bearing alkylsulfonic acid groups, is described, in organic synthesis and in technical applications. Although sulfonated polysiloxanes have been reported in the literature and have been found to show excellent activities in comparison to conventional polystyrene based cation exchange resins, no large scale technical use has become known thus far. 

Fig. 4 Schematic representation of bifunctional polysiloxane catalysts and ionically modified polystyrene cation exchange resins.

Comparison data were presented, that demonstrate the use of the polysiloxane material as an advantageous substitute for organic cation exchange resins, sulfuric acid, p-toluene sulfonic acid and acidic zeolites. It is demonstrated, that materials like 1 and 2 are cost-efficient and reliable catalysts in esterification, alkylation, and condensation, whereas use of the bifunctional catalyst 3 gives excellent conversions in hydrogenolysis reactions in general. 

The polysiloxanes are applied by padding followed by drying and heating for a few minutes at 120-150°C to cure the finish, or by exhaust procedures [70b]. Because most textile fabrics have a negative surface potential in water, cationic surfactants are used for emulsifying polysiloxanes for exhaust application. The padding or exhaust application should deposit about 1-2% polysiloxane onto the fabric the amount can be smaller in coapplication with a zirconium or titanium catalyst. ... 

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