Sulfonation resin performance, time

The activity of Nafion as a catalyst has been increased by applying it on silica by the sol-gel method using tetramethoxysilane20 or tetraethoxysilane and dimethyl-diethoxysilane.21 This increased its activity as a solid acid catalyst up to 100 times that of bulk Nafion. It performed better than Nafion on carbon in the dimerization of a methylstyrene. It was a much better catalyst (seven times on a weight basis) than Amberlyst 15, a typical sulfonic acid ion-exchange resin. It was more active in the benzyla-tion of benzene (6.6) than trifluoromethylsulfonic acid, a reaction in which Amberlyst 15 and p-toluenesulfonic acid... 

Amberlyst 15 has also found use as an efficient acid catalyst in the synthesis of low molecular weight esters such as 3-methylbutyl acetate (3) by using acetic acid as the carboxylic acid component (eq 14). This reaction was performed under microwave-mediated conditions, which Illustrates the thermal stability of Amberlyst 15 under these reaction conditions. A related sulfonic acid resin, Amberlite IR-100, has been used as an acid catalyst for the hydrolysis of ethyl acetate to give acetic acid and ethanol by conducting the reaction in water (eq 15). It is interesting to note that the use of a less acidic polymeric supported carboxylic acid resin (Wofatit C) was at least 20 times less efficient than Amberlite IR-100 Itself. 

The degree of inversion may be varied by time and temperature of the reaction, which is limited by the formation of - 5-hydroxymethyllurfural under forced conditions. Enrichment to high fructose contents is performed by chromatographic separation on columns filled with calcium polystyrene sulfonate ion exchange resins. 

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