Nafion resin catalyst, solid superacid

Substantial progress has been made to carry out alkylation in the gas phase over solid superacid catalysts. Nafion-H, a perfluorinated resin-sulfonic acid, for example, catalyzes the methylation of benzene and methylbenzenes with methyl alcohol under relatively mild conditions. The reaction shows low substrate selectivity.203... 

The following subchapters cover various solid superacids, including perfluorinated sulfonic acid resins (Nafion resins). Furthermore, in the past, various attempts have been made to obtain solid superacids by either (a) enhancing the intrinsic acidity of a solid acid by treatment with a suitable co-acid or (b) physically or chemically binding a liquid superacid to an otherwise inert surface. We will briefly review some of these attempts because most of these catalysts rapidly lose activity and need to be regenerated. 

This review summarizes the recent works on syntheses of solid superacids and their catalytic action, including Lewis acids and liquid superacids in the solid state, as discussed in Sections Il-IV. Sections VI and VII describe new types of solid superacids we have studied in this decade sulfate-supported metal oxides and tungsten or molybdenum oxide supported on zirconia. Perfluorinated sulfonic acid, based on the acid form of DuPont s Nafion brand ion membrane resin, is also gaining interest as a solid superacid catalyst Nafion-H-catalyzed reactions are reviewed in Section V. 

Another type of solid superacid is based on perfluorinated resin sulfonic acids, such as the acid form of DuPont s Nafion resin, a copolymer of a perfluorinated epoxide and vinylsulfonic acid, or higher perflu-oroalkanesulfonic acids such as perfluorodecanesulfonic acid, CF3(CF2) 03H. Such solid catalysts were found to be very efficient in alkylation of aromatic hydrocarbons and other Friedel-Crafts reactions. A comprehensive review is available on the application of Nafion-H in organic catalysis. ... 

Another industrial route to obtain a,oo hydroxy-telechelic PTHF is based on the transfer reaction with anhydrides (7.11). The polymerisation reaction is based on a mixture of anhydrides (usually acetic anhydride) and a superacid (HSbF6, HC104, CF3S03H or even in the presence of a polymeric superacid with -CF2-CF2-S03H groups (Nafion resins, solid analogue of triflic acid) [26, 27] or Lewis acids (BF3, SbF5) [20, 24], or solid acidic clays [29]. The real catalyst is the oxocarbenium salt formed by the reaction of acetic anhydride and the superacid ... 

For the esterification of FFA, superacid solid catalysts can be applied, such as ion-exchange resins (Amberlist, Nafion) or sulfated zirconia [22-24], The preferred environment is a reactive-distillation column. 

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