Nanostructured lyotropic liquid crystal resins for heterogeneous acid catalysis

In designing heterogeneous catalysts, it would be desirable to have complete control of the formation and position of the active sites, the environment around the active sites, and the path to these active sites. In other words, it is desirable to have complete control of catalyst formation at the atomic or molecular level. A lyotropic liquid crystal (LLC) molecular self-assembly approach was explored as a new method to make nanoporous heterogeneous Bronsted acid catalysts. These resulting novel nanostructured acid resins have uniform, monodisperse nanochannels like those in inorganic zeolites and MCM-41 mesoporous sieves. Furthermore, the use of organic-based starting materials affords a high degree of processability and tunability, compared to inorganic zeolites and mesoporous sieves.; A new type of solid acid catalyst formed by the self-assembly and copolymerization of two acidic LLC monomers, was designed, synthesized, and characterized. This new family of polymeric acid resins is composed of a columnar hexagonal polymer network containing uniform nanochannels lined with sulfonic acid groups. A LLC acid resin containing alkylsulfonic acid groups (resin 6) showed a much higher ester/ether product selectivity than the commercial amorphous acid resins, Amberlyst-15 and Nafion NR50, in a simple esterification test reaction of 1-hexanoic acid with benzyl alcohol. Furthermore, LLC acid resin 6 provided ca. 40% product yield and a higher initial rate than amorphous Amberlyst-15 in a second esterification step involving the formation of dioctyl phthalate, an important plasticizer, from the mono-octyl phthalate intermediate. It was found that the uniform nanopore structure present in the nanostructured LLC acid resin 6 plays a major role in its enhanced catalytic activity and selectivity in these esterification reactions.; A LLC acid resin containing more acidic arylsulfonic acid groups (resin 11) was then developed and applied to the formation of bisphenol A (BPA), a different type of acid-catalyzed condensation reaction. Compared to Amberlyst-15, LLC resin 11 showed a higher catalytic activity, but a slightly lower selectivity in batch reactions. The formation of BPA is a multi-step reaction involving multiple active sites. Control studies indicated that the uniform nanopore structure present in the LLC arylsulfonic acid resin enhances its catalytic activity, but surprisingly decreases its BPA product selectivity slightly compared to amorphous Amberlyst-15.