Recycling Polyisobutylene Catalysts and Polymers
Abstract
In recent years, the Bergbreiter group has investigated the use of polyisobutylene (PIB) as a selective phase anchor for catalysts and dyes into a nonpolar or alkane solvent phase. The selectivity of these polymeric supports for nonpolar solvents has allowed for separation of catalysts from polar products after reaction by simple extraction with polar solvents. Additionally, the ease with which the PIB chain facilitates separation of homogeneous catalysts from products can also be used to recover and reuse the PIB bound species as well.
This work expands on these ideas of recycling and repurposing PIB. First, PIB was depolymerized by using a trifluoromethanesulfonic acid (triflic) catalyst and an arene solvent. This allowed for the PIB to be converted into tert-butyl arenes. This reaction is catalyzed by triflic acid as long as the PIB is suitably end functionalized and there is an available arene solvent to attack the monomer units as they are formed.
The second PIB recycling method was through the use of PIB bound sulfonic acid catalysts that were dissolved into poly(α-olefin) solvents (PAO). This acid/solvent system could be recycled due to its low leaching and low vapor pressure. This work explores the use of this recyclable system in the formation of esters, acetals, and heterocycles. This acid/solvent system was also compatible with a variety of workups including vacuum distillation, filtration, and extraction.
The final PIB recycling method used a PIB bound Rose Bengal catalyst in PAOs that could be recycled due to its phase selectivity. Although this catalyst did suffer from photo bleaching, we hypothesize that additional care with storage and reaction conditions could allow this PIB bound catalyst to be recycled multiple times.
The following work will discuss these three recyclable systems for PIB in further detail.
Citation
Watson, Christopher B (2021). Recycling Polyisobutylene Catalysts and Polymers. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /193091.