(20b) Design of a Novel Polymeric Acid Catalyst for Biomass Hydrolysis
A novel polymeric solid acid catalyst consisting of dual functional chains for biomass hydrolysis was successfully synthesized. A poly (styrene sulfonic acid) (PSSA) polymer chain is immobilized on a substrate and used to catalyze biomass hydrolysis. A neighboring poly (vinyl imidazolium chloride) ionic liquid (PIL) polymer chain is grafted to help solubilize lignocellulosic biomass and enhance the catalytic activity. The immobilized polymeric catalyst demonstrates over 97% total reducing sugar (TRS) yield in ionic liquid. This solid acid catalyst is highly efficient, stable, reusable and environmentally friendly. In order to understand its catalytic activity and further optimize its performance, the acidity of PSSA chains as well as the interactions among the PSSA, PIL polymer chains and cellulose were investigated using combined quantum mechanical (QM) and classical molecular dynamics (MD) simulations. In addition, the interaction free energies were determined using metadynamics (MTD) simulations. Our results demonstrate that polymer chain length and chain density play a crucial role in the catalytic activities of this polymer catalyst. Additional improvement for catalytic activity by substitution or copolymerization was suggested. This solid acid catalyst can be tuned and potentially be used for many other catalytic conversions.