Novel solid acid catalysts for cellulose hydrolysis and dehydration

Dual functional polymeric solid acid catalysts are synthesized to facilitate cellulose dissolution and catalyze its hydrolysis and dehydration reactions. Our solid acid catalysts consist of two neighboring polymer chains, a poly (styrene sulfonic acid) (PSSA) polymer chain catalyzing biomass hydrolysis and its subsequent dehydration to 5-hydroxymethyfurfural (HMF), and a poly (vinyl imidazolium chloride) ionic liquid (PIL) polymer chain helping solubilize lignocellulosic biomass and enhance the catalytic activity. The polymer catalysts are immobilized on glass or ceramic membrane substrates. The acidic polymeric PSSA chain was synthesized via surface initiated atom-transfer radical polymerization (ATRP) whereas the adjacent PIL chain was synthesized via UV-initiated radical polymerization. The two chains were grafted from randomly immobilized UV and ATRP initiators on the substrate surface.  It is possible to tune independently the relative ratio as well as the chain length, chain density of the two polymeric nanostructures to optimize the catalytic activity for cellulose hydrolysis and dehydration reactions. Our synthesized solid acid catalysts demonstrate over 97% total reducing sugar yields for cellulose hydrolysis in ionic liquid [EMIM]Cl in less than 6 hours at 130^oC. Moreover, at slightly elevated temperature of 135^oC, HMF yield of over 70% has been achieved. These solid acid catalysts are stable and maintain high catalytic activity after repeated runs.