Elucidating the Energetics and Effects of Solvents on Cellulose Hydrolysis Using a Polymeric Acid Catalyst

Xiaoquan Sun,Xianghong Qian

doi:10.3390/app8101767

Abstract

A novel polymeric acid catalyst immobilized on a membrane substrate was found to possess superior catalytic activity and selectivity for biomass hydrolysis. The catalyst consists of two polymer chains, a poly(styrene sulfonic acid) (PSSA) polymer chain for catalyzing carbohydrate substrate, and a neighboring poly(vinyl imidazolium chloride) ionic liquid (PIL) polymer chain for promoting the solvation of the PSSA chain to enhance the catalytic activity. In order to elucidate the mechanism and determine the energetics of biomass catalytic processing using this unique catalyst, classical molecular dynamics (MD) coupled with metadynamics (MTD) simulations were conducted to determine the free energy surfaces (FES) of cellulose hydrolysis. The critical role that PIL plays in the catalytic conversion is elucidated. The solvation free energy and the interactions between PSSA, PIL, and cellulose chains are found to be significantly affected by the solvent.

Highlights

Cellulose is one of the major polymers in the plant cell wall
The different behaviors of polymeric catalysts and cellulose chains are critically affected by the solvent. [EMIM]Cl is an excellent solvent of cellulose, and has been widely applied to study cellulose hydrolysis catalyzed by different catalysts [61,62,63,64]
Our molecular dynamics (MD)-MTD simulations clearly demonstrate that the solvent plays a critical role in the cellulose

Summary

Introduction

Deconstruction of cellulosic biomass is a critical step in the production of sugars and biofuels, as an alternative to depleting fossil fuels [1,2,3,4,5,6,7]. In the biochemical platform of biomass conversion, a pretreatment step is required to open up the biomass structures, relocate lignin, or to partially hydrolyze hemicelluloses [8,9,10,11]. Dilute acid pretreatment is one of the leading technologies, among several other approaches [12,13,14]. The pretreated lignocellulosic biomass is typically further hydrolyzed to monomeric sugars using an enzyme cocktail [15,16]

Methods

Results

Conclusion