Propyl-sulfonic acid functionalized (PS) nanoparticles with various levels of functionalization were synthesized, characterized and evaluated as catalysts for pretreatment of corn stover. The degree of functionalization was measured as a function of the hydronium ion concentration, the total organic loading, and the elemental sulfur content. The acid concentration, organic loading, and sulfur concentration of the nanoparticles varied between 0.05 and 0.40 mmol H+/g, between 5.0 and 30.0%, and between 1.0-18.0%, respectively. FTIR spectra revealed variation on the intensity of the peaks associated with the acid groups on the nanoparticles. The performance of PS nanoparticles on the pretreatment of corn stover was evaluated at 160 ºC for 1 h. The biomass and catalyst loads used during the pretreatment were 2.5% and 0.25%, respectively. After pretreatment, the liquid and solid fractions were physically separated. The nanoparticles were magnetically separated from the liquid fraction. The concentration of monomer sugars and oligosaccharides as well as the concentration of degradation products in solution were measured by HPLC. The composition of the solid fraction was analyzed for determination of cellulose and hemicellulose recoveries. The solid fraction was digested with a commercial cocktail of cellulases at 50 °C for 120 h. Biomass digestibility was analyzed against the surface characteristics of the nanoparticles that were used during pretreatment. PS nanoparticles increased the biomass susceptibility to enzyme hydrolysis; therefore, they can be used as an effective catalyst for the pretreatment of corn stover.
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