Study Of Efficient Conversion Of Lignocellulosic Materials For Production Of Bio-based Platform Chemicals

Lignocellulosic biomass is a renewable carbon source,which is regarded as one of the best raw materials for the production of biofuels,biopolymers,and value-added chemical intermediates.Furfural,5-hydroxymethylfurfural,and levulinic acid are important bio-based platform chemicals connecting biomass with fuels,chemicals,and polymer materials,which could be converted from lignocellulose or its constitute monomers.The objective of this research is to establish an efficient pretreatment method to deconstruct the lignocellulose structure and fractionate cellulose,hemicellulose,and lignin.On top of that,efficient catalytic systems are established to convert hemicellulose and cellulose to their derivative platform chemicals,such as furfural,HMF,and levulinic acid,in order to realize the valorization of lignocellulose components in high efficiency.The key findings of this research were summarized as following:?1?A stepwise sodium hydroxide and organic acid pretreatment method was developed to remove lignin and hemicellulose from lignocellulose and generate highly digestible cellulose residue.The pretreatment conditions were optimized by orthogonal and response surface methods,which were determined as 1 wt%NaOH,under 70?for 1 h?first step?and 0.5 wt%acetic acid,80?for 40 min?second step?.About 60.42%of lignin was successfully removed and a reducing sugar concentration of 20.74 g/L was achieved for the regenerated cellulose solid during enzymatic hydrolysis.?2?A novel SO₄^2-/SnO₂-MMT solid catalyst was developed in this study and applied to catalytic conversion of corncob and corncob hydrolysate to produce furfural in a biphasic reaction system.The catalyst loading,organic to water phase ratio,NaCl loading,reaction temperature and time were investigated to optimize the furfural yield and reaction selectivity.The highest furfural yields of 66.1%and 81.7%were achieved,for corncob and corncob hydrolysate respectively.?3?This study established a biphasic system based on deep eutectic solvents?DES?to catalytically convert corncob and glucose solution to HMF.The optimal catalytic conditions were determined by evaluation of the key impact factors,which were determined as:ChCl-H₂O-acetone with a mass ratio of 1:2:3,reacted at 190?for 10 min.The highest HMF yields obtained from glucose and corncob were 75.41%?0.135 wt%H₂SO₄?and 64.21%?0.36 wt%H₂SO₄?,respectively.?4?This reaction kinetics of lignocellulose degradation and the production of primary products?glucose and xylose?,secondary products?furfural,HMF,LA?,and by-products?formic acid,acetic acid,humins?by using SnCl₄ as catalyst was investigated in this study.The catalytic system was found to be beneficial to the degradation process of glucose and HMF,and the generation of LA.A highest LA yield of 76.0%was obtained under the reaction conditions of 50 g/L substrate,82 mM SnCl₄,at 193?for 17 min.