Fractionation of lignocellulosic is a fundamental step in the production of value-added biobased products. This work proposes an initiative to efficiently extract lignin from the corn stover using a single-step solvothermal fractionation in the presence of an acid promoter (H2SO4). The organic solvent mixture used consists of ethyl acetate, ethanol, and water at a ratio of 30: 25:45 (v/v), respectively. H2SO4 was utilized as a promoter to improve the performance and selectivity of lignin removal from the solid phase and to increase the amount of recovered lignin in the organic phase. The optimal conditions for this extraction, based on response surface methodology (RSM), are a temperature of 180°C maintained for 49.1 min at an H2SO4 concentration of 0.08 M. The optimal conditions show an efficient reaction with 98.0% cellulose yield and 75.0% lignin removal corresponding to 72.9% lignin recovery. In addition, the extracted lignin fractions, chemical composition, and structural features were investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D-HSQC NMR). The results indicate that the recovered lignin primarily contains a β-O-4 linking motif based on 2D-HSQC spectra. In addition, new C–C inter-unit linkages (i.e., β-β, and β-5) are not formed in the recovered lignin during H2SO4-catalyzed solvothermal pretreatment. This work facilitates effective valorization of lignin into value-added chemicals and fuels.
Lignocellulose is a promising raw material for the production
of second-generation biofuels. In this study, the effects of acid-catalyzed
liquid hot water (LHW) on pretreatment of corn stover (CS) for subsequent
hydrolysis and conversion to ethanol were studied. The effects of
reaction temperature, acid concentration, and residence time on glucose
yield were evaluated using a response surface methodology. The optimal
condition was 162.4 °C for 29.5 min with 0.45% v/v of sulfuric
acid, leading to the maximum glucose yield of 91.05% from enzymatic
hydrolysis of the cellulose-enriched fraction. Conversion of the solid
fraction to ethanol by simultaneous saccharification and fermentation
resulted in a theoretical ethanol yield of 93.91% based on digestible
glucose. Scanning electron microscopy revealed disruption on the microstructure
of the pretreated CS. Increases of crystallinity index and surface
area of the pretreated biomass were observed along with alteration
in the functional group profiles, as demonstrated by Fourier transform
infrared spectroscopy. This work provides an insight into the effects
of LHW on the enzymatic susceptibility and modification of the physicochemical
properties of CS for further application on bioethanol production
in biorefinery.
Sugarcane bagasse can be considered a potential raw material in terms of quantity and quality for the production of alternative biofuels. In this research, liquid hot water (LHW) was studied as a pretreatment process to enhance the digestibility of pretreated material for further conversion into bioethanol. Different variables (temperature, residual time, and acid concentration) were determined to predict the optimized condition. LHW pretreatment showed an impact on the hemicellulose structure. The optimized condition at 160 °C for 60 min with 0.050 M acid concentration reached the highest glucose yield of 96.86%. Scanning electron microscopy (SEM) showed conspicuous modification of the sugarcane bagasse structure. The effect of LHW pretreatment was also demonstrated by the changes in crystallinity and surface area analysis. FTIR techniques revealed the chemical structure changes of pretreated sugarcane bagasse. The prepared material was further converted into ethanol production with the maximized ethanol concentration of 19.9 g/L.
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