| Several pretreatment techniques have been used in biomass pretreatment,such as chemical,physical,biological methods.Among all these methods,ionic liquids are thought to be alternative green solvents.However,there are some limitations in the industrial applications,such as poor biodegradability,high cost,high viscosity and unrenewable synthetic materials etc.In addition,the research on the pretreatment and transformation mechanism of straw in multi-hydrogen bond system is insufficient In order to solve the above problems,the pretreatment and conversion of com straw were studied in this thesis,which focused on ionic liquid/low eutectic solvent based multiple pretreatment solvent system,the main innovative results are as follows:(1)A process of pretreatment-detoxification-enzymatic hydrolysis transformation was put forward to reduce the cost of pretreatment and improve the efficiency of pretreatment.Corn straw was pretreated with binary system of water-choline glycine ionic liquid.The activities of cellulase and Bacillus sp.strain P38 were almost not inhibited by low concentrations less than 0.5 wt%of[Ch][Gly].Under simplified detoxification procedures,the maximum cellulose digestibility and glucose yield were 99.2%and 230.1 mgglucose/PUILs,respectively.The simplified detoxification method was used to avoid the high cost caused by a large amount of water washing and energy consumption,which showed industrial application prospects in lignocellulosic biorefinery processes(2)Using[BHEM]mesy-high boiling alcohol(from biomass based platform)multi-hydrogen bonds co-solvent system for the efficient pretreatment of corn straw.Among them,ionic liquid-ethylene glycol co-solvent system has the best pretreatment efficiency.The removal ratio of lignin is up to 96.0%with the yield of glucose 97.0%,when the research is conducted at 120? for 2 h with[BHEM]mesy:ethylene glycol 3:7,(m:m)system.The spectrum experiment and MD simulation results confirmed that the addition of the co-solvent can increase the total hydrogen bond of the pretreatment system and promote the destruction of ?-O-4 bonds in lignin to improve the removal rate of lignin.(3)Using a low concentration ionic liquid-ethylene glycol co-solvent system with both solvent and catalyst functions to pretreat the corn straw and subsequent fermentation into L-lactic acid.The highest preprocessing efficiency was acquired by mass fraction 5%of[BHEM]messy and mass fraction 95%of ethylene glycol co-solvent system with 95.5%.The results indicate that the effect of selective removal lignin from corn straw was the remarkably strong hydrogen bonding by the multiple sites synergistic action from co-solvent system.The substitution of H in sulfonate anions and ethanolamine cation by the CH3 group were instead at the same time,the dissolution of lignin presents a remarkable enhancement by the synergistic action(4)Five novel low eutectic pretreatment agents for biomass pretreatment composed of amino acids and ethanolamine were designed and synthesized.The highest ligninremoval ratio(94.6%)was achieved with one-hour pretreatment.It was found that if there is a substitution of H in amino acid terminal position by the OH,COOHor NH2,which can form strong hydrogen bonds interactions with ethanolamine and they can form joint effect of multiple hydrogen bonds with lignin achieving the efficient removal of lignin from corn straw.It confirmed that multiple H-bonding joint effect not only can be applied in the ionic liquid-co-solvent pretreatment system,but also apply to the low eutectic pretreatment system(5)Sugar(natural monosaccharide from biomass)-acid(lactic acid,monosaccharide fermentation product)-salt were designed and synthesized multiple low eutectic solvent systems to pretreat com straw.When the content of sodium chtoride is 0.3 mol,the removal rate of lignin is 74.2%while with no sodium chloride added is only 24.6%.It was confirmed that chloride ion in ternary low eutectic solvent could form strong hydrogen bond with lignin dimer,which promoted the dissolution of corn straw in ternary low eutectic solvent.Further explore the efficient removal of lignin by the combined effect of multiple hydrogen bonds,providing the possible for closed loop biorefinery. |
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