Removal Of Lignin From Straw By Ionic Liquid Alkaline Solution

With the overexploitation and drying up of fossil resources,people pay more and more attention to the research and development of renewable resources.Biomass has the advantages of cheap and easy to be degradable.As an agricultural country,China is rich in straw resources,the straw contains rich cellulose.How to remove lignin efficiently from raw materials is one of the keys to prepare fuel ethanol from cellulose.In this paper,two ionic liquid alkaline solutions([Amim]Cl?[Emim][CH3COO])are used to pretreat corn straw.First of all,we use NaOH solution for treatment of straw,We found that alkali has a certain removal effect on lignin,but at the same time cause unnecessary loss of cellulose and hemicellulose.we investigated the removal efficiency of lignin from straw by two kinds of ionic liquid alkaline solution from three aspects: reaction temperature,reaction time and solid-liquid ratio.The single factor and Box-Behnken design experiment were used to get the suitable process conditions: in the reaction temperature of 98.5 ?,reaction time of 1.31 h,solid-liquid ratio of 1:8.5,the theoretical value of cellulose at this time is 86.1458%.The average cellulose content of 86.11%,hemicellulose content of 9.1% and lignin content of 2.27% in the corn straw pretreated by [Emim][CH3COO] ionic liquid alkaline solution.the lignin removal rate was 87.4%.The pretreatment of two kinds of choline ionic liquids([Ch][Ac],[Ch][Lys])showed that [Ch][Lys] pretreatment had the best effect.In pretreatment time of 12 h,The content of cellulose is 60.5%,the removal rate of lignin is 36.7%.Electrochemical pretreatment can oxidize the straw to a certain extent.In the electrochemical system,a Pt plate is used as the anode and a Ti plate is used as the cathode and the electrode spacing of 15 mm.The effect of the straw pretreat by two ionic liquid aqueous solutions([Emim]Cl,[Hmim]Cl)was studied.The results showed that 20% [Hmim]Cl aqueous solution was the best solution for the pretreatment of straw,the yield of reducing sugar is 88.43% in 520 min and the reducing sugar concentration is 3.28 g·L-1.The optimal conditions of cellulase enzymatic hydrolysis were studied from three factors of enzyme dosage,p H value and reaction temperature by cellulase.The optimal enzymatic hydrolysis conditions are obtained through orthogonal experiment design.The straw pretreated by [Emim][CH3COO] ionic liquid alkaline solution showed the best results in the enzymolysis.The optimal enzymolysis conditions are as follows: in the reaction temperature of 45 ?,pH value of 5.0,enzyme dosage of 150 U·mL-1,the reducing sugar concentration is 13.91 g·L-1 in 72 h.