| Due to the depletion of petrochemical resources,environmental pollution is increasingly serious,the development of clean renewable energy is the theme of today's world.Lignocellulosic biomass resource is a renewable resource,which is rich in nature,but it is seriously discarded,so how effective use of biomass resources becomes a key issue.The traditional pretreatment methods exist high cost,serious pollution,huge energy consumption and other defects,while ionic liquid and ultrasonic technology as a new pretreatment have been widely concerned.However,the effect of the two methods on the pretreatment of biomass alone is limited,therefore,in order to obtain the maximum effect of the pretreatment of the ionic liquid,the ultrasonic liquid pretreatment of the ionic liquid pretreatment is added and the reaction is carried out by the microwave-solid acid/ionic liquid system in the reaction process to achieve the maximum utilization of biomass.In this paper,microbial cellulose was used to simulate the biomass material to study the effect of the pretreatment of ultrasonic-ionic liquid system on the enzymatic hydrolysis and acid hydrolysis of the biomass.Then use the wheat straw(difficult to hydrolyze)and bagasse(relatively easy to hydrolyze)as raw materials for practical research.Finally,the effects of pretreatment of ultrasonic-ionic liquid system on the conversion of 5-HMF in microwave-solid acid/ion-liquid system were investigated.The main contents and results are as follows:Wheat straw and bagasse were used as raw materials enzymatic hydrolysis and acid hydrolysis on the biomass and the microwave-solid acid/ionic liquid system to 5-HMF after pretreatment of biomass by ultrasonic-ionic liquid system.(1)In this paper,wheat straw and bagasse were used as raw materials to study the effect of pretreatment of ultrasonic-ionic liquid system on conversion of biomass to sugar by enzymatic hydrolysis and acid hydrolysis and conversion of biomass to 5-HMF by microwave-solid acid/ionic liquid system.The [Bmim]Cl and [Bmim]OAc ionic liquids were synthesized by one-step method and two-step method respectively and the synthesis was confirmed by FT-IR,1H-NMR and UVs,then,microcrystalline cellulose was used as raw material to pretreated by ionic liquid was carried out under 50 kHz,100 W condition ultrasonic condition,the ionic liquid and cellulose were recovered and the regenerated microcrystalline cellulose was characterized by FT-IR,XRD and SEM.Finally,the regenerated cellulose was subjected to acid hydrolysis and enzymatic hydrolysis to obtain reducing sugar and the reducing sugar content was determined by DNS method.The results show that the three characterization spectra determined the synthesis of two kinds of ionic liquids.The characterization of regenerated cellulose showed that the microcrystalline cellulose was changed from cellulose type I to cellulose type II,the crystallinity of cellulose decreased by 36.64 ~ 47.27%,the pretreatment effect was obvious.The results of hydrolysis reaction also showed that the biomass hydrolysis rate after pretreatment by ultrasonic-ionic liquid was increased from 21.87%(enzymatic hydrolysis)and 10.07%(acid hydrolysis)to 42.16% and 31.05%,indicating that the ultrasonic-ionic liquid pretreatment The hydrolysis of microcrystalline cellulose into sugar has a very good effect.(2)Bagasse and wheat straw as raw materials were pretreated at 20,35,40 and 50 kHz for 30 min by ultrasonic and ionic liquids at 80?.The ionic liquid was recovered and the recovery rate was measured.The regenerated biomass was analyzed by FT-IR,XRD and TG.The regenerated biomass was subjected to acid hydrolysis and enzymatic hydrolysis and content of reducing sugar and the composition and content of each sugar component were determined by DNS method and HPLC method.The results showed that the biomass did not undergo derivatization after pretreatment of biomass samples in [Bmim]Cl and [Bmim]OAc,the macroscopic structure of biomass remained stable,and the crystallinity of cellulose were reduced from 39.22%(wheat Straw)and 36.78(bagasse)to 29.75% and 25.14%.After the addition of ultrasonic assistance,the biomass remained relatively stable in the macroscopic structure,but the degree of crystallinity reduction was more obvious,the lowest reduction was 17.55% and 14.83%.The degree of biomass hydrolysis of the pretreatment by ionic liquid pretreatment is higher than that of untreated biomass,and the degree of biomass hydrolysis by ultrasonic-ionic liquid pretreatment is greatly improved compared with that of the former two,and the total amount of TRS is increased by 38%.The optimal frequencies of [Bmim]Cl and [Bmim]OAc solvent systems under acid hydrolysis are 20 and 28 kHz,and 40 and 50 kHz in enzymatic hydrolysis.(3)Bagasse as raw material were pretreated by ultrasonic-ion liquid The 5-HMF was obtained by microwave heating of the pretreated biomass with the acidic ion exchange resin as the catalyst and the ionic liquid as the solvent,the time,temperature,solvent and catalyst of the microwave digestion were studied to investigate the effects of ultrasonic-liquid pretreatment on biomass biodegradation of 5-HMF.The results showed that the optimum temperature appeared at 140? and the reaction time was 25 min when the solvent and catalyst were stable.In the range of 100~140?,5~40 min,the catalytic effect of D001-cc is more effective,the solvent effect of [Bmim] OAc is the best,the yield of 5-HMF is up to 24.76%.The 5-HMF yield of the microwave digestion of the biomass after pretreatment with ultrasonic-ion liquid was consistent with the law of biomass microwave digestion without pretreatment,indirectly shows that it did not destruction of the molecular structure of biomass composition.However,the highest yields of 5-HMF were 35.79%,40.21%,51.26%,65.72% and 59.77% respectively after microwave treatment with 20,28,35,40 and 50 kHz ultrasonic-ionic liquid pretreatment biomasses,the yield of 5-HMF was increased by 39.73% ~ 165.43% compared with the untreated biomass(24.76%)after microwave digestion.It is shown that the pretreatment of ultrasonic-ionic liquid reduces the crystallinity of the biomass fiber and reduces the crystallization area,which makes the reaction more fully.In addition,40 kHz at five frequencies shows a better pretreatment effect,indicating that 40 kHz can produce more cavitation and mechanical effects,resulting in an increase in the cellulose amorphous region and the intermolecular hydrogen bond breakage,making the biomass microwave digestion reaction maximization. |
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