Research On Separation And Conversion Of Bamboo Hydrothermal Residue Components Based On Ionic Liquid

Bamboo is rich in cellulose,and its yield is huge,which made it be thought as one of the most ideal chemical industrial feedstock in biomass.In this study,bamboo hydrothermal conversion residue was chosen as the raw material,designed ionic liquid/ethanol was used in the components separation,and the process conditions of lignin and cellulose separation was investigated.Then the mild hydrogenolysis on lignin and enzymatic saccharification and catalytic conversion on cellulose were investigated,respectively.The whole process is efficient,mild,high-yield,eco-friendly and recyclable,which completely meet the requirement of green chemistry.Ionic liquid/ethanol was used in bamboo hydrothermal conversion residue to separate lignin and cellulose.The optimal dissolution conditions were as follows:reaction temperature160?,reaction time 150 min,volume ratio of[AMIM]Cl to ethanol 1:1,solid to liquid ratio1:10.In this condition,the dissolution rate was 41.7%,the purity of crude lignin was 86.7%,while that of cellulose product was 92.0%.And the recycling effect of ionic liquid/ethanol was ideal.The crude lignin contained many syringyls,aromatic ether bond and ester bond were broken after treatment of[AMIM]Cl/ethanol.Lignin was largely removed by solvent system,but the crystal structure of cellulose had not been destroyed,its crystallinity increased with the degradation of lignin.Method of hydrogenolysis was used for regenerated bamboo lignin after[AMIM]Cl/ethanol pretreatment using high-pressure batch autoclave with a H₂ pressure of 2MPa,at 260?,80 min,and a rotation rate of 450 rpm/min.And the GC-MS analysis showed that the most of hydrogenolysis products of lignin are phenolic compounds or aromatic compounds containing phenol hydroxyl with short chains.Then the hydrogenolysis products of lignin was used to substitute for phenol to synthesize phenol-furfural resins?PFU?,and the effects of substitution rates of hydrogenolysis products of lignin to phenol on bond strength,solid content,curing time,free formaldehyde content,free phenol content and viscosity were investigated.The results showed that the lignin based PFU?LPFU?prepared under a substitution rate of 60%is of high bond strength?up to 2.06 MPa?as well as low free phenol content?lower than those regulated by Chinese National Standard?.And LPFU was superior to PFU because of its short curing time.Differential scanning calorimetry?DSC?analysis showed that LPFU exhibited high thermostability.Cellulose enzymatic saccharification under cellulase catalysis was investigated in different conditions,and optimum process condition was as follows:reaction temperature50?,reaction time 48 h,enzyme concentration 2 g/L,pH=4.5,when enzymatic saccharification yield reached to 83.7%.The cellulose crystal structure was destroyed and the its degree of crystallinity was decreased after enzymatic saccharification.Then the tanning process was used in the cellulase recycle,and the enzymatic saccharification yield was still72.9%after repeat use for 3 times.Glucose was used to converse to 5-hydroxymethylfurfural under Bronst acids or Lewis acids catalysis in ionic liquid[AMIM]OAc.And it was found that the catalytic effect of Bronst acids investigated was not good,while that of Lewis acids was good,especially CrCl₃.Choosing CrCl₃ as catalyst,optimum process condition was as follows:solid to liquid ratio1:10,10 mol%?based on glucose?CrCl₃,160°C,3 h,when the 5-hydroxymethylfurfural yield reached to 56.8%.[AMIM]OAc/CrCl₃ system kept effective after repeat use for 5 times.5-HMF prepared was used to converse to 5-ethoxymethylfurfural?EMF?under organic acids catalysis.It was found that the conversion result of 5-HMF was much better than fructose.And the optimum process conditions were 15%of oxalic acid/choline chloride dosage,20 g of ethanol amount,80?and 8 h,the yield of EMF reached up to 49.2%.Glucose prepared was also used to converse to EMF.And it was found the yield of EMF could reach to 11.3%under the catalysis of?oxalic acid/CrCl₃?/choline chloride DES at 100?and 8 h with 15%dosage and 20 g of ethanol amount,when the molar ratio of oxalic acid to CrCl₃ was 1:2.