Comparative Study In Acid And Base Pretreatment Of Lignocellulose

Several chemicals were applied in lignocellulose pretreatments in order toinvestigate the mass transformation law during pretreatment and enzymatic hydrolysis,and achieve the high enzymatic conversion.Corn stover was pretreated with sulfuric, oxalic, citric, tartaric and acetic acid at50and90mM from130to190°C. The xylan balance for each different acid wasdistinct, but all balances were very close to100%by determining xylan recovery,xylooligomer yield, xylose yield and furfural yield. The effects of combined severityon the recovery or yields of these components were also studied. The acid pKavalueaffected the proportion of xylan degradation products. The maximum value of xyloseand xylooligomer yield for specific acid pretreatment was also determined by pKa.The maximum xylose yield was obtained after pretreatment with sulfuric and oxalicacid, but more xylooligomers were obtained after pretreatment with weaker acids.Methylamine compared with ammonia was using to obtain an optimalpretreatment condition by response surface experimental design. The maximumenzymatic glucose conversion for high temperature methylamine and ammoniapretreatment was about95%and88%, at180°C/10%/2h and180°C/20%/3h,respectively. The maximum total glucose yield for either pretreatment was both90.5%, but the pretreatment condition for methylamine was lower than ammonia,indicating the advantage of methylamine. In addition, lignin removal after hightemperature methylamine pretreatment was obviously higher than ammonia. However,there is no evident relationship between enzymatic conversion and lignin removal.Rice straw was pretreated using dilute sulfuric acid and ethanol with differentconcentrations. After the pretreatment using2%acid concentration with50%ethanol,glucose concentration and yield is53.9g/L and71.5%respectively, which is higherthan other pretreatment conditions obviously. Glucose yield in enzymatic hydrolysisis linearly dependent on the overall loading of xylan, lignin and others at thebeginning of hydrolysis. The degradation products were determined by GC-MS andanalyzed by principle composition analysis, which reveals6markers for differentpretreatment conditions.