Study Of Extraction Of Hemicellulose And Production Of Furfural From Corn Stovers

The three major components(cellulose,hemicellulose,lignin)of lignocellulose are connected with different bonds to form a complex structure.Hemicellulose is one of the most abundant natural carbohydrates after cellulose comprised of a wide variety of monosaccharides.Hemicellulose is amorphous and versatile which is usually associated with cellulose via hydrogen bonds,with lignin via covalent bonds to form lignin-carbohydrate complexes(LCCs).This makes it difficult to separate hemicellulose from lignocellulose.In addition,the amorphous structure of hemicellulose makes it extremely easy to be destroyed in the process of extraction and conversion,which makes its conversion and utilization more difficult.To solve the above problems,this present study carried out the following invetigation:Firstly,the effects of different pretreatment methods on the extraction of hemicellulose were studied.The corn stovers were pretreated with water,ethanol,toluene-ethanol and acetic acid-sodium chlorite solution,separately.After pretreatment,the hemicellulose was extracted with NaOH solution from the pretreated solid residue.The results show that the purity of hemicellulose was increased after pretreatment,while the color value and the thermal stability were decreased.Among them,the purity of the hemicellulose obtained from corn stover pretreated with water was the highest(68.09%)and the molecular weight(58434)was the highest.The color value of hemicellulose obtained from corn stover pretreated with acetic acid-sodium chlorite was observed to be the lowest.Secondly,the corn stovers were treated with 1,3,5,7 and 10%(w/v)NaOH solutions successively to extract the hemicellulose.The results show that the molecular weight,branch degree,color value and thermal stability of the hemicellulose extracted with different NaOH concentration were different.The molecular weight(25260 D),purity(39.70%)of the hemicellulose extracted by 1%NaOH were the lowest.However,the branch degree(0.33),thermal stability and color value(1844988)were the highest.The molecular weight(48254 D)of the hemicellulose extracted by 10%NaOH was the highest,while the branch degree(0.16)was the lowest.Finally,furfural production from the alkali-extracted hemicellulose as raw material was investigated.The effect of acetic acid concentration,AlCl₃·6H₂O concentration,temperature and time on furfural yield were studied.The results show that both acetic acid and AlCl₃·6H₂O can promote the formation of furfural.The optimal reaction condition was 5%acetic acid(contain 3%AlCl₃·6H₂O), temperature 180?,time 120 min.At this condition,the furfural yield of 91.54 mol%was achieved.