Extration And Isolation Of Hemicellulose From Lignocellulosic Biomass

As the important structural component of corn stover, hemicellulose could be converted into a variety of high value-added products. Xylan, as one of the main components of corn stovers, could not be fully utilized due to extraction rate and product quality. To improve the extraction yield and quality of xylan, sodium hydroxide solution was employed to seperate xylan as well as cellulose and lignin from corn stover. NaOH mass concentration, extraction temperature and removal of non-structural materials from corn stover were selected to study the influence on yield, purity and structural characteristics of xylan.Dewaxed corn stovers were treated with 4,6,8,10,12,16,20 and 24% (w/v) NaOH solution to obtain xylans. Comparison of recovery and chemical composition of xylan indicated that NaOH concentration of 10% got better extraction results that recovery and purity of xylan were 76.20% and 59.35%. Then seven xylan samples were seperated by 10% NaOH solution at 30,60,80, 90,100,110 and 121?, respectively. The extractability and structural characterization of xylan were elucidated by high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). The results demonstrated that NaOH concentration was a more obvious factor affecting xylan extraction than temperature. The optimal extraction conditions were:NaOH concentration 10%, reaction temperature 90?, the xylan dissolution ratio, yield and purity were 86.37%,76.92% and 63.90% under the conditions, respectively. GPC showed that the weight average molecular weight (Mw) of xylan decreased from 48.62 kD to 32.02 kD with increasing alkaline concentration. Mw of xylan increased first and then decreased with the temperature. Studies have shown that combination of suitable alkali concentration and temperature could obtain higher xylan recovery on the premise of ensuring product quality.Corn stovers, as raw materials, were treated by removing non-structural components with four pretreatment methods to compare the extraction efficiency and quality of hemicellulose. In addition, the color values of hemicellulose were also investigated to optimize hemicellulose extraction method from corn stovers. The results indicate that hemicellulose dissolution ratio, recovery, purity and color value were 88.07%,84.41%,72.23% and 5.5×105 respectively when corn stover materials were firstly pretreated by immersing 2 h with 60? ethanol followed by soaking with 80? water, and then extracted by 10%(w/v) NaOH solution. Compared to Soxhlet pretreatment, the combination of water and ethanol pretreatment achieved xylan, which purity increased 13.04%, dissolution ratio and recovery increased 1.94% and 9.74%, color value decreased 5.34%. The results provide a theoretical basis for further improving the recovery ratio and quality of the corn stover xylan and realizing the sustainable utilization of the corn stover.