Study On The Hemicellulose Extraction Of Acacia Wood By Prehydrolysis And Its Separation And Recovery With Ethanol

The isolation and recovery of hemicelluloses from the Acacia wood hydrolysate byethanol precipitation was mainly studied in this paper. hemicellulose degradation that inabundant in hydrolysate is a potential raw materials in chemical production. Before andafter the prehydrolysis，the changing regularity between each component of material in solidand liquid phase under different time and temperature is mainly discussed. The bestprehydrolysis condition of Vietnam acacia wood and the extraction method and process ofhemicellulose had been determined，which has been prepared for the later study ofseparating medium pulping and ethyl alcohol pulping.Experimental results shou that，during the prehydrolysis of the Acacia mangium，with thealysis of sugar component in liquid phase，extraction liquid contain hexose and pentose sugarssuch as xylose and arabinose，glucose and galactosum，and callobiose. The condition ofprehydrolysis process have a big effect on the content of sugar component in extractingsolution， especially on the Significant changing regularity under different times andtemperatures. From the solid phase we can learn that，the loss ratio of first strff and rawconstituent increased with the passage of time and increasing the rise of temperature beforeand after prehydrolysis. And then，extraction component in solid phase is more than that inliquid phase.From the analysis of solid phase，we can learn that，by the best process of prehydrolysisin pulping，the ratio of liquid is1:4，the highest temperature is170℃，the heating up time is45min，and the holding time was120min.The condition of prehydrolysis: to obtain the highestconcentration of xylose for19.059g/l.In order to obtain hemicellulose by method ofprehydrolysis as much as possible， the ratio of liquid will be1:4，the highest temperaturewill be170℃，and the heat up time will be45min to achieve the best process. Under thiscondition，the highest concentration of xylose for12.449g/l could be obtained.By ethanol precipitation，the hemicellulose is obtained by means of prehydrolysis inthis experiment.The principle is that hemicellulose insoluble in organic solvents. And liquid separation after precipitation separation for subsequent comparative study of the separationof liquid pulping with ethanol pulping is prepared. Through the combination of the additionamount of the ethanol and the evaporation capacity of hydrolysate，we can acquired the bestcondition for hemicellulose extracting. The best condition to acquire the largest amount ofprecipitation is170℃for highest temperature，45min for heating up time1:9for volumeratio of Pre-hydrolysate to alcohol，and80%for rate of concentration of Pre-hydrolysate. Asanalysis of the structure and purity for the deposit by the infrared spectra，thermogravimetric analysis，ultraviolet spectrum and ICS，we proved the non-selectiveprecipitate process for hemicellulose by Ethanol precipitation. We learned that the bestcondition to obtain the highest purity product is170℃for the highest temperature，45minforheating up time，20min for soaking time，1:6for volume ratio of Pre-hydrolysate toalcohol，and80%for rate of concentration of Pre-hydrolysate.