Study On Characteristics Of Substrate By Steam Explosion And Steam Explosion-Ethanol Pretreatment

The growing demand for energy, depletion of fossil resources and increasing concerns of environment issues have brought wide attention on the development of alternative energy sources. Ethanol production from lignocellulosic biomass comprises the following main steps:pretreatment of lignocellulosic materials, hydrolysis of cellulose and hemicelluloses, then ethanol is achieved with a further fermentation. In this paper, Chinese triploid poplar was selected as a raw material, and the contents of the research were described below:effect of different pretreatment (steam explosion pretreatment and steam explosion-ethanol extraction pretreatment) on physical and chemical properties of Chinese triploid poplar substrate, and the effect of different conditions of pretreatment on enzymatic hydrolysis yield.RSM (Response surface Methodology) was used to optimize the conditions of pretreatments, and then the mathematical model between characteristics of raw material and conditions of pretreatment was established and internal connection between conditions of pretreatment and indexes such as cellulose content, holocellulose content, lignin content and cellulose XRD crystallinity were quantitatively described. The optimum process of steam explosion pretreatment was obtained as:pressure:1.80MPa, holding time 3min. Individually under the optimum process of steam explosion pretreatment, holocellulose content was 63.54%, cellulose content was 62.28%, lignin content was 9.81% and cellulose XRD crystallinity was 50.75%. The optimum process of steam explosion-ethanol pretreatment was found to be:Ethanol consistency:55%, ratio of wood to liquor:1:6, temperature:165℃ and holding time:15min. Under the optimum process of steam explosion-ethanol pretreatment, holocellulose content was 71.51%, cellulose content was 66.74%, lignin content was 7.23% and cellulose XRD crystallinity was 46.26%.Combined approach using orthogonal experiments and single-factor experiments, get the best conditions for enzymatic hydrolysis:enzyme dosage 28IU/g dry substrate, pH value 5.5, temperature 50℃, substrate concentration 1%, and time 60h. Under this condition, the steam explosion pretreated poplar and steam explosion-ethanol poplar were both hydrolyzed. For steam explosion pretreated poplar, the enzymatic hydrolysis yield is increased with the increase pressure and reaction time. For steam explosion-ethanol pretreated poplar, the enzymatic hydrolysis yield increased at first and then decreased as the ethanol processing conditions exacerbated trend. Under the optimum conditions for enzymatic hydrolysis, the enzymatic hydrolysis yield for raw material, steam explosion pretreated poplar and steam explosion-ethanol poplar were 7.97%,83.60% and 94.50%.