乙酸预处理对木质纤维素结构及性能的影响
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摘要
对木质纤维素进行乙酸预处理及三段磨浆,分析了不同试样的化学组分,并进行了结构表征。结果显示,经乙酸预处理及三段磨浆后,相思木木片表面出现大量坍塌、裂纹及孔洞,纤维间的结合也变得更为疏松,木片超微结构受到不同程度的破坏。试样中半纤维素含量显著降低,纤维素及木质素所占比例相对增加,纤维素的结晶度指数有所降低。核磁共振波谱(P31NMR)分析结果表明,经预处理及磨浆后,试样中木素的脂肪族羟基含量降低,酚羟基含量增加,酚型/非酚型木素值增加,S/G(紫丁香基/愈创木基型木素)值增加,且随着预处理温度的升高,酚型/非酚型值下降,S/G值增加。热重-红外(TG-IR)分析结果表明,经预处理及磨浆后,DTG曲线在280℃左右少一个肩峰,半纤维素的降解产物木聚糖的特征吸收峰大幅降低,纤维素降解产物的特征吸收峰强度略微增强,木质素热解产物的特征吸收峰强度略有下降。为探讨预处理及磨浆对木质纤维素孔结构的影响,采用低温氮气吸附法(BET)对试样进行分析,结果显示,试样的比表面积增大,大孔所占比例减小,介孔所占比例增加。
Eucalyptus chip was pretreated by acetic acid under different temperatures followed by a three-stage refining process. Then, the chemical composition and the structure of different treated samples were analyzed and characterized. The results showed that after acetic acid pretreatment and refining process,some collapses and holes appeared on the eucalyptus chip surface,and the ultrastructure was looser. The percentage of hemicellulose decreased significantly,while the percentage of cellulose and lignin increased after the treatment. In addition,the crystallinity index of cellulose decreased. Based on the nuclear magnetic resonance spectrometry(31 P NMR) analysis of lignin samples,the aliphatic hydroxyl content decreased while the content of phenolic hydroxyl groups increased,and the ratio of phenolic/non-phenolic hydroxyl groups to syringa/guaiacum lignin(S/G) increased. In addition,the ratio of phenolic/non-phenolic hydroxyl groups decreased while the S/G increased with the increase of treatment temperature. The thermogravimetric infrared radiation(TG-IR) analysis showed that a shoulder peak around 280 ℃ on the differential thermal gravity(DTG) curve disappeared due to the degradation of hemicelluloses. The intensity of xylan absorption peak decreased significantly and those of cellulose degradation products increased slightly. In addition,the products from lignin pyrolysis decreased slightly. The treated samples were also analyzed and characterized by the low-temperature nitrogen adsorption method(BET) to investigate the effect of pretreatment and refining on the pore structure of lignocellulose. The results showed that the surface area and the amount of mesopore increased,while the amount of macropore decreased after the treatment.
Eucalyptus chip was pretreated by acetic acid under different temperatures followed by a three-stage refining process. Then, the chemical composition and the structure of different treated samples were analyzed and characterized. The results showed that after acetic acid pretreatment and refining process,some collapses and holes appeared on the eucalyptus chip surface,and the ultrastructure was looser. The percentage of hemicellulose decreased significantly,while the percentage of cellulose and lignin increased after the treatment. In addition,the crystallinity index of cellulose decreased. Based on the nuclear magnetic resonance spectrometry(31 P NMR) analysis of lignin samples,the aliphatic hydroxyl content decreased while the content of phenolic hydroxyl groups increased,and the ratio of phenolic/non-phenolic hydroxyl groups to syringa/guaiacum lignin(S/G) increased. In addition,the ratio of phenolic/non-phenolic hydroxyl groups decreased while the S/G increased with the increase of treatment temperature. The thermogravimetric infrared radiation(TG-IR) analysis showed that a shoulder peak around 280 ℃ on the differential thermal gravity(DTG) curve disappeared due to the degradation of hemicelluloses. The intensity of xylan absorption peak decreased significantly and those of cellulose degradation products increased slightly. In addition,the products from lignin pyrolysis decreased slightly. The treated samples were also analyzed and characterized by the low-temperature nitrogen adsorption method(BET) to investigate the effect of pretreatment and refining on the pore structure of lignocellulose. The results showed that the surface area and the amount of mesopore increased,while the amount of macropore decreased after the treatment.
引文
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[19]迟聪聪,柳咪,来贤,等.助剂强化碱预处理对玉米秸秆酶解糖化的影响[J].陕西科技大学学报,2016,34(3):22-27.CHI C C,LIU M,LAI X,et al. Effects of alkaline pretreatment enhanced by additives on the enzymatic saccharification of corn straw[J]. Journal of Shaanxi University of Science and Technology,2016,34(3):22-27.
[20]YANG H P,YAN R,CHEN H P,et al. In-depth investigation of biomass pyrolysis based on three major components:hemicellulose,cellulose and lignin[J]. Energy and Fuels,2006,20(1):388-393.
[2]WOJTUSIK M,ZURITA M,VILLAR J C,et al. Enzymatic saccharification of acid pretreated corn stover:empirical and fractal kinetic modelling[J]. Bioresource Technology, 2016, 220:110-116.
[3]HEALEY A L,LUPOI J S,LEE D J,et al. Effect of aging on lignin content, composition and enzymatic sacc-harification in Corymbia hybrids and parental taxa between years 9 and 12[J].Biomass and Bioenergy,2016,93:50-59.
[4]TALEBNIA F,KARAKASHEY D,ANGELIDAKI I,et al. Production of bioethanol from wheat straw:an overview on pretreatment,hydrolysis and fermentation[J]. Bioresource Technology,2010,101(13):4744-4753.
[5]陈理恒.基于酸处理的木质纤维酶水解及纳米纤维素特性的研究[D].广州:华南理工大学,2016.CHEN L H. Study on enzymatic hydrolysis of lignocellulose and characteristic of nanocellulose based on acid treatment[D].Guangzhou:South China University of Technology,2016.
[6]SABANCI K,BUYUKKILECI A O. Comparison of liquid hot water,very dilute acid and alkali treatments for enhancing enzymatic digestibility of hazelnut tree pruning residues[J]. Bioresource Technology,2018,261:158-165.
[7]秦磊.木质纤维素酸碱预处理的比较研究[D].天津:天津大学,2012.QIN L. Comparative study in acid and base pretreatment of lignocellulose[D]. Tianjin:Tianjin University,2012.
[8]ZEACHEM. Announces technology institure&processing services[EB/OL].[2015-04-22]http://www. zeamchem. com/press/pressrelease.php,2015.
[9]PAN X J. Role of functional groups in lignin inhibition of enzymatic hydrolysis of cellulose to glucose[J]. Journal of Biobased Materials and Bioenergy,2008,2(1):25-32.
[10]YANG Q,PAN X J. Correlation between lignin physicochemical properties and inhibition to enzymatic hydrolysis of cellulose[J].Biotechnology and Bioengneering,2016,113(6):1213-1224.
[11]SEGAL L,CRELLY J J,AEM J R,et al. An empirical method for estimating the degree of crystallinity of native cellulose using the X-Ray diffractometer[J]. Textile Research Journal,1959,29(10):786-794.
[12]迟聪聪.阔叶木生物质精炼两种利用模式的研究—与碱法制浆相结合/转化制备生物乙醇[D].广州:华南理工大学,2010.CHI C C. Study on hardwood biorefinery tow pathways:pretreatment for alkaline pulping and/or enhacing bioethanol coversion[D]. Guangzhou:South China University of Technology,2010.
[13]娄瑞.非木材纤维木素在不同热化学条件下的产物形成规律与调控途径[D].广州:华南理工大学,2011.LOU R. Formation rules and pathways of pyrolysates derived from nonwood ligin different thermochemical conditions[D]. Guangzhou:South China University of Technology,2011.
[14]CHI C C,HUI Z Z,LIU M. Effect of acetic acid pretreatment on wood pore structure and fractal dimension[J]. Bioresources,2017,12(2):3905-3917.
[15]DONOHOE B S,DECKER S R,TUKER M P,et al. Visualizing lignin coalescence and migration through maize cell walls following thermochemical pretreatment[J]. Biotechnology and Bioengineering,2010,101(5):913-925.
[16]WEIMER P J,HACKNEY J M,FRENCH A D. Effects of chemical treatment and heating on the crystallinity of celluloses and their implications for evaluating the effect of crystallinity on cellulose biodegradation[J]. Biotechnology and Bioengineering,1995,48(2):169-178.
[17]LI J B,HENRIKSSON G,GELLERSTEDT G. Carbohydrate reactions during high-temperature steam treatment of aspen wood[J]. Applied Biochemistry and Biotechnology,2005,125(3):175-188.
[18]LI J B,HENRIKSSON G,GELLERSTEDT G. Lignin depolymerization/repolymerization and its critical role for delignification of aspen wood by steam explosion[J]. Bioresource Technology,2007,98(16):3061-3068.
[19]迟聪聪,柳咪,来贤,等.助剂强化碱预处理对玉米秸秆酶解糖化的影响[J].陕西科技大学学报,2016,34(3):22-27.CHI C C,LIU M,LAI X,et al. Effects of alkaline pretreatment enhanced by additives on the enzymatic saccharification of corn straw[J]. Journal of Shaanxi University of Science and Technology,2016,34(3):22-27.
[20]YANG H P,YAN R,CHEN H P,et al. In-depth investigation of biomass pyrolysis based on three major components:hemicellulose,cellulose and lignin[J]. Energy and Fuels,2006,20(1):388-393.
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