摘要
【目的】研究杏壳半纤维素的结构组成、微观形貌以及其热解特性和产物生成规律,为杏壳热化学利用提供理论基础。【方法】采用碱抽提和乙醇纯化方式分离杏壳半纤维素,基于红外光谱、核磁共振、扫描电子显微镜对其结构组成和微观形貌进行表征,利用热重分析、热重红外连用分析杏壳半纤维素的热解特性。【结果】从杏壳中分离出半纤维素的得率为29.44%,红外光谱特征吸收峰主要集中在1 620～600 cm~(-1)范围内,半纤维素成分以吡喃环结构的木糖为主。核磁共振图谱表明,杏壳半纤维素是以β-D-吡喃木糖形成的木聚糖为主链,在木糖基的C-2位连接4-O-甲基-α-D-葡萄糖醛酸,C-3位连有α-L-呋喃阿拉伯糖。扫描电子显微镜分析显示,半纤维素存在团聚现象,微观形态呈堆砌状的近似球形结构,半纤维素结构有一定的破坏。杏壳半纤维素的主要热解温度范围为210～380℃,在240℃出现一个肩状峰,在308℃出现最大失重尖峰,失重过程在600℃左右结束,800℃时热解残炭量为25.33%。杏壳半纤维素热解时各产物析出量在310℃时达到最高,小分子气体产物主要有CO_2、CO、CH_4,且CO_2和CO量远高于CH_4。【结论】杏壳半纤维素得率为29.44%,是以β-D-吡喃木糖形成的木聚糖为主链,呈堆砌状的近似球形结构,热解产物以CO_2、CO及乙酸、糠醛、丙酮等为主。
【Objective】 In order to study the complex pyrolysis behavior based on biomass components, the structure composition and micromorphology of the hemicellulose of apricot shell were analyzed, and its pyrolysis properties and product formation rule might be expected to provide theoretical basis for its thermal chemical utilization.【Method】 Apricot shell hemicellulose were separation by the alkali extraction and ethanol purification method. The composition, structure and microstructure were characterized by infrared spectrometer, nuclear magnetic resonance imaging, scanning electron microscope. The pyrolysis properties of apricot shell hemicellulose were investigated by thermogravimetric analysis and thermal infrared continuous analysis.【Result】 The hemicellulose was isolated from apricot shell at a rate of 29.44%, and the FTIR spectrum characteristic absorption peaks were mainly concentrated in 1 620-600 cm~(-1) which showed that the main components of hemicellulose were xylose of pyran ring structure. ~1H-NMR showed that apricot shell hemicellulose was the main chain of xylan composed of β-D-pyran xylose, which connected 4-O-methyl-α-D-glucuronic acid in xylose C-2 and α-L-furan arabinose in C-3. The SEM showed that hemicellulose was reuniting, the microstructure was approximate spherical structure, and the hemicellulose structure had some damage. Apricot shell hemicellulose main pyrolysis temperature ranged in 210-380 ℃, there were a shoulder peak at 240℃and a weightlessness peak at 308 ℃. The weightlessness process was at the end of the 600 ℃, the pyrolytic carbon residue content was 25.33% at 800 ℃. The pyrolysis product of apricot shell hemicellulose reached the highest at 310 ℃, small molecule gas products mainly include CO_2, CO, and CH_4, and CO, CO_2 were far higher than CH_4.【Conclusion】 The content of hemicellulose in apricot shell was 29.44%, which was the main chain of β-D-pyran xylose xylan, and had an approximate spherical structure. Pyrolysis products were mainly CO_2, CO and acetic acid, furfural and acetone. The result of this study would provide a theoretical reference for the thermochemical transformation of the apricot shell hemicellulose.
引文
胡亿明, 蒋剑春, 孙云娟, 等. 2014. 纤维素与半纤维素热解过程的相互影响. 林产化学与工业, 34(4):1-8.(Hu Y M, Jiang J C, Sun Y J, et al. 2014. Interaction during the pyrolysis process of cellulose and hemicellulose. Chemistry and Industry of Forest Products, 34(4):1-8. [in Chinese])
黄金保, 吴隆琴, 童红,等. 2016. 半纤维素模型化合物热解机理的理论研究. 燃料化学学报, 44(8):911-920.(Huang J B, Wu L Q, Tong H, et al. 2016. Theoretical study on thermal degradation mechanism of hemicellulose model compound. Journal of Fuel Chemistry and Technology, 44(8):911-920. [in Chinese])
蒋新元, 廖媛媛, 郭忠,等. 2015. 7种果壳的热解特性及与主要组分相关性分析. 林业科学, 51(12):79-86.(Jiang X Y, Liao Y Y, Guo Z, et al. 2015. Pyrolysis characteristics and correlation analysis with the major components of seven kinds of nutshell. Scientia Silvae Sinicae, 51(12):79-86. [in Chinese])
刘晓光, 徐兆翮, 彭艳芳,等. 2017. 承德山杏产业现状、存在问题及发展对策. 北方园艺,(6):185-189.(Liu X G, Xu Z H, Peng Y F, et al. 2017. Status, problems and development countermeasures of Prunus armeniaca industry in Chengde city. Northern Horticulture,(6):185-189. [in Chinese])
彭红, 胡铮瑢, 余紫苹,等. 2012.超声波辅助碱分离毛竹半纤维素. 农业工程学报, 28(9):250-256.(Peng H, Hu Z R, Yu Z P, et al. 2012. Extraction of hemicelluloses from bamboo with ultrasound-assisted alkaline. Transactions of the Chinese Society of Agricultural Engineering, 28(9): 250-256. [in Chinese])
彭云云, 武书彬. 2009. TG-FTIR联用研究半纤维素的热裂解特性. 化工进展, 28(8):1478-1484.(Peng Y Y, Wu S B. 2009. Characteristics and kinetics of sugarcana bagasse hemicellulose pyrolysis by TG-FTIR. Chemical Industry and Engineering Progress, 28(8):1478-1484. [in Chinese])
石峰, 何春霞, 朱碧华,等. 2017. 4种植物壳纤维成分及理化性能对比研究. 南京农业大学学报, 40(2):359-365.(Shi F, He C X, Zhu B H, et al. 2017. A comparative study on the components and physicochemical properties of four kinds of plant husk fibers. Journal of Nanjing Agricultural University, 40(2):359-365. [in Chinese])
孙康, 冷昌宇, 蒋剑春,等. 2017. 热解自活化法制备生物质基微孔型活性炭. 新型炭材料, 32(5):451-459.(Sun K, Leng C Y,Jiang J C,et al. 2017. Microporous activated carbons from coconut shells produced by self-activation using the pyrolysis gases produced from them,that have an excellent electric double layer performance. New Carbon Materials, 32(5):451-459. [in Chinese])
王树荣, 郑赟, 文丽华,等. 2006. 半纤维素模化物热裂解动力学研究. 燃烧科学与技术, 12(2):105-109.(Wang S R, Zheng Y, Wen L H, et al. 2006. Kinetic research on pyrolysis of model compound of hemicellulose. Journal of Combustion Science and Technology, 12(2):105-109.[in Chinese])
王霏, 郑云武, 黄元波,等. 2016. ZSM-5催化生物质三组分和松木热解生物油组分分析. 农业工程学报, 32(S2):331-337.(Wang F, Zheng Y W, Huang Y B, et al. 2016. Component analysis of pyrolysis bio-oil from three major components of biomass and Pinus yunnanensis by ZSM-5 catalytic. Transactions of the Chinese Society of Agricultural Engineering, 32(S2): 331-337. [in Chinese])
许凤, 钟新春, 孙润仓, 等. 2005. 秸杆中半纤维素的结构及分离新方法综述. 林产化学与工业, 25(S1):179-182.(Xu F, Zhong X C, Sun R C, et al. 2005. Chemical structure and new isolation methods of cereal straw hemicellulose. Chemistry and Industry of Forest products, 25(S1):179-182. [in Chinese])
余紫苹.2012.毛竹半纤维素分离及结构研究.南昌:南昌大学硕士学位论文.(Yu Z P. 2012. Study on the separation and structure of hemicellulose. Nanchang: MS thesis of Nanchang University. [in Chinese])
Fang J M, Sun R C, Tomkinson J. 2000. Isolation and characterization of hemicelluloses and cellulose from rye straw by alkaline peroxide extraction. Cellulose, 7(1):87-107.
Hu J, Xiao R, Shen D K. 2013. Structural analysis of lignin residue from black liquor and its thermal performance in TG-FTIR. Bioresource Technology, 128(1):633-639.
Khan E A, Shahjahan, Khan T A. 2018. Adsorption of methyl red on activated carbon derived from custard apple(Annona squamosa)fruit shell: equilibrium isotherm and kinetic studies. Journal of Molecular Liquids, 249(1): 1195-1211.
Peng Y, Wu S. 2010. The structural and thermal characteristics of wheat straw hemicelluloses. Journal of Analytical and Applied Pyrolysis, 88(2):134-139.
Ponder G R, Richards G N. 1991. Thermal synthesis and pyrolysis of a xylan. Carbohydrate Research, 218:143-155.
Shen D K, Gu S, Bridgwater A V. 2010. Study on the pyrolytic behaviour of xylan-based hemicellulose using TG-FTIR and Py-GC-FTIR. Journal of Analytical & Applied Pyrolysis,87(2):199-206.
Shen D K, Gu S. 2009. The mechanism for thermal decomposition of cellulose and its main products. Bioresourse Technology, 100(24): 6469-6504.
Sun J X, Sun X F, Sun R C, et al. 2004. Fractional extraction and structural characterization of sugarcane bagasse hemicelluloses. Carbohydrate Polymers, 56(2):195-204.
Xu F, Liu C F, Geng Z C, et al. 2006. Characterisation of degraded organosolv hemicelluloses from wheat straw. Polymer Degradation & Stability, 91(8):1880-1886.
Yang K, Gao Q, Tan Y, et al. 2015. Microporous carbon derived from Apricot shell as cathode material for lithium-sulfur battery. Microporous & Mesoporous Materials, 204:235-241.
Yuan T Q, Xu Fe, He J, et al. 2010. Structural and physico-chemical characterization of hemicelluloses from ultrasound-assisted extractions of partially delignified fast-growing poplar wood through organic solvent and alkaline solutions. Biotechnology Advances, 44(1): 29-39.
Zhang H, Xiao R, Jin B, et al. 2013. Catalytic fast pyrolysis of straw biomass in an internally interconnected fluidized bed to produce aromatics and olefins: effect of different catalysts. Bioresource Technology, 137:82-87.
