Structure characterization of pine lignin extracted by different alcohol solvents

doi:10.11949/0438-1157.20191523

Abstract

Abstract:

To further understand the impact of lignin extracted by organic solvent and the influence of their structure, the effects of solvent polarity on the yield of lignin extracted by 6 organic alcohol solvents (methanol, ethanol, n-propanol, glycol, 1,3-propylene glycol and 1,4-butanediol) were systematically studied. At the same time, SEM (scanning electron microscope), GPC (gel permeation chromatography), NMR and other methods were used to further explore the effect of different alcohol solvents on lignin morphology, molecular weight and functional groups. The results showed that the polarity, length of carbon chain and number of hydroxyl groups had significant effects on lignin yield and the characteristic, such as morphology, molecular weight and functional groups. With the same number of hydroxyl groups, the longer the carbon chain and the weaker the polarity, the higher the lignin yield as well as the higher the average molecular weight they were. The content of C and H elements in lignin extracted from monohydric alcohol solvent system decreased with the increase of carbon chain length, while the content of C and H elements in lignin extracted from dihydric alcohol system showed an opposite trend. With the increase of hydroxyl groups, the yield and the average molecular weight of lignin decreased.

Key words: alcohol, biomass, lignin, solvent extraction, structure

摘要：

为进一步理解有机溶剂对木质素的提取率以及结构的影响，系统地研究了6种有机醇溶剂（甲醇、乙醇、正丙醇、乙二醇、1,3-丙二醇和1,4-丁二醇）在提取过程中溶剂极性等特性对木质素收率的影响；同时采用SEM（扫描电镜）、GPC（凝胶渗透色谱仪）、NMR等方法进一步探讨了不同醇溶剂对木质素形貌、分子量与官能团等的影响。结果表明，在所研究的6种有机醇溶剂中，极性、碳链长度与羟基数目对木质素收率、形貌、分子量、官能团等具有显著的影响；羟基数相同时，碳链越长、极性越弱，木质素的收率越高，重均分子量相对越大；一元醇溶剂体系提取的木质素中C、H元素的含量随着碳链长度的增长而降低，而二元醇体系中提取的木质素中C、H元素的含量呈相反的变化趋势；同等碳数的有机醇溶剂随羟基数增多，木质素的收率降低，重均分子量也相应减小。

关键词: 醇, 生物质, 木质素, 溶剂萃取, 结构

CLC Number:

TQ 028.8

Dongling WANG, Wenjin WANG, Zifang PENG, Ying XU, Jianguo LIU, Haiyong WANG, Chenguang WANG, Qi ZHANG, Longlong MA. Structure characterization of pine lignin extracted by different alcohol solvents[J]. CIESC Journal, 2020, 71(8): 3761-3769.

王东玲, 王文锦, 彭梓芳, 徐莹, 刘建国, 王海永, 王晨光, 张琦, 马隆龙. 醇溶剂提取松木木质素及其结构表征[J]. 化工学报, 2020, 71(8): 3761-3769.

Figures/Tables 8

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溶剂	极性参数	催化剂	温度/℃	时间/min	得率/% (质量)
甲醇	6.6	乙酸+硫酸	160	60	57.87
乙醇	4.3	乙酸+硫酸	160	60	77.02
正丙醇	4	乙酸+硫酸	160	60	81.35
乙二醇	6.9	乙酸+硫酸	160	60	36.35
1,3-丙二醇	—	乙酸+硫酸	160	60	70.66
1,4-丁二醇	—	乙酸+硫酸	160	60	91.73

溶剂	极性参数	催化剂	温度/℃	时间/min	得率/% (质量)
甲醇	6.6	乙酸+硫酸	160	60	57.87
乙醇	4.3	乙酸+硫酸	160	60	77.02
正丙醇	4	乙酸+硫酸	160	60	81.35
乙二醇	6.9	乙酸+硫酸	160	60	36.35
1,3-丙二醇	—	乙酸+硫酸	160	60	70.66
1,4-丁二醇	—	乙酸+硫酸	160	60	91.73

木质素	M_w	M_n	M_z	PD
甲醇木质素	1339	583	2499	2.29
乙醇木质素	2065	676	4766	3.05
正丙醇木质素	2315	654	5930	3.53
乙二醇木质素	1283	608	2242	2.11
1,3-丙二醇木质素	1695	684	3274	2.48
1,4-丁二醇木质素	2267	657	5614	3.45

木质素	M_w	M_n	M_z	PD
甲醇木质素	1339	583	2499	2.29
乙醇木质素	2065	676	4766	3.05
正丙醇木质素	2315	654	5930	3.53
乙二醇木质素	1283	608	2242	2.11
1,3-丙二醇木质素	1695	684	3274	2.48
1,4-丁二醇木质素	2267	657	5614	3.45

木质素	C	H	O^①	经验式	HHV^②/(MJ/kg)	Ω^③
甲醇木质素	69.32	6.81	23.87	C₉H_10.61O_2.32	28.89	4.70
乙醇木质素	67.88	6.72	25.40	C₉H_10.69O_2.53	28.00	4.65
正丙醇木质素	67.55	6.74	25.71	C₉H_10.78O_2.57	27.87	4.61
乙二醇木质素	65.38	6.44	28.18	C₉H_10.64O_2.91	26.27	4.68
1,3-丙二醇木质素	66.29	6.71	27.00	C₉H_10.93O_2.75	27.17	4.54
1,4-丁二醇木质素	66.93	6.57	26.50	C₉H_10.60O_2.67	27.27	4.70