木质纤维素类生物质水热炭化机理及水热炭应用进展

doi:10.16085/j.issn.1000-6613.2022-1223

摘要/Abstract

摘要：

通过水热炭化方法（HTC）制备纤维类生物质炭材料，是当前废弃生物质高值化处理的一种方式。生物质具有种类繁多、结构复杂的特点，在不同的水热条件下涉及水解、降解、聚合等复杂反应。制备的水热炭性质如形貌、孔结构、表面官能团分布等受原料物理化学结构和水热反应条件影响较大，而水热炭的性质直接影响水热炭的应用。木质素炭化需要较高的水热强度，生成的水热炭石墨化程度和稳定性更高，可应用于导电、耐高温材料等领域；纤维素、半纤维素相对于木质素炭化温度低，更易形成多孔结构，获得更高的比表面积。另外二者因富含羟基，制备的水热炭表面具有丰富的含氧官能团，有利于通过静电吸附、离子交换等过程实现污染物吸附，进一步应用于环境治理等领域。水热温度主要影响炭化程度和水热炭得率，而水热时间则对水热炭形貌具有更明显的作用。通过改性可以定向调控水热炭性能，扩大其应用领域范围。为明晰不同条件下水热炭的结构变化，本文综述了纤维类生物质的种类、原料组成及水热条件对水热炭结构的影响，深入分析了水热炭生成机理，探讨了生物炭改性方法，归纳了生物炭在不同领域的应用并展望了未来的发展方向和前景，为生物质基水热炭研究提供参考。

关键词: 生物质, 水热, 炭材料, 炭化路径, 结构调控

Abstract:

Hydrothermal carbonization (HTC) is an efficient way to convert the lignocellulosic biomass to high-value added products. The wide variety of lignocellulosic biomass has complex physiochemical structures, resulting in complicated reactions including hydrolysis, degradation, and polymerization during HTC at different conditions. Characteristics of the hydro-char, such as morphology, pore structure, and the surface functional groups distribution are determined not only by the structure of the raw materials but also the hydrothermal reaction conditions, and directly affect the application of hydro-char. Lignin carbonization requires higher hydrothermal strength than cellulose and hemicellulose. In addition, the resulted hydro-char has a higher degree of graphitization and stability. It could be used as electrical and high temperature resistant materials. Compared to lignin, cellulose and hemicellulose can form porous structure more easily. In the meanwhile, they are rich in hydroxyl groups, the prepared hydro-char has abundant oxygen-containing functional groups, which is beneficial to the electrostatic adsorption and ion exchange. The generated biochar can be applied to the fields of environmental treatment. The hydrothermal temperature mainly affects the degree of carbonization and the yield of hydro-char, while the reaction time affects the morphology of the hydro-char obviously. The properties of hydro-char can be regulated by modification to expand its application. In this paper, the relationship among the composition of raw materials, HTC conditions and the structural characters of hydrothermal products were reviewed; the mechanism of carbonization process was deeply analyzed; the modification methods of hydro-char were discussed; the application of hydro-char in different fields was summarized; and the further development directions of HTC were proposed to provide a reference for the research of biomass-based hydro-char.

Key words: biomass, hydrothermal, carbon material, carbonization mechanism, structure adjustment

中图分类号:

TQ351.9

王雪, 徐期勇, 张超. 木质纤维素类生物质水热炭化机理及水热炭应用进展[J]. 化工进展, 2023, 42(5): 2536-2545.

WANG Xue, XU Qiyong, ZHANG Chao. Hydrothermal carbonization of the lignocellulosic biomass and application of the hydro-char[J]. Chemical Industry and Engineering Progress, 2023, 42(5): 2536-2545.

图/表 6

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类别	原料	纤维素质量分数/%	半纤维素质量分数/%	木质素质量分数/%	应用	参考文献
木材生物质	桉木	54	18	21	CO₂ 捕集	[13]
	橡木	40.4	35.9	24	污水处理	[14]
	松木	42~50	24~27	20	固体燃料	[15]
	混合木屑	40~50	11~30	20~30	固体燃料	[16]
农林废弃物	黑麦秆	41.2	21.2	19	功能炭材料	[17]
	稻杆	29~35	23~26	17~19	功能炭材料	[18]
	稻壳	28~36	12~30	15~20	固体燃料	[19]
	燕麦壳	37	35	7	污水处理	[20]
	玉米秸秆	33~42	32~36	6~16	污水处理	[21]
	核桃壳	30	27	38	电极材料	[22]
	毛竹	36	27	22	功能炭材料	[23]

类别	原料	纤维素质量分数/%	半纤维素质量分数/%	木质素质量分数/%	应用	参考文献
木材生物质	桉木	54	18	21	CO₂ 捕集	[13]
	橡木	40.4	35.9	24	污水处理	[14]
	松木	42~50	24~27	20	固体燃料	[15]
	混合木屑	40~50	11~30	20~30	固体燃料	[16]
农林废弃物	黑麦秆	41.2	21.2	19	功能炭材料	[17]
	稻杆	29~35	23~26	17~19	功能炭材料	[18]
	稻壳	28~36	12~30	15~20	固体燃料	[19]
	燕麦壳	37	35	7	污水处理	[20]
	玉米秸秆	33~42	32~36	6~16	污水处理	[21]
	核桃壳	30	27	38	电极材料	[22]
	毛竹	36	27	22	功能炭材料	[23]

水热温度/℃	水热时间	原料	水热炭结构特性	参考文献
160~220	24h	纤维素	在较低的水热温度（160℃）下，纤维结构较为完整。当水热温度为220℃时，开始形成不均匀球形颗粒	[17]
210~230	9h	棕纤维素	棕纤维素水热炭结构复杂，其表面呈球形	[29]
240	22h	木质素	当水热温度达到240℃时，硫酸盐木质素的结构开始降解，生成的炭表面有较小的颗粒附着	[30]
160~240	24h	麦秆	当水热温度超过240℃时，纤维结构开始破坏，微球状水热炭开始生成。但部分生物质原始宏观结构仍然保留	[17]
200~260	10min	杉木	当水热温度高于240℃时，水热炭颜色发生了明显的变化。木质素结构几乎未被破坏	[31]
200~260	6h	玉米秸秆	随着水热温度的增加，水热炭脱羧反应更剧烈，表面的炭微球数量增加，形状更均一	[32]
180~300	0~3h	毛竹	当水热温度为180℃时，水热炭表面粗糙，纤维结构有降解倾向；当温度达到260℃时，颗粒状炭含量增加	[23]
200	6~48h	木片	水热6h后，在无定形炭表面有球形炭生成，但炭球尺寸分布不均匀，直径在1~5μm	[33]
240	30min~24h	水葫芦	随着保温时间的延长，水热炭更趋向于生成微球状，当保温时间达到24h时，水热炭表面形貌呈现海绵状结构	[34]

水热温度/℃	水热时间	原料	水热炭结构特性	参考文献
160~220	24h	纤维素	在较低的水热温度（160℃）下，纤维结构较为完整。当水热温度为220℃时，开始形成不均匀球形颗粒	[17]
210~230	9h	棕纤维素	棕纤维素水热炭结构复杂，其表面呈球形	[29]
240	22h	木质素	当水热温度达到240℃时，硫酸盐木质素的结构开始降解，生成的炭表面有较小的颗粒附着	[30]
160~240	24h	麦秆	当水热温度超过240℃时，纤维结构开始破坏，微球状水热炭开始生成。但部分生物质原始宏观结构仍然保留	[17]
200~260	10min	杉木	当水热温度高于240℃时，水热炭颜色发生了明显的变化。木质素结构几乎未被破坏	[31]
200~260	6h	玉米秸秆	随着水热温度的增加，水热炭脱羧反应更剧烈，表面的炭微球数量增加，形状更均一	[32]
180~300	0~3h	毛竹	当水热温度为180℃时，水热炭表面粗糙，纤维结构有降解倾向；当温度达到260℃时，颗粒状炭含量增加	[23]
200	6~48h	木片	水热6h后，在无定形炭表面有球形炭生成，但炭球尺寸分布不均匀，直径在1~5μm	[33]
240	30min~24h	水葫芦	随着保温时间的延长，水热炭更趋向于生成微球状，当保温时间达到24h时，水热炭表面形貌呈现海绵状结构	[34]

改性方法	调控条件	实例	目的	参考文献
化学试剂预处理	盐溶液浸渍	饱和KCl溶液浸渍	利用K⁺、Cl^-等离子的刻蚀作用造孔，阻止碎片交联，形成骨架均一的片层结构	[63]
水热添加剂	催化剂	硫酸	水热炭表面的微孔体积和比表面积均显著增加	[62]
		碳酸钾	微孔比表面积和表面含氧量增加	[62]
		FeCl₃盐溶液	铁在炭表面反应有助于形成炭颗粒，可作为吸附剂有效去除废水中的营养物质	[64]
	乳化剂	聚苯乙烯磺酸钠	制备尺寸小于100nm的炭微球	[65]
	乳化剂	聚丙烯酸钠	提高水热炭的分散程度，形成均一稳定炭微球	[65]
水热后处理	活化剂活化	KOH浸渍	制备的玉米秸秆炭材料吸附容量可达到30.15mg/g，可作为污水中重金属吸附剂	[66]
	热解活化	热解+KOH浸渍	低温水热条件下即可得到完整的微球状水热炭，其粒径分布在3~6μm	[67]
	蒸汽活化	蒸汽活化磷酸浸渍	水热炭微孔结构、比表面积、吸附能力显著提升，可明显观察到微球状水热炭生成	[20]