Progress of molten salt-assisted thermochemical high-value conversion of biomass

doi:10.11949/0438-1157.20250550

Abstract

Abstract:

With the rapid development of new energy under the “dual carbon” goals, molten salt-assisted high-value conversion of biomass has attracted widespread attention. Biomass, as the fourth largest energy source globally and the sole renewable carbon resource, stands as a prominent candidate for replacing traditional fossil fuels. Thermochemical conversion technologies enable the transformation of biomass into value-added products including bio-oil, syngas, and carbon materials, with molten salts serving as reaction media to enhance conversion efficiency and product value. The exceptional heat transfer capabilities of molten salts create optimal reaction environments for fast pyrolysis, significantly improving bio-oil yield. The strong catalytic activity of abundant alkali metal ions in molten salts facilitates chemical bond cleavage and formation, enabling targeted regulation of bio-oil composition and directional enrichment of high-value chemicals. During the gasification process, these alkali metal ions enhance gasification efficiency and promote syngas production, while the tunable composition and types of molten salts establish an optimal reaction environment for the production of syngas with controllable ratios. Furthermore, the etching effects and redox reactions between molten salts and carbon matrices optimize the physicochemical properties of carbon materials, particularly porosity. The innovative thermoelectric synergistic processes in molten salt media further elevate the added value of biochar products. This review systematically summarizes recent advancements in molten salt-assisted valorization of biomass, elucidates the critical roles and mechanisms of molten salts in different product-oriented conversion scenarios, and outlines the challenges and imperative research directions for molten salt-based thermochemical technologies.

Key words: molten salt, biomass, pyrolysis, gasification, bio-oil, syngas, carbon material

摘要：

随着“双碳”目标下新能源的迅猛发展，熔融盐辅助生物质高值化转化受到了广泛关注。鉴于此，综述了熔融盐在辅助生物质高值化转化领域的研究进展，讨论了面向不同产物制备场景下熔融盐的关键作用及机理，并总结概述了熔融盐热化学技术面临的挑战和亟需开展的研究方向，具体结果如下：熔融盐中丰富的金属阳离子能够催化化学键的断裂和形成，实现生物油中高值化学品的定向富集；灵活的熔融盐种类和组成可促进气化反应，提高合成气产量，还为比例可调控的合成气产出提供了良好的反应环境；此外，熔融盐刻蚀作用以及与炭基质的氧化还原反应改善了炭材料的孔隙率等理化特性，且熔融盐介质中热-电协同的新工艺可进一步提高生物炭材料的附加值。

关键词: 熔融盐, 生物质, 热解, 气化, 生物油, 合成气, 炭材料

CLC Number:

TK 6

Wenxuan CAO, Boyang WU, Jun LI, Tianji LIU, Kuo ZENG, Haiping YANG, Hanping CHEN. Progress of molten salt-assisted thermochemical high-value conversion of biomass[J]. CIESC Journal, 2025, 76(10): 4976-4987.

曹文轩, 吴泊洋, 李俊, 刘天冀, 曾阔, 杨海平, 陈汉平. 熔融盐辅助生物质热化学高值化转化研究进展[J]. 化工学报, 2025, 76(10): 4976-4987.

Figures/Tables 8

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反应介质	温度	原料	气化剂	产率	浓度	文献
Li₂CO₃-Na₂CO₃-K₂CO₃	850℃	棉秆	CO₂	CO：850 ml/g	CO＞80%	[39]
	750℃	杉木锯末	H₂O（S/B=1）	H₂：807.53 ml/g	H₂≈55%（体积分数）	[40]
	1200 K	纤维素	H₂O+O₂（φ=1~8.8）	—	H₂/CO：0.76~1.7	[41]
NaOH	450℃	红木锯屑	—	H₂：65.39 g/kg	H₂＞85%（体积分数）	[42]
NaOH	450℃	水稻秸秆	—	H₂：780 ml/g	H₂：90.6%（体积分数）	[43]
NaOH-Na₂CO₃	750℃	微拟球藻	—	H₂：71.48 mmol/g	H₂：86.1%	[44]

反应介质	温度	原料	气化剂	产率	浓度	文献
Li₂CO₃-Na₂CO₃-K₂CO₃	850℃	棉秆	CO₂	CO：850 ml/g	CO＞80%	[39]
	750℃	杉木锯末	H₂O（S/B=1）	H₂：807.53 ml/g	H₂≈55%（体积分数）	[40]
	1200 K	纤维素	H₂O+O₂（φ=1~8.8）	—	H₂/CO：0.76~1.7	[41]
NaOH	450℃	红木锯屑	—	H₂：65.39 g/kg	H₂＞85%（体积分数）	[42]
NaOH	450℃	水稻秸秆	—	H₂：780 ml/g	H₂：90.6%（体积分数）	[43]
NaOH-Na₂CO₃	750℃	微拟球藻	—	H₂：71.48 mmol/g	H₂：86.1%	[44]

反应介质	前体	温度/℃	比表面积/(m²/g)	性能	文献
ZnCl₂	花生壳	480	1642	甲基蓝吸附：876 mg/g	[60]
CaCl₂	花生壳花生壳	850 850	316	—	[7] [7]
Na₂CO₃-K₂CO₃	花生壳花生壳	850 850	408	比电容：160 F/g	[7] [7]
Na₂CO₃-K₂CO₃	煮熟的咖啡豆	800	436	比电容：161 F/g	[61]
KOH	树脂	600	1094.14	机械强度：0.35 MPa	[62]

反应介质	前体	温度/℃	比表面积/(m²/g)	性能	文献
ZnCl₂	花生壳	480	1642	甲基蓝吸附：876 mg/g	[60]
CaCl₂	花生壳花生壳	850 850	316	—	[7] [7]
Na₂CO₃-K₂CO₃	花生壳花生壳	850 850	408	比电容：160 F/g	[7] [7]
Na₂CO₃-K₂CO₃	煮熟的咖啡豆	800	436	比电容：161 F/g	[61]
KOH	树脂	600	1094.14	机械强度：0.35 MPa	[62]

盐类型	相对产量/%	比表面积/(m²/g)
LiCl-KCl	100	82
LiCl/KCl+KOH	10.3	997
LiCl/KCl+NaBO₂	93	137
LiCl/KCl+K₂CO₃	52.7	1064
LiCl/KCl+KNO₃	32.6	1912
LiCl/KCl+KH₂PO₄	93.7	64
LiCl/KCl+K₂SO₄	55.4	1520
LiCl/KCl+KClO₃	40.2	1252