Abstract:

In order to expand the high value utilization of lignin, the lignin biochar-supported iron catalysts were prepared with lignin and iron salt as raw materials by co-pyrolysis method. The influence of iron precursors, iron loading amount, heating rate and pyrolysis temperature on the decomplexation of Ni-EDTA and iron-leaching were investigated, and the effect of pyrolysis temperature on the catalysis performance was systematically discussed through the analysis of the pore structure, surface elements and crystal structure of the catalysts prepared at different pyrolysis temperatures. The results showed that the elemental composition, polarity and iron distribution on the surface of the catalysts were determined by iron precursors, and Fe(NO₃)₃·9H₂O was the best one. The number of active sites on the catalyst surface was increased with iron loading amount, while heating rate changed the porous structure of biochar, and pyrolysis temperature determined the formation of carbonaceous structure and the fixation capacity of iron on its surface. The iron transferred from catalyst surface to its interior when pyrolysis temperature increased, and iron-leaching was lower than 1.0mg/L above 600℃, making the decomplexation of Ni-EDTA transformed from homogeneous Fenton reaction to heterogeneous Fenton one. Meanwhile, high pyrolysis temperature caused the reduction of O, N and S active sites on catalyst surface, resulting in the deactivation of catalyst and decreased decomplexation of Ni-EDTA. The above results provide the basic data for the design and preparation of lignin biochar as catalyst carrier.

Key words: lignin, pyrolysis, catalyst support, catalyst, Ni-EDTA, oxidation decomplexation, deactivation

摘要：

为加强木质素高值化利用，以木质素和铁盐为原料，采用共热解法制备木质素生物炭载铁催化剂。考察铁源前体类型、铁负载量、升温速率和热解温度等制备条件对催化剂催化破络Ni-乙二胺四乙酸（EDTA）性能和铁活性组分浸出的影响，并结合不同热解温度下催化剂孔隙结构、表面元素及晶体结构等表征分析，系统阐述热解温度对催化剂性能的影响机制。结果表明，铁源前体类型直接决定催化剂表面元素组成、极性及Fe活性组分分布情况，以硝酸铁为铁源前体时催化剂性能最佳。负载铁活性物种有助于增加催化剂表面活性位点数量，升温速率可以改变生物炭孔隙结构，热解温度则决定生物炭碳质结构的形成及对Fe活性组分的固载能力。随着热解温度的升高，Fe活性组分逐渐向催化剂内部迁移，600℃时Fe浸出量始终低于1.0mg/L，催化氧化过程由均相Fenton反应为主向非均相反应转变；与此同时，催化剂表面O、N、S活性位点减少，其共同作用致使催化剂失活和Ni-EDTA破络效果降低。上述结果为以木质素生物炭为催化剂载体设计与制备提供了基础数据。

关键词: 木质素, 热解, 催化剂载体, 催化剂, 镍-乙二胺四乙酸, 氧化破络, 失活