Abstract:

Lignin (LG) has high oxygen content and complex chemical structure, making it difficult to utilize as a resource. The introduction of blending agent and catalyst can greatly strengthen the decomposition of LG and effectively improve its utilization efficiency, but the specific mechanism of this process needs to be further analyzed. In present work, the effects of the addition of low density polyethylene (PE) and transition metals regarding to Ni, Fe and Mn on the evolution of surface functional groups of LG derived from black liquor were investigated by using in situ Fourier infrared spectroscopy (in situ FTIR). LG began to decompose gradually from the C—C bond at about 200℃ (at 2044 cm^-1), while the oxygen-containing surface functional groups including —OH, C—O, C—O—C and C\stackrel{}{̿}O at 1040—1645 cm^-1 and 3450—3600 cm^-1 began to decrease after 500℃. The addition of PE can start to promote the removal of oxygen-containing surface functional groups of LG at about 400℃, and can achieve the removal of most oxygen-containing surface functional groups at about 500℃. Furthermore, the introduction of Ni can enhance the interaction between LG and PE, resulting in the removal of most oxygen-containing surface functional groups in the rapid decomposition stage of PE at about 460℃. In addition, the process parameters including the type of transition metal, the concentration of transition metal, the mixing ratio of LG and PE and the heating rate all show certain degree effects on the interaction between LG and PE. This study provides important technical guidance for the resource utilization of LG from the perspective of the quality of pyrolysis process and the change of surface functional groups.

Key words: biomass, pyrolysis, catalysis, surface functional groups, in situ FTIR

摘要：

木质素（LG）含氧量高，化学结构复杂，难于资源化利用。共混剂和催化剂的介入，能够强化LG分解，有效提高其利用效率，但具体机制尚待进一步剖析。本文基于原位红外手段，考察低密度聚乙烯（PE）和过渡金属（Ni、Fe、Mn）的添加对造纸黑液LG表面官能团演变的影响。研究结果显示，LG在200℃左右从C—C连接键开始逐渐分解（波数在2044 cm^-1处），而含氧表面官能团在500℃以后才开始减少（波数在1040~1645 cm^-1和3450~3600 cm^-1处的—OH、C—O、C—O—C和C\stackrel{}{̿}O等）。PE的介入，在400℃左右即能开始促进LG含氧表面官能团的脱除，在500℃左右即能实现大部分含氧表面官能团的脱除。而Ni的添加，能够强化LG与PE之间的相互作用，使得LG中大部分含氧表面官能团在PE快速分解阶段（460℃左右）即脱除。另外，工艺参数，包括过渡金属种类、过渡金属浓度、LG与PE混合比例、升温速率等均对混合体系中LG和PE的相互作用存在不同程度的影响。本文从表面官能团变化的角度为LG的资源化利用提供了重要技术指导。

关键词: 生物质, 热解, 催化, 表面官能团, 原位红外