毫米级沥青小球的诱导氧化不融化研究

Coal pitch is a cheap product, however, its value will be significantly increased if coal pitch is used to prepare spherical activated carbon with high performance. The problem for converting from coal pitch to spherical activated carbon is that thermoplastic pitch needs to be oxidative stabilized during the process, which has been widely studied but difficult to solve, especially for mili-scale coal pitch spheres. Therefore, coal pitch doped with free radical-releasing inductive agent will be adopted to achieve a controllable oxidation reaction in this study. Free radicals from the inductive agent will induce coal pitch to release free radicals to accomplish a homogeneous oxidation of mili-scale coal pitch spheres from the inside to the outside. This new method will give a promising solution to the problem and shed a light to the mechanism of inducing oxidative stabilization of pitch spheres. Moreover, since the composition of pitch will have a great influence on oxidation without melt performance of pitch spheres, this study will also investigate the oxidizability of different components of pitch and establish a relationship between the oxidizability of various components and properties of products. This study aims at having a deep understanding of the mechanism of inducing oxidative stabilization of of pitch spheres. Furthermore, we will come up with an original method to produce activated carbon spheres by using mili-scale pitch spheres, successfully solving the major problem during fabrication of high-performance spherical activated carbon and opening a pathway for more innovative thinking in the design and preparation of spherical activated carbon using coal pitch.

煤沥青目前主要是作为低值的产品所使用，而若将其转化为高性能的球状活性炭则可显著提升其价值。在将其制备为炭材料过程中，热塑性的沥青必须经历氧化不融化，而这一直是研究的热点和难点，尤其是毫米级煤沥青小球的氧化不融化更为困难。针对该问题，本项目提出在沥青内部掺杂能够可控释放自由基的诱导剂，以此在氧化反应进行到一定程度时由诱导剂释放出自由基来诱导沥青分子产生自由基，从而实现毫米级沥青小球由内到外的均匀氧化，突破毫米级沥青小球的均质氧化不融化技术，揭示氧化不融化的诱导机理；此外，沥青的组成结构也显著影响其氧化不融化，为此本项目将沥青组分分离后研究其氧化的反应性，并与最终样品的性能进行关联。本项目旨在从反应机理出发，研制出适合毫米级沥青小球氧化不融化的方法，解决煤沥青转变为高性能的球状活性炭过程中的关键科学问题，并对此学科的创新性思维理念起到提示性作用。

低值的煤沥青转化为高性能的球状活性炭可显著提升其价值。在将其制备为炭材料过程中，热塑性的沥青必须经历氧化不融化，而这一直是研究的热点和难点，尤其是毫米级煤沥青小球的氧化不融化更为困难。对此，本项目从机理出发，首先以高软化点的沥青为研究对象，采用2,3-二甲基-2,3-二苯基丁烷（DMDPB）作为自由基引发剂促进其氧化不融化。在300C氧化时，添加10 wt.% DMDPB的改性沥青中自由基浓度为原料沥青中自由基浓度的2.2倍。针对低软化点沥青氧化不融化更加困难的问题，通过掺杂热分解温度依次增加的氧化氢异丙苯、过氧化二异丙苯和2, 3-二甲基-2, 3-二苯基丁烷，以“梯度接力”诱导的方式使改性沥青中的自由基浓度从3.501018 spins g-1逐步增加到90.851018 spins g-1，实现了低软化点沥青的氧化不融化，为从低软化点沥青制备相应的球状活性炭提供了解决办法，突破了毫米级沥青小球的均质氧化不融化技术。此外，也进行了前躯体沥青的组成、结构与活性炭孔结构控制的相关性研究，阐明了沥青氧化程度及其组成对活性炭孔结构发展的影响机制。研究发现沥青各族组分在元素组成、分子大小和化学结构等方面的差异影响它们在热解和活化过程中微观形貌和孔隙结构的形成与发展：当TS和PS组分经KOH活化后，活性炭表面展现出蜂窝状孔形貌，而QS组分经KOH和水蒸汽活化后均呈现出层状堆积形貌；KOH活化的轻组分具有发达的微孔和中孔结构，而水蒸气活化后更倾向于在重组分中形成孔隙。随沥青中甲苯可溶物（TS）含量增加，活性炭总比表面积和总孔体积先增后减，窄中孔的比例（V2-4 nm/VTotal）持续增大，当沥青中TS含量达到68 wt.%时，V2-4 nm/VTotal趋于最大值38%。本项目的成功研究，解决了沥青从热塑性快速而均质地转化为热固性的难题，为低值煤沥青的高值化沥青奠定了重要的学术基础。