生物质选择性富氮热解过程中氮素迁徙与功能化调控机制的基础研究

Bio-oil and biochar can be obtained via biomass pyrolysis. However, bio-oil contains too much oxygen, which greatly reduces the availability of bio-oil. Meanwhile, biochar is not purposefully functionalized, thus it has not been utilized extensively. In order to enhance the added value of pyrolysis products, this project proposes a new scheme to obtain high value-added nitrogenous chemicals and nitrogen-doped carbon materials by replacing the oxygen atoms in the product with nitrogen atoms during nitrogen-rich pyrolysis of biomass. However, nitrogen-rich pyrolysis produces many kinds of nitrogen-containing products with low yields. In this regard, molecular sieve catalyst and green activator are introduced to coordinately control the nitrogen-rich pyrolysis process so as to achieve high-selectivity and high-yield oriented generation of nitrogenous chemicals and nitrogen-doped carbon materials. This project aims to deeply reveal the novel mechanisms of migration and transformation of endogenous and exogenous nitrogen during biomass nitrogen-rich pyrolysis, and investigate the regulating mechanism of oriented production of nitrogenous compounds under the action of molecular sieve catalyst, and study the generation and regulation mechanism of the pore structure and nitrogen-containing structure of biochar under the interaction of green activator and nitrogen. Finally, with obtaining the coupling mechanism of nitrogen, molecular sieve catalyst and green activator, new technology of selective nitrogen-rich pyrolysis of biomass for co-production of high value-added nitrogenous chemicals and nitrogen-doped carbon materials will be developed. The results of this project will benefit the exploration of new approach realizing high value-added conversion of biomass.

生物质热解能够得到生物油和焦炭，但生物油含有较多氧，极大地降低了生物油的附加值，而焦炭功能性不强，利用空间有限。为了提升热解产品附加值，本项目提出用氮原子取代产物中氧原子，从而得到高附加值含氮化学品与掺氮碳材料的生物质富氮热解新思路。然而富氮热解得到含氮产品种类多、产率低，对此拟通过引入分子筛催化剂和绿色活化剂协同调控富氮热解过程，以实现含氮化学品与掺氮碳材料高选择性与高产率的定向生成。本项目将以深入揭示生物质富氮热解过程中原生氮与外源氮迁移转化新机制为立足点，研究分子筛催化剂作用下挥发分中氮素功能化调控定向生成含氮化学品的反应机理，研究绿色活化剂与氮素交互作用下焦炭中孔隙和含氮结构的生成及调控机制，最后通过解答氮素、分子筛催化剂、绿色活化剂的耦合作用机制，实现生物质选择性富氮热解联产含氮化学品与掺氮碳材料的新工艺。本项目的研究成果将有利于探索出一条高值转化生物质的新途径。

本项目在实验研究和理论分析的基础上，研究了生物质富氮热解制备高值化学品和掺氮炭材料，揭示了生物质热解制备功能型掺氮炭材料过程中的活化、掺氮、和活化-掺氮协同机理，以及生物质热解制备高附加值酚类物质的催化机理及反应路径等，为生物质向高附加值的功能型掺氮炭和含氧化学品转化提供了理论支撑，有利于实现生物质的高值化利用。.本项目的主要成果是：.1．探究了生物质与氨基酸共热解特性，揭示了共热解过程中的交互反应机理。生物质与氨基酸共热解显著提高了生物油品质，并有效控制氮向生物油中转化。.2．揭示了生物质热解过程中KOH的活化机理及生物炭形成机制，并提出了针对生物质等活性原料的KOH活化反应路径。.3．提出了生物质“热解-活化-掺氮”一步协同调控制备多孔掺氮炭的新方法，并揭示了协同调控机制，制备了高孔隙率高含氮量的掺氮炭产品。.4．提出了掺氮炭催化热解生物质制备高值酚类物质的新方法，得到了高选择性的4-乙烯基苯酚，并揭示了掺氮炭的催化反应机理及酚类物质形成机理。.5．结合实验研究和密度泛函理论计算，揭示了NH3对木质素热解生成4-乙烯基苯酚的作用路径，制备了高选择性高产率的4-乙烯基苯酚。