生物质富氮热解联产高值含氮油炭产品的机制研究

Conversion of biomass for high value products by pyrolysis is an important development direction for biomass utilization. It has a good potential to preparation of high value products that introducing the exogenous nitrogen into the biomass pyrolysis process and forming a named biomass nitrogen-riched pyrolysis to generate nitrogen-containing products. This project will propose a new biomass conversion technology based on biomass nitrogen-riched pyrolysis to co-generation of high- value nitrogen-containing chemicals and nitrogen-doped carbon electrode material. In this study, the migration and transformation mechanism of nitrogen in the distribution of the pyrolysis product during nitrogen-riched pyrolysis process will be systematically detected. In this study, the migration and transformation mechanism of nitrogen in the distribution of the pyrolysis product during nitrogen-riched pyrolysis process will be systematically detected. At first, the precipitation and distribution characteristics of liquid products after nitrogen-riched pyrolysis is studied, to reveal the formation and regulatory mechanism of nitrogen-containing chemical based on Maillard reaction and establish the Maillard reaction path during nitrogen-riched pyrolysis. Then , the evolution of porosity characteristics and nitrogen-containing functional groups for charcoal formed during nitrogen-riched pyrolysis will be studied, and the formation and regulation mechanism of the electric double layer capacitor structure will be revealed by the understanding of the reaction between exogenous nitrogen and carbon matrix of charcoal in the complex reaction system, simultaneously, the transformation model for nitrogen in the carbon matrix will be built. And finally, to achieve the objective of co-generation high-value products by nitrogen-riched pyrolysis, the collaborative influence mechanism on the yield of quality of nitrogen-riched pyrolysis products will be studied and the Maillard reactions in vapor combined the formation mechanism of nitrogen-doped structure in solid phase will be revealed. The research result of this project will be beneficial to explore a new way for high value nitrogen-containing products.

生物质热解转化为高值产品是生物质利用的重要发展方向，在热解中引入外源氮素形成富氮热解，具有制备高值含氮产品的潜力。本项目提出了一种生物质富氮热解联产高值含氮化学品与掺氮电极碳材的新工艺，系统的解析不同阶段外源氮素在热解产物中的迁徙转化规律，研究生物质富氮热解液体产物的析出与分布特性，构建富氮热解条件下外源氮素与挥发分反应路径，揭示热解挥发分中含氮化学品的形成与调控机制；研究富氮热解过程中焦炭孔隙特性与含氮官能团的演变规律，建立氮元素在碳基质中的迁徙转化模型，揭示外源氮素与焦炭碳基质在复杂反应体系中构建掺氮电容结构的反应与调控机制；研究富氮热解产物产量与品质的协同调控规律，揭示含氮化学品与掺氮电极焦形成反应的耦合作用机制，实现生物质富氮热解联产高值产品的目标。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。

生物质热解转化为高值产品是生物质利用的重要发展方向，在热解中引入外源氮素形成富氮热解，具有制备高值含氮产品的潜力。为更好掌握生物质富氮热解行为，本项目对计划任务书进行了适当调整，首先从生物质自身氮素出发，考察了氮素存在形态及其在热解中的迁移特性。进一步研究了外源负载有机氮尿素和无机氮NH3对生物质产物析出与分布特性的影响，掌握了引入足量氮素的调控机制，引入尿素能够促进生物质热解活性，导致更多的氮被固定，但其液体油产物中尿素分解物占比较多；氨气气氛下，焦炭和热解油的固氮能力相对较弱，但热解油中杂环氮物质较多。进一步研究了生物质富氮热解产物的理化性质，掌握了热解挥发分中含氮化学品的形成与调控机制，掌握了固体焦炭理化结构演变及掺氮电容结构形成调控机制，尿素浸渍下，热解油主要富含酰胺类和含氮杂环物质，单N原子杂环氮含量随浸渍浓度的增加而增加，热解炭表面主要是一些C=N、C-N以及N-COO官能团，但随着温度的升高焦炭表面只保留有吡啶型N和吡咯型N；氨气氛围下，NH3高温形成的NH2*和NH*自由基会与生物质热解产生的含氧中间体反应生成胺基类物质，并在后续脱水、缩合及环化反应中形成含氧杂环类化合物，同时NH3、NH2*和NH*会与焦炭含氧官能团反应，生成大量的吡咯-N、吡啶-N等；两种外源氮添加方式均能够在焦炭中引入吡啶氮和吡咯氮，形成具有赝电容特性的焦结构。最后，探索了生物质氮素功能化调控的方法，协同制备了含氮液体化合物和掺氮焦电极材料。随着NH3和KOH的引入，生物油中有大量含氮物质生成，而酚类、芳香类和含氧类物质骤减；生物焦的比表面积、含氮官能团都明显增加。随着KOH增加，生物焦比表面积急剧增加，最大值(BC-0.4-N)达1873 m2/g (9.1 wt.% N)，表现出优异比电容特性(187 F/g)。两者的引入也促进了H2的形成，其含量超过50 vol.%。本项目研究取得了丰硕的成果，共发表论文18篇，其中SCI 14篇，申请专利10项，授权4项，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。