双流化床生物质分级热解/在线提质制液体燃料的方法与机理

The liquid fuel produced by traditional biomass pyrolysis technology is difficult to use directly, due to its complex composition, high water and oxygen content, strong acidity, low calorific value and poor stability. In order to improve the quality of liquid fuels, complex refining process is necessary; and to explore new ways and mechanisms of biomass grading conversion has become the research forefront and trend. Based on the important features “different biomass components have thermal stability diversity”, a new method coupling biomass grading pyrolysis in a dual fluidized bed reactor with in situ upgrading of pyrolysis vapors for production of high-quality liquid fuels is proposed. By biomass staging pyrolysis, the polysaccharide (cellulose and hemicellulose) and lignin components are converted into the strong polar compounds and aromatic compounds respectively, and then the pyrolysis vapors are upgraded online by esterification or catalytic cracking to produce the high grade liquid fuels. In this project, a “fast fluidized bed - spouted fluidized bed” staging pyrolysis system will be established, and the research will be focused on the three main components (cellulose, hemicellulose and lignin) directional grading pyrolysis mechanisms, the online esterification and catalytic cracking of the pyrolysis vapors, the coupling mechanisms of staging pyrolysis and online upgrading. With very good work foundation, it is expected to establish a new integrated method of biomass staging pyrolysis/online upgrading to produce liquid fuels, to improve the quality of target products and simplify the technological process.

传统生物质热解工艺制备的液体燃料成分复杂、含水含氧量高、酸性强、粘度大、热值低、稳定性差，需再通过复杂的分离精制程序提升品质，探索分级分质转化新途径与机制已成为研究的前沿和趋势。本项目抓住“生物质不同组分具有热稳定性差异”的重要特性，提出双流化床生物质分级热解/在线提质制备高品位液体燃料新方法，即通过双流化床分级热解，分别将多糖（纤维素和半纤维素）、木质素组分转化为强极性化合物和芳香族化合物，进而对热解蒸气在线提质（酯化、催化裂解）制备高品位液体燃料。拟构建“快速流化床-喷动流化床”分级热解系统，重点研究生物质三大组分（纤维素、半纤维素、木质素）定向分级热解反应机理、分级热解产物在线酯化和催化裂解方法、分级热解与在线提质的耦合匹配机制。项目具有很好的前期工作基础，通过研究有望建立一种生物质分级热解/在线提质制备液体燃料一体化新方法，提高目标产物的品质，且简化工艺流程。

传统生物质热解工艺制备的液体燃料成分复杂、品质低下，需再通过复杂的分离精制程序提升品质，探索分级分质转化新途径与机制已成为研究的前沿和趋势。本项目选取不同种类的生物质及组分模化物，通过TG-FTIR和Py-GC/MS深入解析了生物质组分热稳定性差异及其分级转化途径，进而在固定床上开展了生物质的分级热解，以及低温烘焙生物质的热解特性研究，实现了多糖和木质素热解产物的高效分离。在此基础上，探索了低温烘焙预处理与催化热解相结合，以及金属氧化物同分子筛共催化热解以提高生物油品质和促进目标产物富集的方法，改性制备出高催化活性和选择性的Ni-Mo2N/HZSM-5催化剂，并提出CaO与HZSM-5分子筛组合催化的方式。在流化床热解-固定床催化裂化反应系统上，研究了解耦流化床单元、固定床单元的优化操作条件，进而掌握其耦合调控规律，整体反应系统对于提高生物质热解的芳香烃产率和选择性具有较好的效果。.重要结果有：（1）与直接热解相比，分级热解在低温段中富集到了酸类和醇类，而左旋葡萄糖和绝大部分酚类、酮类都在中温段富集，有效地降低了热解产物的复杂性，提高了生物油的品质；（2）烘焙预处理可预先去除半纤维素组分，有效减少热解油中酸、醛等含氧化合物的产量，结合Ni-Mo2N/HZSM-5催化，相比于未改性的HZSM-5分子筛，苯产量提高了1.27倍，同时萘、甲基萘等产量分别下降为原来的56.48%和32.73%；（3）热解蒸汽经过金属氧化物先裂解为小分子脂肪烃，继而进入HZSM-5的孔道，经催化显著提高了芳香烃的产量，其中C6-C8单环芳香烃碳产率达到了17.41 C-mol%，而萘等多环芳香烃的碳产率被控制在4.53 C-mol%。项目提出的制备方法简化了工艺流程，有望在更大容量的装置上开展连续性实验，进一步评估和验证，推进生物质催化热解制备高品位液体燃料/化学品的应用研究。