生物质与废塑料定向热解耦合制芳烃过程基础

The valuable liquid fuels and chemicals produced from biomass and plastic wastes is of immense significance to mitigate the severe energy shortage and environmental pollution. Fundamental studies on the aromatics production by coupled pyrolysis of biomass and plastic wastes are conducted in this project, in order to solve the problems accompanied with the conventional co-catalytic cracking of biomass and plastic wastes, such as coking of catalyst, low-yield of target product, and poor variability of operating conditions. The utilization of staged catalytic cracking could improve the selectivity to intermediates with synergistic action and thereby strengthen the synergic effect during the coupling reaction. Isotope tracer method is adopted to identify key synergetic substances in reaction process based on model compounds. The impact of essential characteristics of synergistic substances on the distribution of products is also investigated to establish the “structure-activity” relationship between reactants and products. Accompanied with the online monitoring and quantification of active intermediates through in-situ FTIR and in-situ UV/vis, the mechanism of synergistic strengthening reaction is elaborated by means of computational chemistry. Combined with the optimization of process reaction parameters and verification test, an oriented conversion of biomass and plastic wastes for aromatic products technology is finally formed with high yield and selectivity.

以生物质和塑料废弃物作为原料生产高品质燃料和化学品对于缓解我国能源紧张和环境污染问题具有重要意义。本项目针对目前生物质与塑料共催化热解研究中存在的诸如催化剂易结焦、目标产物产率较低、反应参数可调变性差等问题，提出生物质与塑料定向热解耦合制芳烃技术思路: 拟通过分级热解催化，选择性提高关键协同物质产率，以强化耦合反应过程的协同作用促进芳烃形成。基于模型化合物水平，采用同位素示踪法对反应过程关键协同物质进行识别；研究协同物质本质特征对产物分布特性影响规律，以构建反应物-产物间“构-效”关系；采用In-situ FTIR和In-situ UV/Vis等分析手段对活性中间产物进行原位在线监测与量化研究，并借助计算化学对协同作用强化反应作用机理进行阐述；结合过程反应参数优化与验证试验，形成生物质/废塑料基高产率、高选择性芳烃产物定向制备调控技术。

本项目主要开展生物质与塑料定向热解耦合制芳烃基础研究，按照项目要求完成了相关研究任务。首先基于Py-GC/MS开展了小分子模型化合物（不同H/Ceff、不同官能团）的择形催化共热解实验结合过程产物的系统表征分析，初步实现对关键协同物质进行有效识别，明确了生物质与废塑料定向热解制备芳烃过程反应物与目标产物间“构-效”关系；基于此采用固定床开展典型生物质（核桃壳）与塑料（LDPE）分段催化共热解（TSCCP）制备富芳烃油验证实验，通过多因素条件实验结合产物的定性定量分析，系统研究了热解定向转化过程反应参数对目标产物形成的影响规律并对进行参数优化，获得了高产率、高选择性芳烃产物的定向转化方法，实现最优反应条件下的热解油产物中烃类及芳烃选择性分别达到99%及82.5%，含氧组分降至1%。并从应用角度出发，针对生物质与塑料共热解转化存在的原料混合不均及固固接触影响传质、传热等科学与应用问题，采用原料的复合成型预处理，通过增强热解中间产物间的协同作用，提高了芳烃的产率和选择性，降低了热解油中含氧组分的选择性，提升了产物品质，最优反应条件下油相产物中芳烃选择性高达90.4%，芳烃总产率为29.6%，TSCCP工艺较传统直接共热解在热解油产物脱氧提质及促进芳烃转化方面优势显著。进一步通过转化过程热解半焦等中间产物的分析表征结合小分子模型化合物催化转化实验，对生物质与LDPE的TSCCP制芳烃反应机理进行了阐释:生物质衍生呋喃类、醇醛酸酮类、酚类三组主要含氧组分与LDPE衍生烯烃之间均存在积极的协同作用，显著促进了芳烃的生成；基于热解特征温度建立的分步热解方式有效避免了纤维素和半纤维素组分与LDPE共热解芳烃产物在第二步高温环境的不利二次反应；第一步木质素组分发生活化促进了其与LDPE协同共转化生成芳烃。.本项目研究构建了生物质与废塑料定向热解耦合反应制芳烃过程的强化协同作用理论与研究方法，形成了产物定向转化调控技术，为生物质与废塑料定向热转化制高附加值的燃料和化学品技术奠定了理论基础与科学指导。.