生物质催化热解中间产物实时在线探测及焦炭生成机理研究

The deactivation of zeolite catalysts caused by carbon deposits is always the bottleneck to the oriented conversion of biomass through catalytic pyrolysis process. The key to solve this problem is to dissect the conditions and mechanism of coke formation during the biomass catalytic pyrolysis. But for now, it is still difficult to uniformly and accurately understand the biomass coke in zeolite catalysts, relating to ‘where does it come from?’, ‘how it is formed?’ and ‘how to well control its conversion?’ et al. The basic reason why it is far from answering these questions is the lack of a deep understanding of key intermediates and their conversion pathways in the catalytic pyrolysis reactions.. In this project, synchrotron vacuum ultraviolet photoionization mass spectrometry connected to the microfluidized-bed and double-stage microfixed-bed reactors are selected as the main research method to explore the roles of key catalytic pyrolysis intermediates (CPIs) in the coke formation during the biomass catalytic pyrolysis. Thanks to on-line monitoring the composition and concentration of CPIs as well as other products, the accurate formation rules and conversion pathways of CPIs under different experimental conditions can be realized. Meanwhile, the quantitative relationship between CPIs, target products and coke is established. In this way, the coking and deactivation mechanism of zeolite catalysts as well as some related influence factors can be elucidated from a new perspective. All results in this project are beneficial to promote the researches such as catalyst modification, optimization of catalytic conditions and directional control of biomass catalytic pyrolysis.

分子筛催化剂积碳失活一直是困扰生物质催化热解定向转化途径的瓶颈问题，解决此问题的关键在于深入剖析生物质催化热解中焦炭形成的机理和条件。然而目前文献中关于分子筛催化剂中生物质焦炭究竟从何而来、如何形成、如何调控等问题仍难以形成统一准确的认识。究其原因，是缺乏对催化热解反应中关键中间产物及其转化路径的深入理解和研究。. 本项目拟采用同步辐射光电离质谱结合微型流化床和双极微型固定床反应器作为主要研究手段，探索生物质催化热解中关键中间产物在焦炭形成中的作用机理。通过实时在线监测催化热解中间产物及其它产物的种类和浓度变化信息，准确解析催化热解中间产物在不同实验条件下的形成规律和转化路径。同时构建催化热解中间产物、目标产物以及焦炭三者之间组分分布的定量关联，从新的角度深入阐释分子筛催化剂结焦失活的机制及影响因素，为今后催化剂改性、催化反应条件优化以及生物质催化热解定向调控提供实验依据。

催化热解技术为生物质制备高价值燃料和化学品提供较为经济的转化途径。然而，催化剂失活速率过快且催化效率难以稳定是目前制约生物质高值化利用的瓶颈问题。借助先进的实验手段，从分子水平上对不同条件下催化热解中间产物进行实时、在线、准确地定性定量对深入研究分子筛催化剂积炭失活机理具有重要意义。. 为此，本项目负责人设计了双极微型固定床反应器以及微型流化床/固定床反应器，并分别将它们连接于同步辐射光电离质谱检测装置，进而发展出了一套快速热反应表征方法，并将其用于不同种类生物质（如木质生物质、藻类生物质、多种模型化合物等）的催化热解反应过程研究。. 利用此套装置，先后开展了生物质初级及二次热解产物分布研究，典型催化热解中间产物形成及转化规律研究以及焦炭形成机理研究。实验重点探索了生物质催化热解过程中的稳定中间产物（如苯并呋喃、苯甲醛、苯二酚、呋喃类等）、轻质活性中间产物（醛类、长链烯烃类、烯酮类、亚甲基环戊烯类等）以及重质活性中间产物（酚池类寡聚物、多甲基苯类、多甲基环戊二烯类等）的形成以及它们随催化剂失活中的变化规律。. 通过分析中间产物的形成和转化规律，提出了碳氢模型化合物、木质素类模型化合物、藻类生物质等在分子筛催化下的催化转化总路径，对生物质催化热解反应机理有了更深的认识，如大质量芳香烃形成路径、简单酚类化合物（如苯酚、甲基苯酚等）的角色、轻质烯烃的形成差异、侧链活性对催化剂失活的影响、催化剂失活的“traffic jam”原理、木质素催化转化中“酚池”原理、多甲基化合物的形成以及催化剂种类对coke形成的影响等。. 本项目研究紧紧围绕催化热解中间产物的形成规律和转化路径，为催化热解反应机理研究提供了新的思路。项目所发展的实验方法可推广到其它固态燃料的催化热解反应过程研究，项目所提出的催化热解反应机理可为后续的新型催化剂设计和改性提供实验依据和理论指导。