生物质与塑料共催化热解制备芳烃中含镓MFI分子筛的研究

Catalytic fast pyrolysis (CFP) is a promising biorefinery technology that can convert lignocellulosic biomass directly to valuable aromatic hydrocarbons. However, because lignocellulosic biomass contains high contents of oxygen but insufficient hydrogen, it also produces large amounts of coke in CFP. The coke deposits would result in rapid catalyst deactivation, which has severely limited the development of CFP technology. To minimize the coke formation, we have proposed co-CFP of biomass with hydrogen-rich plastic wastes. Our preliminary study investigated co-CFP of pine wood with polyethylene, which were used as model compounds for biomass and plastics, respectively. The results show that pine wood and polyethylene have a significant synergistic effect in co-CFP that not only increases the yields of aromatic products considerably, but also improves the yields and selectivities of high value-added products catalyzed by Gallium-containing zeolite. This improves the economic competitiveness of CFP technology greatly. The result suggests that co-CFP of biomass with plastic wastes may offer a viable way to overcome the main barrier to CFP of biomass. In light of this, the main objectives of this study are to investigate the fundamental mechanisms of the synergy between biomass and plastics in co-CFP over Gallium-containing zeolite, and to enhance the synergy via zeolite synthesis, conversion process optimization, etc. This work will advance the development of biorefinery technology significantly, and may provide a promising way to valorize solid wastes such as municipal wastes, which contain considerable amounts of biomass and plastic wastes.

木质纤维素生物质催化快速热解制备芳烃化合物是一项极具潜力的生物炼制新技术。但是，木质纤维素的氧含量高、氢含量少，在催化热解时易产生积炭进而引起分子筛催化剂的失活，严重制约了该技术的发展。针对此问题，我们选择富含氢的废弃塑料聚乙烯与松木共催化热解，发现两者在共催化热解时存在显著的协同作用：高附加值芳烃化合物的收率大幅增加，而含镓MFI分子筛显著提高了目标产物的收率和选择性。研究结果表明，生物质与废塑料共催化热解有望为解决制约生物质催化热解技术发展的瓶颈问题提供一条切实可行的途径。据此，本课题拟深入研究含镓MFI分子筛在共催化热解中的协同作用机制，并在此基础上，优化合成分子筛、研究分子筛积炭失活机理，提高共催化热解的转化效率。研究成果将推动生物质炼制技术的发展，并为城市生活垃圾等富含生物质与塑料的废弃物资源化提供一条极具经济潜力的新技术路线。

木质纤维素生物质催化快速热解制备芳烃化合物是一项极具潜力的生物质炼制新技术。但是，木质纤维素富氧少氢，在催化热解过程中易导致催化剂积炭失活，严重制约了该技术的发展。针对此问题，我们使用富含氢的废塑料和木质纤维素共同催化热解，发现二者在反应中存在显著的协同效应：高附加值芳烃产物的产率大幅增加，而含镓MFI分子筛显著提高了目标产物的收率和选择性。据此，本课题深入研究了含镓MFI分子筛在木质纤维素与废塑料共催化热解的协同作用机制，并在此基础上，通过合成高效镓MFI分子筛、研究催化反应机理等手段来提高共催化热解反应的效率。具体研究结果是：（1）制备不同类型的含镓MFI分子筛并研究其在纤维素和聚乙烯共催化热解的催化活性，水热合成的含镓MFI分子筛由于孔道中存在非骨架镓氧化物，能够提高芳烃选择性和收率；（2）研究水热法制备含镓MFI分子筛中最佳的镓源、铝源配比及分级孔道的影响，改变镓/铝配比及碱处理可以调整孔径和孔径分布，进而调整芳烃产物分布；（3）研究含镓MFI分子筛和ZSM-5的介孔孔道对纤维素和聚乙烯共催化热解的影响，介孔孔道分布能够缓解积炭生成，提高液体产物芳烃产率；（4）研究含镓MFI分子筛在木质纤维素生物质与废塑料共催化热解反应中的主要催化机理，非骨架的镓氧化物利于烯烃、环烃的脱氢芳构化反应；（5）研究微波甲酸预处理对木质纤维素生物质催化快速热解的影响，微波甲酸预处理能够选择性地移除半纤维素和木质素，利于纤维素高效转化制芳烃。本研究成果将推动生物质炼制技术的发展，并为富含生物质与塑料的废弃物资源化提供一条极具经济潜力的新技术路线。