沸石基磁性微结构催化剂的构筑及其用于微藻水热液化的催化机理研究

Hydrothermal liquefaction of the microalgae (without pre-drying and algae oil extraction procedures) for biocrude (bio oil) production is an energy-efficient conversion process. The reaction conditions are milder than those of pyrolysis and gasification. The liquefied biocrude must be upgraded before refining because its oxygen and nitrogen content is much higher than the conventional crude. This project aims to fabricate iron oxide(s)/zeolite core/shell magnetic microstructured catalysts in which the bio oil was "in situ" deoxygenated. The microcell catalyst consists of the shell, modified natural zeolite (clinoptilolite, mordenite, etc.), in which microalgae could be decomposed on the acid sites, and the core, magnetic iron oxide (Fe3O4, Fe2O3), in which the oxygen containing organic compounds could be deoxygenated via hydrolysis or decarboxylation. The catalyst would be used for consecutive liquefaction of microalgae with subsequent non-hydrogenation deoxygenation in subcritical water below 300 ℃, to obtain high quality bio oil with less oxygen contents. Our considerable efforts should be made to tune the active sites on the catalyst, to build the channel for intermediates diffusion, and to characterize the strong interaction between core and shell of the microstructured catalyst, further to study model reactants diffusion and kinetics, and to evaluate the activity of microalgae to bio oil. The project will explore "controlling" the reaction pathway by rational construction of the catalyst, to tackle the major challenges intrinsic to the high efficient conversion of microalgae to low oxygen bio oil on the specific active sites via consecutive reactions, microalgae hydrothermal liquefaction and in situ deoxygenation of biocrude. The proposed research will provide theoretical basis for building of a new microalgae catalytic liquefaction process.

微藻不经预干燥和藻油提取直接水热液化制备生物原油的过程，是一种较热解和气化反应条件温和的高效能量转化过程。针对液化后生物油的氧含量、氮含量高的问题，本项目拟采用具有催化微藻解聚的强酸中心的改性天然沸石（如斜发沸石、丝光沸石等）、包覆在具有催化含氧有机物水解或脱羧反应的磁性氧化铁（Fe3O4、Fe2O3）微球表面,构筑酸催化液化产物"原位"脱氧的磁性核-沸石壳微结构催化剂，用于300℃以下微藻亚临界水热液化-非临氢改质一体化制备低氧生物油的过程。通过进行催化剂活性中心的调变、中间产物扩散通道的构建、及核壳之间强相互作用的表征，结合模型反应物的扩散行为和动力学研究、微藻转化生物油活性评价，探索利用此类微结构催化剂的合理构筑实现反应途径的调控，解决微藻水热液化-生物油原位脱氧耦合过程中序贯反应在特定活性中心上高效进行的关键问题，为新型微藻水热催化体系构建提供理论依据。

针对微藻液化生物油的氧含量、氮含量高的问题，采用两步包覆法制备出水热稳定性好的Fe2O3@M-SiO2@MCM-41磁性结构化催化剂，用于微藻水热液化生物油模型化合物十六酸的脱氧提质反应。研究了催化剂性质（载体Si/A比、孔结构）及反应条件（温度、时间，溶剂种类）对脱氧活性及产物分布的影响。研究了催化剂上的十六酸脱羧反应动力学，进行了原位DRIFT红外光谱表征，甄别出此类催化剂上十六酸脱羧产物CO2的脱附是速率控制步骤，进而推测出催化剂的失活机理。在谷氨酸存在时，该催化剂上CO2的脱附温度降低为295℃，说明在催化剂上十六酸与谷氨酸存在着一定的交互作用，并反应生成有机（酰）胺等产物。制备出纳米金属氧化物均匀分散的Fe2O3/clin、NiO/clin、NiO/Mordenite、及Fe2O3/Mordenite催化剂，研究了此类催化剂对小球藻水热液化-原位提质反应中产物分布的影响，结合模型化合物的催化热解反应动力学研究，推测出载体Si/Al比、孔结构等参数对脂肪酸（酯）、氨基酸及有机酸-氨基酸二元混合物的脱氧转化、脱胺转化等反应途径的影响。对十六酸、十八酸、谷氨酸等在Fe2O3/clin催化剂上的热解动力学研究计算，得出各化合物热解的活化能。采用一步合成法制备出Fe-Al-SBA-15催化剂和沉淀法制备出CuO/Al-SBA-15、ZnO/Al-SBA-15及CuO-ZnO/Al-SBA-15催化剂用于模型化合物棕榈酸甲酯的水热脱氧转化，研究了催化剂上脂肪酸甲酯FAME的吸附及CO2的脱附与脱氧产物分布之间的关系。本项目构筑出的磁性微孔和磁性介孔结构化催化剂，实现了亚临界水、非临氢条件下的微藻催化液化-原位脱氧提质，研究了磁性沸石基催化剂上藻油模型化合物的脱氧转化和表观反应动力学，确定出速率控制步骤，提出通过催化剂表面酸碱中心协调作用，从而实现液化油中脂肪酸（酯）类反应物在温和条件下脱羧（脱羰）转化。为脂肪酸类、氨基酸类模型化合物在特定催化活性中心上高效进行的关键问题的解决提供实验基础和理论依据。