介孔限域包覆纳米镍催化转化废油脂制备生物航油

China has a large amount of waste oil (15 million tons/year). Converting waste oil into bio-aviation fuel by the nano-catalytic technology is a crucial and effective method. There are two key problems: one is the leaching of metal active center from conventional supported nickel-based catalyst, the other is the poisoning effect on the active sites of catalytic material from the high content organic acids and trace metal ions in the waste oil. These all will lead to the decrease of catalyst activity and stability. To overcome these problems, an innovative mesoporous pore Al-SBA-15 confinement and nano-silica encapsulate can anchoring of nickel particles, That will enhance the stability of metal particles and the synergistic effect of mesoporous carriers. Through this method, a highly efficient and stable mesoporous encapsulated nano-nickel catalyst will be prepared. The catalyst particle size, pore structure, and thickness of the coating layer will be controlled through mediating the amount of nickel, co-solvent, and TEOS. The structure-activity relationship between the catalyst performance and the hydro-isomerization bio-aviation fuels products will be investigate. The isomerization mechanism and the intermediates of waste oils catalytic hydrogenation will be studied. The impact from organic acids and metal ions in waste oil on the pore structure, acid properties and the metal activity center of the catalyst will also be analyzed. Above all, this project will provide a reliable theoretical support for the efficient and green preparation of bio-aviation fuels from waste oil.

我国拥有大量餐饮废油(1500万吨/年)，利用纳米催化技术将其转化为绿色生物航油是实现废油脂变废为宝重要途径之一。本项目针对镍基负载型催化剂金属组分易于流失及废油脂复杂组分对催化材料的影响，导致催化剂活性及稳定性下降的难题，创新采用有序介孔Al-SBA-15限域与纳米二氧化硅包覆增强金属颗粒稳定性及介孔载体的协同作用，双重锚定金属镍颗粒，制备高效稳定介孔包覆纳米镍催化材料；通过镍负载量、共溶剂含量及正硅酸乙酯含量等实现金属颗粒大小、孔径大小及包覆层厚度可控调节，研究废油脂加氢异构产物与催化剂性能之间的构效关系，揭示废油脂催化加氢关键中间产物及异构反应机理，解析废油脂中有机酸、金属离子对介孔限域包覆纳米镍催化材料孔道结构、酸性位点及金属中心影响机制，为废油脂高效、绿色制备生物航空燃料提供可靠的理论支撑。

全球经济的高速发展促进航空运输业急剧扩张，急需大量航空燃料，现阶段，我国拥有大量且廉价的废油脂，将废油脂一步加氢脱氧、异构裂解为生物航油组分是实现废物有效利用的重要手段。本课题研究中，采用原位种子诱导蒸汽法制备介孔SAPO-11分子筛及其晶化机理，通过调控介孔模板剂及阻聚剂比例，成功合成了不同形貌（海胆型和棒形的）介孔分子筛。分别研究了金属位点、Brønsted酸位点和Lewis酸位点在油脂转化过程中的主要功能及作用机制，通过碱性离子交换和螯合剂/分散剂双溶剂等方法，实现了对催化剂酸性位点和金属中心的定向调控，进而实现了对生物航油产物组分分布的可控制备。深入分析了双功能催化剂在废油脂加氢过程中失活的原因，主要是因为金属中心的流失和积碳引起失活。为了阻碍金属中心的流失，采用石墨烯封装方法封装镍解决了反应过程中催化剂镍流失的问题，考察不同碳源材料，碳和金属中心的比例等因素对油脂加氢性能的影响。基于以上研究，该项目成功合成了多级孔分子筛负载的镍基/SAPO-11, NiO-LiZSM-5, Ni@C/LiZSM-5双功能催化剂，实现了废油脂高效转化为生物航油组分（91.7%），异构选择性最高达到75.4%，有效降低产物的冷滤点。深入解析了废油脂转化过程的主要途径及反应机理，其中加氢脱氧包括氢解、加氢脱水及脱羰脱羧等，由Ni金属中心缺电子d空轨道催化；双功能催化裂解异构过程遵循正碳离子机理，催化裂解主要发生于强Brønsted酸位点，异构反应需Brønsted酸和Lewis酸位点协同催化。综上所述，本项目的完成，实现了催化反应路径定向调控与生物航油目标产物可控合成，构建出一条废油脂制备生物航油全组分合成路线，为废油脂催化加氢制备生物航油工业应用提供可靠理论基础。