镍基Al/SBA-15合成调变及催化转化废油脂制备生物航油组分

China has abundant and cheap waste oil. Converting this waste oil into bio-aviation fuel is a crucial and effective method to realize clean aviation fuel production using one-step hydrogenation/ isomerization/cracking process. With respect to this process, there are two key problems: one is the physic-chemical characteristics striking and poisoning to the active sites of catalytic material from the high content organic acids and trace metal ions contained in the waste oil; the other is the non-coordination of hydrogenation and isomerization in hydro treating process catalyzed by mesoporous catalysis material for production of bio-aviation fuel. To solve these two problems, a kind of acid mesoporous nickel-based Al/SBA-15 catalyst with specific scale aperture will be constructed through sol-gel source synthesis method. The specific scale aperture will be achieved through regulating the ratio of hydrophilic/hydrophobic groups in template reagent upon parsing the molecular dynamic radius of the oil. Based on the hydrogenation and isomerization process of the waste oil, the impact from organic acids and metal ions to the pore structure, acid properties and the acid/metal catalysis center of the catalyst, as well as the mechanism of selective β-cracking and isomerization of the carbenium ion intermediate, will be explored and analyzed. Sol-gel source synthesis method and metal doped method will be applied to regulate the distribution of metal centers and acid centers in the catalysts and to control one-step hydrogenation/isomerization/cracking processes for production of bio-aviation fuel ingredients from waste oil. This project will diversify and deepen the understanding of regulation method of the acid catalysts nickel-based Al/SBA-15 and provide a theoretic foundation and technical support of the one-step process of effective converting waste oil to bio-aviation fuel.

我国拥有大量且廉价的废油脂，将其一步加氢异构裂解制备生物航油是实现航空燃料清洁化的重要与有效途径。本项目针对废油脂高浓度有机酸与微量金属离子复杂环境对催化材料物理化学性质影响与活性位点的毒化，及现油脂在介孔催化材料上催化合成生物航油存在的裂解异构不匹配两个关键科学问题，通过溶胶-凝胶源头直接合成法调控模板剂亲疏水基比例，结合油脂分子动力学直径构建特征尺度孔径酸性介孔镍基Al/SBA-15催化材料。基于油脂加氢异构反应过程，解析有机酸与金属离子对催化材料孔结构、酸性质及酸/金属中心毒化机理，以及碳正离子中间产物选择性β裂解和异构反应机理。通过源头合成与金属掺杂，同步调控催化材料金属中心与酸中心分布特性，实现对废油脂一步加氢裂解异构合成生物航油组分反应途径的可控调变，丰富和深化对酸性催化材料镍基Al/SBA-15的认识与调控，并为废油脂一步法高效催化合成生物航油组分提供理论基础与技术支撑。

全球经济的高速发展促进航空运输业急剧扩张，航空燃料的大量消耗带来的碳排放问题亦愈渐显著。但由于航空燃料的特殊应用场景，无法用核能、太阳能、电能等代替。我国拥有大量且廉价的废油脂，将其一步加氢异构裂解制备生物航油是实现航空燃料清洁化的重要与有效途径。在本课题研究中，我们深入探究了Al/SBA-15分子筛合成过程中的晶化机制，通过调控模板亲疏水比例，利用双模板剂成功合成了多级孔分子筛。解析了废油脂转化过程中各主要反应机制：其中加氢脱氧包括氢解、加氢脱水及脱羰脱羧等，在Ni金属中心上完成，由金属中心缺电子d空轨道催化；催化裂解主要发生于强B酸位点，固体酸催化裂解异构过程遵循正碳离子机理，异构反应需B酸和L酸位点协同催化；芳烃组分由裂解反应形成C6-C8小分子烯烃经Diels-Alder环化及脱氢等芳构化反应形成。分别研究了金属位点、B酸位点和L酸位点在油脂转化过程中的主要功能及作用机制，通过控制离子交换，实现了对催化剂酸位点和金属位点的定向调控，进而实现了对产物组分分布的定向调控。阐明了废油脂杂质组分中水、有机酸及金属离子等对催化剂的影响机制，研究发现废油脂杂质组分可与固体酸发生协同催化酯化反应，金属离子显L酸酸性，但易与固体酸质子位点发生离子交换，易导致催化剂失活。基于以上研究，我们成功合成了多级孔分子筛负载的高分散镍基Al/SBA-15催化剂、高分散双金属NiW/SiO2催化剂、SAPO系列分子筛以及NiO-LiZSM-5分子筛催化剂，实现了对废油脂产物的高效定向转化（收率可达64wt%，生物航油C8-C16组分收率可达83.4mol%），产物的冷滤点得到有效降低；创新采用CO2替代H2气氛，促进油酸分子内源氢氢重排，实现航油烷烃组分高效制备，并为温室气体CO2化学利用提供了一条创新路径。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定向合成，构建出一条废油脂出发生物航油全组分合成路线，加深了金属催化及酸催化本质及协同效应的理论认识。