生物质基含氧化合物低耗H2高效加氢脱氧Ni基催化剂的构建及选择性调控

Hydrodeoxygenation plays an important role for the conversion of biomass to fuel and chemicals. For the hydrodeoxygenation of bio-based oxygen-containing compounds (for example, fatty acid ester and phenolic compound) on Ni catalysts, apart from the normal H2 consumption due to deoxygenation, benzene hydrogenation, C-C bond hydrogenolysis and methanation enhance the H2 consumption. In the present project, we plan to prepare the M'O2-Al2O3(M'=Ti, Zr and Ce) composite oxide supported Ni-M (M= Zn, Ga and In) alloy and intermetallic compound catalysts from the hydrotalcite-like compounds. Metal M has high oxygen affinity, low electronegativity but very inferior activity for benzene hydrogenation, C-C bond hydrogenolysis and methanation. In the Ni-M alloy and intermetallic compound, the geometrical and electronical property of Ni is modified by M, which is favorable for reducing H2 consumption. Meanwhile, the different active sites (such as Ni site, M site, Lewis acid site and oxygen vacancy) on the catalyst are synergetic to reach a highly efficient hydrodeoxygenation. We will investigate the relationship between the catalyst structure (including the crystalline structure and crystallite size of Ni-M alloy and intermetallic compound, the oxygen affinity and electronegativity of M, the Ni and M electronic interaction as well as the catalyst acidity, basicity and oxygen vacancy) and the performance (including activity for hydrodeoxygenation, benzene hydrogenation, C-C hydrogenolysis and methanation as well as deoxygenation pathway). From the structure-performance relationship, how to regulate and control the product selectivity can be obtained. The results will provide theory basis and new idea for rationally designing the Ni-based hydrodeoxygenation catalyst with low H2 consumption and high activity.

加氢脱氧在生物质转化为燃料及化学品过程中具有重要作用。金属Ni催化剂上生物质基含氧化合物（如脂肪酸酯及酚类化合物）加氢脱氧过程中，除了脱氧耗氢外，苯环加氢、C-C键氢解及甲烷化等反应增加了耗H2量。针对该问题，本申请拟以类水滑石前驱体制备具有酸碱中心及/或氧空位的M'O2-Al2O3（M'为Ti、Zr和Ce）负载Ni-M（M为Zn、Ga和In）合金及金属间化合物催化剂，利用M亲氧性高、电负性低及苯环加氢、C-C键氢解和甲烷化活性差等特点调节金属Ni的几何电子结构以降低耗H2量，通过催化剂表面不同活性中心集成协同作用实现高效加氢脱氧。研究不同合金及金属间化合物晶体结构及晶粒尺寸、M亲氧性及电负性、Ni与M电子作用及载体表面酸碱性、氧空位与催化剂加氢脱氧活性、脱氧途径及苯环加氢、C-C键氢解、甲烷化性能之间的关系，获得产物选择性调控规律，为低耗氢高效加氢脱氧镍基催化剂设计提供理论依据及新思路。

生物质是唯一可以转化为含碳液体燃料及化学品的可再生能源，加氢脱氧是生物质催化转化利用的重要手段。例如，动植物油脂经加氢脱氧可制得柴油类烃，木质素基生物质油中主要成分酚类化合物经加氢脱氧可制得芳烃。金属Ni催化剂活性高、成本低，但同时也具有很高的苯加氢、脱羰/脱羧、C-C键氢解和甲烷化活性，降低了加氢脱氧产物收率、增加了耗氢量。针对金属镍催化剂在加氢脱氧中存在的上述问题，本项目采用共沉淀、浸渍及溶胶-凝胶法制备了负载Ni-M（M为亲氧性金属Zn、In及Ga）合金及金属间化物催化剂。研究发现，Ni与M之间形成合金及金属间化合物的结构取决于Ni/M原子比。合金及金属间化合物中，Ni原子被M原子“隔离”，同时发生Ni到Zn及Ga、In到Ni的电子转移；随Ni/M原子比降低，“隔离”和电子转移程度增加。在酚类化合物及脂肪酸甲酯脱氧反应中，亲氧性M通过调变金属镍几何和电子性质明显抑制了苯加氢、C-C键氢解、甲烷化及脱羰/脱羧活性，借此可调控催化剂脱氧活性及产物选择性。在Ni-M合金和金属间化合物中，Ni3Ga金属间化合物具有较佳的酚类化合物加氢脱氧性能，其中Ni和Ga协同作用促进了酚类化合物直接脱氧；在苯甲醚加氢脱氧反应中，SiO2负载Ni3Ga活性及苯选择性均高于Ni/SiO2，苯收率可达87.8%。在脂肪酸甲酯脱氧制烃反应中，形成Ni-Zn及Ni-Ga合金及金属间化合物可明显抑制脱羰/脱羧、C-C键氢解、甲烷化活性，显著提高了目的产物烃的收率（>95%）；Ni-In金属间化合物上更有利于脂肪酸甲酯选择加氢制脂肪醇。Ni与亲氧性M之间的协同作用对催化剂加氢脱氧及选择加氢活性及选择性具有重要影响。研究结果为低耗氢高效加氢脱氧镍基催化剂设计提供了依据。