抗Ostwald熟化机制用于高稳型铜基催化剂对酯类碳-氧键氢解的研究

The selective hydrogenolysis of C-O bonds, is one of the important reactions related to the transformation of bio-polyols, acids, esters, ethers, and bio-ols by pyrolysis or liquefaction to fuels and added-value chemicals. The present research project chooses the selective hydrogenolysis/hydrogenation of typical compounds with C-O bonds like esters，for example, dimethyl oxalate as model and target reactions. According to the easy deactivation of traditional copper catalyst due to Ostwald ripening, modifying the electronic and geometrical structure to ehance the interaction of copper atom and connected metals and support is adopted to retard Ostwald ripening， with the purpose to increase the stability and improve the catalytic performance. The activity control and structure stability of the catalysts are two crucial challenges of the present project. The effects of various factors such as the types and chemical states of active components and additives, the size and morphology of active metals, the properties and the porous structures of supports on catalytic performances are to be investigated systematically. Based on these results, the project will propose effective strategies to increase the stability. By exploiting the novel nanomaterials emerging in recent years and the novel synthetic methods, the project aims at designing and preparing new catalyst systems for the target reactions with high activity and stability, and understanding the nature of catalysis on the atomic scale.

C-O键选择性氢解，是与多元醇、酸、醚、酯和生物质裂解油等碳资源制燃料和精细化学品密切相关的重要催化反应。本项目选择含C-O键的典型底物，如草酸二甲酯的选择性加氢/氢解为模型和目标反应，针对传统负载型铜基催化剂在该反应体系中易发生Ostwald熟化并较快失活这一问题，通过对铜基催化剂的电荷和几何结构进行调控，增强铜原子与接触金属和载体的作用力,以抑制Ostwald熟化为基础，提高催化酯类加氢稳定性为目标，解决铜基催化剂在催化过程中的失活问题。围绕活性调控和催化剂结构稳定性这2个关键科学问题，系统考察催化剂活性金属的组分、化学状态、尺寸和形貌以及载体物性等因素对催化剂稳定性能的影响。在此基础上，项目将提出提高稳定性的有效策略，利用不断涌现的纳米新材料和纳米催化材料的制备方法，研制目标反应高效高稳的定向转化的新催化剂体系，在原子水平上认识催化作用本质。

负载型铜基催化剂因其廉价易得,并且具有相对高的反应活性，在非均相催化应用中被广泛用于甲醇合成，选择加氢，偶联反应以及点击化学。 但是对于铜基催化剂长期存在的一个问题是催化剂失活，催化剂的失活极大限制了这类材料的工业应用。铜基催化剂的碳-氧键选择性氢解是其中一类重要的化工反应。基于前期研究，铜基催化剂会发生Ostwald熟化而导致颗粒烧结，致使反应活性位点减少，造成活性降低。我们通过构建页硅酸铜包裹CNTs得到催化前驱体，还原得到促进型半包裹铜硅催化剂。这种材料能对活性中心的电荷和几何结构进行调控,增强铜原子与接触金属和载体的作用力,抑制铜纳米催化剂的Ostwald熟化,提高催化酯类加氢稳定性,解决铜基催化剂在催化过程中的失活问题。研究发现，页硅酸铜的前驱体结构具有记忆效应，在还原气氛中仍可以稳定亚铜物种，增强金属载体相互作用，从而抑制Ostwald熟化的发生。同时，硅物种对铜纳米颗粒形成半包裹形态，在保证活性中心暴露的同时，抑制烧结的发生。具有良好的导电导热能力的CNTs的引入进一步促进铜基催化剂的稳定。本研究提供了一种有效合成策略，可以得到CNTs支撑的半包裹铜/钴/镍基催化剂。同时，研究探讨了表界面铜硅物种的协同效应，能够有效进行酯类碳-氧键的氢解。之后，我们开发了更具实用性的富勒烯促进型铜基催化剂在草酸二甲酯制乙醇酸甲酯/乙二醇/乙醇、生物质脂肪酸酯(马来酸二甲酯和乳酸酯等)制醇/碳氢化合物等催化加氢/氢解反应有优异的表现。进一步印证了碳材料对铜纳米颗粒的电荷调控有助于含碳-氧键物种的稳定和高效转化。