【作者】 袁磊；

【导师】 戴立言； 张世界；

【作者基本信息】 浙江大学 ， 化学工程（专业学位）， 2023， 硕士

【摘要】 对氯苯甲醛作为一种应用十分广泛的精细有机化工中间体,在新型染料、医药、农药、香水等领域有着重要的应用价值。目前,温和条件下将甲基芳香烃高效催化氧化为芳醛的报道较少,开发出一种廉价易得、环境友好、可循环利用的新型非均相催化剂,将对氯甲苯高效地转化为对氯苯甲醛意义重大。过渡金属氧化物因其优异的氧化还原行为在甲基芳香烃的选择性氧化方面具有巨大的潜力,但是目前绝大多数非贵金属催化剂具有催化活性较低的缺点,而催化剂的活性与结构密切相关,因此通过合理设计催化剂的结构来提高其活性具有重要意义。本论文从过渡金属氧化物出发,首先选用Cu、Cr作为活性组分,通过煅烧去除模板剂来构建蠕虫状介孔Si O₂载体,采用共沉淀法制备了二氧化硅负载铜铬金属催化剂。研究发现,双金属催化剂的催化活性明显优于单金属催化剂,铜铬金属之间相互作用形成的Cu Cr O₂和Cu Cr₂O₄两相修饰了催化剂表面性质,为催化反应提供了更多的活性位点。在最佳条件下,Cu Cr₂/Si O₂催化对氯甲苯的转化率为33.2%,对氯苯甲醛的选择性为81.4%,且六次重复使用实验结果表明催化剂的循环稳定性良好。Cu纳米颗粒在Si O₂中的均匀分散以及Cu²⁺/Cu⁺和Cr⁶⁺/Cr³⁺多个氧化还原对的存在是对氯甲苯高效选择性氧化的关键。在双过渡金属氧化物的基础上,选用Fe、Co、Ni、Cr、Mn五元过渡金属元素作为活性组分,通过共沉淀法和物理研磨法成功制备了尖晶石型高熵氧化物（Fe Co Ni Cr Mn）₃O₄。其中,共沉淀法制备的c-Fe Co Ni Cr Mn催化剂在最优条件下对氯甲苯的转化率为38.7%,对氯苯甲醛的选择性为91.8%,且该催化剂可以通过简单的磁吸回收利用,然后催化剂在六次循环后活性没有显著损失。研究发现,Fe和Mn是该催化反应的主要活性位点,其他三种金属（Co、Ni、Cr）作为催化助剂协同提高催化活性。DFT计算表明,高熵氧化物中氧空位的存在有利于对氯甲苯分子在催化剂表面的吸附,促进了中间产物*Cl Ph CH₂O和目标产物对氯苯甲醛的形成。c-Fe Co Ni Cr Mn催化剂具有较大的比表面积、较小的粒径和较多的氧空位是其催化活性优越的主要原因。更多还原

【Abstract】 As a widely used fine organic chemical intermediate,p-chlorobenzaldehyde has significant application value in areas such as new dyes,pharmaceuticals,pesticides,and perfumes.Currently,there are few reports on the selective catalytic oxidation of methyl aromatic hydrocarbons to aromatic aldehydes under mild conditions.The development of a new type of heterogeneous catalyst that is inexpensive,readily available,environmentally friendly,and recyclable would be of great significance for the efficient conversion of p-chlorotoluene to p-chlorobenzaldehyde.Transition metal oxides have enormous potential in the selective oxidation of methyl aromatic hydrocarbons due to their excellent redox behavior.However,the majority of non-noble metal catalysts currently have the drawback of low catalytic activity,and the activity of catalysts is closely related to the structure,so it is of great significance to improve its activity by designing the structure of the catalyst.Based on transition metal oxides,this thesis first selected Cu and Cr as active components and used worm-like porous Si O₂ modified by calcination to remove templating agent as a carrier.A silica-supported Cu-Cr bimetallic catalyst was prepared by co-precipitation method.The study found that the catalytic activity of the bimetallic catalyst was significantly higher than that of the monometallic catalyst.The Cu Cr O₂ and Cu Cr₂O₄ phases formed by the interaction between Cu and Cr metals modified the surface properties of the catalyst.In addition,the Si O₂carrier rich in pore structure also increased the specific surface area of the catalyst,providing more active sites for the catalytic reaction.Under optimal conditions,the conversion of p-chlorotoluene by Cu Cr₂/Si O₂ catalyst was 33.2%,and the selectivity of p-chlorobenzaldehyde was 81.4%.Moreover,the six cycle test results showed that the catalyst had good cycle stability.The homogeneous dispersion of Cu nanoparticles in Si O₂ and the presence of Cu²⁺/Cu⁺and Cr⁶⁺/Cr³⁺redox pairs were critical for the highly selective oxidation of p-chlorotoluene.On the based of bimetallic transition metal oxides,Fe,Co,Ni,Cr,and Mn were selected as active components,and a spinel-type high-entropy oxide（Fe Co Ni Cr Mn）₃O₄ was successfully prepared by co-precipitation and physical mixing methods.Among which,the c-Fe Co Ni Cr Mn catalyst prepared by the co-precipitation method had a conversion rate of 38.7%of p-chlorotoluene and a selectivity of 91.8%of p-chlorobenzaldehyde under the optimal conditions.Moreover,the catalyst can be easily recovered and reused by magnetic separation,and the catalyst had no significant loss of activity after six cycles.It was found that Fe and Mn were the main active sites for the catalytic reaction,and the other three metals（Co,Ni,Cr）could act as catalytic promoters to synergistically enhance the catalytic activity.DFT calculations disclosed that the presence of oxygen vacancy in the prepared high entropy oxide was favorable for the adsorption of p-chlorotoluene molecule on catalyst surface,and promoted the formation of intermediate*Cl Ph CH₂O and the desired p-chlorobenzaldehyde.The superior catalytic activity of the c-Fe Co Ni Cr Mn catalyst is mainly due to its large specific surface area,small particle size,and high number of oxygen vacancies.更多还原