论文总字数：21628字

摘 要

环己酮是一种重要的有机合成中间体，其下游产品己内酰胺和己二酸聚合重排分别可以生产尼龙6和尼龙66。近几年来，国内对己内酰胺和己二酸的需求量大幅度增加，因此，环己酮工业生产工艺的优化一直是学术界及工程界关注的热点。工业上生产环己酮的工艺主要包括三种，分别是环己烷氧化法、苯催化加氢氧化法和苯酚加氢法。这三种工艺都是多步反应合成工艺，并且存在环境污染严重、耗能较大、催化剂易失活等问题。苯酚一步加氢法制备环己酮，具备过程简单、副产物较少等优点。本文前期开发了膜反应分离耦合强化连续苯酚加氢制环己酮工艺，采用钯负载在掺杂氮的活性炭上制备Pd@CN催化剂，结果表明：在低浓度苯酚（10%）加氢反应中催化剂表现出高活性（选择性、转化率gt;97%），重复使用时没有出现明显失活现象，但在高浓度苯酚（30%）加氢反应中，出现了较为明显的活性降低和催化剂的失活。本文使用介孔比例较大的介孔碳代替活性炭作为载体，并掺杂氮，负载活性组分钯，从而制备获得Pd@CN催化剂。介孔碳以介孔为主，而活性炭以微孔为主，相对于活性炭，以介孔碳作为载体制备的催化剂有较大的孔道，更利于传质，不会轻易吸附有机物造成堵孔现象。

在制备催化剂的过程中，对制备催化剂过程中的一些参数进行优化：（1）N源的量增加，Pd纳米颗粒的分散度提高，从而使Pd纳米颗粒的有效反应位增加，进而提高催化剂的转化率，N源的量过多，介孔碳的孔道会被有机物堵塞，导致表面积减少，使得Pd在表面积上不能均匀分散，从而使转化率降低。（2）使用旋蒸分离可以使氮源更多的留在介孔碳的孔道和表面，从而加强Pd纳米颗粒的分散，提高了催化剂的活性。（3）CN煅烧温度的提高可以使介孔碳表面和孔道内的氮源形成更多的含氮基团，加强Pd纳米颗粒的分散，提高催化剂的活性。而温度过高，导致介孔碳材料发生分解，使催化剂活性降低。（4）Pd负载量的增加，使催化剂的活性迅速提高，在Pd含量高于11%后，催化剂的活性趋于稳定。原因是随着加入的Pd纳米粒子的增加，Pd纳米颗粒的分散度提高，从而使Pd纳米颗粒的有效反应位增加，进而提高催化剂的转化率。（5）氢气的还原温度对催化剂的活性无影响。

关键字：环己酮 介孔碳 催化剂 选择性

Abstract

Cyclohexanone is an important organic synthesis intermediate. Its downstream product, caprolactam and adipic acid, can produce nylon 6 and nylon 66 when they are rearranged, respectively.In recent years, domestic demand for caprolactam and adipic acid has increased significantly. Therefore, optimization of the industrial production process of cyclohexanone has been a focus of concern in the academic and engineering communities. The industrial production of cyclohexanone mainly includes three processes, namely, cyclohexane oxidation, benzene-catalyzed oxidation and phenol hydrogenation. These three processes are almost all multi-step reaction synthesis processes, and there are problems such as serious environmental pollution, large energy consumption, and easy deactivation of the catalyst. Cyclohexanone is prepared by one-step hydrogenation of phenol, which has the advantages of simple process and less by-products. In the earlier part of this paper, a membrane reaction separation coupling enhanced continuous phenol hydrogenation to cyclohexanone process was developed. Pd@CN prepared on palladium-supported activated carbon which was doped with nitrogen was used as a catalyst. The results showed that during the hydrogenation of phenol at a low concentration (10%), the catalyst showed high activity (selectivity, conversion rategt;97%). No obvious deactivation occurred during repeated use. However, in the hydrogenation reaction of high-concentration phenol (30%), a significant reduction in activity and inactivation of catalysts was observed.. The microstructure of the catalyst was analyzed and found that organic substances were adsorbed in the micropores of the catalyst and caused pore blocking on the surface of the catalyst, which was not conducive to mass transfer, resulting in a decrease in activity. With the application of experiments, micropores were further blocked and the activity gradually decreased.

In this paper, mesoporous carbon with a large mesoporous ratio is used instead of activated carbon as a carrier, nitrogen and the active component palladium are doped to obtain a Pd@CN catalyst. Mesoporous carbon is dominated by mesopores, while activated carbon is dominated by micropores. Relative to activated carbon, mesoporous carbon is used as a catalyst to prepare catalysts with larger pores, which is more conducive to mass transfer and does not easily absorb organic substances and cause pore blocking. . The microstructure of the prepared catalyst was tested and the catalytic performance was tested in order to improve the activity and stability of the catalyst.

During the preparation of the catalyst, changes in some parameters will affect the catalytic performance of the catalyst. In order to prepare the Pd@CN catalyst with low cost, high catalytic performance and high stability, some parameters in the preparation of the catalyst are optimized for optimization. The parameters are: the amount of N source addition, CN separation method, CN calcination temperature, Pd loading amount, hydrogen reduction temperature. The results show （1）The amount of N source increases, and the dispersion of Pd nanoparticles increases, so that the effective reaction sites of Pd nanoparticles increase, thereby increasing the conversion rate of the catalyst. The amount of N source is too much, and the mesoporous carbon pores are blocked by organic substances. The decrease in surface area makes it impossible to uniformly disperse Pd on the surface area, resulting in a decrease in conversion.（2）The use of spin-separation allows the nitrogen source to remain more in the pores and surfaces of the mesoporous carbon, thereby enhancing the dispersion of the Pd nanoparticles and increasing the activity of the catalyst.（3）The increase of CN calcining temperature can form more nitrogen-containing groups on the surface of mesoporous carbon and nitrogen sources in pores, enhance the dispersion of Pd nanoparticles, and increase the activity of the catalyst. However, if the temperature is too high, the mesoporous carbon material will decompose and the activity of the catalyst will decrease.（4）With the increase of Pd loading, the activity of the catalyst increases rapidly. After the Pd content is higher than 11%, the activity of the catalyst tends to be stable. The reason is that as the added Pd nanoparticles increase, the dispersity of the Pd nanoparticles increases, so that the effective reaction sites of the Pd nanoparticles increase, thereby increasing the conversion rate of the catalyst.（5）The reduction temperature of hydrogen has no effect on the activity of the catalyst.

Keywords: Cyclohexanone；Mesoporous；carbon；Catalys;Selectivity.

目录

第一章 文献综述 1

1.1课题背景 1

1.2催化剂载体 1

1.2.1金属氧化物 1

1.2.2碳材料 1

1.2.3金属有机骨架 2

1.2.4 其他载体 3

1.3助剂的添加 3

1.3.1 金属的加入 3

1.3.2 助剂的添加 3

1.4 催化剂的改性及预处理 4

1.5 研究目的和实验思路 5

1.5.1 研究目的 5

1.5.2 实验思路 5

第二章 实验部分 6

2.1 实验试剂与实验仪器 6

2.1.1 实验药品 6

2.1.2 实验仪器 6

2.2 催化剂的制备 7

2.2.1 CN载体的制备 7

2.2.2 H₂PdCl₄（氯钯酸）的配制 7

2.2.3负载钯及还原 7

2.3 催化剂的活性测试 8

2.4 分析计算方法 8

2.5 催化剂的优化 8

2.5.1 N源的加入量 9

2.5.2 CN分离方式 9

2.5.3 CN煅烧温度 9

2.5.4 Pd的负载量 9

2.5.5 氢气还原温度 9

第三章 结果与讨论 10

3.1 催化剂优化结果与分析 10

3.1.1 N源的加入量 10

3.1.2 CN分离方式 11

3.1.3 CN煅烧温度 11

3.1.4 Pd的负载量 13

3.1.5 氢气还原温度 15

请支付后下载全文，论文总字数：21628字