催化学报 ›› 2018, Vol. 39 ›› Issue (4): 664-672.DOI: 10.1016/S1872-2067(17)62988-7

• 论文 • 上一篇    下一篇

氮掺杂碳包覆纳米钴颗粒用于硝基芳烃室温选择性加氢

高睿杰a,b, 潘伦a,b, 李正稳a, 张香文a,b, 王莅a,b, 邹吉军a,b   

  1. a 天津大学化工学院, 绿色合成与转化教育部重点实验室, 天津 300372;
    b 天津化学化工协同创新中心, 天津 300372
  • 收稿日期:2017-11-29 修回日期:2017-12-22 出版日期:2018-04-18 发布日期:2018-04-08
  • 通讯作者: 邹吉军
  • 基金资助:

    国家自然科学基金(U1462119);天津市自然科学基金(16JCQNJC05200).

Cobalt nanoparticles encapsulated in nitrogen-doped carbon for room-temperature selective hydrogenation of nitroarenes

Ruijie Gaoa,b, Lun Pana,b, Zhengwen Lia, Xiangwen Zhanga,b, Li Wanga,b, Jijun Zoua,b   

  1. a Key Laboratory for Green Chemical Technology of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;
    b Collaborative Innovative Center of Chemical Science and Engineering(Tianjin), Tianjin 300072, China
  • Received:2017-11-29 Revised:2017-12-22 Online:2018-04-18 Published:2018-04-08
  • Contact: 10.1016/S1872-2067(17)62988-7
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (U1462119) and the Tianjin Municipal Natural Science Foundation (16JCQNJC05200).

摘要:

通过硝基芳烃选择性加氢能高效地制备芳香胺和环胺,其中芳香胺作为重要的化工中间体应用于多个领域(精细化工、商业产品和聚合物).在加氢反应过程中,硝基的还原伴随着生成一些副产物(如亚硝基和偶氮化合物).同时对于含还原性基团的取代硝基苯,硝基的选择还原也面临着很大的挑战.金属钴是常用的硝基加氢催化剂活性成分,但是由于对反应底物的过度吸附,导致其选择性不高.早期研究发现,氮掺杂碳催化剂能有效吸附硝基基团,从而在硝基苯加氢中表现出一定活性,但对分子氢的活化不足.因此,氮掺杂碳作为吸附材料与钴构建复合催化剂,能够发挥吸附和活化氢的协同作用,从而高效催化硝基苯加氢.
基于此,本课题组发展了一种制备方法,可将钴颗粒尺寸限制在10nm左右,且包覆在氮掺杂碳中,并应用于对硝基苯酚的室温选择性加氢反应中,发现相较于碳负载钴和氮掺杂碳催化剂,所制催化剂在室温下表现出了很好的活性和选择性.在此基础上,本文采用元素分析、X射线光电子能谱(XPS)和拉曼光谱(Raman)等手段对催化剂形貌和结构进行了研究.
表征结果表明,保持钴前驱体的量不变,随着氮化碳加入量的增加,催化剂中氮掺杂浓度提高;当氮化碳/钴>1时,氮掺杂浓度不变.红外结果表明,与普通碳载体相比,氮掺杂碳对硝基苯有很强的吸附作用,而氮掺杂碳包覆的钴催化剂也表现出同样的结果.通过调节氮的掺杂浓度,一方面可以修饰碳载体的电子结构,增加表面缺陷的浓度,提高与反应底物的相互作用;另一方面可以促进电子由钴颗粒转移至与之相连的氮原子上,因此进一步促进钴颗粒对分子氢的活化作用.该复合结构的催化剂实现了底物吸附和氢活化的协同作用,氮掺杂碳将反应底物吸附在表面,钴颗粒活化氢,随后解离的氢原子与表面吸附物反应,从而实现硝基苯的高效加氢.其中Co@NC-1催化活性最高,并在循环套用10次后,仍维持较高的催化活性,同时对含其它取代基的硝基苯均表现很高的活性和选择性.

关键词: 钴颗粒, 氮掺杂碳, 硝基芳烃, 选择加氢, 氢活化, 多相催化

Abstract:

Here, we report cobalt nanoparticles encapsulated in nitrogen-doped carbon (Co@NC) that exhibit excellent catalytic activity and chemoselectivity for room-temperature hydrogenation of nitroarenes. Co@NC was synthesized by pyrolyzing a mixture of a cobalt salt, an inexpensive organic molecule, and carbon nitride. Using the Co@NC catalyst, a turnover frequency of~12.3 h-1 and selectivity for 4-aminophenol of >99.9% were achieved for hydrogenation of 4-nitrophenol at room temperature and 10 bar H2 pressure. The excellent catalytic performance can be attributed to the cooperative effect of hydrogen activation by electron-deficient Co nanoparticles and energetically preferred adsorption of the nitro group of nitroarenes to electron-rich N-doped carbon. In addition, there is electron transfer from the Co nanoparticles to N-doped carbon, which further enhances the functionality of the metal center and carbon support. The catalyst also exhibits stable recycling performance and high activity for nitroaromatics with various substituents.

Key words: Cobalt nanoparticle, Nitrogen-doped carbon, Nitroarenes, Selective hydrogenation, Hydrogen activation, Heterogeneous catalysis